Original paper

Interrelationships between phosphorus loading and common carp in the regulation of phytoplankton biomass

Chumchal, Matthew M.; Drenner, Ray W.

Abstract

The interrelationship between phosphorus loading and common carp in the regulation of phytoplankton biomass was examined in a four-week summer mesocosm experiment. The factorial design consisted of two levels of phosphorus loading (with/ without) cross-classified with two levels of common carp (with/without). At the conclusion of the mesocosm experiment, common carp were removed from mesocosms and a nutrient excretion and defecation trial was performed. A significant interaction effect was detected between phosphorus loading and common carp for chlorophyll-a (a proxy for phytoplankton biomass), total nitrogen, and nitrogen : phosphorus. Common carp had modest effects on chlorophyll-a in mesocosms without phosphorus loading but relatively large enhancement effects on chlorophyll-a in mesocosms with phosphorus loading. Common carp increased total nitrogen in mesocosms with phosphorus loading but had no effect on total nitrogen in mesocosms without phosphorus loading. The synergistic effect of phosphorus loading and common carp on chlorophyll-a was due to nitrogen excretion and defecation by common carp and the subsequent enhancement of nitrogen in mesocosms with phosphorus loading.

Keywords

mesocosm experimentnutrientsphytoplankton productionnitrogenexcretion