19 Periphytic algae as bioindicators of nitrogen inputs in lakes

Abstract

Increased nitrogen levels has been shown to be a problem in Southern New Jersey lakes, with anthropogenic loadings being the most serious concern (Aber, 1992). It has been suggested that biomass, diversity, and community structure of periphytic algae are good biotic indicators for monitoring water quality and nutrient enrichment in fresh water lakes. (Biggs, 1989). Since, for algae and many other aquatic organisms, nitrogen is one of the most important factors for growth, a good correlation it is expected between nitrogen loading and algal growth. In this bench‐scale microcosm study the periphytic community was analyzed using chlorophyll a, dry‐ash weight biomass and cell counts, as well as the diversity and community structure for a six‐month period, in three tanks with different nitrogen levels (control=non‐detectable; low and high). Physical (T/DO/pH) and chemical (nutrients) parameters were measured monthly. Biological parameters were compared with the different nitrogen loading using correlation analysis to show whether nitrogen is a factor in the over‐enrichment of New Jersey lakes. To compare the bench‐scale microcosm study with the natural settings periphytic algae from two Southern New Jersey lakes, Oswego Lake (no nitrogen) and Oakford Lake (high nitrogen), were also collected during fall of 2002 to summer of 2003.