PARENT SESSION
Contributed Oral Session 10: Aquatic Trophic Systems I
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal
Food webs and parasites: Biomass patterns in a freshwater community.
Hernandez, Alexander*,1, Sukhdeo, Michael1, 1 Rutgers, The State University, New Brunswick, NJ, USA
ABSTRACT- Natural systems are inherently complex, but study of the dynamics and processes that help shape these systems can be simplified by thinking of them in terms of food webs. Studies that include parasites show that food web structure changes when parasites are considered. However, how parasites fit into patterns of community function remains a relatively unexplored question. Eltonian pyramids are a way to represent patterns of energy flow through food webs and they can be constructed by estimating the numbers or biomass of species at different trophic levels. We studied food webs from a stream community from the New Jersey Pinelands over 8 continuous seasons, and focused on the 4 most abundant helminth parasite species infecting fish and macroinvertebrates within this community. Acanthocephalus sp. and Fessisentis sp. (Acanthocephala) are parasites of the intestine of fishes and utilize isopods as intermediate hosts. Phyllodistomum sp. and Crepidostomum sp. (Digenea) are parasites of the fish urinary bladder and intestine, respectively, and can use fingernail clams, caddis flies, mayflies, or crustaceans as intermediate hosts. We measured the number and biomass of parasites and their macroinvertebrate and fish hosts, and found that parasites form an inverted pyramid of numbers, which is consistent with Elton's original predictions. However, biomass patterns form the familiar trophic pyramid, and parasite biomass comprises the equivalent of 5-15% of the biomass in the top trophic level. Measures of total parasite biomass for any ecosystem are rare, and these results suggest that parasite biomass are limited by thermodynamic principles of energy flow in biotic systems. Recent modeling efforts suggest that the slope of biomass pyramids provide a measure of ecosystem stability, and our results suggest that parasite biomass is not negligible and that adding parasites to food webs will add rigor to food web studies.
Key words: food webs, parasites, biomass, energy flow