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  • 1. Andrade, Carlos A. P.
    et al.
    Nascimento, Francisco
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Conceicao, Luis E. C.
    Linares, Fatima
    Lacuisse, Marc
    Dinis, Maria T.
    Red Porgy, Pagrus pagrus, Larvae Performance and Nutritional Condition in Response to Different Weaning Regimes2012In: Journal of the World Aquaculture Society, ISSN 0893-8849, E-ISSN 1749-7345, Vol. 43, no 3, p. 321-334Article in journal (Refereed)
    Abstract [en]

    Red porgy, Pagrus pagrus, is a candidate species for aquaculture diversification. The aim of this work was to assess whether an early supply of enriched Artemia (D1) or a direct step to dry diets (D3) would be advantageous weaning strategies for red porgy larvae, compared to a later supply of Artemia followed by dry diets (D2). Direct weaning to dry diet resulted in significantly lower growth, survival, pancreatic (trypsin and lipase), and intestinal (alkaline phosphatase) enzyme-specific activity, with the exception of leucine-alanine peptidase. The direct weaning strategy presented severe nutritional restrictions from early weaning stages with an associated delay of the maturation of digestive system. The two-step strategy presented in D1 and D2 resulted in comparable results in most parameters, including survival. Weaning using enriched Artemia as an intermediate step is confirmed as the most adequate strategy for red porgy larvae. Digestive enzymes and selected fatty acids correlated well with performance responses to dietary regimes, thereby supporting the use of these parameters as sensitive and reliable indicators of red porgy nutritional or physiological status during larval stages.

  • 2. Andrade, Carlos A. P.
    et al.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nogueira, Natacha
    Pimenta, Filomena
    Dinis, Maria T.
    Narciso, Luis
    Allometric Growth in Red Porgy Larvae: Developing Morphological Indices for Mesocosm Semi-Intensive Culture2013In: North American Journal of Aquaculture, ISSN 1522-2055, E-ISSN 1548-8454, Vol. 75, no 1, p. 42-49Article in journal (Refereed)
    Abstract [en]

    We studied the morphological development, allometric growth, and cannibalistic behavior of Red Porgy Pagrus pagrus reared in mesocosm semi-intensive culture. The study was conducted from hatching to 32 d after hatching (DAH). Red porgy ontogeny was characterized by strong positive allometric growth of body depth at anus (BDA) to 6.7mm total length (TL) at about 2122 DAH. The BDA combined with standard length (SL) in a morphometric index was found to be better correlated with dry weight than TL and provided an improved method to estimate larval growth. Mouth size also exhibited strong positive allometric growth at early larval stages that, together with inflation of the swim bladder, may have contributed to improve feeding ability, in preparation for the high energy demands of metamorphosis. A predictive regression model developed for cannibalism underestimated prey size. Cannibalism coincided with the development of acidic digestion and was first evident at 27 DAH as larvae reached about 23% of their maximum size variation. We hypothesize that cannibalism is associated with larval size and condition, but is prompted by physiological and energetic factors. The bivariate morphometric index developed in this study can be used to mitigate cannibalism by controlling larval size variation and improving feed supply. The morphological measurements and morphometric indices that result from this study provide important tools for improving red porgy larvae culture. Received December 13, 2011; accepted July 12, 2012

  • 3.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Callac, Nolwenn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Vicenzi, Alessandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chi Fru, Ernest
    Stockholm University, Faculty of Science, Department of Geological Sciences. Cardiff University, UK.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Methane fluxes from coastal sediments are enhanced by macrofauna2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 13145Article in journal (Refereed)
    Abstract [en]

    Methane and nitrous oxide are potent greenhouse gases (GHGs) that contribute to climate change. Coastal sediments are important GHG producers, but the contribution of macrofauna (benthic invertebrates larger than 1 mm) inhabiting them is currently unknown. Through a combination of trace gas, isotope, and molecular analyses, we studied the direct and indirect contribution of two macrofaunal groups, polychaetes and bivalves, to methane and nitrous oxide fluxes from coastal sediments. Our results indicate that macrofauna increases benthic methane efflux by a factor of up to eight, potentially accounting for an estimated 9.5% of total emissions from the Baltic Sea. Polychaetes indirectly enhance methane efflux through bioturbation, while bivalves have a direct effect on methane release. Bivalves host archaeal methanogenic symbionts carrying out preferentially hydrogenotrophic methanogenesis, as suggested by analysis of methane isotopes. Low temperatures (8 °C) also stimulate production of nitrous oxide, which is consumed by benthic denitrifying bacteria before it reaches the water column. We show that macrofauna contributes to GHG production and that the extent is dependent on lineage. Thus, macrofauna may play an important, but overlooked role in regulating GHG production and exchange in coastal sediment ecosystems.

