Brantley, Lake
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A part of the Big Wekiva Watershed
Lake Brantley
Florida Department of Environmental Protection (FDEP) developed a lake bioassessment protocol for monitoring and assessment of the biological condition of Florida lakes. Generally speaking, bioassessment entails the collection of aquatic insects from lake and stream locations. The presence or absence of certain types (species) and their numbers (abundance), provides great insight regarding the current as well as historic water quality of a waterbody. Seminole County biologists monitor lakes and streams to protect and manage ecosystem health. Lake bioassessment protocol is employed as part of the ambient monitoring program in support of Florida's water quality standards. In this webpage, we discuss lake biomonitoring, biomonitoring data, and present the condition of the waterbody using special "grading" systems commonly know indices. Indices are mathematical combinations of data that provide an overall grade or summary pertaining to lake condition or health.
Seminole County have implemented the use of the Lake Condition Index (LCI) developed by FDEP. Click here to learn more about LCI. The LCI method divides each lake into 12 equal segments (Figure 1) and a grab is taken in each segment using the Ekman sampler (Figure 2). The 12 grabs are then combined into a single composite sample, and each sample is randomly subsampled to a count of at least 100 organisms, which are identified to the lowest practical taxonomic level. Lakes greater than 1000 acres are divided into two or more basins and are retained as separate samples.
Lake Brantley is a solution basin (lake basin formed by the solution of surficial and underlying rock) covering a surface area of 288 acres, with a mean depth of 12 ft. and maximum depth of 28 ft. Brantley is a private lake located in Longwood, Seminole County, surrounded by high density urban development, Nevertheless, it remains an oligotrophic lake evidenced by its Trophic State Index (TSI) average of 35.8. Click here to learn more about TSI. This private, urban lake is considered one of the more oligotrophic lakes located in Seminole County because of its deep light penetration, exceptional water clarity, extensive submersed native plant community including stonewort (Nitella), baby tears (Micranthemum glomeratum) and eelgrass (Vallisneria americana).
Macroinvertebrate Community Results:
The results for Lake Brantley a LCI score of 'very good' as it has many sensitive and diverse taxa (groups) including gastropods, bivalves, mayflies, caddisflies and dragonflies. Lake Brantley contains Hexagenia orlando, a sentinel mayfly species that is endemic to Central Florida and is only found in lakes. A sentinel species is one whose presence, absence, or relative well-being is indicative of the health of the environment in which it historically has been found. Hexagenia orlando is a rare species since it is highly intolerant of poor water quality. Factors that threaten the health of all surface water bodies and groundwater include, but are not limited to: stormwater runoff (e.g., lawn fertilizers, animal wastes and automobile residues); leaking sewage collection systems; loss of watershed and wetlands, and invasive plants and animals.
Currently Lake Brantley is infested with two dominant exotic species that may disrupt the native ecosystem thus contributing to changes in macroinvertebrate structure. These species are the exotic channel apple snail (Pomacea insularum) and aquatic plant hydrilla (Hydrilla verticillata).
Seminole County samples the benthic macroinvertebrate community in Lake Brantley biannually, once in the summer and once in the winter.