Type of suspended clay influences lake productivity and phytoplankton community response to phosphorus loading

Abstract

The effects on phytoplankton and limnetics of two different types of suspended sediments and their interactions with P loading were tested in a small North Carolina piedmont lake. Limnocorrals were used in a complete, triplicated six-treatment, blocked design. Treatments were loaded with P, kaolinitic clay (K), K+P, montmorillonitic clay (M), and M+P. M caused more turbidity and stayed in suspension longer than K. Consequently, the light-dependent parameters, net community productivity (NCP), chlorophyll concentration, and algal density were lowest in the M and highest in the P treatment. Combined P and clay loading promoted clearing for both sediments and mitigated their effects on algal densities and NCP. Flagellated algae and nonfilamentous cyanophytes dominated the control community. The P treatment had blooms of Anabaena. Without fertilization, both clays resulted in sparse, flagellate-dominated communities. The M+P community, like that of the P treatment, was dominated by Anabaena, but total algal densities were suppressed. In contrast, the K+P community lacked Anabaena and was similar to the control in algal quantity and composition.