  • 4.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nascimento, Francesco
    Stockholm University, Faculty of Science, Department of Geological Sciences. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bartoli, Marco
    University of Parma.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    EFFECT OF MEIOFAUNA ON BENTHIC ELEMENT CYCLING IN A BALTIC SEA COASTAL AREA2013Conference paper (Refereed)
    Abstract [en]

    We have studied the role of meiofaunal communities for nutrient cycling and organic matter mineralization in coastal sediments of the Baltic Sea. Although meiofauna is orders of magnitude more abundant than macrofauna and has commonly a much more diverse community structure, its importance for sediment biogeochemical pathways is poorly understood because of objective experimental difficulties when manipulating meiofauna communities due to small body sizes (0.04 to 1 mm) and inherent fragility. We used a density extraction method to separate intact and living metazoans from sediment and tested the effect of low meiofauna and high meiofauna abundances in the presence and absence of macrofauna for exchange rates of nutrients, O2, DIC, N2, and CH4. High abundances of meiofauna stimulated O2 uptake and the net N2 efflux by 16% and 34%, respectively, but did not change oxygen penetration depths significantly. By contrast, macrofauna increased oxygen penetration depths by 21% and stimulated methane emissions by a factor of 8. These results demonstrate the importance of meiofauna in the regulation of aerobic and anaerobic microbial processes and benthic fluxes in marine sediments.

  • 5.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bartoli, M.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bruchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meiofauna increases bacterial denitrification in marine sediments2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 5133-Article in journal (Refereed)
    Abstract [en]

    Denitrification is a critical process that can alleviate the effects of excessive nitrogen availability in aquatic ecosystems subject to eutrophication. An important part of denitrification occurs in benthic systems where bioturbation by meiofauna (invertebrates <1mm) and its effect on element cycling are still not well understood. Here we study the quantitative impact of meiofauna populations of different abundance and diversity, in the presence and absence of macrofauna, on nitrate reduction, carbon mineralization and methane fluxes. In sediments with abundant and diverse meiofauna, denitrification is double that in sediments with low meiofauna, suggesting that meiofauna bioturbation has a stimulating effect on nitrifying and denitrifying bacteria. However, high meiofauna densities in the presence of bivalves do not stimulate denitrification, while dissimilatory nitrate reduction to ammonium rate and methane efflux are significantly enhanced. We demonstrate that the ecological interactions between meio-, macrofauna and bacteria are important in regulating nitrogen cycling in soft-sediment ecosystems.

  • 6.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rämö, Robert
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Marzocchi, Ugo
    Le Bouille, Léonie
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Leermakers, Martine
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Capping with activated carbon reduces nutrient fluxes, denitrification and meiofauna in contaminated sediments2019In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 148, p. 515-525Article in journal (Refereed)
    Abstract [en]

    Sediment capping with activated carbon (AC) is an effective technique used in remediation of contaminated sediments, but the ecological effects on benthic microbial activity and meiofauna communities have been largely neglected. This study presents results from a 4-week experiment investigating the influence of two powdered AC materials (bituminous coal-based and coconut shell-derived) and one control material (clay) on biogeochemical processes and meiofauna in contaminated sediments. Capping with AC induced a 62‒63% decrease in denitrification and a 66‒87 % decrease in dissimilatory nitrate reduction to ammonium (DNRA). Sediment porewater pH increased from 7.1 to 9.0 and 9.7 after addition of bituminous AC and biomass-derived AC, respectively. High pH (>8) persisted for at least two weeks in the bituminous AC and for at least 24 days in the coconut based AC, while capping with clay had no effect on pH. We observed a strong impact (nitrate fluxes being halved in presence of AC) on nitrification activity as nitrifiers are sensitive to high pH. This partly explains the significant decrease in nitrate reduction rates since denitrification was almost entirely coupled to nitrification. Total benthic metabolism estimated by sediment oxygen uptake was reduced by 30 and 43 % in presence of bituminous coal-based AC and coconut shell-derived AC, respectively. Meiofauna abundances decreased by 60‒62 % in the AC treatments. Taken together, these observations suggest that AC amendments deplete natural organic carbon, intended as food, to heterotrophic benthic communities. Phosphate efflux was 91 % lower in presence of bituminous AC compared to untreated sediment probably due to its content of aluminum (Al) oxides, which have high affinity for phosphate. This study demonstrates that capping with powdered AC produces significant effects on benthic biogeochemical fluxes, microbial processes and meiofauna abundances, which are likely due to an increase in porewater pH and to the sequestration of natural, sedimentary organic matter by AC particles.

  • 7.
    Bradshaw, Clare
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Meseh, Dina A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Alasawi, Hiba
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Qiang, Ma
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Snoeijs-Leijonmalm, Pauline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Joint effects of gamma radiation and cadmium on subcellular-, individual-and population-level endpoints of the green microalga Raphidocelis subcapitata2019In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 211, p. 217-226Article in journal (Refereed)
    Abstract [en]

    Interpreting and predicting the combined effects of toxicants in the environment is an important challenge in ecotoxicology. How such effects are connected across different levels of biological organisation is an additional matter of uncertainty. Such knowledge gaps are particularly prominent with regards to how ionising radiation interacts with contaminants. We assessed the response of twelve endpoints at the subcellular, individual and population level in a green microalga when exposed singly and jointly to gamma radiation and cadmium (Cd). We used a fully factorial experimental design where observed effects were compared to those predicted by the Independent Action (IA) model for mixture toxicity to determine whether they deviated from additivity. Subcellular endpoints (e.g., catalase, thiamine diphosphate, xanthophyll cycle pigments) showed an increased antioxidant and/or photoprotective response. However, our results indicate that this protection was not sufficient to prevent lipid peroxidation, which also increased with dose. At ecologically relevant doses, most interactions between gamma radiation and Cd regarding subcellular-, individual- and population-level endpoints were additive as predicted by the IA model. However, exposure to binary mixtures displayed antagonistic interactions between gamma radiation and Cd at the higher end of the tested dose spectrum. No correlations were observed between subcellular endpoints and higher-level endpoints, but there were linkages between individual and population endpoints. Our results suggest that antagonistic interactions between gamma radiation and Cd can occur at higher doses and that these interactions seem to disseminate from subcellular and individual to population level. Possible consequences for aquatic primary production and food-web interactions are discussed.

