Organisms living in coastal waters are exposed daily to low oxygen conditions (hypoxia). Some animals adapt to hypoxia by increasing levels of the respiratory pigment that delivers O2 to tissues. For example, humans make more red blood cells at high altitude where O2 is limited than at sea level. Other organisms, such as deep-diving and hibernating animals, can lower their metabolism, reducing their need for O2. Estuarine organisms rely on these and other strategies to tolerate hypoxia. Less well-recognized is that high levels of CO2, hypercapnia, occur naturally with hypoxia in coastal waters, causing significant acidification. Yet, virtually nothing is known about the combined effects of hypoxia and hypercapnia on estuarine species. In the current studies Pacific whiteleg shrimp, Litopenaeus vannamei, and Atlantic blue crabs, Callinectes sapidus, will be exposed to combinations of low O2 and high CO2. Changes in O2 delivery to tissues will be quantified by measuring heart and breathing rates, as well as the molecular composition of their respiratory pigment and its ability to bind O2. Next, we will look for changes in metabolism and the energetically expensive process of protein synthesis. Finally we will test how shrimp and crabs respond to low O2 and high CO2 when performing energetically demanding activities. With these studies we expect to show that hypercapnia interferes with normal adaptations to hypoxia in estuarine crustaceans. While testing this idea, we will continue to teach, train and publish with students from two primarily undergraduate institutions. The proposed work also draws attention to the future vitality of shrimp and crab populations which, world-wide, form the basis of a multi-billion dollar seafood market. These results should also prove useful in understanding how these economically and ecologically important species will be impacted in response to future global changes.
