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High temperature decreases the PIC/POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
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2014 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, 3531-3545 p.Article in journal (Refereed) Published
Abstract [en]

Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon through photosynthesis (POC production) and into particulate inorganic carbon through calcification (PIC production). As calcification produces a net release of CO2, the ratio of PIC to POC production determines whether coccolithophores act as a source (high PIC / POC) or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and high temperature on the physiology and the PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large and heavily calcified species is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. One of the subspecies was subjected to a 5 °C temperature increase from 10 °C to 15 °C, which did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. This temperature increase reduced the PIC / POC ratio by 40–60%, whereas the PIC / POC ratio did not differ between P-limited and nutrient-replete cultures when the subspecies were grown near their respective isolation temperature. Both P-limitation and elevated temperature significantly increased coccolith malformations. Our results suggest that a temperature increase may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, thus favouring CO2 sequestration over release. It seems unlikely that P-limitation by itself causes changes in the PIC / POC ratio in this species.

Place, publisher, year, edition, pages
2014. Vol. 11, 3531-3545 p.
Keyword [en]
coccolithophores, culture experiments, phosphate limitation, calcification
National Category
Natural Sciences
Research subject
Biology; Earth Science with specialization in Environmental Analysis
URN: urn:nbn:se:uu:diva-220830DOI: 10.5194/bg-11-3531-2014ISI: 000339265800008OAI: diva2:706566
Available from: 2014-03-20 Created: 2014-03-20 Last updated: 2016-09-13Bibliographically approved
In thesis
1. Phenotypic variation and adaptive strategies in calcifying marine phytoplankton (Coccolithophores)
Open this publication in new window or tab >>Phenotypic variation and adaptive strategies in calcifying marine phytoplankton (Coccolithophores)
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Uppsala universitet, 2015
National Category
Ecology Evolutionary Biology Cell Biology
urn:nbn:se:uu:diva-253357 (URN)
2015-04-24, Hambergsalen, Villavägen 16, Uppsala, 15:34 (English)
Available from: 2015-06-02 Created: 2015-05-26 Last updated: 2016-02-09Bibliographically approved
2. Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)
Open this publication in new window or tab >>Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 54 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1427
Coccolithophores, Life-Cycle, Phytoplankton, Nutrient limitation, Temperature, Microscopy, High-throughput sequencing, Taxonomy
National Category
Evolutionary Biology Environmental Sciences
urn:nbn:se:uu:diva-302903 (URN)978-91-554-9689-0 (ISBN)
Public defence
2016-10-28, Hambergsalen, Department of Earth Sciences, Villavägen 16, Uppsala, 13:00 (English)
Available from: 2016-10-07 Created: 2016-09-12 Last updated: 2016-10-11

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