  • 8.
    Broman, Elias
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Motwani, Nisha H.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Southern Denmark, Denmark.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Sjöling, Sara
    Denitrification responses to increasing cadmium exposure in Baltic Sea sediments2019In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 217, article id 105328Article in journal (Refereed)
    Abstract [en]

    Benthic ecosystems have come under intense pressure, due to eutrophication-driven oxygen decline and industrial metal contamination. One of the most toxic metals is Cadmium (Cd), which is lethal to many aquatic organisms already at low concentrations. Denitrification by facultative anaerobic microorganisms is an essential process to transform, but also to remove, excess nitrate in eutrophied systems. Cd has been shown to decrease denitrification and sequester free sulfide, which is available when oxygen is scarce and generally inhibits complete denitrification (i.e. N2O to N2). In polluted sediments, an interaction between oxygen and Cd may influence denitrification and this relationship has not been studied. For example, in the Baltic Sea some sediments are double exposed to both Cd and hypoxia. In this study, we examined how the double exposure of Cd and fluctuations in oxygen affects denitrification in Baltic Sea sediment. Results show that oxygen largely regulated N2O and N2 production after 21 days of exposure to Cd (ranging from 0 to 500 μg/L, 5 different treatments, measured by the isotope pairing technique (IPT)). In the high Cd treatment (500 μg/L) the variation in N2 production increased compared to the other treatments. Increases in N2 production are suggested to be an effect of 1) enhanced nitrification that increases NO3− availability thus stimulating denitrification, and 2) Cd successfully sequestrating sulfide (yielding CdS), which allows for full denitrification to N2. The in situ field sediment contained initially high Cd concentrations in the pore water (∼10 μg/L) and microbial communities might already have been adapted to metal stress, making the effect of low Cd levels negligible. Here we show that high levels of cadmium pollution might increase N2 production and influence nitrogen cycling in marine sediments.

  • 9.
    Broman, Elias
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sommer, Christian
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Creer, Simon
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Salinity drives meiofaunal community structure dynamics across the Baltic ecosystem2019In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 28, no 16, p. 3813-3829Article in journal (Refereed)
    Abstract [en]

    Coastal benthic biodiversity is under increased pressure from climate change, eutrophication, hypoxia, and changes in salinity due to increase in river runoff. The Baltic Sea is a large brackish system characterized by steep environmental gradients that experiences all of the mentioned stressors. As such it provides an ideal model system for studying the impact of on‐going and future climate change on biodiversity and function of benthic ecosystems. Meiofauna (animals < 1 mm) are abundant in sediment and are still largely unexplored even though they are known to regulate organic matter degradation and nutrient cycling. In this study, benthic meiofaunal community structure was analysed along a salinity gradient in the Baltic Sea proper using high‐throughput sequencing. Our results demonstrate that areas with higher salinity have a higher biodiversity, and salinity is probably the main driver influencing meiofauna diversity and community composition. Furthermore, in the more diverse and saline environments a larger amount of nematode genera classified as predators prevailed, and meiofauna‐macrofauna associations were more prominent. These findings show that in the Baltic Sea, a decrease in salinity resulting from accelerated climate change will probably lead to decreased benthic biodiversity, and cause profound changes in benthic communities, with potential consequences for ecosystem stability, functions and services.

  • 10.
    Griffiths, Jennifer R.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kadin, Martina
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Tamelander, Tobias
    Törnroos, Anna
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences. Lund University, Sweden.
    Bonsdorff, Erik
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gårdmark, Anna
    Järnström, Marie
    Kotta, Jonne
    Lindegren, Martin
    Nordström, Marie C.
    Norkko, Alf
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre. University of Helsinki, Finland.
    Olsson, Jens
    Weigel, Benjamin
    Zydelis, Ramunas
    Blenckner, Thorsten
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Niiranen, Susa
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    The importance of benthic-pelagic coupling for marine ecosystem functioning in a changing world2017In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 23, no 6, p. 2179-2196Article, review/survey (Refereed)
    Abstract [en]

    Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems, and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function are strongly affected by anthropogenic pressures; however, there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures - climate change, nutrient loading, and fishing - using the Baltic Sea as a case study and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g., nutrient exchange and sedimentation of organic material) are to some extent quantifiable, but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers, but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world.

