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  • 151.
    Sagerman, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Enge, Swantje
    Pavia, Henrik
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Low feeding preference of native herbivores for the successful non-native seaweed Heterosiphonia japonica2015In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, no 12, p. 2471-2479Article in journal (Refereed)
    Abstract [en]

    Non-native seaweeds constitute a conspicuous component of many benthic coastal communities. Seaweed invaders are known to significantly affect invaded communities, but relatively little is known about the mechanisms underlying their success. In this study, we explored the feeding preferences of three generalist herbivores for the successful non-native red alga Heterosiphonia japonica and native seaweed competitors. The experiments were conducted on the Swedish Skagerrak coast (58A degrees 52'N, 11A degrees 08'E) from July to August. Additionally, chemical and physical traits of the seaweeds were assessed to mechanistically explain herbivore preferences. The results showed that H. japonica was of low preference to native herbivores and that this was most likely explained by chemical properties of the invader. We were, however, not able to determine whether the low preference was caused by deterrent metabolites or low nutritional quality. We conclude that herbivore avoidance may be important for the survival and success of H. japonica in the introduced range and that efficient means of escaping herbivory may be a common feature of invaders in seaweed communities.

  • 152. Sagerman, Josefin
    et al.
    Hansen, Joakim P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Effects of boat traffic and mooring infrastructure on aquatic vegetation: A systematic review and meta-analysis2020In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 49, no 2, p. 517-530Article, review/survey (Refereed)
    Abstract [en]

    Sustainable management of coastal and inland water areas requires knowledge of how tourism and recreation affects the ecosystems. Here, we present the first systematic review and meta-analysis to quantify to what extent recreational boat traffic and infrastructure for mooring affect the abundance of submerged vegetation on soft bottoms. Our systematic search yielded 25 studies containing data on effects of boat traffic, docks and mooring buoys on vegetation abundance. The abundance below docks was on average 18% of that in controls, and areas with boat traffic had on average 42% of the abundance in control areas. Mooring buoys often created scour areas without vegetation. However, the effects were variable and there were too few studies to test the reasons for this variability. We conclude that boating can cause significant declines in submerged vegetation but that informed management of boat traffic and improved design of docks and buoys can reduce negative impacts.

  • 153.
    Sagerman, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Pavia, Henrik
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Competition between the non-native Fucus evanescens and the native congener Fucus vesiculosusManuscript (preprint) (Other academic)
  • 154.
    Sagerman, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Staberg, Nichlas
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Pavia, Henrik
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Decomposition rates differ between two seaweed invaders with different ecophysiological traitsManuscript (preprint) (Other academic)
  • 155. Sampaio, E.
    et al.
    Rodil, Iván F.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Porto, Portugal; University of Helsinki, Finland.
    Vaz-Pinto, F.
    Fernandez, A.
    Arenas, F.
    Interaction strength between different grazers and macroalgae mediated by ocean acidification over warming gradients2017In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 125, p. 25-33Article in journal (Refereed)
    Abstract [en]

    Since the past century, rising CO2 levels have led to global changes (ocean warming and acidification) with subsequent effects on marine ecosystems and organisms. Macroalgae-herbivore interactions have a main role in the regulation of marine community structure (top-down control). Gradients of warming prompt complex non-linear effects on organism metabolism, cascading into altered trophic interactions and community dynamics. However, not much is known on how will acidification and grazer assemblage composition shape these effects. Within this context, we aimed to assess the combined effects of warming gradients and acidification on macroalgae-herbivore interactions, using three cosmopolitan species, abundant in the Iberian Peninsula and closely associated in nature: the amphipod Melita palmata, the gastropod Gibbula umbilicalis, and the green macroalga Ulva rigida. Under two CO2 treatments (triangle CO2 similar or equal to 450 mu atm) across a temperature gradient (13.5, 16.6, 19.9 and 22.1 degrees C), two mesocosm experiments were performed to assess grazer consumption rates and macroalgae-herbivore interaction, respectively. Warming (Experiment I and II) and acidification (Experiment II) prompted negative effects in grazer's survival and species-specific differences in consumption rates. M. palmata was shown to be the stronger grazer per biomass (but not per capita), and also the most affected by climate stressors. Macroalgae-herbivore interaction strength was markedly shaped by the temperature gradient, while simultaneous acidification lowered thermal optimal threshold. In the near future, warming and acidification are likely to strengthen top-down control, but further increases in disturbances may lead to bottom-up regulated communities. Finally, our results suggest that grazer assemblage composition may modulate future macroalgae-herbivore interactions.

  • 156.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Large-Scale Nutrient Dynamics in the Baltic Sea, 1970–20162018In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 5, article id 95Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea is one of the world's marine areas well-covered by both long-term observations and oceanographic studies. It is also a large coastal area in which eutrophication had already been recognized half a century ago. While the mechanisms of eutrophication are largely understood, several features are less recognized and sometimes neglected, including: (a) natural and anthropogenic North-South and East-West nutrient gradients within the drainage basin and marine ecosystems; (b) the compensatory potential of the interconnectivity between the Baltic Sea basins; (c) long nutrient residence times and high buffer capacity of the system, resulting in slow responses to nutrient load reductions. Particularly important is the interaction of (d) naturally occurring saltwater inflows sporadically ventilating deep water layers and (e) a partly man-made intensification of biological oxygen consumption. Resulting redox alterations of biogeochemical nitrogen and phosphorus cycles are locked in a “vicious circle” that promotes cyanobacterial nitrogen fixation, thereby hindering nitrogen load reduction and sustaining an elevated trophic state. This tight coupling of natural environmental variation and human impacts complicates both scientific studies and management recommendations. Our primary objective is to describe all these features and mechanisms with the best available data on nutrient loads, and unique estimates of the basin-wide nutrient pools. These data are presented as both long-term time series and empirical nutrient budgets. The analysis is supplemented by results of biogeochemical modeling. A second, more practical objective is to make these time series available to the community.

  • 157.
    Savchuck, Oleg P.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Myths of the Baltic Sea eutrophication2018In: Journal of Aquaculture & Marine Biology, ISSN 2378-3184, Vol. 7, no 2, p. 92-93Article in journal (Other academic)
  • 158. Schneider, Bernd
    et al.
    Dellwig, Olaf
    Kuliński, Karol
    Omstedt, Anders
    Pollehne, Falk
    Rehder, Gregor
    Savchuck, Oleg
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Biogeochemical cycles2017In: Biological Oceanography of the Baltic Sea / [ed] Pauline Snoeijs-Leijonmalm, Hendrik Schubert, Teresa Radziejewska, Dordrecht: Springer, 2017, p. 87-122Chapter in book (Refereed)
    Abstract [en]

    1. The internal cycles of carbon, nitrogen and phosphorus in the Baltic Sea are, like in other seas, mainly controlled by biological production and degradation of organic matter (OM).

    2. Biological activity also modulates the acid/base balance (pH), which is mainly a function of alkalinity and the total CO2 concentration.

    3. Particulate organic matter (POM) produced in the photic zone sinks into deeper water layers and is deposited on the sediment surface, where it is mineralised. Mineralisation is a form of microbial oxidation and thus leads to oxygen depletion. Due to its semi-enclosed position and its bottom topography, large-scale oxygen depletion of deep bottoms is common in the Baltic Sea.

    4. Under anoxic conditions, the burial of phosphorus bound to ferric oxide is inhibited and the availability of phosphate for incorporation in new OM production increases.

    5. In stagnant waters, the oxic/anoxic interface may migrate from the sediment into the water column, forming a pelagic redoxcline. Such a redoxcline occurs in large areas of the Baltic Sea.

    6. At oxygen concentrations close to zero, nitrate acts as an oxidant and is reduced to elemental nitrogen (denitrification). After the exhaustion of both oxygen and nitrate, OM is oxidised by sulphate, which is reduced to toxic hydrogen sulphide.

    7. The final step in the mineralisation process is the microbial formation of methane in deeper sediment layers, which reflects the internal oxidation/reduction of OM.

    8. A significant fraction of the organic carbon, nitrogen and phosphorus escapes mineralisation and is permanently buried in the sediment. On a long-term basis, this loss, together with export to the North Sea and internal sinks, is mainly balanced by riverine inputs and atmospheric deposition to the Baltic Sea.

