Ocean acidification elicits different energetic responses in an Arctic and a boreal population of the copepod Pseudocalanus acuspes

Anthropogenic emissions cause the global CO2 partial pressure (pCO2) to increase, and atmospheric models predict a pCO2 of ~1,000 µatm by the year 2100. About one-third of emitted CO2 is absorbed by the world’s oceans, causing a decrease in ocean pH. Experiments show varying effects of this so-called ocean acidification (OA) on marine animals, and it has proven exceedingly difficult to establish general rules for OA effects among species. In the present study, we found different energetic OA effects in populations from Svalbard and Skagerrak of the same calanoid copepod species, Pseudocalanus acuspes. In the Svalbard population, ingestion rates showed an inverted U-shaped hormesis-like response with higher rates at pH 7.80 than at pH 7.95 and pH 7.61 at medium and high prey concentrations. On the other hand, ingestion rates were lower at pH 7.70 and pH 7.47 than at pH 7.95 only at high prey concentrations in the Skagerrak population. Secondly, we found significant interactions between the effects of pH and prey concentration on both ingestion rate and respiration rate in the Skagerrak population, which indicates that OA may influence the way ingestion and respiration relate to prey concentration. In conclusion, the results suggest that OA effects may be far from linearly related to pH in copepods, and moreover, the effects may vary within species between populations from different regions.

Thor P. & Oliva E. O., in press. Ocean acidification elicits different energetic responses in an Arctic and a boreal population of the copepod Pseudocalanus acuspes. Marine Biology. Article (subscription required).


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