  • 11. Hansen, K.
    et al.
    Stockett, Mark H.
    Stockholm University, Faculty of Science, Department of Physics. Aarhus University, Denmark.
    Kaminska, Magdalena
    Stockholm University, Faculty of Science, Department of Physics. Jan Kochanowski University, Poland.
    Nascimento, Rodrigo F.
    Stockholm University, Faculty of Science, Department of Physics. Centro Federal de Educacao Tecnologica Celso Suckow da Fonseca, Brazil.
    Anderson, Emma K.
    Stockholm University, Faculty of Science, Department of Physics.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Chartkunchand, Kiattichart C.
    Stockholm University, Faculty of Science, Department of Physics.
    Eklund, Gustav
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Schmidt, Henning T.
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Spontaneous decay of small copper-cluster anions Cu-n(-) (n=3-6), on long time scales2017In: Physical Review A, ISSN 2469-9926, Vol. 95, no 2, article id 022511Article in journal (Refereed)
    Abstract [en]

    We have measured the spontaneous neutral particle emission from copper-cluster anions ( Cu-n(-), n = 3-6) stored at cryogenic temperatures in one of the electrostatic ion storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The measured rate of emission from the stored Cu-3(-) ions follows a single power-law decay for about 1 ms but then decreases much more rapidly with time. The latter behavior may be due to a decrease in the density of available final states in Cu-3 as the excitation energies of the decaying ions approach the electron detachment threshold. The emissions from Cu-4(-), Cu-5(-), and Cu-6(-) are well described by sums of two power laws that are quenched by radiative cooling of the stored ions with characteristic times between a few and hundreds of milliseconds. We relate these two-component behaviors to populations of stored ions with higher and lower angular momenta. In a separate experiment, we studied the laser-induced decay of Cu-6(-) ions that were excited by 1.13- or 1.45-eV photons after 46 ms of storage.

  • 12.
    Karlson, Agnes M. L.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Näslund, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Higher diversity of deposit-feeding macrofauna enhances phytodetritus processing2010In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 91, no 5, p. 1414-1423Article in journal (Refereed)
    Abstract [en]

    The link between biodiversity and ecosystem functioning is an important question that remains unresolved, particularly in marine systems, in which cycling of organic matter by benthic organisms is of global significance. Direct observations of specific resource use by each species in single- and multispecies communities, as quantified by stable isotopes, facilitates a mechanistic understanding of the importance of each species for ecosystem functioning. We tested the effects of altered biodiversity (species richness) of deposit-feeding macrofauna on incorporation and burial of phytodetritus in combinations of three species representing natural communities found in the sediments of the species-poor Baltic Sea. The three species, two amphipods and a bivalve, had different rates of incorporation and burial and different needs for carbon (C) and nitrogen (N). The amphipods exhibited clear resource partitioning in sympatry, as a result of vertical separation in the sediment and consequent differential use of food. Communities of several species incorporated more C and N than expected from the respective single-species treatments, due to higher incorporation by surface feeders in multispecies treatments. Community incorporation of N in the most diverse treatment even exceeded N incorporation by a single-species treatment of the best-performing species, showing transgressive over-yielding. This over-yielding was primarily due to positive complementarity in all treatments. Diverse soft bottoms are also likely to be more productive in the long run, as species-specific traits (subsurface feeding) preserve fresh phytodetritus by burying it to depths in the sediment at which the mineralization rate is low. The more diverse sediment communities showed more efficient trophic transfer of phytodetritus, a finding of general significance for understanding biological processes driving the transformation of nutrients and energy in benthic ecosystems.

  • 13.
    Karlson, Agnes M. L.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sanna, Suikkanen
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Benthic fauna affects recruitment from sediments of the harmful cyano­bacterium Nodularia spumigena 2012In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 20, p. 126-131Article in journal (Refereed)
    Abstract [en]

    Physical disturbance and feeding by macrofauna in the sediment can potentially affect bloom initiation of phytoplankton species that have benthic stages in their life cycle. In this experimental study, we investigated how different species of macrozoobenthos can affect the recruitment of Nodularia spumigena from the sediment to the water column. N. spumigena is a toxic, nitrogen-fixing filamentous cyanobacterium, which forms large summer blooms in the Baltic Sea. Benthic recruitment from resting stages (akinetes) and vegetative cells deposited on the seafloor have long been suspected to initiate the blooms. We found that, depending on species-specific traits, deposit-feeding macrofauna (an amphipod, Monoporeia affinis, a bivalve, Macoma balthica and an invasive polychaete, Marenzelleria cf. arctia) has the potential to either reduce or facilitate recruitment of this cyanobacterium. Shorter filament length in treatments with fauna than in the treatment without indicates feeding on or mechanical destruction of N. spumigena by the animals. Our results show the importance of an often overlooked aspect of phytoplankton bloom initiation, the role of macrozoobenthos.

  • 14.
    Karlson, Agnes
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nascimento, Francisco
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Incorporation and burial of carbon from settling cyanobacterial blooms by deposit-feeding macrofauna2008In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 53, no 6, p. 2754-2758Article in journal (Refereed)
    Abstract [en]

    Summer blooms of filamentous, nitrogen-fixing cyanobacteria are typical of the Baltic Sea, and recent findings indicate that cyanobacteria may be an important food source for the benthos below the euphotic zone. In a 2-week laboratory experiment, we measured incorporation of cyanobacterial carbon by the deposit-feeding amphipod Monoporeia affinis when exposed to 14C-radiolabeled, natural blooms of cyanobacteria dominated by either the toxic Nodularia spumigena or non-toxic Aphanizomenon sp. Carbon from both cyanobacterial blooms was used, with greater incorporation from Aphanizomenon-dominated bloom material than from N. spumigena, indicating that the latter is less suitable as food. However, neither cyanobacterium supported significant amphipod growth. Also, less cyanobacterial carbon was mixed down in the sediment in the N. spumigena treatment, indicating lower bioturbation activity in this treatment. Long-term effects on feeding and survival remain to be studied, especially for the toxic N. spumigena.

