Stoichiometry of nutrient excretion by fish: interspecific variation in a hypereutrophic lake

Abstract

This study investigates how nutrient cycling rates and ratios vary among fish species, with a particular focus on comparing an ecologically dominant detritivore (gizzard shad) to other fishes in a productive lake. We also examined how nutrient cycling rates are mediated by body size (as predicted by allometry theory), and how variation in nutrient cycling is related to body and food nutrient contents (according to predictions of ecological stoichiometry). As predicted by allometry, per capita nitrogen and phosphorus excretion rates increased and mass-specific excretion rates decreased, with increasing mass. Body phosphorus content was correlated with body mass only in one species, bluegill. Contrary to stoichiometric predictions, there was no relationship between body P and mass-normalized P excretion rate, or between body N:P and excreted N:P, when all individuals of all species were considered. However, at the species level, we observed some support for a body nutrient content effect on excretion as predicted by stoichiometry theory. For example, gizzard shad had lower body P (high body N:P) and also excreted P at higher rates (lower N:P) than bluegill, which had high body P (lower body N:P). We applied the Sterner (1990) homeostatic stoichiometry model to the two most common species in the study Á gizzard shad and bluegill -and found that food N:P had a greater effect than consumer body N:P on excreted N:P. This indicates that, in terms of variation among these species, nutrient excretion may be more of a function of food nutrient content than the nutrient content of the consumer. These results suggest that stoichiometry can provide a framework for variation among species in nutrient cycling and for evaluating the ecosystem consequences of biodiversity loss.

Compound feeds and cereals as potential tools for improved carp Cyprinus carpio production

“…In our study, we found that content of dry matter and phosphorus was generally higher in harvested fish than in stocked fish. This is in accordance with the literature data (Shearer 1984, Deegan 1986, Torres & Vanni 2007, which shows that phosphorus varies in a fish's body from early to later stages of growth. In our previous study (Hlaváč et al 2016), we found that carp body phosphorus and nitrogen content varied from early to later stages of growth, with a noticeable increase in dry matter content during the growing season.…”

“…Such data would improve model output and help to clarify the role of fish in nutrient cycles and budgets (Sterner & George 2000, Dantas & Attayde 2007. Fish body chemical content is species-specific (Sterner & George 2000, Tanner et al 2000, Griffiths 2006) and varies greatly throughout the year depending on a range of factors, including fish length and mass (Dantas & Attayde 2007, Torres & Vanni 2007. In our study, we found that content of dry matter and phosphorus was generally higher in harvested fish than in stocked fish.…”

Nutrient recycling by coastal macrofauna: intra- versus interspecific differences

“…Torres & Vanni 2007). However, these correlations were stronger when considering the 3 classes of invertebrates and fish than when considering only the 8 fish species.…”

“…To go further it would be necessary to compare excretion rate differences from a bioenergetic perspective by accounting for N and P body concentrations and to compare them with food item composition , Torres & Vanni 2007. Indeed, excretion rates are driven by ecophysiological constraints and reflect the imbalance between N and P inputs from food and the demand on them for metabolism and growth.…”

“…Vanni 2002, Hood et al 2005, Torres & Vanni 2007, McIntyre et al 2008, while only few studies have focused on marine ecosystems (Meyer & Schultz 1985, Haertel-Borer et al 2004, Layman et al 2011. Organisms differ in their ability to recycle nutrients , Hood et al 2005, as a result of the imbalance between their diet (i.e.…”