Abstract
Globally, rivers and estuaries have been exposed to heavy exploitation, pollution, and landscape alterations, leading to losses of habitat and ecological functions. In particular, submerged aquatic vegetation (SAV) habitats have declined globally, impacting the ecological functions they contribute. The Caloosahatchee River and Estuary are located on the southwest coast of Florida. Development and hydrologic alteration in the Caloosahatchee watershed have drastically altered the ecology of the river and estuary. This has led to loss of SAV, which serves as an indicator of the overall health of the system. The aim of this project was to examine factors affecting the growth of restoration plantings of the freshwater SAV Vallisneria americana in the Caloosahatchee River. Factors examined included sediment characteristics, planting densities, herbivore exclosure size, and genetic strain of donor plants. Response variables included the number of rosettes and blades, blade morphology, and total plant biomass. Significant differences were found between the two strains in terms of mean number of rosettes and blades. No significant differences were found between the two sites used in Phase I. In comparing the mean final percent frequency of occurrence among sites in Phase II, a significant difference was found with strain. In comparing the final number of rosettes among sites in Phase II, a significant difference was found with site. Significant differences were found with average blade length and average leaf area among the sites in Phase II. Average blade length, width, and leaf area were significantly different when compared between strains in Phase II. Determining the difference of small versus large exclosures was strictly a qualitative assessment. Differences and similarities were observed when examining transportation and deployment, planting and sampling effort, wave action, and herbivory. When examining planting density the results indicate the initial planting density had no effect on the growth of V. americana. Although planting density lacks a vital role in the growth and establishment of V. americana, genetics may account for observed differences. Preparation for a SAV restoration that includes an investigation of the donor plants genetic makeup should be standard practice. Restoration of any species to an extirpated site will involve attempting to find appropriate genetic material often from geographically separated populations. In addition to genetics the site selection is another critical factor when considering a SAV restoration attempt.