  • 15.
    Nascimento, F.J.A.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Karlson, A.M.L.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, R.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Settling blooms of filamentous cyanobacteria as food for meiofauna assemblages.2008In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 53, no 6, p. 2636-2643Article in journal (Refereed)
    Abstract [en]

    Summer blooms of filamentous nitrogen-fixing cyanobacteria in the Baltic Sea are normally dominated by Aphanizomenon sp. and the toxin-producing Nodularia spumigena. In a 2-week laboratory experiment, we followed the uptake by representative benthic meiofauna species of C-14-labeled organic carbon from blooms, each dominated by one of these cyanobacteria. Natural bloom material was collected and labeled by incubation with (NaHCO3)-C-14. Uptake of cyanobacterial carbon was recorded for the major meiofauna taxa living in the first-centimeter layer, namely ostracods, harpacticoids, and nematodes. The uptake rates were within the range found for diatoms in other studies, indicating that cyanobacteria may be an important food resource for the meiobenthos. The uptake of cyanobacterial carbon varied significantly among species, even within the same class. The ostracod Candona neglecta showed the highest uptake values, whereas two other ostracod species took up very little of the label. There was no significant difference in utilization of carbon from Aphanizomenon sp. and N. spumigena and no reduction in the abundance of the meiofaunal taxa analyzed compared to unexposed controls, indicating that Baltic meiofaunal assemblages in general experience no mortality when exposed to settled cyanobacteria, even the hepatotoxic N. spumigena.

  • 16.
    Nascimento, Francisco
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    The effects of settling cyanobacterial blooms on meiofaunal assemblages of the Baltic Sea2007Licentiate thesis, monograph (Other academic)
  • 17.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bradshaw, Clare
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Direct and indirect effects of ionizing radiation on grazer-phytoplankton interactions2016In: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 155, p. 63-70Article in journal (Refereed)
    Abstract [en]

    Risk assessment of exposure to radionuclides and radiation does not usually take into account the role of species interactions. We investigated how the transfer of carbon between a primary producer, Raphidocelis subcapitata, and a consumer, Daphnia magna, was affected by acute exposure to gamma radiation. In addition to unexposed controls, different treatments were used where: a) only D. magna (Z treatment); b) only R. subcapitata (P treatment) and c) both D. magna and R. subcapitata (ZP treatment) were exposed to one of three acute doses of gamma radiation (5, 50 and 100 Gy). We then compared differences among treatments for three endpoints: incorporation of carbon by D. magna, D. magna growth and R. subcapitata densities. Carbon incorporation was affected by which combination of species was irradiated and by the radiation dose. Densities of R. subcapitata at the end of the experiment were also affected by which species had been exposed to radiation. Carbon incorporation by D. magna was significantly lower in the Z treatment, indicating reduced grazing, an effect stronger with higher radiation doses, possibly due to direct effects of gamma radiation. Top-down indirect effects of this reduced grazing were also seen as R. subcapitata densities increased in the Z treatment due to decreased herbivory. The opposite pattern was observed in the P treatment where only R. subcapitata was exposed to gamma radiation, while the ZP treatment showed intermediate results for both endpoints. In the P treatments, carbon incorporation by D. magna was significantly higher than in the other treatments, suggesting a higher grazing pressure. This, together with direct effects of gamma radiation on R. subcapitata, probably significantly decreased phytoplankton densities in the P treatment. Our results highlight the importance of taking into account the role of species interactions when assessing the effects of exposure to gamma radiation in aquatic ecosystems.

  • 18.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Dahl, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Deyanoya, Diana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lyimo, Liberatus D.
    Bik, Holly M.
    Schuelke, Taruna
    Pereira, Tiago José
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Creer, Simon
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Above-below surface interactions mediate effects of seagrass disturbance on meiobenthic diversity, nematode and polychaete trophic structure2019In: Communications biology, ISSN 2399-3642, Vol. 2, article id 362Article in journal (Refereed)
    Abstract [en]

    Ecological interactions between aquatic plants and sediment communities can shape the structure and function of natural systems. Currently, we do not fully understand how sea- grass habitat degradation impacts the biodiversity of belowground sediment communities. Here, we evaluated indirect effects of disturbance of seagrass meadows on meiobenthic community composition, with a five-month in situ experiment in a tropical seagrass meadow. Disturbance was created by reducing light availability (two levels of shading), and by mimicking grazing events (two levels) to assess impacts on meiobenthic diversity using high- throughput sequencing of 18S rRNA amplicons. Both shading and simulated grazing had an effect on meiobenthic community structure, mediated by seagrass-associated biotic drivers and sediment abiotic variables. Additionally, shading substantially altered the trophic structure of the nematode community. Our findings show that degradation of seagrass meadows can alter benthic community structure in coastal areas with potential impacts to ecosystem functions mediated by meiobenthos in marine sediments.

