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by Dave Grant  "The channel by which we went to and returned...was bordered on each side by mangroves, which sprang like a miniature forest out of the greasy mud-banks. The bright green colour of these bushes always reminded me of the rank grass in a churchyard: both are nourished by putrid exhalations; the one speaks of death past, and the other too often of death to come." Charles Darwin -The Voyage of the Beagle Rookery Bay is a high-salinity estuarine system on the southwest coast of Florida. Like other estuaries along the Eastern seaboard, it is a drowned river valley that formed as sea level rose during the last 8,000 years. The Bay is shallow even by Floridian standards (just two and a half feet); and local skippers advise you that: "If you fall overboard, just stand up and walk to the shore!" Its waters and wetland plants are traps for fine particles washed off the adjacent lands, and the flat geographical profile of Florida make these Florida bays the shallowest along our coast.   The estuary is a nutrient trap as well, supporting abundant phytoplankton populations, sub-tidal seagrass beds, Spartina marshes, and mangroves. Of the seven seagrass species here, Thallasia (Turtle grass) is the most common; and of the emergent plants, the mangroves predominate, crowding out Spartina grasses in this almost tropical wetland environment. Mangroves are especially important in southern Florida, where protected from the cold; they provide food, substrate and shelter to a host of animals in and out of the water. Three mangrove species: red, white, and black, produce detritus from their fallen leaves that supports large numbers of scavengers like sheepshead minnows and shrimp; predators like speckled sea trout, fish-eating birds, and ultimately, humans. Like other wetlands, these forests of the sea support over 70 percent of the local fish and shellfishes. Mangroves are also crucial as buffers against erosion, and in many instances, even build up new land. Over 150 species of birds have been reported here. Many waterbirds require this unique environment for nesting - hence the name - Rookery Bay. The area, designated a National Estuarine Preserve in 1978, is best seen by boat, and that is exactly what American Littoral Society members did on a collecting trip in December 1987. Gary Lytton, a marine resources specialist and expert guide at the preserve, accompanied the group during several trawls in the up- stream Henderson Creek area and downstream in Little Marco Pass. Upstream salinity was 30-ppt (parts per thousand), and in the Pass, 36-ppt (Slightly saltier than the average for ocean waters). The water temperature was uniform, 66°F throughout the system. Species collected up stream included sponges, flatworms, periwinkles, squid, scuds, mud and blue crabs, mangrove tunicates, Lane snappers, and silver jenny. In the Pass we found sponges, sea-whips, hermit and stone crabs, and a much more interesting assortment of fishes, including: silver perch, snapper, hard-headed catfish, and two polka-dot batfish. Bird sightings included many of the tropical fish eaters: pelicans, cormorants, royal and Forster's terns, egrets, great white herons, ospreys, and a bald eagle. Noticeably absent from the catches were seagrasses and the pinfish, a relative of the porgy. There is some concern that human activities in the estuary and its upstream watershed may be having a negative impact on these species. Florida is besieged by 7,000 new residents a week and 70-percent of them settle along the coast. ("There ain't much point livin' down here unless you're near some water.") Dredging and filling destroys wetlands, upsets circulation patterns, and reduces oxygen levels. Boat wakes erode shorelines and "prop-dredging" destroys sensitive and valuable seagrass beds. Indirect impacts, such as sewage and runoff, promote undesirable macroalgae growth, eutrophication and fish kills miles downstream from the estuary's source. To the north, Tampa Bay, once one of the most
productive estuaries in the country, has lost So far over 6,000 acres have been set aside for research and educational purposes, and efforts are being made to acquire the remaining 3,000 acres around Keewaydin Island, the barrier beach that separates the Bay from the Gulf of Mexico. Rookery Bay is a small piece of what Florida
looked like a thousand years ago. Although its neighbor, Naples,
is the fastest growing city in America, this remnant of wilderness
should remain relatively if its watershed can be protected and
the surrounding islands can be saved from development. NOTE: Grant is a Society naturalist and
field trip leader. The drawings are by Susan Draxler, a naturalist/illustrator
who works for the Monmouth County (NJ) Park System. |