An Inventory and Assessment of the Distribution of Submersed Aquatic Vegetation at Jean Lafitte National Historical Park and Preserve

Poirrier, M; Burt-Utley, K; Utley, J.; Spalding, E

The 18,400-acre Barataria Preserve (Preserve) of Jean Lafitte National Historical Park and Preserve (JELA) is located in the ecologically significant Barataria-Terrebonne Estuary. The estuary is undergoing anthropogenic changes that are directly affecting aquatic resources. A baseline study of submersed aquatic vegetation (SAV) was conducted because SAV provides critical habitat for fish and wildlife and serves as an indicator of water quality. Study objectives included: determining the relative abundance and distribution of native, exotic, and nuisance SAV; the habitats where they occur; and any special management concerns. SAV habitats throughout the Preserve were surveyed. Results were placed in a geo-referenced database to track future trends and serve Preserve education and management needs. Seven native species were found: Cabomba caroliniana; Ceratophyllum demersum; Heteranthera dubia; Najas guadalupensis; Potamogeton pusillus; Vallisneria americana; and Zannichellia palustris. Three exotic species were also present: Egeria densa; Hydrilla verticillata; and Myriophyllum spicatum. These ten species are regarded as true SAV because they are rooted and have leaves that are always submersed. Three species that could be confused with true SAV were also present: Myriophyllum aquaticum (an exotic species with emergent leaves); Potamogeton epihydrus (a native species with floating leaves); and Utricularia cf. radiata (a native, floating species). The presence of the highly-invasive, exotic, floating fern Salvinia molesta was also documented. Salinities characteristic of freshwater prevailed throughout the interior waters of the Preserve and SAV did not conform to the general estuarine management paradigm of decline and loss. Instead, as commonly occurs in nutrient-rich freshwater habitats, many species were abundant at the nuisance level. Sufficient light was present to support robust SAV growth in Preserve ponds, canals and Lake Cataoutche. The native species Ceratophyllum demersum and Najas guadalupensis and the exotics Hydrilla verticillata and Myriophyllum spicatum formed large surface mats that clogged waterways. Vallisneria americana may be decreasing due to the increase in nuisance SAV and floating plants. Management concerns include: the potential increase in giant salvinia; the abundance of floating aquatics, filamentous algae and exotic SAV; effects of herbicide application on SAV community structure and a possible decrease in V. americana.

An Inventory and Assessment of the Distribution of Submersed Aquatic Vegetation at Jean Lafitte National Historical Park and Preserve

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