Effects of non-algal turbidity on cyanobacterial biomass in seven turbid Kansas reservoirs

Abstract

One of the most visible consequences of eutrophication in freshwater lakes is an increase in the biomass of cyanobacteria. While growth of cyanobacteria has been shown to be coupled to water column concentrations of total phosphorus (TP) in natural lakes, the ecological behavior of cyanobacteria in turbid impoundments is less well understood. Patterns of cyanobacterial biovolume in 7 turbid Kansas (USA) reservoirs exhibited overlap with published data from natural lakes in North America. Non-algal turbidity (NAT) influenced the relationship between cyanobacteria and TP in these systems. Relative to yields predicted from natural lakes, the biomass of cyanobacteria per unit TP was typically higher in the reservoirs, except in those systems that had exceptionally high levels of NAT (>∼2.0 2/m) where observed concentrations were mostly lower than predicted. A more consistent pattern was observed with respect to the effects of NAT on yields of chlorophyll-a per unit TP in the reservoirs: across almost the entire NAT gradient, observed chlorophyll-a concentrations were typically lower than those predicted from natural lakes. Taken together, our results confirm that NAT plays an important role in regulating relationships between TP and phytoplankton biomass in reservoir ecosystems.