  • 159. Schneider, Bernd
    et al.
    Eilola, Kari
    Lukkari, Kaarina
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Neumann, Thomas
    Environmental Impacts - Marine Biogeochemistry2015In: Second Assessment of Climate Change for the Baltic Sea Basin / [ed] The BACC II Author Team, Springer, 2015, p. 337-361Chapter in book (Refereed)
    Abstract [en]

    Marine biogeochemistry deals with the budgets and transformations of biogeochemically reactive elements such as carbon, nitrogen and phosphorus. Inorganic nitrogen and phosphorus compounds are the major nutrients and control organic matter (biomass) production in the surface water. Due to various anthropogenic activities, the input of these nutrients into the Baltic Sea has increased drastically during the last century and has enhanced the net organic matter production by a factor of 2-4 (eutrophication). This has led to detrimental oxygen depletion and hydrogen sulphide production in the deep basins of the Baltic Sea. Model simulations based on the Baltic Sea Action Plan (BSAP) indicate that current eutrophication and thus extension of oxygen-depleted areas cannot be reversed within the next hundred years by the proposed nutrient reduction measures. Another environmental problem is related to decreasing pH (acidification) that is caused by dissolution of the rising atmospheric CO2. Estimates indicate a decrease in pH by about 0.15 during the last 1-2 centuries, and continuation of this trend may have serious ecological consequences. However, the concurrent increase in the alkalinity of the Baltic Sea may have significantly counteracted acidification.

  • 160. Schneider, Bernd
    et al.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Sadkowiak, Bernd
    Control of the mid-summer net community production and nitrogen fixation in the central Baltic Sea: An approach based on pCO2 measurements on a cargo ship2014In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 136, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Automated measurements of the surface CO2 partial pressure, pCO2, were performed since 2003 on a cargo ship along a transect between Helsinki in the Gulf of Finland and Lübeck/Gdynia in the southwest of the Baltic Sea. The temporal and spatial resolution of the measurements amounted to 2–4 days and about 2 nautical miles, respectively. Based on temperature and salinity records and on the mean alkalinity, the total CO2 concentrations, CT, were calculated from the mean pCO2 in the northeastern Gotland Sea. The CT data were used to establish a CO2 mass balance for the period from mid-June to the beginning of August in 2005, 2008, 2009 and 2011. Taking into account the air–sea CO2 gas exchange, the mass balance yielded the net organic matter (Corg) production which is fuelled by nitrogen fixation at this time of the year. Several production events were detected with rates up to 8 μmol-C L− 1 d− 1. The production rates were not related to temperature, but showed a distinct correlation with the rate of the temperature increase. This led to the conclusion that the exposure of nitrogen fixing cyanobacteria to irradiance is the dominating control for the Corg production. Therefore, we suggest using the ratio of irradiance to the mixed layer depth as a variable for the parameterization of nitrogen fixation in biogeochemical models. The Corg production and thus the nitrogen fixation rates remained almost constant as long as continuous rising temperatures indicated favorable irradiation conditions. A limitation of the rates by phosphate or any other factor could not be detected. Based on the C/N ratio of particulate organic matter during a cyanobacteria bloom, the Corg production was used to estimate the mid-summer nitrogen fixation. The values varied from 102 mmol m− 2 to 214 mmol m− 2 (mean: 138 mmol m− 2) for the different years and did not show any correlation with the phosphate excess after the spring nitrate depletion.

  • 161. Seidel, Michael
    et al.
    Manecki, Marcus
    Herlemann, Daniel P. R.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Schulz-Bull, Detlef
    Jürgens, Klaus
    Dittmar, Thorsten
    Composition and Transformation of Dissolved Organic Matter in the Baltic Sea2017In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 5, article id 31Article in journal (Refereed)
    Abstract [en]

    The processing of terrestrial dissolved organic matter (DOM) in coastal shelf seas is an important part of the global carbon cycle, yet, it is still not well understood. One of the largest brackish shelf seas, the Baltic Sea in northern Europe, is characterized by high freshwater input from sub-arctic rivers and limited water exchange with the Atlantic Ocean via the North Sea. We studied the molecular and isotopic composition and turnover of solid-phase extractable (SPE) DOM and its transformation along the salinity and redox continuum of the Baltic Sea during spring and autumn. We applied ultrahigh-resolution mass spectrometry and other geochemical and biological approaches. Our data demonstrate a large influx of terrestrial riverine DOM, especially into the northern part of the Baltic Sea. The DOM composition in the central Baltic Sea changed seasonally and was mainly related to autochthonous production by phytoplankton in spring. Especially in the northern, river-dominated basins, a major fraction of riverine DOM was removed, likely by bio- and photo-degradation. We estimate that the removal rate of terrestrial DOM in the Baltic Sea (Bothnian Bay to the Danish Straits/Kattegat area) is 1.6-1.9 Tg C per year which is 43-51% of the total riverine input. The export of terrestrial DOM from the Danish Straits/Kattegat area toward the North Sea is 1.8-2.1 Tg C per year. Due to the long residence time of terrestrial DOMin the Baltic Sea (total of ca. 12 years), seasonal variations caused by bio- and photo-transformations and riverine discharge are dampened, resulting in a relatively invariant DOM molecular and isotopic signature exported to the North Sea. In the deep stagnant basins of the Baltic Sea, the DOM composition and dissolved organic nitrogen concentrations changed seasonally, likely because of vertical particle transport and subsequent degradation releasing DOM. DOM in the deep anoxic basins was also enriched in sulfur-containing organic molecules, pointing to abiotic sulfurization of DOM under sulfidic conditions.

  • 162. Sinkko, Hanna
    et al.
    Hepolehto, Iina
    Lyra, Christina
    Rinta-Kanto, Johanna M.
    Villnäs, Anna
    Norkko, Joanna
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Imonen, Sari T.
    Increasing oxygen deficiency changes rare and moderately abundant bacterial communities in coastal soft sediments2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 16341Article in journal (Refereed)
    Abstract [en]

    Coastal hypoxia is a major environmental problem worldwide. Hypoxia-induced changes in sediment bacterial communities harm marine ecosystems and alter biogeochemical cycles. Nevertheless, the resistance of sediment bacterial communities to hypoxic stress is unknown. We investigated changes in bacterial communities during hypoxic-anoxic disturbance by artificially inducing oxygen deficiency to the seafloor for 0, 3, 7, and 48 days, with subsequent molecular biological analyses. We further investigated relationships between bacterial communities, benthic macrofauna and nutrient effluxes across the sediment-water-interface during hypoxic-anoxic stress, considering differentially abundant operational taxonomic units (OTUs). The composition of the moderately abundant OTUs changed significantly after seven days of oxygen deficiency, while the abundant and rare OTUs first changed after 48 days. High bacterial diversity maintained the resistance of the communities during oxygen deficiency until it dropped after 48 days, likely due to anoxia-induced loss of macrofaunal diversity and bioturbation. Nutrient fluxes, especially ammonium, correlated positively with the moderate and rare OTUs, including potential sulfate reducers. Correlations may reflect bacteria-mediated nutrient effluxes that accelerate eutrophication. The study suggests that even slightly higher bottom-water oxygen concentrations, which could sustain macrofaunal bioturbation, enable bacterial communities to resist large compositional changes and decrease the harmful consequences of hypoxia in marine ecosystems.

  • 163. Slomp, Caroline P.
    et al.
    Mort, Haydon P.
    Jilbert, Tom
    Reed, Daniel C.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Wolthers, Mariette
    Coupled Dynamics of Iron and Phosphorus in Sediments of an Oligotrophic Coastal Basin and the Impact of Anaerobic Oxidation of Methane2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 4, article id e62386Article in journal (Refereed)
    Abstract [en]

    Studies of phosphorus (P) dynamics in surface sediments of lakes and coastal seas typically emphasize the role of coupled iron (Fe), sulfur (S) and P cycling for sediment P burial and release. Here, we show that anaerobic oxidation of methane (AOM) also may impact sediment P cycling in such systems. Using porewater and sediment profiles for sites in an oligotrophic coastal basin (Bothnian Sea), we provide evidence for the formation of Fe-bound P (possibly vivianite; Fe-3(PO4)(2)center dot 8H(2)O) below the zone of AOM with sulfate. Here, dissolved Fe2+ released from oxides is no longer scavenged by sulfide and high concentrations of both dissolved Fe2+ (>1 mM) and PO4 in the porewater allow supersaturation with respect to vivianite to be reached. Besides formation of Fe(II)-P, preservation of Fe-oxide bound P likely also contributes to permanent burial of P in Bothnian Sea sediments. Preliminary budget calculations suggest that the burial of Fe-bound P allows these sediments to act as a major sink for P from the adjacent eutrophic Baltic Proper.

  • 164. Snelgrove, Paul V. R.
    et al.
    Soetaert, Karline
    Solan, Martin
    Thrush, Simon
    Wei, Chih-Lin
    Danovaro, Roberto
    Fulweiler, Robinson W.
    Kitazato, Hiroshi
    Ingole, Baban
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Parkes, R. John
    Volkenborn, Nils
    Global Carbon Cycling on a Heterogeneous Seafloor2018In: Trends in Ecology & Evolution, ISSN 0169-5347, E-ISSN 1872-8383, Vol. 33, no 2, p. 96-105Article, review/survey (Refereed)
    Abstract [en]

    Diverse biological communities mediate the transformation, transport, and storage of elements fundamental to life on Earth, including carbon, nitrogen, and oxygen. However, global biogeochemical model outcomes can vary by orders of magnitude, compromising capacity to project realistic ecosystem responses to planetary changes, including ocean productivity and climate. Here, we compare global carbon turnover rates estimated using models grounded in biological versus geochemical theory and argue that the turnover estimates based on each perspective yield divergent outcomes. Importantly, empirical studies that include sedimentary biological activity vary less than those that ignore it. Improving the relevance of model projections and reducing uncertainty associated with the anticipated consequences of global change requires reconciliation of these perspectives, enabling better societal decisions on mitigation and adaptation.

