SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Time: 2:45:00 PM
Location: Oak Bay
 
DefewEC, Gatty Marine Laboratory, St Andrews, United Kingdom, ecd2@st-andrews.ac.uk
Hagerthey, S, E, Center for Freshwater Studies, University of Alabama, Tuscaloosa, USA, sehagert@bama.ua.edu
Paterson, D, M, Gatty Marine Laboratory, St Andrews, United Kingdom, dp1@st-andrews.ac.uk
 
THE INFLUENCE OF GRAZING ON MICROPHYTOBENTHOS UNDER DIFFERENT NUTRIENT AND TEMPERATURE REGIMES
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Epipelic diatoms dominate the microphytobenthos of estuarine sediments where they drive ecological processes such as primary productivity, secondary production and sediment stability. Grazing activity regulates community level processes by influencing assemblage species composition and biomass. This has been confirmed in a limited number of studies using microphytobenthos. However, it has also been shown that predation effects on species richness differ under contrasting nutrient conditions (e.g. the grazer reversal hypothesis). These interactions have not yet been examined for depositional systems. This laboratory study investigated the relative impact of grazing by two macrofaunal species, having quite different feeding strategies and bioturbation effects, on assemblage composition. The grazing influence was examined under different nutrient and temperature regimes since environmentally-regulated structural differences could alter grazing impacts and grazer impacts may also mask environmental effects. It was found that, regardless of temperature or nutrient status, assemblages grazed by Corophium volutator tended toward a similar species composition, whereas Hydrobia ulvae had little effect. This work indicated a clear interaction between grazing mechanism, nutrient status and assemblage composition.