Geology topics

Research about Everglades

Source-linked reports with geographic coverage including Everglades.

121 records · Page 7Linked to original sources

USGS1999

Vertical exchange of ground water and surface water in the Florida Everglades

Introduction and Project Objectives Knowledge about hydrologic exchange between surface water and ground water is critical to understanding the movement of water and dissolved chemical constituents (solutes) in the Florida Everglades. This fact sheet describes a study that will quantify vertical exchange of water and solutes in the Everglades as part of the U.S. Geological Survey's (USGS) South Florida Ecosystem Program. The two sites selected for the initial investigation are shown in the report. Those sites are the location of ongoing research projects concerned with movement and transformation of nutrients and mercury. Research results are being used by the South Florida Water Management District (SFWMD) to guide in the planning of Stormwater Treatment Areas, which will be large constructed wetlands designed to remove excess nutrients from agricultural drainage. The objectives of the project described here are to (1) quantify vertical exchange of water (also referred to as seepage) between ground water and surface water, (2) use seepage estimates to assist in the development of chemical mass balances for mercury and nutrients, and (3) relate seepage fluxes to subsurface hydrogeologic properties, management of surface-water levels in canals and water conservation areas, and the regional water balance in the northern Everglades.

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USGS1998

Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release (up to 35 μM total dissolved mercury) from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca 2+ . Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in DI water (pH = 6.0) had no detectable (<2.5 nM) dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates (determined by 13 C NMR) correlated positively with enhanced cinnabar dissolution. ζ-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar (pH pzc = 4.0) at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

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USGS1998

Bacterial methylmercury degradation in Florida Everglades peat sediment

Methylmercury (MeHg) degradation was investigated along an eutrophication gradient in the Florida Everglades by quantifying 14 CH 4 and 14 CO 2 production after incubation of anaerobic sediments with [ 14 C]MeHg. Degradation rate constants ( k ) were consistently ≤0.1 d - 1 and decreased with sediment depth. Higher k values were observed when shorter incubation times and lower MeHg amendment levels were used, and k increased 2-fold as in-situ MeHg concentrations were approached. The average floc layer k was 0.046 ± 0.023 d - 1 ( n = 17) for 1−2 day incubations. In-situ degradation rates were estimated to be 0.02−0.5 ng of MeHg (g of dry sediment) - 1 d - 1 , increasing from eutrophied to pristine areas. Nitrate-respiring bacteria did not demethylate MeHg, and NO 3 - addition partially inhibited degradation in some cases. MeHg degradation rates were not affected by PO 4 3 - addition. 14 CO 2 production in all samples indicated that oxidative demethylation (OD) was an important degradation mechanism. OD occurred over 5 orders of magnitude of applied MeHg concentration, with lowest limits [1−18 ng of MeHg (g of dry sediment) - 1 ] in the range of in-situ MeHg levels. Sulfate reducers and methanogens were the primary agents of anaerobic OD, although it is suggested that methanogens dominate degradation at in-situ MeHg concentrations. Specific pathways of OD by these two microbial groups are proposed.

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USGS1998

Landscape modeling for Everglades ecosystem restoration

A major environmental restoration effort is under way that will affect the Everglades and its neighboring ecosystems in southern Florida. Ecosystem and population-level modeling is being used to help in the planning and evaluation of this restoration. The specific objective of one of these modeling approaches, the Across Trophic Level System Simulation (ATLSS), is to predict the responses of a suite of higher trophic level species to several proposed alterations in Everglades hydrology. These include several species of wading birds, the snail kite, Cape Sable seaside sparrow, Florida panther, white-tailed deer, American alligator, and American crocodile. ATLSS is an ecosystem landscape-modeling approach and uses Geographic Information System (GIS) vegetation data and existing hydrology models for South Florida to provide the basic landscape for these species. A method of pseudotopography provides estimates of water depths through time at 28 ?? 28-m resolution across the landscape of southern Florida. Hydrologic model output drives models of habitat and prey availability for the higher trophic level species. Spatially explicit, individual-based computer models simulate these species. ATLSS simulations can compare the landscape dynamic spatial pattern of the species resulting from different proposed water management strategies. Here we compare the predicted effects of one possible change in water management in South Florida with the base case of no change. Preliminary model results predict substantial differences between these alternatives in some biotic spatial patterns. ?? 1998 Springer-Verlag.