  • 165. Sobota, Daniel J.
    et al.
    Compton, Jana E.
    McCrackin, Michelle L.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Singh, Shweta
    Cost of reactive nitrogen release from human activities to the environment in the United States2015In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 10, no 2, article id 25006Article in journal (Refereed)
    Abstract [en]

    Leakage of reactive nitrogen (N) from human activities to the environment can cause human health and ecological problems. Often these harmful effects are not reflected in the costs of food, fuel, and fiber that derive from Nuse. Spatial analyses of damage costs attributable to source at management-relevant scales could inform decisions in areas where anthropogenic N leakage causes harm. We used recently compiled data describing N inputs in the conterminous United States (US) to assess potential damage costs associated with anthropogenic N. We estimated fates of N leaked to the environment (air/deposition, surface freshwater, groundwater, and coastal zones) in the early 2000s by multiplying watershed-level N inputs (8-digit US Geologic Survey Hydrologic Unit Codes; HUC8s) with published coefficients describing nutrient uptake efficiency, leaching losses, and gaseous emissions. We scaled these N leakage estimates with mitigation, remediation, direct damage, and substitution costs associated with human health, agriculture, ecosystems, and climate (per kg of N) to calculate annual damage cost (US dollars in 2008 or as reported) of anthropogenic N per HUC8. Estimates of N leakage by HUC8 ranged from <1 to 125 kg N ha(-1) yr(-1), with most N leaked to freshwater ecosystems. Estimates of potential damages (based on median estimates) ranged from $1.94 to $2255 ha(-1) yr(-1) across watersheds, with a median of $252 ha(-1) yr(-1). Eutrophication of freshwater ecosystems and respiratory effects of atmospheric N pollution were important across HUC8s. However, significant data gaps remain in our ability to fully assess N damages, such as damage costs from harmful algal blooms and drinking water contamination. Nationally, potential health and environmental damages of anthropogenic N in the early 2000s totaled $210 billion yr(-1) USD (range: $81-$441 billion yr(-1)). While a number of gaps and uncertainties remain in these estimates, overall this work represents a starting point to inform decisions and engage stakeholders on the costs of N pollution.

  • 166.
    Soerensen, Anne. L.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Schartup, Amina T.
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Undeman, Emma
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Björn, Erik
    Eutrophication Increases Phytoplankton Methylmercury Concentrations in a Coastal Sea-A Baltic Sea Case Study2016In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 21, p. 11787-11796Article in journal (Refereed)
    Abstract [en]

    Eutrophication is expanding worldwide, but its implication for production and bioaccumulation of neurotoxic monomethylmercury (MeHg) is unknown. We developed a mercury (Hg) biogeochemical model for the Baltic Sea and used it to investigate the impact of eutrophication on phytoplankton MeHg concentrations. For model evaluation, we measured total methylated Hg (MeHgT) in the Baltic Sea and found low concentrations (39 +/- 16 fM) above the halocline and high concentrations in anoxic waters (1249 +/- 369 fM). To close the Baltic Sea MeHgT budget, we inferred an average normoxic water column HgII methylation rate constant of 2 x 10-4 d-1. We used the model to compare Baltic Seas present-day (2005-2014) eutrophic state to an oligo/mesotrophic scenario. Eutrophication increases primary production and export of organic matter and associated Hg to the sediment effectively removing Hg from the active biogeochemical cycle; this results in a 27% lower present-day water column Hg reservoir. However, increase in organic matter production and remineralization stimulates microbial Hg methylation resulting in a seasonal increase in both water and phytoplankton MeHg reservoirs above the halocline. Previous studies of systems dominated by external MeHg sources or benthic production found eutrophication to decrease MeHg levels in plankton. This Baltic Sea study shows that in systems with MeHg production in the normoxic water column eutrophication can increase phytoplankton MeHg content.

  • 167. Sonesten, Lars
    et al.
    Svendsen, Lars M.
    Tornbjerg, Henrik
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Frank-Kamenetsky, Dmitry
    Haapaniemi, Juuso
    Sources and pathways of nutrients to the Baltic Sea: HELCOM PLC-62018Report (Other academic)
    Abstract [en]

    Eutrophication caused by oversupply of the Baltic Sea by nutrients remains the major environmental pressure on the marine ecosystem. In order to mitigate eutrophication, HELCOM countries have agreed on a joint effort to reduce nutrient load on the marine ecosystem, reflected in the HELCOM Baltic Sea Action Plan as a nutrient input reduction scheme. Compilations of pollution load data, designed to follow up on the implementation of the scheme, have been an integral part of the HELCOM assessment system since 1987. This assessment of major sources and pathways of nitrogen and phosphorus into the marine environment is a vital part of the HELCOM Pollution Load Compilation (PLC) and one of the main products of the HELCOM Sixth Pollution Load Compilation project (PLC-6). The product includes an assessment of three major pathways of nutrients – riverine, airborne and via direct sources – and more detailed assessment of sources of riverine load.

    The previous (PLC-5) assessment, published in 2013, was based on the data on nutrient inputs in 2006. Current assessment illustrates the contribution of various sources of nitrogen and phosphorus into total loads in 2014 (2012 for Germany and Poland). The assessment also illustrates changes in proportion of different pathways since 1995.

  • 168. Stalnacke, P.
    et al.
    Pengerud, A.
    Vassiljev, A.
    Smedberg, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Hägg, H. E.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Humborg, Christop
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Andersen, H. E.
    Nitrogen surface water retention in the Baltic Sea drainage basin2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 2, p. 981-996Article in journal (Refereed)
    Abstract [en]

    In this paper, we estimate the surface water retention of nitrogen (N) in all the 117 drainage basins to the Baltic Sea with the use of a statistical model (MESAW) for source apportionment of riverine loads of pollutants. Our results show that the MESAW model was able to estimate the N load at the river mouth of 88 Baltic Sea rivers, for which we had observed data, with a sufficient degree of precision and accuracy. The estimated retention parameters were also statistically significant. Our results show that around 380 000 t of N are annually retained in surface waters draining to the Baltic Sea. The total annual riverine load from the 117 basins to the Baltic Sea was estimated at 570 000 t of N, giving a total surface water N retention of around 40 %. In terms of absolute retention values, three major river basins account for 50% of the total retention in the 117 basins; i.e. around 104 000 t of N are retained in Neva, 55 000 t in Vistula and 32 000 t in Oder. The largest retention was found in river basins with a high percentage of lakes as indicated by a strong relationship between N retention (%) and share of lake area in the river drainage areas. For example in Gota alv, we estimated a total N retention of 72 %, whereof 67% of the retention occurred in the lakes of that drainage area (Lake Vanern primarily). The obtained results will hopefully enable the Helsinki Commission (HELCOM) to refine the nutrient load targets in the Baltic Sea Action Plan (BSAP), as well as to better identify cost-efficient measures to reduce nutrient loadings to the Baltic Sea.

  • 169.
    Staveley, Thomas A. B.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. AquaBiota Water Research, Sweden.
    Hernvall, Patrick
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. AquaBiota Water Research, Sweden.
    Stjärnkvist, Nellie
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    van der Meijs, Felix
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. AquaBiota Water Research, Sweden.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Gothenburg, Sweden.
    Exploring seagrass fish assemblages in relation to the habitat patch mosaic in the brackish Baltic Sea2020In: Marine Biodiversity, ISSN 1867-1616, E-ISSN 1867-1624, Vol. 50, no 1, article id 1Article in journal (Refereed)
    Abstract [en]

    Assessing the influence of habitat patch dynamics on faunal communities is a growing area of interest within marine ecological studies. This study sets out to determine fish assemblage composition in Zostera marina (L.) meadows and ascertain how habitat structural complexity and seascape structure (i.e. composition and configuration of habitat patches) influenced these assemblages in the northern Baltic Sea. Using ten seascapes (600 m in diameter), the fish assemblage was surveyed both in summer and autumn using beach seine. We found that the fish assemblage was clearly dominated by sticklebacks, followed by pipefish and with a general absence of larger piscivorous species. Biomass of fish did not differ between seasons, and low-level carnivores dominated the trophic structure. Overall, at the larger seascape-scale in summer, the proportion of bare soft sediment showed a negative relationship with fish biomass, while diversity of patches was found to exhibit a positive association with fish biomass. At the smaller habitat scale, both seagrass shoot height and density had a negative influence on fish biomass in both seasons. This study outlines new knowledge regarding how the mosaic of habitat patches shape seagrass fish assemblages in the northern Baltic Sea.

