The Effect of Wastewater Effluent and a Flood Event on Resident Amphibian and Reptilian Communities
Date
2002-05
Authors
Dean, Roy Blake
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Abstract
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.
Description
Keywords
Reptiles, Amphibians, Sewage disposal, Rivers, Lakes, Water pollution
Citation
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.