| 1. |
- Vehmaa, Anu, et al.
(författare)
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Copepod reproductive success in spring-bloom communities with modified diatom and dinoflagellate dominance
- 2012
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 69:3, s. 351-357
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Tidskriftsartikel (refereegranskat)abstract
- Dinoflagellates have increased and diatoms decreased in the Baltic Sea in recent decades, possibly because of changes in the climate and altered patterns of stratification. The hypothesis that grazing copepods would benefit from the change in species composition was tested experimentally by studying the reproductive output of the crustacean copepod Eurytemora affinis in five Baltic Sea phytoplankton spring communities dominated by different dinoflagellates (Biecheleria baltica, Gymnodinium corollarium) and diatoms (Chaetoceros cf. wighamii, Skeletonema marinoi, and Thalassiosira baltica). After a 5-d acclimation and a 4-d incubation, egg production, egg hatching success, and the RNA: DNA ratio of E. affinis were measured. Egg production was highest on a G. corollarium-dominated diet and lowest on a S. marinoi-dominated diet and on a B. baltica-dominated natural spring bloom, but there were no differences in hatching success. The results demonstrate strong species-specific effects unconstrained by the dominating group. Hence, the hypothesis of specific effects derived from a diatom or dinoflagellate diet is too simplistic, and there is a need to explore phytoplankton taxa at a species level to reveal the reasons for copepod reproductive success.
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| 2. |
- Vehmaa, Anu, et al.
(författare)
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How will increased dinoflagellate:diatom ratios affect copepod egg production? : a case study from the Baltic Sea
- 2011
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 401:1-2, s. 134-140
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Tidskriftsartikel (refereegranskat)abstract
- Mild winters are modifying the plankton spring bloom composition so that diatoms are decreasing and dinoflagellates increasing. We used two common spring bloom phytoplankton species, a diatom and a dinoflagellate to study the effects of changing bloom composition on the reproduction of the calanoid copepod Acartia bifilosa Giesbrecht, a dominant species in the northern Baltic Sea. Egg production was significantly higher when copepods were fed with Scrippsiella hangoei (Schiller) Larsen dinoflagellates or a mixture of Scrippsiella and Skeletonema marinoi Sarno and Zingone diatoms than when they were provided with Skeletonema only. This effect was observed despite the fact that the Skeletonema strain did not produce polyunsaturated aldehydes (PUAs) and its nutritional quality was high according to polyunsaturated fatty acid (PUFAs) and sterol measurements, and moderate according to mineral (C:N and C:P) measurements. When offered mixtures of Skeletonema and Scrippsiella, copepods ingested both, even when the other one was rare. This indicates potential positive effect of multispecies diets not verified in this study. Here we show that increasing dinoflagellate:diatom ratio might have a positive effect on copepod reproduction.
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| 3. |
- Vehmaa, Anu, et al.
(författare)
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Ocean acidification challenges copepod phenotypic plasticity
- 2016
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 13:22, s. 6171-6182
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Tidskriftsartikel (refereegranskat)abstract
- 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 (fCO(2) similar to 365-1231 mu atm) 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 fCO(2), 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 mu m) 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.
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