  • 170.
    Staveley, Thomas
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Hernvall, Patrick
    Stjärnkvist, Nellie
    van der Meijs, Felix
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Exploring seagrass fish assemblages in relation to the habitat patch mosaic in the brackish Baltic SeaManuscript (preprint) (Other academic)
  • 171.
    Sun, Xiaole
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Geological Sciences.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gustafsson, Bo
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Temporal and spatial variations of rock weathering and CO2 consumption in the Baltic Sea catchment2017In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 466, p. 57-69Article in journal (Refereed)
    Abstract [en]

    This study provides the first estimate of silicate and carbonate weathering rates and derived CO2 consumption rates for the Baltic Sea catchment using river chemistry data of 78 rivers draining into the Baltic Sea. The silicate weathering rates (denoted as total dissolved solids) of individual river basin range from 0.014 Tg/year to 4.55 Tg/year and the carbonate weathering rates range from 0.079 Tg/year to 6.49 Tg/year. The total CO2 consumption across the Baltic catchment is approximately 3.9 Tg C/year and is almost equally shared by silicates and carbonates. Uncertainty associated with the weathering estimate is around 32%, which is mainly caused by incomplete pollution correction for a few major rivers in the south. The calculations for the boreal river basins have higher certainties because of less human impacts. The CO2 consumption rate of individual river basin vary between 0.53 and 5.66 g C/m(2)/year with an average of 2.97 g C/m(2)/year, in which carbonates consume CO2, 1.4 g C/m(2)/year and silicates take 1.5 g C/m(2)/year. This is in the same range as has been reported for the Mackenzie River and Siberian river basins, but at the lower range of tropical rivers, suggesting the Baltic Sea catchment holds solid weathering signals for high-latitude systems, especially in the pristine boreal silicatedominated areas. The amount of CO2 consumed by weathering in the Baltic Sea catchment accounts for approximately 3-30% of the net ecosystem carbon exchange (10-100 g C/m(2)/year), implying that weathering contributes as a significant sink of atmospheric CO2. Although many studies have shown the positive relation between temperature and weathering rates in various river catchments, multiple regression analysis using the 40-year continuous records of river chemistry in the boreal area of the Baltic Sea catchment reveals a strong correlation between weathering flux and precipitation, but no statistically significant correlation between weathering and temperature. This suggests not only that temperature is not necessarily to be primary controlling factor for weathering rates, but also besides precipitation, other factors, like increased soil organic matter contents and water path changes may have high impact on weathering rates. The 40-year data analysis also shows generally increasing weathering fluxes by 10-20% in the pristine boreal area over the past decades. This indicates that increased CO2 consumption by weathering and the resulting elevated dissolved inorganic carbon delivery to the ocean act as a negative feedback for ocean acidification, such as the Arctic Ocean that has become more acidic due to high terrestrial organic carbon delivery together with increased river water input.

  • 172.
    Sun, Xiaole
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Porcelli, Don
    Kutscher, Liselott
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Hirst, Catherine
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Murphy, Melissa J.
    Maximov, Trofim
    Petrov, Roman E.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Schmitt, Melanie
    Andersson, Per S.
    Stable silicon isotopic compositions of the Lena River and its tributaries: Implications for silicon delivery to the Arctic Ocean2018In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 241, p. 120-133Article in journal (Refereed)
    Abstract [en]

    Silicon isotope values (delta Si-30(DSi)) of dissolved silicon (DSi) have been analyzed in the Lena River and its tributaries, one of the largest Arctic watersheds in the world. The geographical and temporal variations of delta Si-30(DSi) range from +0.39 to +1.86% with DSi concentrations from 34 to 121 mu M. No obvious patterns of DSi concentrations and delta Si-30(DSi) values were observed along over 200 km of the two major tributaries, the Viliui and Aldan Rivers. In summer, the variations of DSi concentrations and delta Si-30(DSi) values in the water are either caused by biological uptake by higher plants and phytoplankton or by mixing of water masses carrying different DSi concentrations and delta Si-30(DSi) values. DSi in tributaries from the Verkhoyansk Mountain Range seems to be associated with secondary clay formation that increased the delta Si-30(DSi) values, while terrestrial biological production is likely more prevalent in controlling delta Si-30(DSi) values in Central Siberian Plateau and Lena Amganski Inter-River Area. In winter, when soils were frozen, the delta Si-30(DSi) values in the river appeared to be controlled by weathering and clay formation in deep intrapermafrost groundwater. During the spring flood, dissolved silicate materials and phytoliths were flushed from the upper thawed soils into rivers, which reset delta Si-30(DSi) values to the values observed prior to the biological bloom in summer. The results indicate that the Si isotope values reflect the changing processes controlling Si outputs to the Lena River and to the Arctic Ocean between seasons. The annual average delta Si-30(DSi) value of the Lena Si flux is calculated to be +0.86 +/- 0.3 parts per thousand using measured delta Si-30(DSi) values from each season. Combined with the estimate of + 1.6 +/- 0.25 parts per thousand for the Yenisey River, an updated delta Si-30(DSi) value of the major river Si inputs to the Arctic Ocean is estimated to be + 1.3 +/- 0.3 parts per thousand. This value is expected to shift towards higher values in the future because of the impacts from a variety of biological and geochemical processes and sources under global warming.

  • 173.
    Sun, Xiaole
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Olofsson, Martin
    Andersson, Per S.
    Fry, Brian
    Legrand, Catherine
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms2014In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 130, p. 156-166Article in journal (Refereed)
    Abstract [en]

    Studies of silicon (Si) isotope fractionation during diatom growth in open ocean systems have documented lower Si isotopic values (delta Si-30) in the biogenic silica of diatom frustules compared to dissolved silicon. Recent findings also indicate that Si isotope fractionation occurs during dissolution of diatom frustules, producing higher delta Si-30 values in the remaining biogenic silica. This study focuses on diatoms from high production areas in estuarine and coastal areas that represent approximately 30-50% of the global marine primary production. Two species of diatoms, Thalassiosira baltica and Skeletonema marinoi, were isolated from the brackish Baltic Sea, one of the largest estuarine systems in the world. These species were used for laboratory investigations of Si isotope fractionation during diatom growth and the subsequent dissolution of the diatom frustules. Both species of diatoms give an identical Si isotope fractionation factor during growth of -1.50 +/- 0.36 parts per thousand (2 sigma) for Si-30, which falls in the range of -2.09 parts per thousand to -0.55 parts per thousand of published data. Our results also suggest a dissolution-induced Si isotope fractionation factor of -0.86 parts per thousand at early stage of dissolution, but this effect was observed only in DSi and no significant Si isotope change was observed for BSi. The growth and dissolution results are applied to a Baltic Sea sediment core to reconstruct DSi utilization by diatoms, and found to be in agreement with the observed DSi uptake rates in the overlying water column during diatom growth.

  • 174.
    Svanbäck, Annika
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    McCrackin, Michelle L.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Swaney, Dennis P.
    Linefur, Helena
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Howarth, Robert W.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Reducing agricultural nutrient surpluses in a large catchment - Links to livestock density2019In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 648, p. 1549-1559Article in journal (Refereed)
    Abstract [en]

    The separation between crop- and livestock production is an important driver of agricultural nutrient surpluses in many parts of the world. Nutrient surpluses can be symptomatic of poor resource use efficiency and contribute to environmental problems. Thus, it is important not only to identify where surpluses can be reduced, but also the potential policy tools that could facilitate reductions. Here, we explored linkages between livestock production and nutrient flows for the Baltic Sea catchment and discuss management practices and policies that influence the magnitude of nutrient surpluses. We found that the majority of nutrients cycled through the livestock sector and that large nitrogen and phosphorus surpluses often occurred in regions with high livestock density. Imports of mineral fertilizers and feed to the catchment increased overall surpluses, which in turn increased the risk of nutrient losses from agriculture to the aquatic environment. Many things can be done to reduce agricultural nutrient surpluses; an important example is using manure nutrients more efficiently in crop production, thereby reducing the need to import mineral fertilizers. Also, existing soil P reserves could be used to a greater extent, which further emphasizes the need to improve nutrient management practices. The countries around the Baltic Sea used different approaches to manage agricultural nutrient surpluses, and because eight of the coastal countries are members in the European Union (EU), common EU policies play an important role in management. We observed reductions in surpluses between 2000 and 2010 in some countries, which suggested the influence of different approaches to management and policy and that there are opportunities for further improvement. However, the separation between crop and livestock production in agriculture appears to be an underlying cause of nutrient surpluses; thus, further research is needed to understand how policy can address these structural issues and increase sustainability in food production.

