The effect of ocean acidification and warming on survival and growth of Atlantic cod (Gadus morhua) larvae

• Main Author: Stiasny, Martina
• Format: Thesis
• Language: English
• Published: 2013
• Subjects: Course of study: MSc Biological Oceanography; atlantic cod; Gadus morhua; Ocean acidification
• Online Access: https://oceanrep.geomar.de/id/eprint/22985/; https://oceanrep.geomar.de/id/eprint/22985/1/M.Sc.%202013%20Stiasny,%20M.pdf

Rising C02 emissions lead to increasing acidification of the world's oceans. At the same time, temperatures in the atmosphere are rising resulting in ocean warming. Possible economic and ecological consequences are still being assessed. One important point is the synergistic effect of ocean acidification and warming on fish larvae especially of economically important fish species. This study investigated the effect of ocean acidification and warming on the survival of Atlantic cod (Gadus morhua) larvae. It aimed not only to answer, whether there is an increase in mortality during early development under increased C02 concentrations and higher temperatures, but also what decides the mortality risk in these conditions. In order to answer these questions, an indoor experiment was performed, in which cod larvae were reared in 90 L tanks in a full factorial design with two C02 concentrations (400 and 1000 ppm) and two temperatures (7° C and 9° C). Daily mortality was measured and samples of alive and dead larvae were taken regularly for growth measurements and otolith analysis. These were analyzed in order to assess, whether an increased C02 concentration leads to an increase in growth rate or size-selective mortality by causing higher mortality rates in smaller larvae. During early development there appeared to be a selection for larger otolith core areas, which is correlated to the size of the eggs and the larvae at hatch, while later on there was a selection for larvae with larger otolith growth. Furthermore, there was a noticeable increase in standard length and myotome height in the larvae in the high C02 treatments. The results clearly showed that increased C02 concentrations had a significant negative effect on the survival of the larvae. An increase in temperature, however, did not further increase mortality, but resulted in increased growth. Results of the growth and otolith measurements strongly hint towards both, an increase in growth rate and sizeselective mortality selecting for larger larvae under ...