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publications > paper > PP 1011 > south florida's hydrologic systems > water quality > water quality of the big cypress swamp
South Florida's hydrologic systems
Water quality of the Big Cypress Swamp
The natural processes of plants and animals help to determine the concentration of dissolved oxygen in water. Dissolved oxygen is necessary for plants and animals to flourish and for bacteria to break down organic materials. In the Big Cypress Swamp, dissolved oxygen concentrations are sometimes naturally low because of the dense forest cover, which reduces penetration of sunlight. On occasion, fish deaths are caused by low concentrations of dissolved oxygen in the waters of the Big Cypress Swamp (Klein and others, 1973).
Several nutrient elements are essential for life. Among the most important and most publicized are phosphorus and nitrogen. When they are abundant in water, they may cause excessive growth of aquatic plants, which can degrade the recreational and esthetic values. Concentrations of phosphorus and nitrogen (as nitrate) are low in the Big Cypress Swamp compared with other areas in south Florida: average values are 0.03 mg/l as phosphorus and 0.10 mg/l as nitrogen (Klein and others, 1973).
Although the quality of the water in much of the Big Cypress Swamp is considered to be little changed from the natural state, agricultural development and drainage in the northern and western parts have disrupted natural cycles, modified the hydrology of the watershed, accelerated the rate of soil oxidation and erosion, and added pollutants to canals and estuaries (Horvath, 1973).
Nutrients transported from drained parts of the Big Cypress Swamp to the estuaries exceed those transported by overland sheet flow in the undrained parts. The Faka Union Canal transports to the estuaries almost 5 times as much Kjeldahl nitrogen (ammonia and organic nitrogen), 10 times as much total phosphorus, and 7 times as much organic carbon as the Fakahatchee Strand transports by sheet flow (Carter and others, 1973). Heavy metals are also transported to the estuaries by canals that extend to agricultural land in the north. The heavy metals derived from agricultural areas are concentrated in fine-grained (less than 20 p) Sediments, particularly organic sediments (Mattraw, 1973). These sediments are readily transported when canal flow is high and are deposited in the estuaries where organic detritus from mangrove trees is thereby enriched in heavy metals. Because mangrove detritus is a major food source, its enrichment may provide a pathway for the metals to enter into the estuarine and marine food chains (Mathis, 1973).
Chokoloskee Bay, which receives heavy metals from the Barron River Canal, has greater loads of these metals in its waters and sediments than more remote bays and estuaries to the south that do not receive canal flows (Horvath, 1973; Mattraw, 1973). Concentrations of lead in the waters of Chokoloskee Bay are greater than concentrations to the south, and the maximum concentration has exceeded the maximum value recommended by Federal water-quality criteria. Manganese, iron, cobalt, copper, zinc, and cadmium in Chokoloskee Bay are also above natural levels but are not sufficient to cause acute ecological effects (Mattraw, 1973). Long-term chronic effects, however, remain a possibility.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:04 PM (KP)
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