  • 19.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Karlson, Agnes M. L.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Näslund, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Diversity of larger consumers enhances interference competition effects on smaller competitors2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 166, no 2, p. 337-347Article in journal (Refereed)
    Abstract [en]

    Competition between large and small species for the same food is common in a number of ecosystems including aquatic ones. How diversity of larger consumers affects the access of smaller competitors to a limiting resource is not well understood. We tested experimentally how species richness (0-3 spp.) of benthic deposit-feeding macrofauna changes meiofaunal ostracods' incorporation of fresh organic matter from a stable-isotope-labeled cyanobacterial bloom, using fauna from the species-poor Baltic Sea. Presence of macrofauna mostly decreased meiofaunal incorporation of bloom material, depending on the macrofauna species present. As expected, the species identity of macrofauna influenced the incorporation of organic matter by meiofauna. Interestingly, our results show that, in addition, species richness of the macrofauna significantly reduced meiofauna incorporation of freshly settled nitrogen and carbon. With more than one macrofauna species, the reduction was always greater than expected from the single-species treatments. Field data from the Baltic Sea showed a negative correlation between macrofauna diversity and meiofaunal ostracod abundance, as expected from the experimental results. We argue that this is caused by interference competition, due to spatial niche differentiation between macrofauna species reducing the sediment volume in which ostracods can feed undisturbed by larger competitors. Interference from macrofauna significantly reduces organic matter incorporation by meiofauna, indicating that diversity of larger consumers is an important factor controlling the access of smaller competitors to a limiting food resource.

  • 20.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Bangor University, United Kingdom.
    Lallias, Delphine
    Bik, Holly M.
    Creer, Simon
    Sample size effects on the assessment of eukaryotic diversity and community structure in aquatic sediments using high-throughput sequencing2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 11737Article in journal (Refereed)
    Abstract [en]

    Understanding how biodiversity changes in time and space is vital to assess the effects of environmental change on benthic ecosystems. Due to the limitations of morphological methods, there has been a rapid expansion in the application of high-throughput sequencing methods to study benthic eukaryotic communities. However, the effect of sample size and small-scale spatial variation on the assessment of benthic eukaryotic diversity is still not well understood. Here, we investigate the effect of different sample volumes in the genetic assessment of benthic metazoan and non-metazoan eukaryotic community composition. Accordingly, DNA was extracted from five different cumulative sediment volumes comprising 100% of the top 2 cm of five benthic sampling cores, and used as template for Ilumina MiSeq sequencing of 18 S rRNA amplicons. Sample volumes strongly impacted diversity metrics for both metazoans and non-metazoan eukaryotes. Beta-diversity of treatments using smaller sample volumes was significantly different from the beta-diversity of the 100% sampled area. Overall our findings indicate that sample volumes of 0.2 g (1% of the sampled area) are insufficient to account for spatial heterogeneity at small spatial scales, and that relatively large percentages of sediment core samples are needed for obtaining robust diversity measurement of both metazoan and non-metazoan eukaryotes.

  • 21.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Näslund, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Meiofauna enhances organic matter mineralization in soft sediment ecosystems2012In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 57, no 1, p. 338-346Article in journal (Refereed)
    Abstract [en]

    We investigated the influence of meiofauna on the benthic decomposition of a radiolabeled diatom bloom by measuring the production of (CO2)-C-14 in a laboratory microcosm. Mineralization of the diatom bloom material in the sediment was significantly enhanced in the treatment with high meiofauna abundance, with cumulative mineralization values, on average, 50% greater in the treatment with high meiofaunal abundance after 17 d, compared to sediments with low meiofauna abundance. In addition, bacteria species composition in the treatment with high meiofauna abundance was significantly different from the treatment with low meiofauna abundance, indicating that the activities of meiofauna in the sediments had an effect on the bacterial community composition. Meiofauna can enhance the mineralization of organic matter, probably by stimulating the activity of sediment bacterial community, indicating that positive biological interactions such as facilitation from meiofauna are important for ecosystem processes in soft sediments.

  • 22.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Svendsen, Claus
    Bradshaw, Clare
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Combined Effects from gamma Radiation and Fluoranthene Exposure on Carbon Transfer from Phytoplankton to Zooplankton2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 17, p. 10624-10631Article in journal (Refereed)
    Abstract [en]

    Risk assessment does not usually take into account mixtures of contaminants, thus potentially under- or overestimating environmental effects. We investigated how the transfer of carbon between a primary producer, Pseudokirchneriella subcapitata, and a consumer, Daphnia magna, is affected by acute exposure of gamma radiation (GR) in combination with the polycyclic aromatic hydrocarbon fluoranthene (FA). We exposed D. magna to five concentrations of FA and five acute doses of GR as single contaminants and in nine binary combinations. We compared the observed data for three end points (incorporation of carbon by D. magna, D. magna ingestion rates, and growth) to the predicted joint effects of the mixed stressors based on the independent action (IA) concept. There were deviations from the IA predictions, especially for ingestion rates and carbon incorporation by D. magna, where antagonistic effects were observed at the lower doses, while synergism was seen at the highest doses. Our results highlight the importance of investigating the effects of exposure to GR in a multistressor context. In mixtures of GR and FA, the IA-predicted effects seem to be conservative as antagonism between the two stressors was the dominant pattern, possibly due to stimulation of cellular antioxidative stress mechanisms.

