Influence of seasonality and rooted aquatic macrophyte on periphytic algal community on artificial substratum in a shallow tropical reservoir

Abstract

The interrelationships of periphyton with macrophytes and phytoplankton are quite complex and poorly investigated in tropical reservoirs. We investigated the changes in the periphytic algal community structure at equidistant sites with and without macrophyte growth in four seasons in a shallow tropical reservoir. Our main objective was to evaluate the influence of the presence and absence of macrophytes, as well as seasonality, on changes in the periphytic algal community. Glass slides were submerged for 30 days for periphyton colonization. Environmental data on physical and chemical variables, periphyton, phytoplankton chlorophyll a, and macrophyte coverage were recorded for each site. Periphyton structure was analyzed for chlorophyll a, AFDM, algal density, biovolume, species richness, and N:P molar ratio. Principal component analysis mainly ordinated sites along a gradient of temperature and nutrient concentration. Cluster analysis showed that the lowest similarity of periphytic algal species composition was between seasons. The highest periphyton biomass and algal abundance occurred in the dry season when there was reduced macrophyte coverage and phytoplankton chlorophyll a. Periphytic algal descriptor species and total density were more sensitive to the presence/absence of macrophytes than were other structural attributes. We found that the periphytic algal community structure on artificial substratum was influenced by seasonality and presence of macrophyte (Nymphaea spp.), as well as by the interaction of these factors. Our results highlight the importance of macrophyte coverage and phytoplankton chlorophyll a to the periphytic algal community structure in the littoral zone. The relationship between primary producers needs further investigation in shallow tropical reservoirs.