PARENT SESSION
Contributed Oral Session 5: Aquatic Ecology: System Heterogeneity
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Vertical distribution of epiphyton metabolism in different types of macrophyte stands.
Vis, Chantal*,1, Hudon, Christiane1, Carignan, Richard2, 1 St. Lawrence Centre, Montreal, Quebec, Canada2 Universite de Montreal, Montreal, Quebec, Canada
ABSTRACT- We measured attached algal productivity and respiration within different types of macrophyte stands over two growing seasons in Lake St.Pierre, a large fluvial lake of the St. Lawrence River. Based on this data, we modelled the vertical distribution of epiphyton primary production and respiration to examine how the balance between gross production and respiration varies with macrophyte growth-form and other environmental factors. In canopy-forming stands (e.g. Potamogeton spp.), the top half of the water column had a P/R > 1, whereas the bottom portion of the stand had a P/R < 1. In stands in which the majority of macrophyte biomass or available substratum was in the lower part of the water column (e.g. Vallisneria americana), net community production of epiphytes could be either positive or negative, depending on light conditions. Low water levels in 2001 led to the compression of macrophyte canopies in the water column, which in turn resulted in stronger depth gradients in epiphyton net metabolism. Results emphasise the importance of integrating the vertical complexities in light and biomass of macrophyte stands when scaling-up estimates of epiphyton production, to determine its contribution to whole-system production.
Key words: epiphyton, macrophyte, production, respiration