Graduation Year

2004

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Biology

Major Professor

McCoy, Earl D.

Co-Major Professor

Mushinsky, Henry R.

Keywords

wellfield, reproductive success, tadpole, amphibian, biological monitoring

Abstract

Understanding wetland responses to human perturbations is essential to the effective management of Florida's surface and ground water resources. Southwest Florida Water Management District (SWFWMD) Rules (Chapter 40D-2.301(c) FAC) prohibit adverse environmental effects to wetlands, fish and wildlife caused by groundwater withdrawal. Numerous studies have documented the responses of biological attributes across taxa and regions to human disturbance. Biological assessment can provide information about ecological condition. Based on long-term monitoring conducted by the SWFWMD, the anthropogenic changes observed on the Starkey Wellfield are attributed to groundwater withdrawal. Biological indicators are species, species assemblages, or communities whose presence, abundance, and condition are indicative of a particular set of environmental conditions.

Monitoring early indicators of ecosystem stress may shorten response time by shifting attention to the relatively quick response of sensitive species. Species used to assess biological condition should be abundant and tractable elements of the system that provide an early, diagnosis. Regulatory requirements within 40D-2 F.A.C. dictate an extensive analysis be conducted twice yearly on wetlands within all wellfields. This quantitative analysis provides information on the wetland plant community through the collection of eighteen categorized vegetative and physical variables. Because of the size of the area in which monitoring is required and the large number of wetlands, a rapid qualitative monitoring method was developed using vegetation and physical variables to classify wetlands into one of three categories based on their perceived health.

Wetland plants have many characteristics suited to assessments of biological condition including their diversity, taxonomy, distribution, relative immobility, well developed sampling protocols, and, for herbaceous species, their moderate sensitivity to disturbance (U.S. EPA 2002, Doherty et al. 2000). Because amphibians occupy both aquatic and terrestrial habitats in their life history, have physiological adaptations and specific microhabitat requirements, they are considered to be extremely sensitive to environmental perturbations and excellent barometers of the health of the aquatic and terrestrial habitats in which they reside (Vitt et al. 1990, Wake 1998, Blaustein 1994, Blaustein et al. 1994). The purpose of my study was to 1) compare a qualitative method of wetland vegetation monitoring to a quantitative method, 2) document the reproductive success of anurans, and 3) compare anuran reproductive success to the vegetation monitoring results on the

J. B. Starkey Wellfield (SWF). The results are published in chapters, with each chapter addressing one of the topics stated above. The results show a rapid, qualitative measure of wetland health is useful for the determination of severely affected wetlands. The anuran reproductive success reflected similar results. The results show that wetlands can be categorized based solely on amphibian reproductive success variables. The anuran categorization, qualitative vegetative categorization, and quantitative vegetative categorization overlap on the high and low success wetlands. The low degree of overlap observed in the intermediate category could be attributed to fish predation in a wetland otherwise suited for amphibian reproduction, natural variability in the two years of anuran data collected or lag time inherent in vegetative monitoring. Strong correlative evidence suggests hydroperiod regulates anuran reproductive success on the J. B. Starkey Wellfield.

The average length of inundation was correlated with the number of tadpoles captured per unit effort and the number of tadpole species captured per year (R=0.73, p<.01; R=0.70, p<.05). The average Julian date of inundation was negatively correlated with the same two tadpole variables (R=0.81, p<.01, R=0.78, p<.01). The Julian date of inundation at which breeding attempts stopped and no tadpoles were observed was weeks within the published breeding season for many species. I detected a correlation between the number of species calling in each wetland and the number of tadpole species captured per year (R=0.87, p<.001) suggesting call censuses may be used at this site to estimate anuran reproductive success if enough well-timed observations are made.

These findings will allow resource managers and regulators to evaluate and possibly refine land management practices, including existing monitoring methods, and water policy to meet the needs of resident amphibians at the J.B. Starkey Wellfield.

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