Dry Tortugas National Park (DTNP)

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Chapter 4. ECOLOGICAL CRITERIA

(Guidelines and Criteria Section B/ Ecological Criteria) Nominated areas must conform to at least one of the eight ecological criteria. Describe how the nominated site satisfies one or more of the following criteria. (Attach in Annex any relevant supporting documents.)

Representativeness:


As stated above, DTNP protects productive coral reef, seagrass and island habitats with highly diverse assemblages of marine fish, invertebrates, sea turtles and seabird species that are representative or migratory in South Florida and the Wider Caribbean region.

Conservation value:


DTNP provides great value to conservation of fauna for its size due to its relatively intact marine and terrestrial habitats and location. Recent studies conclude that protection offered by the RNA has been important to the recovery of a major mutton snapper spawning aggregation at nearby Riley’s Hump. DTNP also contains one-third to one-half of the adult spawning population for mutton snapper, red grouper, yellowtail snapper, and hogfish, and this proportion has generally increased from 1999 to 2010. Larvae of these fish are transported by the Florida Current throughout the Florida Keys and southeast Florida reef tract.

Rarity:


DTNP contains the only known rookeries for Brown Noddies, Magnificent Frigate Birds, and Masked Boobies in the continental U.S.

Naturalness:


Due to their remoteness, DTNP and the wider Tortugas region have enjoyed some relief from human-caused impacts, especially from urban and agricultural development in South Florida that consume land and water and cause impacts to water quality and quantity. Historical overfishing was a prevalent ecological stressor. Recent management actions to protect spawning, nursery and adult habitats are showing positive results and bode well for further restoring size and abundances of marine fish.

Critical habitats:


DTNP is important to the recovery of several species listed under the U.S. Endangered Species Act including the roseate tern, loggerhead and green sea turtles, staghorn and elkhorn corals, piping plover, and smalltooth sawfish. The Nature Conservancy has established a nursery site at DTNP for propagating elkhorn and staghorn corals as part of a long-term strategy for reestablishing these species in the region. A complete list of species is attached.

Diversity:


U.S. National Park Service has identified 843 species in its inventory of terrestrial and marine vertebrates, vascular plants and stony corals at DTNP. Coral reefs and seagrass beds at DTNP also provide habitat for many additional marine species.

Connectivity/coherence:


The Caribbean Current transports surface waters from the Caribbean Sea through the Yucatan Channel (between the island of Cuba and the Yucatan Peninsula) into the Gulf of Mexico where it joins the Florida current. DTNP is connected to the Wider Caribbean via oceanographic transport of marine species and bird migration. Reproduction in DTNP and the Tortugas region contributes significantly to food supply when the Tortugas Gyre retains and transports locally spawned larvae of conch and lobster and fishes eastward along the Florida Keys.

Resilience:


Various reefs within DTNP contain high densities of live coral cover and massive star coral heads and brain coral heads that are unique to the Dry Tortugas region. Larvae of these corals are transported by the Florida Current throughout the Florida Keys and southeast Florida reef tract. In-situ research is underway on calcification and growth rates of stony corals in DTNP. This research may indicate coral adaptability to lower seawater pH and higher sea surface temperatures.