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USGS1996

Effects of nutrients and hydroperiod on Typha, Cladium, and Eleocharis: Implications for everglades restoration

The recent expansion of Typha domingensis ( Typha ) into areas of the Everglades previously dominated by Cladium jamaicense ( Cladium ) communities has led to competing hypotheses about the importance of nutrient concentration vs. hydroperiod in controlling the distribution of these species. In this study, experimental mixtures of Typha domingensis , Cladium jamaicense , and Eleocharis interstincta ( Eleocharis ), a member of the Cladium community, were subjected to two levels of nutrient concentration and three contrasting hydroperiods to determine how these variables might affect Typha 's ability to displace the Cladium community. Mixtures of the three species were established in outdoor tanks containing soil from the northern Everglades region where the experiment was conducted. Nutrient treatments consisted of nutrient additions to adjust ambient water concentrations to either 50 μg/L phosphorus (P) or 100 μg/L P plus nitrogen (N). The three hydroperiods were achieved by maintaining water depths within ranges observed in the northern Everglades. Maximum water depths of 15, 30, and 60 cm were established throughout the wet season (May‐November) followed by lowering to 5 cm during the dry season. Over a 2‐yr period, biomass was monitored nondestructively and aboveground material was harvested at the end of the experiment. Analysis of the biomass changes over time showed that differences between the species developed by the end of the first growing season. Typha and Eleocharis had initial growth rates substantially higher than those observed for Cladium . Typha 's growth in mixtures responded positively to both elevated nutrients (by as much as 45%) as well as to increased water depth (by as much as 60%), while Cladium and Eleocharis did not increase in response to these variables. Tissue P concentrations were found to be higher for Typha and Eleocharis than for Cladium under nearly all conditions. Net accumulation of P in Typha shoots was 2‐3 times greater than in the other species. The enhancement of Typha by elevated nutrients and increased flooding is associated with a syndrome of life history characteristics that includes rapid growth rates, high tissue concentrations of P, tall leaves, and a greater response to contrasting environmental conditions. Cladium , in contrast, showed a slow growth rate, low tissue concentrations of P, a greater capacity to resist invasion by Typha in shallow waters, and less of a growth response to contrasting environmental conditions, traits that would seem to be well suited to the nutrient‐poor, hydrologically unstable conditions natural to the Everglades. Results from this study suggest that attempts to limit the spread of Typha should consider hydrologic restoration as well as reduction in surface water nutrients.

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USGS1996

Vegetation affects water movement in the Florida Everglades

Introduction The Florida Everglades is a vast, diverse wetland ecosystem characterized by small ground-surface slopes, slowly moving surface waters, and dense aquatic vegetation. Both submersed and emergent vegetation are found in sawgrass and cattail marshes, wet prairies, and sloughs. The south Florida ecosystem has been greatly altered during the last 100 years. A complex water-management system that includes levees, canals, pumps, and water-control structures now regulates flooding and provides a steady supply of fresh water to urban areas and agriculture. Drainage projects have diverted much of the water that originally flowed slowly southward from Lake Okeechobee through the Everglades. Restoration and management of the Everglades ecosystem requires understanding and manipulating the amount and timing of water flows throughout the ecosystem. The spatial and temporal distribution of water and water-borne contaminants in the Everglades must be understood if degradation of the ecosystem is to be halted and reversed. To understand how water moves through the Everglades, it is necessary to quantify the forces affecting the flow. The resistance exerted on the flow by the vegetation through which the water moves is one of the dominant but least understood forces affecting Everglades surface-water flows. The aquatic vegetation of the Everglades affects both the depth of water and the rate at which it moves. The presence of living and dead plant material in the water column creates drag forces on the moving water. Water flows most slowly and the water-surface slope is largest in areas where vegetation is most dense.

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USGS1996

Regional evaluation of evapotranspiration in the Everglades

Understanding the water budget of the Everglades system is crucial to the success of restoration and management strategies. Although the water budget is simple in concept, it is difficult to assess quantitatively. Models used to simulate changes in water levels and vegetation resulting from management strategies need to accurately simulate all components of the water budget. One of the most important components of the Everglades water budget is evapotranspiration (ET). ET is water removed from the surface and soils by direct evaporation and plant transpiration. In South Florida, ET rates may exceed 40 in/yr (inches per year) on the average; during dry years, the ET could exceed rainfall (about 50 in/yr). Thus, most of the water that falls on the land surface as rainfall is returned to the atmosphere by ET. Despite the importance of ET in the Everglades water budget, our knowledge of ET is, at present, only semi-quantitative. Recent advances in instrumentation and measurement techniques have made it possible to continuously measure ET, so that an accurate evaluation of ET in the Everglades can be made.

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USGS1996

Interactions of mercury with dissolved organic carbon in the Florida Everglades

There has been increased awareness by both public and scientific communities over mercury contamination of game fish in South Florida. Effective management strategies for dealing with this problem will require a more thorough understanding of the factors and processes that result in the generation and transport of mercury, and control its reactivity in the Everglades. The role of mercury complexation by dissolved organic carbon (DOC) has been proposed by several investigators as a primary mechanism for the transport of mercury in aquatic systems. However, this relationship has been simply proposed based on a strong correlation between dissolved mercury and DOC concentrations in ground, lake and stream waters. Interactions with DOC may be an important process for controlling the transport and bioavailability of mercury. The issue of carbon reactivity in South Florida is especially relevant due to the high natural production of organic carbon in the peat soils and wetlands, the relatively high carbon content of shallow ground water systems in the region, the interactions of organic matter with mercury, other trace metals, and anthropogenic compounds, accumulation of organic carbon in corals and carbonate precipitates, and the potential changes in the quality and reactivity of dissolved organic carbon (DOC) resulting from land use practices. This study will attempt to meet the need to more clearly understand the dynamics of organic matter mercury interactions in the Florida Everglades by focusing research on the effect of dissolved organic carbon (DOC) on the transport and reactivity of Hg in the Everglades.

