Effects of ocean acidification on the physiology of different life stages of Hyas araneus

The present thesis investigated the effects of elevated seawater PCO2 and temperature on different life stages of the spider crab Hyas araneus. Extracellular pH of adult crabs decreased with increasing seawater CO2. While mRNA expression of several genes important for acid-base regulation was not affected by high seawater PCO2 in larvae, mRNA expression of genes involved in mitochondrial energy metabolism was increased in response to elevated PCO2. The impact of high seawater CO2 on the first larval stage (zoea) with different pre-hatch history was examined. Effects of post-hatching exposure to elevated seawater PCO2 on oxygen consumption and growth in developing zoea I larvae were small, developmental duration and survival remained unaffected. Zoea I larvae pre-exposed to high seawater PCO2 during maternal care showed extremely high mortality rates and severe developmental delay. The temperature tolerance window of different larval stages exposed to different seawater PCO2 was determined. The upper thermal tolerance limit was lowered at high CO2 in zoea larvae. A comparative genetic approach revealed an increased transcriptomic response to acute heat shock with elevated transcript levels of heat shock proteins in larvae exposed to elevated seawater PCO2. The experimental results from this thesis indicate severe impacts of elevated seawater PCO2 in certain early life cycle stages of H. araneus. Carry-over effects between life stages and/or CO2 induced disturbances of the transition phases from one to the next stage have the potential to severely impact species survival.