Nutrient sequestration by a highly invasive armored catfish in a Florida spring ecosystem.

Understanding the effects of species invasions on vulnerable freshwater habitats is crucial to protecting those ecosystems. The vermiculated suckermouth sailfin armored catfish, an abundant, invasive grazer in Florida springs and around the world, may interact with native communities in complex ways, including alteration of nutrient availability, which in turn may influence primary production, with cascading effects through the food web. Armored catfish may differ from native fishes in their body nutrient content because of their high proportion of bony material; therefore, increasing densities of armored catfish may shift nutrient availability to primary producers due to their consumption, excretion, and egestion of nutrients. To evaluate this, we measured N:P ratio of catfish tissues compared to the N:P ratios of two abundant native species and found that catfish had a significantly lower body N:P than native species. We also measured the N and P in catfish gut contents and excreta and found that posterior gut (egesta) N:P was significantly higher than anterior gut (ingesta) N:P. Finally, we measured excreted N and P, finding that excreted N:P was high. These data demonstrate that, because high proportions of P are retained in the bodies of invasive armored catfish, they are a P sink and are, therefore, more likely to limit P availability than native fishes in freshwater spring ecosystems both in Florida and worldwide. [ABSTRACT FROM AUTHOR]