The Effect of Wastewater Effluent and a Flood Event on Resident Amphibian and Reptilian Communities

Dean, Roy Blake
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Properly treated wastewater effluent, although usually considered detrimental to the surrounding environment, may actually have beneficial qualities. Information is presented on the effect of wastewater effluent on amphibian and reptilian communities. Data were collected in Mineola, Texas, from May to August 2000 under the IACUC permit 5QGbKa_02. Fourteen days into the collection period, 16 June, a flood occurred that prevented collection for 12 days. The same data that addressed the effect of wastewater effluent on vertebrate communities was used to study the effects of the flood on the same community. The objectives of this study were to determine if there is a significant difference in the herpetofauna communities of the experimental and control areas and between pre-flood and post-flood periods. Data from fifty-three reptiles and 489 amphibians were collected using drift fence arrays, minnow traps, and incidental observation. Three drift fence arrays and nine minnow traps were used in control and experimental areas. The experimental area was located on Dodson Creek downstream from the effluent discharge, while the control area was located upstream from the discharge point source. Plant biomass and water chemistry data were collected at the study site. The Mann-Whitney U test was used to test for the effect of wastewater on herpetofauna communities. The Chisquaretest was used to determine differences in composition of pre-flood and postflood herpetofauna communities. The abundance of amphibians was significantly greater than that of the control area (U = 665.5, U1 = 2038.5, p < 0.0001). The abundance of reptiles in the control and experimental areas were similar (U = 1229, U1 = 1475, p = 0.4239). There was a significant increase in amphibian :frequency after the flood event (X2 = 7 .609, p < 0.05), but no significant difference in reptile :frequency before or after a flood event (X2 = 1.8148, p > 0.05). Ninety percent of amphibians occurred in the experimental area probably due to the fertilizing effects of the treated effluent and subsequent optimal habitat. Only forty-three percent of the reptiles were found in the experimental area, possibly due to competition pressure of optimal areas. Sixty-nine percent of the amphibians were collected after the flood which may be attributed to the decrease of herbaceous vegetation and lack of home range. Reptiles showed opposite trends from amphibians in that 63 percent were found pre-flood. The discrepancy could be attributed to the possibility that both preflood communities were replaced by a smaller community of individuals from upstream.
Reptiles, Amphibians, Sewage disposal, Rivers, Lakes, Water pollution
Dean, R. B. (2002). <i>The effect of wastewater effluent and a flood event on resident amphibian and reptilian communities</i> (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.