Deformities in larvae and juvenile European lobster (Homarus gammarus) exposed to lower pH at two different temperatures

The ongoing warming and acidification of the world's oceans are expected to influence the marine ecosystems, including benthic marine resources. Ocean acidification may especially have an impact on calcifying organisms, and the European lobster (Homarus gammarus) is among those species at risk. A project was initiated in 2011 aiming to investigate long-term effects of ocean acidification on the early life-cycle of lobster under two temperatures. Larvae were exposed to pCO(2) levels of ambient water (water intake at 90m depth), medium 750 (pH=7.79) and high 1200 mu atm pCO(2) (pH=7.62) at temperatures 10 and 18 degrees C. The water parameters in ambient water did not stay stable and were very low towards the end of the experiment in the larval phase at 10 degrees C, with pH between 7.83 and 7.90. At 18 degrees, pH in ambient treatment was even lower, between 7.76 and 7.83, i.e. close to medium pCO(2) treatment. Long-term exposure lasted 5 months. At 18 degrees C the development from stage 1 to 4 lasted 14 to 16 days, as predicted under optimal water conditions. Growth was very slow at 10 degrees C and resulted in three larvae reaching stage 4 in high pCO(2) treatment only. There were no clear effects of pCO(2) treatment, on either carapace length or dry weight. However, deformities were observed in both larvae and juveniles. The proportion of larvae with deformities increased with increasing pCO(2) exposure, independent of temperature. In the medium treatment about 23% were deformed, and in the high treatment about 43% were deformed. None of the larvae exposed to water of pH>7.9 developed deformities. Curled carapace was the most common deformity found in larvae raised in medium pCO(2) treatment, irrespective of temperature, but damages in the tail fan occurred in addition to a bent rostrum. Curled carapace was the only deformity found in high pCO(2) treatment at both temperatures. Occurrence of deformities after five months of exposure was 33 and 44% in juveniles raised in ambient and low pCO(2) levels, respectively, and 21% in juveniles exposed to high pCO(2). Deformed claws were most often found in ambient and medium treatment (56%), followed by stiff/twisted walking legs (39%) and puffy carapace (39%). In comparison, at high pCO(2) levels 71% of the deformed juveniles had developed a puffy carapace. Overall, about half of the deformed juveniles from the ambient and medium pCO(2) treatment displayed two or three different abnormalities; 70% had multiple deformities in the high pCO(2) treatment. Some of the deformities in the juveniles may affect respiration (carapace), the ability to find food, or sexual partners (walking legs, claw and antenna), and ability to swim (tail-fan damages).