Invasive aquarium fish transform ecosystem nutrient dynamics

Abstract

Trade of ornamental aquatic species is a multi-billion dollar industry responsible for the introduction of myriad fishes into novel ecosystems. Although aquarium invaders have the potential to alter ecosystem function, regulation of the trade is minimal and little is known about the ecosystem-level consequences of invasion for all but a small number of aquarium species. Here, we demonstrate how ecological stoichiometry can be used as a framework to identify aquarium invaders with the potential to modify ecosystem processes. We show that explosive growth of an introduced population of stoichiometrically unique, phosphorus (P)-rich catfish in a river in southern Mexico significantly transformed stream nutrient dynamics by altering nutrient storage and remineralization rates. Notably, changes varied between elements; the P-rich fish acted as net sinks of P and net remineralizers of nitrogen. Results from this study suggest species-specific stoichiometry may be insightful for understanding how invasive species modify nutrient dynamics when their population densities and elemental composition differ substantially from native organisms. Risk analysis for potential aquarium imports should consider species traits such as body stoichiometry, which may increase the likelihood that an invasion will alter the structure and function of ecosystems.

Quantifying the top-down and bottom-up effects of a non-native grazer in freshwaters

“…The ecological effects of introduced fishes can be severe and can range from behavioral changes in native species, the extirpation of native fish communities, the restructuring of entire food webs, and the alteration of biogeochemical processes (Capps and Flecker 2013a;Cucherousset and Olden 2011). Data on the ecological impacts of invasive species are limited for all but a few taxa (Kulhanek et al 2011a;Strayer 2012), but high densities of low-trophic position taxa, such as grazers, are predicted to have strong effects on energy pathways in invaded systems.…”

“…Stream discharge averaged *1,600 L s -1 during the study period and water temperature in the river ranged from 21 to 28°C. Loricariid density was 2.3 ± 3.4 m -2 (mean ± SD) and loricariid areal biomass was 225 ± 45 g m -2 (mean ± SD) in the study reach during daylight hours in 2010 (Capps and Flecker 2013a). Nutrient concentrations in the study reaches were low to moderate (average: NH 4 ?…”

“…Loricariids frequently attain high population densities in invaded systems (Capps and Flecker 2013a;Mendoza et al 2009). In Mexico, the most common introduced genus of loricariid is Pterygoplichthys, a grazer first documented in the Chacamax River in 2004 (Wakida-Kusunoki et al 2007).…”

Ecological relevance of biomarkers in monitoring studies of macro-invertebrates and fish in Mediterranean rivers

“…Specifically, three theories (biological stoichiometry, the metabolic theory, and the geometric nutritional ecology) try to explain how food-webs are structured based on the balance of multiple chemical elements between individuals and the environment (Allen and Gillooly, 2009;Urabe et al, 2010). A practical example is a study developed in Mexico by Capps and Flecker (2013) that used the elemental composition and excretion rates of the invasive catfish Pterygoplichthys spp. to assess its effect on river biogeochemistry.…”

Does the Growth Rate Hypothesis Apply across Temperatures? Variation in the Growth Rate and Body Phosphorus of Neotropical Benthic Grazers

“…Much empirical work on this topic has been conducted in tropical streams, where grazers can substantially affect aquatic ecosystems through their feeding, recycling, and storage of nutrients (e.g., Taylor et al, 2006;McIntyre et al, 2008;Capps and Flecker, 2013). However, these consumer-mediated impacts are sensitive to changes in the biological community (Capps et al, 2015a).…”