SEMINAR: MBF602 9/23/11 S/A 103, 1:00pm Rachael Heuer: Ocean acidification leads to counterproductive intestinal base loss in the gulf toadfish (Opsanus beta)

["Maxine Williams" <mwilliams@rsmas.miami.edu>]

MBF602 9/23/11 S/A 103, 1:00pm Student Speaker Rachael Heuer

 

Ocean acidification leads to counterproductive intestinal base loss in the gulf toadfish (Opsanus beta)

 

Oceanic CO₂ has increased from 280 to 380ppm since pre-industrial times and is expected to reach 1000 and 1900 ppm by 2100 and 2300, respectively. In addition, levels up to 2300 ppm have been reported from upwelling zones. We recently demonstrated that levels as low as 750 ppm induces acidosis in toadfish, leading to compensation by retention of blood HCO₃^- to defend pH. Since increases in serosal HCO₃^- increases HCO₃^- secretion rates in isolated intestinal tissue, it was hypothesized that elevation of blood HCO₃^-during 1900ppm CO₂ exposure would increase base secretion rates in vivo. Toadfish rectal fluids were measured for pH, osmotic pressure, ionic composition, and total CO₂. Precipitated CaCO₃ from these rectal fluids was analyzed for titratable alkalinity, Mg²⁺ and Ca²⁺ content. As hypothesized, toadfish exposed to 1900ppm exhibited higher rectal base excretion rates, higher fluid [HCO₃^-] and lower fluid [Cl^-] than controls suggesting increased intestinal anion exchange as a result of the compensated respiratory acidosis. This study verifies that elevation of plasma HCO₃^- during exposure to CO₂ levels observed currently in certain regions and expected globally over the next centuries, leads to greater intestinal HCO₃^- loss, a process that acts against compensation for CO₂ induced acidosis.

 

 

Rachael Heuer

University of Florida, B.S. Zoology 2006

Entered Ph.D. Program Fall 2010

Advisor: Martin Grosell