Gardner, W. S.. University of Texas at Austin Marine Science Institute, gardner@utmsi.utexas.edu
Lavrentyev, P. S.. University of Akron, peter3@uakron.edu

 
THE HETEROTROPHIC NANOFLAGELLATE TO BACTERIA BIOMASS RATIO AS AN INDICATOR OF NITROGEN RECYCLING RATES IN LAKE MARACAIBO, VENEZUELA, AND IN TEXAS COASTAL WATERS
 
Ammonium regeneration rates were estimated with N-15 isotope dilution experiments at a variety of stations in Lake Maracaibo, Venezuela, and over a trophic gradient in Texas coastal waters (Corpus Christi Bay, Laguna Madre, and Baffin Bay). These results were compared to microbial characteristics of water samples from the same sites in an attempt to understand the mechanisms and organisms responsible for the observed ammonium regeneration rates. In both studies, a relationship was observed between the independently measured biomass ratio of heterotrophic nanoflagellates (HNAN) to bacteria and ammonium regeneration rates. The relationship was significant (p < 0.01) for samples incubated under natural light but not in the dark for either system. The relationship did not seem to be affected by trophic status, as the two Texas coastal sites with lowest values for both regeneration rates and HNAN:bacteria ratios had the lowest and highest abundance of phytoplankton among the studied sites. These results are consistent with the hypothesis that bacterivory by HNAN is a major mechanism for ammonium regeneration in these waters and that the predictability of this heterotrophic process is influenced by light.
 
Day: Thursday, Feb. 4
Time: 11:30 - 11:45am
Location: Sweeney Center
 
Code: SS39TH1130S