CHANGES IN ALGAL COMMUNITY SUCCESSION IN DIFFERENT NUTRIENT REGIMES

Abstract

Manoylova, K. M. & Stevenson, R. J.Department of Zoology, Michigan State University, East Lansing, MI 48824The purpose of our experiment was to assess changes in relative abundances of algal species during community development under different nutrient concentrations. In artificial streams N and P concentrations were mani‐pulated, when P and N were saturated respectively. Mean algal relative abundance per treatment was assessed. Algal species with relative abundances at least 10 % in any treatment were analyzed in detail. More detailed response was discerned based on the species composition of the benthic algal community than results from total density. Cymbella affinis Kutz. had significantly high (ANOVA, p<0.05) presence in all low nutrient concentrations. The highest relative abundance of this species was 33% at 64 μg/L N and 43% at 2 μg/L P and decreased with increase in the nutrient concentrations. Along the N gradient we had significant (p<0.001) algal species response to the six treatments. Microcystis aeruginosa Kuetz., was present at low and median N concentrations. Some green filamentous algae and known euthrophic diatom species like, Nitzschia palea (Kutz.) W. Smith, were dominant at high N concentrations. Along the P gradient the response of the community was again significant (p<0.001) in all treatments. Diatoms had the highest relative abundances overall; coccoid bluegreen and filamentous green were present when P was greater than 32 μg/L. Following cause‐effect relationships in relative algal abundance in known N and P regimes in artificial streams contributes to our understanding of algal succession when N and P co‐vary in nature.