SS3.10 Ecological Implications of Terrestrial Inputs into Lakes and Ponds
Date: Tuesday, June 11, 2002
Time: 3:15:00 PM
Location: Esquimalt
 
Moreno-AmichR, University of Girona, Girona, Spain, ramon.moreno@udg.es
Brucet, S, , University of Girona, Girona, Spain, sandra.brucet@udg.es
Quintana, X, D, University of Girona, Girona, Spain, xavier.quintana@udg.es
 
CHANGES IN THE SHAPE OF AQUATIC INVERTEBRATES’ BIOMASS-SIZE SPECTRA AT ECOLOGICAL SCALING IN A FLUCTUANT ECOSYSTEM (EMPORDĄ WETLANDS, NE SPAIN)
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Organism abundance is inversely proportional to size, as show the biomass-size spectrum at the primary scaling (whole community). There is a secondary or ecological scaling identifiable at functional-group level (phytoplankton, zooplankton, fish) more closely linked to food requirements in relation to biomass density distributions and predator-prey size ratios. This ecological scaling is more obvious in lightly-structured and fluctuating systems, where the shape is variable from lineal to curved according to the ecological situation. The biomass spectrum, at ecological scaling, of free-living invertebrates in a fluctuating basin of Empordą wetlands was analyzed by adjustment to a model based on the Pareto distribution. Under flooding conditions biomass-size spectra fit a lineal model (Pareto Type I) better, whereas in confinement conditions fit better a no lineal one (Pareto type II). These results suggest that under flooding conditions, nutrient and OM inputs cause population growth, especially of small-sized organisms, resulting in a linear spectrum. During confinement conditions interactions between species would acquire more relevance due to the lack of resources, favouring the displacement of biomass toward larger sizes. The result is a curved spectrum and a decrease of diversity.