Medium-term exposure of the North Atlantic copepod Calanus finmarchicus (Gunnerus, 1770) to CO 2-acidified seawater: effects on survival and development
The impact of medium-term exposure to CO 2-acidified seawater on survival, growth and development was investigated in the North Atlantic copepod Calanus finmarchicus. Using a custom developed experimental system, fertilized eggs and subsequent development stages were exposed to normal seawater (390 ppm CO 2) or one of three different levels of CO 2-induced acidification (3300, 7300, 9700 ppm CO 2). Following the 28-day exposure period, survival was found to be unaffected by exposure to 3300 ppm CO 2, but significantly reduced at 7300 and 9700 ppm CO 2. Also, the proportion of copepodite stages IV to VI observed in the different treatments was significantly affected in a manner that may indicate a CO 2-induced retardation of the rate of ontogenetic development. Morphometric analysis revealed a significant increase in size (prosome length) and lipid storage volume in stage IV copepodites exposed to 3300 ppm CO 2 and reduced size in stage III copepodites exposed to 7300 ppm CO 2. Together, the findings indicate that a pCO 2 level ≤2000 ppm (the highest CO 2 level expected by the year 2300) will probably not directly affect survival in C. finmarchicus. Longer term experiments at more moderate CO 2 levels are, however, necessary before the possibility that growth and development may be affected below 2000 ppm CO 2 can be ruled out.