Chan, F. Cornell University, fc19@cornell.edu
Pace, M. Institute of Ecosystem Studies, PaceM@ecostudies.org
Howarth, R. W. Cornell University, rwh2@cornell.edu
Marino, R. M. Cornell University, rmm3@cornell.edu
Pelletier, D. M. Cornell University, dmp25@cornell.edu

 
PLANKTONIC NITROGEN-FIXING CYANOBACTERIA IN ESTUARIES: AN EXPERIMENTAL TEST OF BLOOM REGULATION BY TOP-DOWN CONTROLS
 
Blooms of filamentous heterocystic cyanobacteria are common features of many freshwater systems. In contrast, blooms of filamentous heterocystic cyanobacteria are restricted to only a small number of estuaries world-wide. Although the contrasting pattern of filamentous cyanobacteria abundance across freshwater and estuarine systems is striking, our understanding of the factors which regulate the dynamics of estuarine cyanobacterial blooms remains limited. To date, experimental and descriptive studies have examined the influences of physical and bottom-up controls. However, much less is known about top-down controls and their interactions with bottom-up forces in bloom regulation. We conducted a mesocosm experiment to directly investigate the roles of copepod grazers and nutrient availability (Mo) in the promoting or suppressing heterocystic cyanobacterial blooms in estuaries. Our experiment employed a 2 X 2 factorial design where the density of grazers and availability of molybdate were manipulated. The presence of copepod grazers resulted in marked differences in the growth and structure of cyanobacterial populations among treatments. Our results indicate that grazing by estuarine copepods can inhibit cyanobacterial blooms and interact with bottom up processes to explain the variable pattern of cyanobacterial abundance across systems.
 
Day: Friday, Feb. 5
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: SS42FR1115E