PARENT SESSION
Contributed Oral Session 108: Aquatic Trophic Systems II
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal
Contrasting impacts of top predators on carbon flow through microbial food webs in two Antarctic lakes.
McKenna, Kerry*,1, Bell, Eleanor2, Madan, Nanette3, Marshall, William3, Moorhead, Daryl1, Laybourn-Parry, Johanna3, 1 University of Toledo, Toledo, OH2 Australian Antarctic Division, Kingston, NC, Tasmania3 University of Nottingham, Nottingham, United Kingdom
ABSTRACT- Models were used to compare carbon flow through the microbial food webs of Lake Fryxell and Ace Lake, Antarctica. Both lakes lack vertebrates, insects and most organisms commonly found in temperate regions. A species of copepod is the only metazoan and top predator in Ace Lake whereas a species of rotifer is the only metazoan and top predator in Lake Fryxell. Carbon flow was calculated to maintain steady state biomass, given basal metabolism, assimilation and production efficiencies, and predation loss of each trophic group. The Fryxell model was based on observations from 18 dates collected over two austral summers (n=90; 1999-2000 and 2001-2002). The Ace model was based on two, whole-year sampling regimes in 1996-1997 and 1999-2002 (n=304). Results indicated high levels of variation in both lakes despite the lack of vertical mixing in the water column, little variation in temperature, and a semi-permanent to permanent ice cover. The presence of rotifers had little impact on energy flow through the Fryxell community, suggesting little influence of the top predator. In contrast, the presence of copepods had significant impacts on energy flow in Ace Lake. The relative amount of total carbon flow through each community that was assimilated by the top predator was small in both lakes, averaging <1% of the total carbon flow in Fryxell and <2% in Ace.
Key words: Food web, microbial loop, carbon dynamics, model