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USGS1980

Demography of the Everglade kite: Implications for population management

Simple deterministic and stochastic population modelsi are used to examine the demographic patterns of the Everglade Kite population. These efforts are directed at making inferences about the evolution of the kite life-history pattern, and at providing guidelines for the management of the kite population. The Everglade Kite has apparently evolved high adult survival rates, in partial response to a variable reproductive output. Proper management of this population should include the protection of adults from catastrophic mortality sources, and the provision of adequate water-levels to ensure reproductive success.

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USGS1975

Relation of water level and fish availability to wood stork reproduction in the southern Everglades, Florida

The wood stork is a species of colonial wading bird in the Everglades that is most sensitive to changes in the availability of food. Previous studies have shown that the initiation and success of wood stork nesting depends on high densities of fish concentrated in ponds and other catchment basins during the dry season. The extreme dependence of the wood stork on the cyclic hydrologic regime of the southern Florida wetlands makes it an indicator of the well-being and ecological stability of the Everglades. The wood stork has declined in numbers over the last 25 years. One reason for the decline in wood stork population was the change in the hydrologic regimen of the Everglades which affected the feeding habitat and the food production. The fish on which the wood stork feeds increase in density during the dry season as water levels fall. In the Everglades marsh, densities were highest in front of the drying edge of surface water at a depth of about 0.3 m. Dry-season densities were greatest when a drought occurred the previous year. Historically wood stork nesting success was associated with high summer water levels, high rates of surface-water discharge and high rates of drying. Before the closure of the south side of Conservation Area 3 in 1962, years of successful and unsuccessful nesting were characterized by different patterns of drying. These patterns changed after 1962 and generally the predictability of successful nesting breaks down thereafter. Only two nesting years after 1962 were successful and in only one of these was the drying rate similar to years of successful nesting before 1962. Two other potentially successful years failed after 1962. This suggests that further changes in the hydrobiological relations occurred within the Everglades after 1962. Lack of successful nesting after 1962 can be attributed in large part to late colony formation and the interruption of nesting by winter rainfall. In this period (1962-72), colonies formed earlier in years of high early drying rates than in years of low early drying rates. Delay of colony formation is ultimately the result of inability to attain a suitable nutritional state since food supply is the primary factor in the initiation of nesting. Many of the complex food associations of the wood stork remain to be explained.

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USGS1975

Chemical and biological quality of water in part of the Everglades, southeastern Florida

A comprehensive monitoring network was established in a part of the Everglades to evaluate the quality of water being delivered to Everglades National Park. Physical, chemical, and biological parameters were determined in surface water, bottom sediment, and bulk precipitation (rainfall and dry fallout). The geology of the area, bottom sediment, bulk precipitation, natural, urban, and agricultural runoff, and the characteristics of the hydrologic system in the Everglades influence the type and concentration of each chemical constituent and how it affects the water quality. The quality of surface water in the agricultural area between Lake Okeechobee and the water conservation areas is markedly different from that of other surface water in southeastern Florida. In general, the water in this area is higher in concentrations of most chemical constituents. Man has engaged in cultural activities, both agricultural and urban, which have affected the water quality in the northern and eastern segments of the area of investigation. The quality of the water improves, however, as it flows to the south and east because there is minimal input from man's activities and many of the constituents are assimilated by plants, sorbed on organic material and clay in the bottom sediments, and entrapped within the sediments. Dilution by rainfall and concentration by evapotranspiration are also important factors that influence the quality of surface water in the area of investigation. The area of investigation in the Everglades is a sink for macronutrients, trace metals, and chlorinated-hydrocarbon insecticides. These constituents do not move through the system freely. They become tied up in various complexes and for that reason, the water being delivered to Everglades National Park is of better quality than the water entering the northern edge of the water conservation areas. The various physical and biological processes and chemical reactions combine to improve the water quality as the water flows southward. The data presented in this report may be used as a baseline for determination of future changes in water quality at the several places in the Everglades where recurrent sampling of rainfall, surface water, and bottom sediments was undertaken during the course of the investigation.

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USGS1966

Water and the Everglades

This fundamental element, whether profuse or scarce, rules the life and character of Florida's great park. But water, like living space, is a resource that civilization demands in ever increasing quantities. Examined here are the economics of water use by Florida's east coast cities and its effects on Everglades ecology.

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USGS1966

Water resources in the Everglades

Aerial photography is playing an important role in the evaluation of the water resources of the almost-inaccessible 1,400 square miles of Everglades in southern Florida. Color, infrared, and panchromatic photographs show salient features that permit evaluation of the overall water resources picture. The fresh water-salt water interface, drainage patterns, ecologic changes resulting from flood and drought, quantities of flow, and other hydrologic features are easily observed or measured from the photographs. Such data permit areal extension of very limited point observations of water resources data, and will assist in providing the necessary guidelines for decisions in water management in the Everglades.

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