Description: Concerns about increasing atmospheric CO2 concentrations and global warming have initiated studies on the consequences of multiple-stressor interactions on marine organisms and ecosystems. We present a fully-crossed factorial mesocosm study and assess how warming and acidification affect the abundance, body size, and fatty acid composition of copepods as a measure of nutritional quality. The experimental set-up allowed us to determine whether the effects of warming and acidification act additively, synergistically, or antagonistically on the abundance, body size, and fatty acid content of copepods, a major group of lower level consumers in marine food webs. Copepodite (developmental stages 1-5) and nauplii abundance were antagonistically affected by warming and acidification. Higher temperature decreased copepodite and nauplii abundance, while acidification partially compensated for the temperature effect. The abundance of adult copepods was negatively affected by warming. The prosome length of copepods was significantly reduced by warming, and the interaction of warming and CO2 antagonistically affected prosome length. Fatty acid composition was also significantly affected by warming. The content of saturated fatty acids increased, and the ratios of the polyunsaturated essential fatty acids docosahexaenoic- (DHA) and arachidonic acid (ARA) to total fatty acid content increased with higher temperatures. Additionally, here was a significant additive interaction effect of both parameters on arachidonic acid. Our results indicate that in a future ocean scenario, acidification might partially counteract some observed effects of increased temperature on zooplankton, while adding to others. These may be results of a fertilizing effect on phytoplankton as a copepod food source. In summary, copepod populations will be more strongly affected by warming rather than by acidifying oceans, but ocean acidification effects can modify some temperature impacts

Description: Data represent isotopic values of plankton community of the eastern tropical Atlantic. Main focus was given to the trophic position of gelatinous zooplankton within the oceanic food web. Sampling was conducted during November and December 2015 on board R/V “MARIA S. MERIAN” (cruise MSM49) at 8 stations in Cape Verdean waters in the ETA, including a shallow seamount (Senghor Seamount, 100-3300 m) and its northwestern and southeastern slopes, a cyclonic eddy, and four oceanic stations. Net sampling was conducted using two types of multiple opening/closing nets and environmental sampling systems (MOCNESS), one with 1 m2 ( three nets, mesh size: 2 mm; and six nets, mesh size: 335 µm) and one with 10 m2 opening (five nets, mesh size: 1.5 mm), towed at a speed of 2 kn. Sampling depth intervals were targeted at 0-50, 50-100, 100-200, 200-400, 400-600, and 600-1000 m. Samples from replicate tows at the same depth and station were pooled for analyses.

Description: Measurements of cell size, cell density, nutrient concentration and genotype composition in a long-term experiment (182 days) with the marine phytoplankton species Chaetoceros affinis and Emiliania huxleyi, each consisting of nine genotypes. The species were cultivated together at three different nutrient regimes (10 N, 20 N, 30 N) with increasing nitrate supply in a semi-continuous batch cycle system. The genotype composition of both species was assessed after 49, 91, and 182 days using microsatellites. In a short-term experiment cell size and density of nine Chaetoceros affinis genotypes separately were measured after 7 days growth at seven nitrate levels (2.5, 5, 7.5, 12.5, 20, 30, and 45 μmol L−1 N).