Abstract


WHAT DO THE ALGAE SAY? WINTER PATTERNS IN NITROGREN-FIXING ALGAL ASSEMBLAGES IN STREAMS IN THE HENGILL REGION OF ICELAND

In summer, nitrogen-poor streams in Iceland are comprised of a high abundance and biomass of N2-fixing algae (cyanobacteria and diatoms in the Rhopalodiaceae) that generally increase concomitantly with N2-fixation rates and stream temperature. Nostoc spp dominate primary producer biomass and inputs of nitrogen via N2-fixation. In the winter however, the shorter days and snow coverage of streams decreases light availability and stream temperatures, reducing light- and temperature-dependent processes like photosynthesis and N2-fixation. These seasonal changes likely set distribution and abundance patterns of algae. We explored algal assemblages in geothermally-heated streams in the Hengill region of Iceland in January 2014. Compared to summer, we observed a significant reduction in biomass and a shift to cold-water tolerant taxa, including Nostoc pruniforme. Epithemia spp were common in one stream. Despite the presence of N2-fixers, N2-fixation rates were negligible in contrast with significantly high rates observed during summer. However, the dominance of N2-fixers during winter could promote early spring N2-fixation as light levels increase and grazing pressure is still low, leading to increased inputs of nitrogen that may influence spring primary and secondary production.

Authors

Furey, P. C., St. Catherine University, USA, pcfurey@hotmail.com

Welter, J. R., St. Catherine University, USA, jrwelter@stkate.edu

Ahles, A., St. Catherine University, USA, amahles@stkate.edu

Goldschmidt, J., St. Catherine University, USA, jbgoldschmidt@stkate.edu

Nelson, D., University of Alabama,Tuscaloosa, USA, dnelson12@crimson.ua.edu

Details

Oral presentation

Session #:024
Date: 5/22/2014
Time: 17:00
Location: E 145 - 146

Presentation is given by student: No