The influence of submerged macrophytes on sedimentary diatom assemblages

Abstract

Submerged macrophytes are a central component of lake ecosystems; however, little is known regarding their long-term response to environmental change. We have examined the potential of diatoms as indicators of past macrophyte biomass. We first sampled periphyton to determine whether habitat was a predictor of diatom assemblage. We then sampled 41 lakes in Quebec, Canada, to evaluate whether whole-lake submerged macrophyte biomass (BiomEpiV) influenced surface sediment diatom assemblages. A multivariate regression tree (MRT) was used to construct a semiquantitative model to reconstruct past macrophyte biomass. We determined that periphytic diatom assemblages on macrophytes were significantly different from those on wood and rocks (ANOSIM R=0.63, P<0.01). A redundancy analysis (RDA) of the 41-lake data set identified BiomEpiV as a significant (P<0.05) variable in structuring sedimentary diatom assemblages. The MRT analysis classified the lakes into three groups. These groups were (A) high-macrophyte, nutrient-limited lakes (BiomEpiV ≥525μg·L-1; total phosphorus [TP] <35μg·L-1; 23 lakes); (B) low-macrophyte, nutrient-limited lakes (BiomEpiV <525μg·L-1; TP <35μg·L-1; 12 lakes); and (C) eutrophic lakes (TP ≥35μg·L-1; six lakes). A semiquantitative model correctly predicted the MRT group of the lake 71% of the time (P<0.001). These results suggest that submerged macrophytes have a significant influence on diatom community structure and that sedimentary diatom assemblages can be used to infer past macrophyte abundance. © 2011 Phycological Society of America.