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  • 1
    Publication Date: 2019-02-01
    Description: Ocean acidification is caused by increasing amounts of carbon dioxide dissolving in the oceans leading to lower seawater pH. We studied the effects of lowered pH on the calanoid copepod Eurytemora affinis during a mesocosm experiment conducted in a coastal area of the Baltic Sea. We measured copepod reproductive success as a function of pH, chlorophyll a concentration, diatom and dinoflagellate biomass, carbon to nitrogen (C : N) ratio of suspended particulate organic matter, as well as copepod fatty acid composition. The laboratory-based experiment was repeated four times during four consecutive weeks, with water and copepods sampled from pelagic mesocosms enriched with different CO2 concentrations. In addition, oxygen radical absorbance capacity (ORAC) of animals from the mesocosms was measured weekly to test whether the copepod's defence against oxidative stress was affected by pH. We found no effect of pH on offspring production. Phytoplankton biomass, as indicated by chlorophyll a concentration, had a strong positive effect. The concentration of polyunsaturated fatty acids in the females were reflected in the eggs and had a positive effect on offspring production, whereas monounsaturated fatty acids of the females were reflected in their eggs but had no significant effect. ORAC was not affected by pH. From these experiments we conclude that E. affinis seems robust against direct exposure to ocean acidification on a physiological level, for the variables covered in the study. E. affinis may not have faced acute pH stress in the treatments as the species naturally face large pH fluctuations.
    Type: Article , PeerReviewed
    Format: text
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  • 2
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    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 13 (22). pp. 6171-6182.
    Publication Date: 2019-02-01
    Description: Ocean acidification is challenging phenotypic plasticity of individuals and populations. Calanoid copepods (zooplankton) are shown to be fairly plastic against altered pH conditions, and laboratory studies indicate that transgenerational effects are one mechanism behind this plasticity. We studied phenotypic plasticity of the copepod Acartia sp. in the course of a pelagic, large-volume mesocosm study that was conducted to investigate ecosystem and biogeochemical responses to ocean acidification. We measured copepod egg production rate, egg-hatching success, adult female size and adult female antioxidant capacity (ORAC) as a function of acidification (fCO2  ∼  365–1231 µatm) and as a function of quantity and quality of their diet. We used an egg transplant experiment to reveal whether transgenerational effects can alleviate the possible negative effects of ocean acidification on offspring development. We found significant negative effects of ocean acidification on adult female size. In addition, we found signs of a possible threshold at high fCO2, above which adaptive maternal effects cannot alleviate the negative effects of acidification on egg-hatching and nauplii development. We did not find support for the hypothesis that insufficient food quantity (total particulate carbon 〈 55 µm) or quality (C : N) weakens the transgenerational effects. However, females with high-ORAC-produced eggs with high hatching success. Overall, these results indicate that Acartia sp. could be affected by projected near-future CO2 levels
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2015-03-25
    Description: The aim of the study was to measure copepod reproduction, mortality and sex ratio in the field before, during and after a cyanobacteria bloom during the summer in the western Gulf of Finland. Environment and zooplankton samples were collected every fortnight, and the copepod Acartia spp. was incubated in the laboratory for reproductive output, i.e. egg production and egg hatching success. Other responses monitored were female:male ratio, mortality and body condition. In addition, molecular analyses of the nodularin-producing cyanobacterium Nodularia in Acartia gut contents (GCs) were assessed. Egg production and body condition decreased with increasing Nodularia GCs. During the bloom, hatching decreased as a response to Nodularia in the copepod gut. Although not related to cyanobacteria variables, male mortality was higher than female mortality, resulting in a female-biased sex ratio over most of the summer. The study demonstrates that Acartia reproductive output is constrained by cyanobacteria blooms in the Baltic Sea, and more generally that copepod population dynamics may be negatively affected by such blooms. This is especially significant considering that toxin-producing blooms are predicted to increase due to warming.
    Print ISSN: 0142-7873
    Electronic ISSN: 1464-3774
    Topics: Biology
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