Abundant feces from an exotic armored catfish, Pterygoplichthys disjunctivus (Weber, 1991), create nutrient hotspots and promote algal growth in a Florida spring

作者：Rubio Vanessa Y; Gibbs Melissa A^*; Work Kirsten A; Bryan Clifford E

来源：Aquatic Invasions, 2016, 11(3): 337-350.

DOI：10.3391/ai.2016.11.3.11

• armored catfish
• feces
• nutrient leaching
• invasive species

Florida springs are relatively unique, stable systems that have experienced increasing and synergistic threats from reductions in water flow, nutrient additions, and invasions of exotic species. The purpose of this study was to evaluate the effects of the egesta of one common exotic loricariid catfish species on nutrient availability and periphyton growth in a central Florida spring. Pterygoplichthys disjunctivus produces copious feces that, unlike excreted nutrients, continue to contribute to nutrient loading when the fish are not present. Fecal abundance, measured using photographs of randomly distributed quadrats, was found to be high in the spring run (total estimates for the spring run averaged 6.1 x 10(5) cm(3) feces). We measured extractable fecal nutrients (N-NO3-, TKN, P-PO43-) from feces collected both from the guts of live fish and from the spring benthos, and leaching rates of nutrients from feces in laboratory flumes. We also measured direct algal growth of feces incubated in nutrient broth and the potential of fecal nutrients to stimulate algal growth downstream in arrays deployed in situ. We found that although each fecal sample leached minute quantities of nutrients, the total quantity of nutrients released in the spring run from local accumulations of feces was substantial. Furthermore, even the relatively small quantities of nutrients released from fecal material from one fish were sufficient to increase algal growth in the in situ experimental arrays. Leachate from P. disjunctivus fecal deposition could create transient biogeochemical hotspots lasting considerably longer than those described for excreta. Although the contributions of the extractable fecal nutrients were small relative to the overall nutrient load to the spring (TKN = 0.18-3.64%, P-PO43- = 2.78-22.2%), these fecal hotspots typically occurred in low-flow areas with structure where algae tend to accumulate and nutrient influx of spring water is slow. Therefore, it is likely that P. disjunctivus fecal leachate significantly alters nutrient availability for algae in this spring system.

• 出版日期2016-7