Estimates of Phosphorus and Nitrogen Cycling by Fish Using a Bioenergetics Approach

Abstract

A modelling approach based on bioenergetics was used to estimate the role of fish in nutrient recycling. Phosphorus excretion (P U ) and nitrogen excretion by young-of-the-year (YOY) and older yellow perch (Perca flavescens) were estimated for a limnetic system: Lake Memphremagog. This model successfully predicted P U by comparison with previous estimates for yellow perch. YOY fish contributed more to limnetic nutrient cycling through excretion than older age-classes, and YOY fish could also serve as an important P sink relative to algal sinking losses. Volumetric P U by YOY yellow perch reached a maximum of 0.3 μg P∙L −1 ∙d −1 ; N excretion peaked at 10 μg N∙L −1 ∙d −1 . The ratio of excreted N: P varied fourfold during the summer. P U estimates were also sensitive to changes in fish P content, for which few values have been reported for early life stages.