Volin, John C.

The aim of this study was to determine the effects of nutrient supply and artificial
defoliation on the growth rate of water hyacinth. The plants were subjected to two levels
of nutrient (high and low) and three levels (0%, 10% and 80%) of defoliation treatment.
The effect of the nutrient and repeated defoliation treatments was detem1ined after six
weeks. Ten percent defoliation did not show any significant difference from control
plants in biomass allocation or relative growth rate (RGR) in either nutrient
concentration, while 80% defoliation caused a significant decrease in the final RGR
under high and low nutrient treatments. High nutrient treatment resulted in higher RGR
and allocation to asexual reproduction, resulting in higher biomass accumulation
compared to the low nutrient treatment, which had higher root growth and allocation to
sexual reproduction. My data provide evidence that water hyacinth can fully compensate
to low levels of defoliation.

I conducted a greenhouse study in order to examine the effects of hydrology
and its interaction with gibberellic acid (GA3) on the invasive exotic Lygodium
microphyllum (Old World climbing fern) growth and physiology. Three hydrological
(flood, drought and field capacity) and three hormonal (gibberellic acid, paclobutrazol
and water) treatments were studied using a 3x3 factorial experimental design. Plants
under flooded conditions had a significantly lower relative growth rate compared to
plants under field capacity or drought. Plants under flooded conditions showed a
significantly lower specific leaf area and area-based photosynthetic rate than plants
under field capacity and drought treatments, resulting in significantly lower massbased
photosynthesis. Overall, the variation in growth response to treatments was
most explained by mass-based photosynthesis (r^2=0.66). Treatments with gibberellic
acid or paclobutrazol (GA inhibitor) resulted in no differences in growth as compared
to untreated plants.

Intensely maintained turfgrass landscapes have some potential for loss of fertilizer nitrogen (N) in both runoff and leaching. Lower maintenance vegetation used in mixed-species landscapes may reduce N leaching and runoff, which is important for reducing environmental pollution of surface and ground waters. However, few studies have examined this paradigm. Therefore, we constructed a field-scale facility to compare fertilizer N runoff and leaching between St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze cv. 'Floratam') and a mixed-species landscape designed by the Florida Yards and Neighborhoods (FYN) program. A blended granular fertilizer was applied at a rate of 300 and 150 kg N ha-1 yr -1 on the turfgrass and mixed-species, respectively. During the 12-month study only one minor runoff event occurred (<0.2 cm) and N losses were insignificant. Annual N leaching losses were significantly greater on the mixed-species landscape, resulting in 4.80 g N m-2 compared to 0.41 g N m-2 for the St. Augustinegrass.

The Everglades ecosystem is home to two species of freshwater crayfish: the Everglades crayfish Procambarus alleni and the slough crayfish Procambarus fallax. These species play a key ecological role by transporting energy from primary producers to higher trophic levels. Understanding the factors that regulate crayfish growth is an essential step in restoring their productivity in the Everglades ecosystem. In order to determine the effect of hydroperiod on crayfish growth, I collected crayfish from the Florida Everglades and subjected them to one of three hydroperiod treatments. The growth of both crayfish species in reduced hydroperiod treatments was significantly less than those in long hydroperiod treatments. Procambarus alleni had a significantly faster initial growth rate than P. fallax, which may give it a competitive advantage in shorter hydroperiod marshes and help explain the distributions of these two species. The results of this study indicate that lengthening hydroperiods in the Everglades ecosystem may have a positive effect on crayfish productivity.

An innovative technique of evaluating resource selection for black rhino (Diceros bicornis) was used to assess the population utilization distribution (PUD) within a rhino sanctuary in Liwonde National Park, Malawi. The PUD enabled an evaluation of responses to habitat variables over a spatial gradient of resource selection. A Geographic Information System (GIS) was constructed using vegetation, browse availability, roads, rivers, water holes and satellite imagery. Linear models were developed to quantify habitat variables within the black rhino sanctuary and park. The sanctuary model was calibrated within a known core area (R^2=0.42, P<0.001), validated in a second area (R^2=0.56, P<0.001) within the sanctuary and, subsequently, used to predict potential black rhino habitat within the remaining sanctuary boundaries. The model for the entire Liwonde National Park predicted additional black rhino habitat (R^2=0.25, P<0.05). Population utilization distribution was found to be a powerful conservation tool for determining suitable black rhino habitat.

