The Science Seminar Series: March 22, 2012
Fish, the inorganic carbon cycle, acid-base balance and ocean acidification
Dr. Martin Grosell
Rosenstiel School of Marine and Atmospheric Science (RSMAS)
University of Miami
Time: 4:00 -5:00pm
Intestinal HCO3- secretion by marine teleost fish is a pivotal component of successful osmoregulation. The intestinal fluids of marine teleosts are alkaline and contain HCO3- concentrations reaching 100 mM which, when combined with Ca2+ from ingested seawater, results in formation of CaCO3 precipitates ultimately excreted to the seawater environment. The recent report that CaCO3 produced by fish contributes significantly to the global carbon cycle illustrates the importance of understanding the physiological processes involved in the formation of CaCO3 in the intestinal lumen. The sources of HCO3- for intestinal secretions are endogenous CO2 from the enterocytes as well as blood plasma HCO3-. Fish compensate effectively for the currently observed increase in atmospheric, and thereby oceanic, CO2 by retaining plasma HCO3- and thus maintaining blood pH. Thus, fish in a high CO2 environment are forced to balance retention of blood HCO3- for acid-base balance with intestinal HCO3- secretion for osmoregulation. Meeting this challenge involves physiological compromises and elevated metabolic cost.