  • 23.
    Nascimento, Francisco J. A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Svendsen, Claus
    Bradshaw, Clare
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Joint Toxicity of Cadmium and Ionizing Radiation on Zooplankton Carbon Incorporation, Growth and Mobility2016In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 50, no 3, p. 1527-1535Article in journal (Refereed)
    Abstract [en]

    The risk of exposure to radioactive elements is seldom assessed considering mixture toxicity, potentially over-or underestimating biological and ecological effects on ecosystems. This study investigated'how three end points, carbon transfer between phytoplankton and Daphnia magna, D. magna mobility and growth, responded to exposure to gamma-radiation in combination with the heavy metal cadmium (Cd), using the MIXTOX approach. Observed effects were compared with mixture effects predicted by concentration addition (CA) and independent action (IA) models and with deviations for synergistic/antagonistic (S/A), dose-level (DL), and dose-ratio (DR) dependency interactions. Several patterns of response were observed depending on the end point tested. DL-dependent deviation from the IA model was observed for carbon incorporation with antagonism switching to synergism at higher doses, while the CA model indicated synergism, mainly driven by effects at high doses of gamma-radiation. CA detected= antagonism regarding acute immobilization, while IA predicted DR dependency. Both CA and IA also identified antagonism for daphnid growth. In general, effects of combinations of gamma-radiation and Cd seem to be antagonistic at lower doses, but synergistic at the higher range of.the doses tested. Our results highlight the importance of investigating the effects of exposure to gamma-radiation in a multistressor context.

  • 24.
    Nascimento, Francisco J.A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Trophic ecology of meiofauna: Response to sedimentation of phytoplankton blooms in the Baltic Sea2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Marine soft sediments are the second largest habitat on Earth. How animal communities in this habitat are structured is a central issue in marine ecology. Food is an important limiting factor for many benthic populations, and settling organic matter from phytoplankton blooms is of vital importance to them. This thesis discusses the effects of settling phytoplankton blooms on benthic meiofaunal populations in the Baltic Sea and how species interactions affect the fate of settled organic matter. Eutrophication in the Baltic Sea has altered phytoplankton community dynamics, with indications that toxin-producing cyanobacterial blooms may reach the benthos in greater quantity than previously. Paper I found that meiofauna feed on settled cyanobacteria, yet suffer no increase in mortality. However, growth of meiofauna is significantly slower on a diet of cyanobacteria than when fed spring bloom diatoms, indicating that the studied cyanobacteria are nutritionally poor (Paper II). In Paper III we found that the presence of macrofauna reduces the access of meiofauna to settled organic matter, presumably through interference competition that increases when several macrofauna species are present. We also found that meiofaunal populations influence the provision of ecosystem services by benthic microbes. Paper IV shows that when meiofauna is abundant, mineralization of organic matter is positively affected, presumably through facilitation mechanisms. In contrast, paper V reports that degradation of the contaminant naphtalene decreases significantly at high meiofauna abundance.

    In conclusion, this thesis shows that type and quality of organic matter available, as well as competition from macrofauna, affect how meiofauna grow and incorporate nutrients. Furthermore we found meiofauna to be an important functional component of the benthic ecosystem, with marked effects on ecosystem processes such as nutrient regeneration and contaminant degradation.

  • 25.
    Nascimento, Francisco
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Karlson, Agnes
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Näslund, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Settling cyanobacterial blooms do not improve growth conditions for soft bottom meiofauna2009In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 368, p. 138-146Article in journal (Refereed)
    Abstract [en]

    Summer blooms of the toxin-producing cyanobacteria Nodularia spumigena are frequent in the Baltic Sea and recent findings suggest that they may be an important food source for the benthos below the euphotic zone. To investigate the effects of settling spring and summer phytoplankton blooms on meiofaunal growth, we assayed concentrations of nucleic acids in three ostracod species (Candona neglecta; Heterocyprideis sorbyana and Paracyprideis fennica) and one genus of nematodes (Paracanthonchus spp.) after incubation in sediments with the one of the following food additions: (1) diatoms, (2) the cyanobacterium Nodularia spumigena, (3) Tetraphyll® as a known high-quality food source, (4) lignin as a refractory artificial food, and (5) control (no added organic matter). The ribosomal ribonucleic acid (RNA) content and RNA:DNA ratios of the tested organisms were lower in the cyanobacteria treatment than in the diatom treatment, with the difference in RNA:DNA ratios being statistically significant for all species except C. neglecta. Moreover, individuals incubated with N. spumigena showed RNA:DNA levels similar to those found in the lignin and control treatments. Furthermore, N. spumigena had lower concentrations of both enzymatically hydrolysable amino acids (EHAA) and eicosapentaenoic acid (EPA) than diatoms suggesting lower nutritional quality for consumers. These results indicate that recently settled summer blooms of N. spumigena are nutritionally poor and do not improve conditions for meiofaunal growth in Baltic sediments. In contrast, input of diatoms to the sediments during spring is crucial for meiofaunal growth.

  • 26.
    Nascimento, Francisco
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Näslund, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Elmgren, Ragnar
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Meiofauna enhances organic matter mineralization in soft sediment ecosystems2010Manuscript (preprint) (Other academic)
    Abstract [en]

    Organic matter mineralization in soft sediments is a key process mediated by benthic fauna and bacteria that is crucial for sustaining primary production in aquatic systems. Few studies have examined the effect of meiofauna on the degradation of labile organic matter in soft sediments. Here we investigated the influence of meiofauna on the benthic decomposition of a radiolabelled diatom bloom by measuring the production of 14CO2 in a laboratory microcosm. Mineralization of the diatom bloom material was significantly enhanced when meiofauna was present in higher abundances, with cumulative mineralization values after 17 days being on average 50% greater in the treatment with high meiofauna abundance compared to sediments with low meiofauna abundance. Our experiment shows that meiofauna can enhance the mineralization of organic matter, probably by stimulating the activity of sediment bacterial community, indicating that positive biological interactions such as facilitation from meiofauna are important for ecosystem processes in soft sediments.