The Big Cypress Swamp and the Everglades of South Florida are inherently oligotrophic ecosystems that in recent decades have been subjected to increasing agricultural nutrient inputs. While extensive research regarding deleterious effects of nutrient impacts has been conducted in the phosphorus-deficient Everglades, there is a lack of research in Big Cypress Swamp. This 12-month field study assessed the responsiveness of Taxodium distichum, Fraxinus caroliniana, and herbaceous vegetation to increased nutrient levels in Big Cypress Swamp. Six nutrient treatments (Control, N, P, K, 2K, and PxK) were applied to the soil surrounding these trees. F. caroliniana had higher photosynthetic rates with 2K treatments and higher growth rates with PxK treatments. T. distichum had higher Leaf Area Index in the P and PxK treatment but did not exhibit other responses to treatment. Herbaceous vegetation showed little response to treatments. This study concluded that potassium may be co-limiting in this ecosystem.

Several models for the evolution of maternal inheritance of mitochondria predict that the sperm mitochondria undergo oxidative damage and pose a threat to the developing embryo. Here, I test the hypothesis that the sperm are damaged by reactive oxygen species generated by aerobic sperm activity. In my first experiment, I found no significant difference in fecundity between worms fertilized by old versus young sperm, suggesting that the sperm nuclear genome is not affected by the extent of sperm activity. In my second experiment, I found that sperm mitochondrial DNA has deletions, indicating damage, but this damage does not accumulate with sperm activity. However, problems with PCR amplification resulted in little experimental data, preventing a conclusive test of the hypothesis.

Analysis of the relationship of velocity to taxonomic composition of periphyton-based stormwater treatment areas, in conjunction with other metrics, is a valuable tool for evaluating the phosphorus removal efficiency of this Everglades restoration advanced treatment technology. Periphyton taxonomic composition, biomass, water and tissue total phosphorus (TP), pH, and temperature were analyzed in three slow velocity (0.22 cm s-1) and three fast velocity (2.0 cm s-1) mesocosms. Loading rate, retention time and surface area were kept constant, with velocity the single variable between treatments. There was no significant difference in taxonomic composition, water TP, tissue TP, or temperature between the slow and fast treatments. However, dominant eutrophic and oligotrophic indicator genera exhibited significant and consistent changes in relative abundance related to location along the treatment path. Biomass accrual was 30% greater in the fast treatment and TP uptake was positively correlated with increased velocity.

This study documented assemblages of native and non-indigenous fishes in restored and natural wetlands within the Big Cypress Swamp. Within the restored wetland, non-indigenous fishes constituted only a minor component of the entire fish community in the restored wetland, although large fish assemblages were dominated by non-indigenous fishes. Among assemblages of species with similar ecologies, nonindigenous species may impact native species in the restored wetland. Within the natural wetlands, non-indigenous fishes became more conspicuous during the second year of this study. Hydroperiod and water depth were important factors influencing fish communities in both study habitats. Attempts to block access of non-indigenous fishes from canals into the restored wetland appeared to limit invasions of non-indigenous species, although it did not entirely exclude them. Two new non-indigenous fish species in the Big Cypress Swamp, Hoplosternum littorale and Belonesox belizanus were also documented.

Old World Climbing Fern, Lygodium microphyllum is an aggressive nonindigenous plant that is on the verge of becoming a major ecological threat in South Florida. Currently, specific habitat characteristics that contribute to success or failure of its establishment are unknown. I studied the pattern of distribution of the fern in Florida's Big Cypress Swamp. Two similar forested wetland sites with high incidence of L. microphyllum infestation were assessed in order to identify broad-scale hydrological and physiographic conditions that may favor high susceptibility to L. microphyllum invasion. On each site, species richness, abundance and distribution of herbs, shrubs and trees were characterized. In addition, several parameters including elevation, substrate depth, percentage substrate water content, percentage substrate organic content, substrate texture, and photosynthetically active radiation were quantified. The patterns of distribution of L. microphyfum indicated that presence of the fern was dependent on relatively low elevation, relatively deep substrate and moderately high substrate water content.