Ecosystem management--Florida

Agricultural sites have been acquired under the Comprehensive Everglades Restoration
Plan (CERP) for the creation of water storage areas. Copper desorption and toxicity to
the Florida apple snail (Pomacea paludosa) were investigated using soils from these
sites. Copper concentrations in II soils ranged from 5 to 234 mg/kg Cu dw, and when
flooded, resulted in overlying water Cu concentrations from 9 to 308 11g/L Cu. Juvenile
apple snails exposed to three flooded soils had high mortality and decreased growth
within 9 to 16 days in two ofthe three soils examined. To assess Cu toxicity to the apple snail at various life stages and water quality
parameters, 96 hour acute toxicity studies were conducted. Copper was more toxic to
juvenile than adult apple snails. Copper toxicity increased as pH decreased and
decreased as DOC increased. Hardness had no effect on Cu toxicity to the apple snail.
Copper toxicity was a function of organism age, DOC and pH.
Copper accumulation by juvenile and adult apple snails was determined for multiple
exposure pathways. For 28 days, juvenile snails were exposed to aqueous Cu and adult
snails were exposed to Cu contaminated soil, water and food. Whole body Cu in juvenile
snails increased with time. The mean Cu bioconcentration factor (BCF) for juvenile
snails was 1493. For adult snails, the dietary exposure pathway resulted in the highest
bioaccumulation factor (BAF). Most Cu accumulated in soft tissue.
During a chronic aqueous exposure, apple snails exposed to 8-16 flg /L Cu for 9 months
had high Cu accumulation and significantly reduced clutch production (8-16 flg /L) and
egg hatching (16 flg/L ). Chronic Cu exposure initially decreased growth in juvenile
snails, but growth rebounded by adulthood and snails appeared to acclimate to chronic Cu
exposure.
When apple snails with high tissue Cu were fed to redear sunfish (Lepomis microlophus)
Cu transfer was minimal, suggesting that the risk of trophic transfer (bioaccumulation) of
Cu from the snail to redear sunfish is low and that biomagnification is unlikely. It is
uncertain if other apple snail predators would be at risk for dietary Cu transfer.

Normal color digital ortho-photos with six inch resolution were used to test the
feasibility of mapping the habitat of the Florida apple snail, the exclusive food
source of the Endangered Florida snail kite. Several remote sensing techniques
such as unsupervised and supervised classifications are evaluated and accuracy
assessed. While the overall ability to classify apple snail habitat is significant,
sparse areas of emergent vegetation which are preferred foraging areas for the kite
were excluded by the classification and needed to be re-introduced for further
analysis. The methodology can be repeated to measure change over time since the
NC imagery of Grassy Waters Preserve is acquired frequently. Additionally, three
spectral levels of density abundance of wetland graminoid species that denote apple
snail habitat were examined for mapping potential on the imagery. A site suitability
analysis using a weighed overlay tool in ArcGIS is suggested as a means to include
numerous other key factors influencing habitat selection by the snail kite in a
mapping project.

The purpose of this thesis was to document human impacts to Grassy Waters Preserve and correlate that to environmental change. Aerial photographs and archives provided a history of human impacts. These impacts included roadways, canals/levees, development, and landfills. To determine if environmental change occurred vegetation maps were digitized and compared from three study areas using 1940 and 1999 aerial photography. These vegetation maps included open water, transitional marsh/prairie, cypress, upland forest and human feature categories. Within all study areas the vegetation maps indicated decreases in the open water community. Within two areas major increases in cypress and uplands occurred. Vegetative shifts varied based on the locations of features like canals and levees. Due to image quality differences statistical analysis of the maps was not possible. However, the magnitude of change suggests that Grassy Waters became more densely vegetated and forested over time.

This study focused on whether use of ArsenalRTM to control an invasive, non-indigenous tree, Schinus terebinthifolius, would either negatively affect the seed bank in treatment areas of the study site or seeds in litter, 0-5 cm or 5-15 cm layers of the bank. Neither examining the whole site nor the two habitats produced conclusive results, but examining the three layers did. The litter layer appeared to be most sensitive to herbicide treatment with a 47% (p=0.03) reduction in seedling emergence after treatment. Analysis of herbicide effect therefore required studying depth, habitat and study site. The litter layer, seldom considered in seed bank studies, produced 33% of emerging seedlings in this study. It is an extremely important component as it is the first place seeds are deposited before they percolate down into the soil. Damage to this layer will not only affect current seedling emergence, but future content of the seed bank below the surface.