  • 175.
    Svanbäck, Annika
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Ulen, B.
    Bergstrom, L.
    Kleinman, P. J. A.
    Long-term trends in phosphorus leaching and changes in soil phosphorus with phytomining2015In: Journal of Soil and Water Conservation, ISSN 0022-4561, E-ISSN 1941-3300, Vol. 70, no 2, p. 121-132Article in journal (Refereed)
    Abstract [en]

    Few mitigation strategies exist to reduce phosphorus (P) losses in leachate once soil P has built up. Phytomining, or harvesting a crop without application of fertilizer P to create a negative P balance, has been proposed as a strategy for lowering soil P levels and preventing P loss to runoff and leachate. In this study crops were grown and harvested over 7 to 16 years in undisturbed soil columns (105 cm [41 in] deep) with contrasting textures (loamy sand, sandy loam, silty clay loam, and clay) and high P levels, while P loss in leachate was measured. Soil test P in the topsoil (0 to 20 cm [0 to 8 in] depth) was significantly decreased from the beginning to the end of the study for all soils, while a significant decreasing trend in dissolved reactive P in leachate was only observed in one soil. Downward movement of P from the topsoil to deeper layers was indicated to occur in three out of four soils. Although phytomining lowered soil test P by 11% to 37% in topsoils over the 7 to 16 year period of the study, results indicate that soils with P content well above agronomic optimum may take a much longer time to reach the agronomic optimum.

  • 176.
    Svedäng, Henrik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Biodiversity and Ecosystem Services in Nordic Coastal Ecosystems – an IPBES-like assessment: Summary for policy makers2018Report (Other academic)
  • 177.
    Svedäng, Henrik
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Swedish Institute for the Marine Environment (SIME), Sweden; Swedish University of Agricultural Sciences (SLU), Sweden.
    Barth, Julia M. I.
    Svensson, Anders
    Jonsson, Patrik
    Jentoft, Sissel
    Knutsen, Halvor
    André, Carl
    Local cod (Gadus morhua) revealed by egg surveys and population genetic analysis after longstanding depletion on the Swedish Skagerrak coast2019In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 76, no 2, p. 418-429Article in journal (Refereed)
    Abstract [en]

    Dramatic and persistent reductions in Atlantic cod (Gadus morhua) are common in many coastal areas. While offshore cod stocks still were abundant and productive, the Swedish west coast showed signs of diminishing adult cod abundance at the beginning of the 1980s, where the local cod component was considered to be extirpated. To survey the present cod spawning activity and stock composition, we initiated egg trawling over two consecutive years (203 hauls in total) in combination with population genetic analyses (425 individually genotyped eggs). Here, we provide evidence of cod spawning at the Swedish Skagerrak coast, suggesting recolonization or that local cod has recovered from a nearly depleted state. Early stage eggs were found inside fjords too far to have been transported by oceanic drift from offshore spawning areas. The cod eggs were genetically similar in early to late life-stages and cluster mainly with the local adult cod, indicating that eggs and adults belong to the same genetic unit. The cod eggs were genetically differentiated from adult North Sea cod, and, to a lesser degree, also from the Kattegat and Öresund cod, i.e. indicating a possible recovery of local coastal stock.

    The patterns of the genetic structure in the inshore areas are, however, difficult to fully disentangle, as Atlantic cod in the North Sea-Skagerrak area seem to be a mixture of co-existing forms: local cod completing their entire life cycle in fjords and sheltered areas, and oceanic populations showing homing behaviours. The egg abundances are considerably lower compared with what is found in similar studies along the Norwegian Skagerrak coast. Nevertheless, the discovery of locally spawning cod along the Swedish west coast—although at low biomasses—is an encouraging finding that highlights the needs for endurance in protective measures and of detailed surveys to secure intraspecific biodiversity and ecosystem services.

  • 178. Tam, Jamie C.
    et al.
    Link, Jason S.
    Rossberg, Axel G.
    Rogers, Stuart I.
    Levin, Philip S.
    Rochet, Marie-Joelle
    Bundy, Alida
    Belgrano, Andrea
    Libralato, Simone
    Tomczak, Maciej
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    van de Wolfshaar, Karen
    Pranovi, Fabio
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Large, Scott I.
    Niquil, Nathalie
    Greenstreet, Simon P. R.
    Druon, Jean-Noel
    Lesutiene, Jurate
    Johansen, Marie
    Preciado, Izaskun
    Patricio, Joana
    Palialexis, Andreas
    Tett, Paul
    Johansen, Geir O.
    Houle, Jennifer
    Rindorf, Anna
    Towards ecosystem-based management: identifying operational food-web indicators for marine ecosystems2017In: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 74, no 7, p. 2040-2052Article in journal (Refereed)
    Abstract [en]

    Modern approaches to Ecosystem-Based Management and sustainable use of marine resources must account for the myriad of pressures (interspecies, human and environmental) affecting marine ecosystems. The network of feeding interactions between co-existing species and populations (food webs) are an important aspect of all marine ecosystems and biodiversity. Here we describe and discuss a process to evaluate the selection of operational food-web indicators for use in evaluating marine ecosystem status. This process brought together experts in food-web ecology, marine ecology, and resource management, to identify available indicators that can be used to inform marine management. Standard evaluation criteria (availability and quality of data, conceptual basis, communicability, relevancy to management) were implemented to identify practical food-web indicators ready for operational use and indicators that hold promise for future use in policy and management. The major attributes of the final suite of operational food-web indicators were structure and functioning. Indicators that represent resilience of the marine ecosystem were less developed. Over 60 potential food-web indicators were evaluated and the final selection of operational food-web indicators includes: the primary production required to sustain a fishery, the productivity of seabirds (or charismatic megafauna), zooplankton indicators, primary productivity, integrated trophic indicators, and the biomass of trophic guilds. More efforts should be made to develop thresholds-based reference points for achieving Good Environmental Status. There is also a need for international collaborations to develop indicators that will facilitate management in marine ecosystems used by multiple countries.

  • 179.
    Tano, Stina A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, A. S.
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tropical seaweed beds as important habitats for juvenile fish2017In: Marine and Freshwater Research, ISSN 1323-1650, E-ISSN 1448-6059, Vol. 68, no 10, p. 1921-1934Article in journal (Refereed)
    Abstract [en]

    Seaweed beds within tropical seascapes have received little attention as potential fish habitat, despite other vegetated habitats, such as seagrass meadows and mangroves, commonly being recognised as important nurseries for numerous fish species. In addition, studies of vegetated habitats rarely investigate fish assemblages across different macrophyte communities. Therefore, the aim of the present study was to investigate the role of tropical seaweed beds as fish habitat, particularly for juvenile fish, by comparing their fish assemblages with those of closely situated seagrass beds. Fish assemblages were assessed by visual census in belt transects, where fish were identified and their length estimated, and habitat variables were estimated for each transect. The abundance of juvenile fish in seaweed beds was twice as high as that in seagrass meadows, whereas there was no difference in total, subadult or adult fish abundance. In addition, the abundance of commercially important and coral reef-associated juveniles was higher in seaweed beds, as was fish species richness. Fish assemblages differed between habitats, with siganids being more common in seagrass meadows and juvenile Labridae and Serranidae more common in seaweed beds. These results highlight that tropical seaweed beds are important juvenile fish habitats and underscore the need to widen the view of the shallow tropical seascape.

  • 180.
    Tano, Stina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, A. S.
    Hailing, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tropical seaweed beds are important habitats for mobile invertebrate epifauna2016In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 183, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Marine macrophyte habitats in temperate regions provide productive habitats for numerous organisms, with their abundant and diverse invertebrate epifaunal assemblages constituting important linkages between benthic primary production and higher trophic levels. While it is commonly also recognized that certain vegetated habitats in the tropics, such as seagrass meadows, can harbour diverse epifaunal assemblages and may constitute important feeding grounds to fish, little is known about the epifaunal assemblages associated with tropical seaweed beds. We investigated the abundance, biomass and taxon richness of the mobile epifaunal community (>= 1 mm) of tropical East African seaweed beds, as well as the abundance of invertivorous fishes, and compared it with that of closely situated seagrass meadows, to establish the ecological role of seaweed beds as habitat for epifauna as well as potential feeding grounds for fish. The results showed that seaweed beds had a higher abundance of mobile epifauna (mean SD: 10,600 +/- 6000 vs 3700 +/- 2800 per m(2)) than seagrass meadows, as well as a higher invertebrate biomass (35.9 +/- 46.8 vs 1.9 +/- 2.1 g per m(2)) and taxon richness (32.7 +/- 11.8 vs 19.1 +/- 6.3 taxa per sample), despite having a lower macrophyte biomass. Additionally, the high abundance of invertivorous fishes found in seaweed beds indicates that they act as important feeding grounds to several fish species in the region.

