Natural resource condition assessment: Biscayne National Park

Byan, David; Luo, Jiangang; Ault, Jerald

doi:10.36967/nrr-2289813

Biscayne National Park (BISC) encompasses a unique tropical marine ecosystem directly adjacent to one the nation’s largest metropolitan areas. Each year, roughly half a million people visit the park and its resources are integral to south Florida’s multibillion-dollar fisheries and tourism industry. The park can be divided into four prominent natural environments: (1) mangrove shorelines, the longest stretch in southeastern Florida that provides a buffer to coastal development and important habitats for birds, juvenile fishes and macroinvertebrates; (2) Biscayne Bay, a shallow estuarine system with a historically rich and productive benthic community; (3) more than 40 limestone keys, including a rare relatively undisturbed tropical hardwood ecosystem; and, (4) extensive patch coral reef and platform coral reef system, which play a critical role in the function and dynamics of the larger south Florida marine ecosystem. This prolific range of natural resources are highly inter-connected, both within the confines of the park, and as part of the broader regional ecosystem. In this NRCA, a selection of nine key natural resources vital to assessment of park’s overall health have been identified; water quality, seagrasses, terrestrial vegetation, corals, marine invertebrates, reef fish/gamefish/sharks, sea turtles, marine mammals/American crocodiles, and birds. The condition and trend for each of these resources was evaluated using the best available science and the NPS structured resource assessment and reporting framework. BISC is a tropical marine park with 95% of its total acreage covered in water. As such, the importance of water quality to the health of the ecosystem is unequivocal. Almost all of the natural resources discussed in this report either exist in, or depend on, the marine environment. Significant hydrological alterations in conjunction with an ever-increasing urban population have affected the quantity, quality and timing of freshwater inflows into BISC and added considerable stress to a finely balanced ecosystem. Salinity levels not meeting desired ecological conditions, high nutrient levels promoting phytoplankton and algal blooms have raised significant public concerns. While the presence of contaminants both in the water and within the animals living in the park is high, monitoring efforts are in place and the park continues to work with neighboring state and federal agencies and the public to improve the quality, quantity and timing of water entering the park. Seagrass beds cover nearly 90% of benthos within BISC. Seagrass provides essential habitats for a wide range of marine species during critical life stages, plays a major role in nutrient cycling in the Biscayne Bay, and helps to stabilize marine sediments. Seagrass monitoring efforts suggest that the acreage of seagrass within the park and the species composition within the nearshore environment of the bay have been relatively stable. However, nutrient loading and persistent algal blooms have deleteriously affected areas adjacent to the park, warranting moderate concern for the nearshore seagrass community. Although only 5% of BISC is land, this area contains a significant portion of the park’s biodiversity and includes terrestrial habitats highly connected with the marine environment and critical for a host of marine species. Mangroves, which make up the largest proportion of terrestrial vegetation in BISC, provide habitat for a wide range of terrestrial and marine fauna. The coastal tropical hardwood hammock community includes many rare and unique tree species, at their most northern limit. Reference conditions for the composition and extent of mangrove and tropical hardwood forests were established in 2013, but there has been no subsequent mapping. Invasive plant species are an ongoing threat; however, restoration projects and removal efforts have appeared to have kept exotic plants under control. The vibrant coral reef ecosystem within BISC...

Natural resource condition assessment: Biscayne National Park

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