Abundance and biomass of zooplankton collected monthly from January 1978 to december 1978 in front of Constanta city, Black Sea

The Est Constanta 1978 dataset contains zooplankton data collected monthly from January 1978 to december 1978 allong a 5 station transect in front of the city Constanta (44°10'N, 28°41.5'E - EC1; 44°10'N, 28°47'E - EC2; 44°10'N, 28°54'E - EC3; 44°10'N, 29°08'E - EC4; 44°10'N, 29°22'E - EC5). Zooplankton sampling was undertaken at 5 stations where samples were collected using a Juday closing net in the 0-10, 10-25, 25-50m layer (depending also on the water masses). The dataset includes samples analysed for mesozooplankton species composition and abundance. Sampling volume was estimated by multiplying the mouth area with the wire length. Taxon-specific mesozooplankton abundance was count under microscope. Total abundance is the sum of the counted individuals. Total biomass Fodder, Rotifera , Ctenophora and Noctiluca was estimated using a tabel with wet weight for each species an stage.

Have we been underestimating the effects of ocean acidification in zooplankton?

Understanding how copepods may respond to ocean acidification (OA) is critical for risk assessments of ocean ecology and biogeochemistry. The perception that copepods are insensitive to OA is largely based on experiments with adult females. Their apparent resilience to increased carbon dioxide (pCO2) concentrations has supported the view that copepods are 'winners' under OA. Here, we show that this conclusion is not robust, that sensitivity across different life stages is significantly misrepresented by studies solely using adult females. Stage-specific responses to pCO2 (385-6000 µatm) were studied across different life stages of a calanoid copepod, monitoring for lethal and sublethal responses. Mortality rates varied significantly across the different life stages, with nauplii showing the highest lethal effects; nauplii mortality rates increased threefold when pCO2 concentrations reached 1000 µatm (year 2100 scenario) with LC50 at 1084 µatm pCO2. In comparison, eggs, early copepodite stages, and adult males and females were not affected lethally until pCO2 concentrations >= 3000 µatm. Adverse effects on reproduction were found, with >35% decline in nauplii recruitment at 1000 µatm pCO2. This suppression of reproductive scope, coupled with the decreased survival of early stage progeny at this pCO2 concentration, has clear potential to damage population growth dynamics in this species. The disparity in responses seen across the different developmental stages emphasizes the need for a holistic life-cycle approach to make species-level projections to climate change. Significant misrepresentation and error propagation can develop from studies which attempt to project outcomes to future OA conditions solely based on single life history stage exposures.

Effect of increasing sea water pCO2 on the northern Atlantic krill species Nyctiphanes couchii

Surprisingly little is known about potential effects of ocean acidification on krill of the Northern Hemisphere as ecologically very important food web component. Sub-adult individuals of the northern Atlantic krill species Nyctiphanes couchii (caught at Austevoll near Bergen, Norway, in January 2013) were exposed in the laboratory to four different levels of pCO2 (430, 800, 1,100, and 1,700 µatm) for 5 weeks in order to assess potential changes in a set of biological response variables. Survival decreased and the frequency of moulting-related deaths increased with increasing pCO2. Survival was considerably reduced at relatively high pCO2 of 1,700 µatm and tended to be negatively affected at 1,100 µatm pCO2. However, the experimental results show no significant effects of pCO2 on inter-moult period and growth at pCO2 levels below 1,100 µatm. No differences in length measurements of the carapace and uropod were observed across pCO2 levels, indicating no effect of changing carbonate chemistry on the morphology of those calciferous parts of the exoskeleton. The results suggest that sub-adult N. couchii may not suffer dramatically from predicted near-future changes in pCO2. However, potential detrimental effects on the moulting process and associated higher mortality at 1,100 µatm pCO2 cannot be excluded. Further experiments are needed in order to investigate whether early life stages of N. couchii show a different sensitivity to elevated sea water pCO2 and whether those results are transferable to other krill species of the Northern Hemisphere.