  • 181.
    Tano, Stina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wikström, Sofia
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, Amelia
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tropical seaweed beds are important habitats for mobile invertebrate epifaunaManuscript (preprint) (Other academic)
    Abstract [en]

    Marine macrophyte habitats in temperate regions are known to provide productive habitats for numerous organisms, with their abundant and diverse invertebrate epifaunal assemblages constituting important linkages between benthic primary production and higher trophic levels. While it is commonly also recognized that certain vegetated habitats in the tropics, such as seagrass meadows, can harbour diverse epifaunal assemblages and may constitute important feeding grounds to fish, little is known about the epifaunal assemblages associated with tropical seaweed beds.

    We investigated the abundance, biomass and taxon richness of the mobile epifaunal community of tropical East African seaweed beds, as well as the abundance of invertivorous fish, and compared it with that of closely situated seagrass meadows, to establish the ecological role of seaweed beds as habitat for epifauna as well as potential feeding grounds for fish. The results showed that seaweed beds had a higher abundance of mobile epifauna (10565±5954 vs 3742±2788 per m2) than seagrass meadows, as well as a higher biomass (35.9±46.8 vs 1.9±2.1 g per m2) and taxon richness (32.7±11.8 vs 19.1±6.3 taxa per sample). Additionally, the high abundance of invertivorous fish found in seaweed beds indicates that they act as important feeding grounds to several fish species in the region.

  • 182.
    Tano, Stina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eggertsen, Maria
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Wikström, Sofia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buriyo, Amelia
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tropical seaweed beds as important habitats for juvenile fish in an East African seascapeManuscript (preprint) (Other academic)
    Abstract [en]

    Seaweed beds within tropical seascapes have received little attention as potential fish habitat despite being a prominent feature within these systems. Other tropical shallow-water habitats such as seagrass meadows and mangroves are relatively well studied and are commonly recognised as important nurseries for several species of coral reef fishes. However, there are indications that structural complexity may be more important for the juvenile fish community than the habitat type itself, which implies that other shallow habitats with high structural complexity, like seaweed beds, could also be important for fish recruitment. This study therefore investigated the role of seaweed beds as fish habitat, particularly for juveniles, in the Western Indian Ocean by comparing their fish assemblages to that of closely situated seagrass beds.

    Fish assemblages were assessed by visual census in belt transects, where fish were identified and their length estimated, and habitat variables were estimated for each transect.

    Total fish abundance was found to be similar between seaweed and seagrass habitats, while abundance of juvenile fishes was higher in seaweed beds than in seagrass meadows (25.0±13.7 vs 10.1±10.3 per transect), with no differences in subadult and adult fish abundance. Species richness was higher in seaweed beds than in seagrass meadows (11.2±3.1 vs 8.2±3.9 per transect), and seaweed beds also had higher juvenile abundance of commercially important (19.6±12.3 vs 7.6±8.9 per transect) and coral reef associated fish species (21.1±13.0 vs 3.9±5.3 per transect) than did seagrass meadows. The total fish assemblages, as well as juvenile family communities, differed between seaweed and seagrass habitat, with the fish communities of seaweed beds being less variable than those of seagrass meadows. These results highlight that tropical seaweed beds are important as juvenile fish habitats, and underscore the need to widen the view of the shallow tropical seascape and incorporate seaweed beds in management actions. 

  • 183.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Technical University of Denmark, Denmark.
    Dinesen, Grete E.
    Hoffmann, Erik
    Maar, Marie
    Stottrup, Josianne G.
    Integrated trend assessment of ecosystem changes in the Limfjord (Denmark): Evidence of a recent regime shift?2013In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 117, p. 178-187Article in journal (Refereed)
    Abstract [en]

    An integrated ecosystem assessment was carried out for the Limfjord over the period from 1984 to 2008 to describe changes in ecosystem structure and potentially important drivers. The Limfjord is a eutrophic transitional Danish fjord system with the main inflow from the North Sea in the west and main outflow to the Kattegat in the east. We showed that from 1990 to 1995, the ecosystem structure shifted from dominance by demersal fish species (eelpout, whiting, flounder, plaice) to that of pelagic fish species (sprat, herring, sticklebacks), small-bodied fish species (black goby, pipefish), jellyfish, common shore crab, starfish and blue mussels. We interpret this change as a regime shift that showed a similar temporal pattern to regime shifts identified in adjacent seas. The observed changes in trophic interactions and food web reorganisation suggested a non-linear regime shift. The analyses further showed the regime shift to be driven by a combination of anthropogenic pressures and possible interplay with climatic disturbance.

  • 184.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Heymans, Johanna J.
    Yletyinen, Johanna
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change ((NorMER).
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Otto, Saskia A.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Ecological Network Indicators of Ecosystem Status and Change in the Baltic Sea2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 10, article id e75439Article in journal (Refereed)
    Abstract [en]

    Several marine ecosystems under anthropogenic pressure have experienced shifts from one ecological state to another. In the central Baltic Sea, the regime shift of the 1980s has been associated with food-web reorganization and redirection of energy flow pathways. These long-term dynamics from 1974 to 2006 have been simulated here using a food-web model forced by climate and fishing. Ecological network analysis was performed to calculate indices of ecosystem change. The model replicated the regime shift. The analyses of indicators suggested that the system's resilience was higher prior to 1988 and lower thereafter. The ecosystem topology also changed from a web-like structure to a linearized food-web.

  • 185.
    Tomczak, Maciej T.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Szymanek, L.
    Pastuszak, M.
    Grygiel, W.
    Zalewski, M.
    Gromisz, S.
    Ameryk, A.
    Kownacka, J.
    Psuty, I.
    Kuzebski, E.
    Grzebielec, R.
    Margonski, P.
    Evaluation of Trends and Changes in the Gulf of Gdansk Ecosystem-an Integrated Approach2016In: Estuaries and Coasts, ISSN 1559-2723, E-ISSN 1559-2731, Vol. 39, no 3, p. 593-604Article in journal (Refereed)
    Abstract [en]

    An integrated trend assessment was conducted for the Gulf of GdaAsk (GoG), Baltic Sea for the period 1994-2010 to describe changes and potentially important drivers of the ecosystem. We found changes in the biota, including an increase in open sea taxa (flatfish, sprat and cod), a decrease in typical coastal species such as eelpout and lumpfish and an increase in primary production. The analyses further suggest that changes in the food web were driven by a combination of anthropogenic pressures (e.g., nutrient loadings and fisheries) and possible interactions with climatic disturbance. Our analyses show that significant changes occurred in the GoG ecosystem between 1994 and 2010. The primary drivers and mechanisms of these changes are discussed. We describe this alteration of the GoG within the context of similar temporal patterns identified in adjacent areas.

  • 186. Turja, Raisa
    et al.
    Lehtonen, Kari K.
    Meierjohann, Axel
    Brozinski, Jenny-Maria
    Vahtera, Emil
    Soirinsuo, Anna
    Sokolov, Alexander
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Snoeijs, Pauline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Budzinski, Helene
    Devier, Marie-Helene
    Peluhet, Laurent
    Paakkonen, Jari-Pekka
    Viitasalo, Markku
    Kronberg, Leif
    The mussel caging approach in assessing biological effects of wastewater treatment plant discharges in the Gulf of Finland (Baltic Sea)2015In: Marine Pollution Bulletin, ISSN 0025-326X, E-ISSN 1879-3363, Vol. 97, no 1-2, p. 135-149Article in journal (Refereed)
    Abstract [en]

    Biological effects of wastewater treatment plant (WWTP) effluents were investigated in Baltic mussels (Mytilus trossulus) caged for one month 800 m and 1100 m from the WWTP discharge site and at a reference site 4 km away. Significant antioxidant, genotoxic and lysosomal responses were observed close to the point of the WWTP discharge. Passive samplers (POCIS) attached to the cages indicated markedly higher water concentrations of various pharmaceuticals at the two most impacted sites. Modeling the dispersal of a hypothetical passive tracer compound from the WWTP discharge site revealed differing frequencies and timing of the exposure periods at different caging sites. The study demonstrated for the first time the effectiveness of the mussel caging approach in combination with passive samplers and the application of passive tracer modeling to examine the true exposure patterns at point source sites such as WWTP pipe discharges in the Baltic Sea.

  • 187.
    Undeman, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Brown, Trevor N.
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Wania, Frank
    Who in the world is most exposed to polychlorinated biphenyls? Using models to identify highly exposed populations2018In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 6, article id 064036Article in journal (Refereed)
    Abstract [en]

    Human subpopulations experience different exposure to persistent organic pollutants (POPs) because of differences in the structure of their food webs and the extent of environmental contamination. Here we quantify the time-variant exposure of different human populations around the world to one representative POP, namely the polychlorinated biphenyl (PCB) congener 153, based on a dynamic simulation of both global environmental fate (using the model BETR-Global) and human food chain bioaccumulation (using the model ACC-HUMAN). The approach identifies subpopulations whose diets include a carnivorous mammal as experiencing the world's highest PCB-153 exposure, i.e. the very large biomagnification potential of their food web more than makes up for the remoteness of their living environment. However, for subpopulations that do not eat warm-blooded carnivores, the proximity to sources of PCBs is more important than food web structure and environmental conditions for differentiating their exposure to PCBs.