  • 27.
    Näslund, J.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Samuelsson, Göran S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nilsson, H. C.
    Cornelissen, Gerard
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Schaanning, M. T.
    Ecosystem effects of materials proposed for thin-layer capping of contaminated sediments2012In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 449, p. 27-U46Article in journal (Refereed)
    Abstract [en]

    Ecotoxicological effects of 2 carbonaceous and 7 mineral capping materials suggested for in situ remediation of contaminated sediments in the Grenland fjords, Norway, were investigated in a mesocosm experiment. The primary objective was to compare the various materials with regard to potentially harmful effects on the benthic ecosystem. The materials assessed were activated carbon, Kraft-lignin, sand and clay materials, and 3 industrial by-products. Using sediment box-core samples with intact benthic communities, effects on structural (bacterial, macro-and meiofauna diversity) and functional (sediment-to-water nutrient fluxes, oxygen fluxes and bacterial production) endpoints were assessed. Significant deviations from the control (no capping) were detected for all of the tested materials for at least one endpoint. Generally, materials similar to the indigenous sediment (clay, sand) had relatively low deviations from the control, whereas industrial products (plaster, 2 types of crushed marble) resulted in deviations for most endpoints and large reductions in community richness and abundance. For example, at the end of the experimental period, the number of macrofauna taxa was <10 in these treatments, compared to >27 in uncapped mesocosm and field control sediments. The results from the study show that reducing harmful ecosystem effects from thin-layer capping by selecting capping materials based on robust, multi-endpoint mesocosm bench-tests is both possible and recommendable. Potential ecosystem impacts are particularly important to consider when large areas and areas with adequate ecological status are considered for thin-layer capping.

  • 28.
    Näslund, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nascimento, Francisco
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gunnarsson, Jonas
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Meiofauna reduces bacterial mineralization of naphthalene in marine sediment2010In: The ISME journal, ISSN 1751-7362, no 4, p. 1421-1430Article in journal (Refereed)
    Abstract [en]

    The role of sediment-living meiofauna, benthic invertebrates smaller than 1000lm, such as nematodes and ostracods, on the mineralization of naphthalene, a common polycyclic aromatic hydrocarbon (PAH), in marine sediment was studied in microcosms using radiorespirometry. A method to extract live meiofauna was developed and used in order to experimentally manipulate meiofauna abundance and group diversity. Higher abundances of meiofauna were found to significantly decrease naphthalene mineralization. Furthermore, a change in the bacterial community composition (studied using terminal restriction fragment length polymorphism) was also observed in presence of higher meiofauna abundance, as well as a lower number of cultivable naphthalene-degrading bacteria. The reduced mineralization of naphthalene and the altered bacterial community composition in the presence of increased meiofauna abundance is likely the result of top-down control by meiofauna. This study shows that higher abundances of meiofauna can significantly decrease the microbial mineralization of PAHs such as naphthalene and also significantly modify the bacterial community composition in natural marine sediments.

  • 29. Quintana, Cintia O.
    et al.
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Forster, Stefan
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kristensen, Erik
    Functional Performance of Three Invasive Marenzelleria Species Under Contrasting Ecological Conditions Within the Baltic Sea2018In: Estuaries and Coasts, ISSN 1559-2723, E-ISSN 1559-2731, Vol. 41, no 6, p. 1766-1781Article in journal (Refereed)
    Abstract [en]

    A 4-week laboratory experiment investigated the behaviour (survival and bioirrigation) and impact of the invasive polychaetes Marenzelleria viridis, M. neglecta and M. arctia on sediment-water solutes exchange, porewater chemistry, and Fe and P interactions in high-salinity sandy sediment (HSS) and low-salinity muddy sediment (LSM) from the Baltic Sea. M. viridis showed deep burrowing with efficient bioirrigation (11 L m−2 day−1) and high survival (71%) in HSS, while M. arctia exhibited shallow burrowing with high bioirrigation (12 L m−2 day−1) and survival (88%) in LSM. M. neglecta behaved poorly in both ecological settings (bioirrigation, 5–6 L m−2 day−1; survival, 21–44%). The deep M. viridis bioirrigation enhanced total microbial CO2 (TCO2) production in HSS by 175% with a net efflux of NH4+ and PO43−, at rates 3- to 27-fold higher than for the other species. Although the shallow and intense bioirrigation of M. arctia in LSM stimulated microbial TCO2 production to some extent (61% enhancement), the nutrient fluxes close to zero indicate that it effectively prevented the P release. Porewater Fe:PO43− ratios revealed that the oxidizing effect of M. arctia bioirrigation increased the PO43− adsorption capacity of LSM twofold relative to defaunated controls while no buffering of PO43− was detected in M. viridis HSS treatment. Therefore, the different behaviour of the three species in various environments and the sharp contrast between M. viridis and M. arctia effects on C, N and P cycling must be considered carefully when the ecological role of Marenzelleria species in the Baltic Sea is evaluated.

1 - 29 of 29
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