  • 188.
    Undeman, Emma
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute.
    McLachlan, Michael S.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Application of a novel modeling tool with multistressor functionality to support management of organic contaminants in the Baltic Sea2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, p. 498-506Article in journal (Refereed)
    Abstract [en]

    Organic contaminants constitute one of many stressors that deteriorate the ecological status of the Baltic Sea. When managing environmental problems in this marine environment, it may be necessary to consider the interactions between various stressors to ensure that averting one problem does not exacerbate another. A novel modeling tool, BALTSEM-POP, is presented here that simulates interactions between climate forcing, hydrodynamic conditions, and water exchange, biogeochemical cycling, and organic contaminant transport and fate in the Baltic Sea. We discuss opportunities to use the model to support different aspects of chemicals management. We exemplify these opportunities with a case study where two emission-reduction strategies for a chemical used in personal care products (decamethylcyclopentasiloxane) are evaluated, and where the confounding influence of future climate change and eutrophication on the impact of the emission-reduction strategies are assessed.

  • 189.
    Undeman, Emma
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Erik
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Gustafsson, Bo G.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    A novel modeling tool with multi-stressor functionality for organic contaminant transport and fate in the Baltic Sea2014In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 497, p. 382-391Article in journal (Refereed)
    Abstract [en]

    The coupled physical-biogeochemical model BALTSEM, previously used to assess nutrient/carbon cycles and eutrophication in the Baltic Sea, has been expanded to include algorithms for calculations of organic contaminant environmental transport and fate. This novel model version (BALTSEM-POP) is evaluated for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and hexachlorobenzene (HCB) in Baltic Sea surface water and sediment. Modeled dissolved concentrations are usually within a factor of 2-4 of observed concentrations, however with larger deviations for furans. Calculated concentrations in particulate organic matter are less accurate (within factors of 1-700), likely due to errors in estimated pelagic biomass, particulate matter-water partitioning, and large natural variability in field data. Concentrations in sediments are usually predicted within a factor of 6. The good performance of the model illustrates its usefulness for exploration of contaminant fate in response to variations in nutrient input and climatic conditions in the Baltic Sea marine environment.

  • 190. Uusitalo, Laura
    et al.
    Tomczak, Maciej T.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Muller-Karulis, Bärbel
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Putnis, Ivars
    Trifonova, Neda
    Tucker, Allan
    Hidden variables in a Dynamic Bayesian Network identify ecosystem level change2018In: Ecological Informatics, ISSN 1574-9541, E-ISSN 1878-0512, Vol. 45, p. 9-15Article in journal (Refereed)
    Abstract [en]

    Ecosystems are known to change in terms of their structure and functioning over time. Modelling this change is a challenge, however, as data are scarce, and models often assume that the relationships between ecosystem components are invariable over time. Dynamic Bayesian Networks (DBN) with hidden variables have been proposed as a method to overcome this challenge, as the hidden variables can capture the unobserved processes. In this paper, we fit a series of DBNs with different hidden variable structures to a system known to have undergone a major structural change, i.e. the Baltic Sea food web. The exact setup of the hidden variables did not considerably affect the result, and the hidden variables picked up a pattern that agrees with previous research on the system dynamics.

  • 191.
    Valman, Matilda
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Stockholm Resilience Centre. Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Beliefs and behavior in international policy making: longitudinal changes in the governance of the Baltic SeaIn: Environmental Policy and Governance, ISSN 1756-932X, E-ISSN 1756-9338Article in journal (Refereed)
  • 192.
    Valman, Matilda
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Stockholm Resilience Centre. Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Duit, Andreas
    Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    HELCOM, we have a problem: gradually unfolding crises and problem detection in international organisationsIn: Global Environmental Change, ISSN 0959-3780, E-ISSN 1872-9495Article in journal (Refereed)
  • 193.
    Valman, Matilda
    et al.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Österblom, Henrik
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Olsson, Per
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Adaptive governance of the Baltic Sea - lessons from elsewhere2015In: International Journal of the Commons, ISSN 1875-0281, E-ISSN 1875-0281, Vol. 9, no 1, p. 440-465Article in journal (Refereed)
    Abstract [en]

    Governance of marine resources is increasingly characterized by integrated, cross sectoral and ecosystem based approaches. Such approaches require that existing governing bodies have an ability to adapt to ecosystem dynamics, while also providing transparent and legitimate outcomes. Here, we investigate how the Baltic Marine Environment Protection Commission (HELCOM), the international governing body for the Baltic Sea, could improve its prospects for working with the ecosystem approach, drawing from the literature on adaptive governance. We construct an ideal type of adaptive governance to which we compare the way in which HELCOM is operating and relate these dynamics to two other international marine environment governance organizations, the Coral Triangle Initiative on Coral Reefs, Fisheries and Food Security (CTI-CFF) and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). We conclude that HELCOM deviates from an ideal type of adaptive governance in several ways but also that the other two case studies provide empirical support for potential ways in which HELCOM could improve its adaptive capacity. Key aspects where HELCOM could improve include increasing stakeholder participation - both in information sharing and decision making. Further, HELCOM need to develop evaluation mechanisms, secure compliance to improve adaptive capacity and organizational effectiveness, which entails the development of structures for conflict resolution. Finally, HELCOM need to increase communication and harmonization between different levels of authority.

  • 194. van Grinsven, Hans J. M.
    et al.
    Bouwman, Lex
    Cassman, Kenneth G.
    van Es, Harold M.
    McCrackin, Michelle L.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Beusen, Arthur H. W.
    Losses of Ammonia and Nitrate from Agriculture and Their Effect on Nitrogen Recovery in the European Union and the United States between 1900 and 20502015In: Journal of Environmental Quality, ISSN 0047-2425, E-ISSN 1537-2537, Vol. 44, no 2, p. 356-367Article in journal (Refereed)
    Abstract [en]

    Historical trends and levels of nitrogen (N) budgets and emissions to air and water in the European Union and the United States are markedly different. Agro-environmental policy approaches also differ, with emphasis on voluntary or incentive-based schemes in the United States versus a more regulatory approach in the European Union. This paper explores the implications of these differences for attaining long-term policy targets for air and water quality. Nutrient surplus problems were more severe in the European Union than in the United States during the 1970s and 1980s. The EU Nitrates and National Emission Ceilings directives contributed to decreases in fertilizer use, N surplus, and ammonia (NH3) emissions, whereas in the United States they stabilized, although NH3 emissions are still increasing. These differences were analyzed using statistical data for 1900-2005 and the global IMAGE model. IMAGE could reproduce NH3 emissions and soil N surpluses at different scales (European Union and United States, country and state) and N loads in the Rhine and Mississippi. The regulation-driven changes during the past 25 yr in the European Union have reduced public concerns and have brought agricultural N loads to the aquatic environment closer to US levels. Despite differences in agro-environmental policies and agricultural structure (more N-fixing soybean and more spatially separated feed and livestock production in the United States than in the European Union), current N use efficiency in US and EU crop production is similar. IMAGE projections for the IAASTD-baseline scenario indicate that N loading to the environment in 2050 will be similar to current levels. In the United States, environmental N loads will remain substantially smaller than in the European Union, whereas agricultural production in 2050 in the United States will increase by 30% relative to 2005, as compared with an increase of 8% in the European Union. However, in the United States, even rigorous mitigation with maximum recycling of manure N and a 25% reduction in fertilizer use will not achieve the policy target to halve the N export to the Gulf of Mexico.

  • 195. Varjopuro, Riku
    et al.
    Andrulewicz, Eugeniusz
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Dolch, Tobias
    Heiskanen, Anna-Stuna
    Pihlajamäki, Mia
    Brandt, Urs Steiner
    Valman, Matilda
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre, Baltic Nest Institute. Stockholm University, Faculty of Social Sciences, Department of Political Science.
    Gee, Kira
    Potts, Tavis
    Psuty, Iwona
    Coping with persistent environmental problems: systemic delays in reducing eutrophication of the Baltic Sea2014In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 19, no 4, p. 48-Article in journal (Refereed)
    Abstract [en]

    In this paper we focus on systemic delays in the Baltic Sea that cause the problem of eutrophication to persist. These problems are demonstrated in our study by addressing three types of delays: (1) decision delay: the time it takes for an idea or perceived need to be launched as a policy; (2) implementation delay: the time from the launch of a policy to the actual implementation; (3) ecosystem delay: the time difference between the implementation and an actual measurable effects. A policy process is one characterized by delays. It may take years from problem identification to a decision to taking action and several years further for actual implementation. Ecosystem responses to measures illustrate that feedback can keep the ecosystem in a certain state and cause a delay in ecosystem response. These delays can operate on decadal scales. Our aim in this paper is to analyze these systemic delays and especially to discuss how the critical delays can be better addressed in marine protection policies by strengthening the adaptive capacity of marine protection. We conclude that the development of monitoring systems and reflexive, participatory analysis of dynamics involved in the implementation are keys to improve understanding of the systemic delays. The improved understanding is necessary for the adaptive management of a persistent environmental problem. In addition to the state of the environment, the monitoring and analysis should be targeted also at the implementation of policies to ensure that the societies are investing in the right measures.

  • 196. Viitasalo, Markku
    et al.
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Gårdmark, Anna
    Kaartokallio, Hermanni
    Kautsky, Lena
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Kuosa, Harri
    Lindegren, Martin
    Norkko, Alf
    Olli, Kalle
    Wikner, Johan
    Environmental Impacts - Marine Ecosystems2015In: Second Assessment of Climate Change for the Baltic Sea Basin / [ed] The BACC II Author Team, Springer, 2015, p. 363-380Chapter in book (Refereed)
    Abstract [en]

    Increase in sea surface temperature is projected to change seasonal succession and induce dominance shifts in phytoplankton in spring and promote the growth of cyanobacteria in summer. In general, climate change is projected to worsen oxygen conditions and eutrophication in the Baltic Proper and the Gulf of Finland. In the Gulf of Bothnia, the increasing freshwater discharge may increase the amount of dissolved organic carbon (DOC) in the water and hence reduce phytoplankton productivity. In winter, reduced duration and spatial extent of sea ice will cause habitat loss for ice-dwelling organisms and probably induce changes in nutrient dynamics within and under the sea ice. The projected salinity decline will probably affect the functional diversity of the benthic communities and induce geographical shifts in the distribution limits of key species such as bladder wrack and blue mussel. In the pelagic ecosystem, the decrease in salinity together with poor oxygen conditions in the deep basins will negatively influence the main Baltic Sea piscivore, cod. This has been suggested to cause cascading effects on clupeids and zooplankton.

  • 197. Villnas, Anna
    et al.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Lehtonen, Kari K.
    Multi-level responses of Macoma balthica to recurring hypoxic disturbance2019In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 510, p. 64-72Article in journal (Refereed)
    Abstract [en]

    The frequency of seasonal and short-term hypoxia is increasing in coastal seas. How such repeated disturbances affect key species that have important roles for ecosystem processes and functions remains, however, unknown. By performing a field experiment we explored if the bivalve Macoma balthica can cope with short-term, recurring hypoxic stress, and investigated how hypoxia affects the condition of surviving bivalves. By combining data on different levels of biological organization, i.e., on physiology (biomarker response), behaviour and demography, we identified stress responses before the population declined. One pulse of hypoxic disturbance (3 days) resulted in behavioural alterations, as adult M. balthica extended their siphons, emerged towards the sediment surface and expressed decreased reburial rates. However, the demographic structure of the population remained unaltered. Several pulses of recurring hypoxic stress resulted in physiological response with changes in glutathione reductase and acetylcholinesterase enzyme activities. The recurring hypoxic disturbance was observed to affect juvenile bivalves before adults, while pro-longed hypoxia reduced the entire bivalve population. Our results clearly show that hypoxic stress changes the behaviour and physiology of M. balthica before demographic changes occur, which is likely to have severe implications for the contribution of this key species to ecosystem functioning. That a combination of measures at different levels of organization can detect disturbances at an early stage suggests that such an approach would be useful for assessing the effects of disturbances on marine ecosystems that are increasingly affected by anthropogenic change.

  • 198. Villnäs, Anna
    et al.
    Hewitt, Judi
    Snickars, Martin
    Westerbom, Mats
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Template for using biological trait groupings when exploringlarge-scale variation in seafloor multifunctionality2018In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 28, no 1, p. 78-94Article in journal (Refereed)
    Abstract [en]

    Understanding large-scale spatial variation in ecosystem properties and associated functionality is key for successful conservation of ecosystems. This study provides a template for how to estimate differences in ecosystem functionality over large spatial scales by using groupings of biological traits. We focus on trait groupings that describe three important benthic ecosystem properties, namely bioturbation, community stability, and juvenile dispersal. Recognizing that groups of traits interact and are constrained within an organism, we statistically define important functional trait subgroups that describe each ecosystem property. The sub-groups are scored according to their weighted ecological impact to gain an overall estimation of the cumulative expression of each ecosystem property at individual sites. Furthermore, by assigning each property a value relative to its observed maximum, and by summing up the individual property values, we offer an estimate of benthic ecosystem multi-functionality. Based on a spatially extensive benthic data set, we were able to identify coastal areas with high and low potential for the considered benthic ecosystem properties and the measure of ecosystem multifunctionality. Importantly, we show that a large part of the spatial variation in functional trait sub-groups and in benthic ecosystem multifunctionality was explained by environmental change. Our results indicate that through this simplification it is possible to estimate the functionality of the seafloor. Such information is vital in marine spatial planning efforts striving to balance the utilization with the preservation of natural resources.

  • 199. Villnäs, Anna
    et al.
    Janas, Urszula
    Josefson, Alf B.
    Kendzierska, Halina
    Nygård, Henrik
    Norkko, Joanna
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Changes in macrofaunal biological traits across estuarine gradients: implications for the coastal nutrient filter2019In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 622, p. 31-48Article in journal (Refereed)
    Abstract [en]

    Benthic macrofaunal communities have a profound impact on organic matter turnover and nutrient cycling in marine sediments. Their activities are of particular importance in the coastal filter, where nutrients and organic matter from land are transformed and/or retained before reaching the open sea. The benthic fauna modify the coastal filter directly (through consumption, respiration, excretion and biomass production) and indirectly (through bioturbation). It is hard to experimentally quantify faunal contribution to the coastal filter over large spatial and temporal scales that encompass significant environmental and biological heterogeneity. However, estimates can be obtained with biological trait analyses. By using benthic biological traits, we explored how the potential contribution of macrofaunal communities to the coastal filter differ between inner and outer sites in an extensive archipelago area and examine the generality of the observed pattern across contrasting coastal areas of the entire Baltic Sea. Estimates of benthic bioturbation, longevity and size (i.e. 'stability') and total energy and nutrient contents differed between coastal areas and inner versus outer sites. Benthic traits indicative of an enhanced nutrient turnover but a decreased capacity for temporal nutrient retention dominated inner sites, while outer sites were often dominated by larger individuals, exhibiting traits that are likely to enhance nutrient uptake and retention. The overarching similarities in benthic trait expression between more eutrophied inner vs. less affected outer coastal sites across the Baltic Sea suggest that benthic communities might contribute in a similar manner to nutrient recycling and retention in the coastal filter over large geographical scales.

  • 200. Virta, Leena
    et al.
    Gammal, Hanna
    Järnström, Marie
    Bernard, Guillaume
    Soininen, Janne
    Norkko, Joanna
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    The diversity of benthic diatoms affects ecosystem productivity in heterogeneous coastal environments2019In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 100, no 9, article id e02765Article in journal (Refereed)
    Abstract [en]

    The current decrease in biodiversity affects all ecosystems, and the impacts of diversity on ecosystem functioning need to be resolved. So far, marine studies about diversity-ecosystem productivity-relationships have concentrated on small-scale, controlled experiments, with often limited relevance to natural ecosystems. Here, we provide a real-world study on the effects of microorganismal diversity (measured as the diversity of benthic diatom communities) on ecosystem productivity (using chlorophyll a concentration as a surrogate) in a heterogeneous marine coastal archipelago. We collected 78 sediment cores at 17 sites in the northern Baltic Sea and found exceptionally high diatom diversity (328 observed species). We used structural equation models and quantile regression to explore relationships between diatom diversity and productivity. Previous studies have found contradictory results in the relationship between microorganismal diversity and ecosystem productivity, but we showed a linear and positive basal relationship between diatom diversity and productivity, which indicates that diatom diversity most likely forms the lowest boundary for productivity. Thus, although productivity can be high even when diatom diversity is low, high diatom diversity supports high productivity. The trait composition was more effective than taxonomical composition in showing such a relationship, which could be due to niche complementarity. Our results also indicated that environmental heterogeneity leads to substantial patchiness in the diversity of benthic diatom communities, mainly induced by the variation in sediment organic matter content. Therefore, future changes in precipitation and river runoff and associated changes in the quality and quantity of organic matter in the sea, will also affect diatom communities and, hence, ecosystem productivity. Our study suggests that benthic microorganisms are vital for ecosystem productivity, and together with the substantial heterogeneity of coastal ecosystems, they should be considered when evaluating the potential productivity of coastal areas.

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