Geology topics

Research about Florida

Source-linked reports with geographic coverage including Florida.

At least 1,297 records · Page 72Linked to original sources

USGS2000

Protection of fish spawning habitat for the conservation of warm temperate reef fish fisheries of shelf-edge reefs of Florida

We mapped and briefly describe the surficial geology of selected examples of shelf-edge reefs (50–120 m deep) of the southeastern United States, which are apparently derived from ancient Pleistocene shorelines and are intermittently distributed throughout the region. These reefs are ecologically significant because they support a diverse array of fish and invertebrate species, and they are the only aggregation spawning sites of gag ( Mycteroperca microlepis ), scamp ( M. phenax ), and other economically important reef fish. Our studies on the east Florida shelf in the Experimental Oculina Research Reserve show that extensive damage to the habitat-structuring coral Oculina varicosa has occurred in the past, apparently from trawling and dredging activities of the 1970s and later. On damaged or destroyed Oculina habitat, reef-fish abundance and diversity are low, whereas on intact habitat, reef-fish diversity is relatively high compared to historical diversity on the same site. The abundance and biomass of the economically important reef fish was much higher in the past than it is now, and spawning aggregations of gag and scamp have been lost or greatly reduced in size. On the west Florida shelf, fishers have concentrated on shelf-edge habitats for over 100 yrs, but fishing intensity increased dramatically in the 1980s. Those reefs are characterized by low abundance of economically important species. The degree and extent of habitat damage there is unknown. We recommend marine fishery reserves to protect habitat and for use in experimentally examining the potential production of unfished communities.

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USGS1999

Freshwater discharge to Florida Bay

The South Florida Ecosystem Program is a collaborative effort by Federal agencies, working with State and local agencies, to help resolve land-use demands and water-supply issues in south Florida. The role of the U.S. Geological Survey in the program is to provide scientific insight into south Florida's hydrology and geology, which are an integral part of the fragile ecosystems of the Everglades, Florida Bay, and the Florida Keys. Historical changes in water-management practices to accommodate a large and rapidly growing urban population along the Atlantic coast, as well as intensive agricultural activities, have resulted in a highly managed hydrologic system with canals, levees, and pumping stations. These structures have altered the hydrology of the Everglades ecosystem, including Florida Bay. Currently, there are plans to change the quantity of water delivered to Everglades National Park and Florida Bay to restore the natural flow of the system. Florida Bay, home to several endangered species, is a valuable breeding ground for marine life and an important recreational and sport fishing area. Florida Bay encompasses about 850 square miles in total area with an average depth of less than 3.5 feet. It is bordered by the mainland portion of Everglades National Park to the north, the Florida Keys to the east and south, and is open to the Gulf of Mexico to the west. During the last decade, Florida Bay has experienced algal blooms and seagrass die-offs which are signals of ecological deterioration that has been attributed to an increase in salinity and nutrient content of bay waters. Salinity and nutrient content are directly related to the amount and quality of freshwater that enters the bay and to flow patterns within the bay. Restoration of the Florida Bay ecosystem requires a better understanding of the linkage between the amount of water and nutrients flowing into the bay and the salinity and quality of the bay environment.

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USGS1999

Ecosystem history: Terrestrial and fresh-water ecosystems of southern Florida

Introduction Plant and animal communities of the historic Everglades have undergone striking changes over the last few decades, including declines in wading bird populations, invasion by exotic (non-native) plant and animal species, and areal expansion of cattails into sawgrass marshes. Many of these changes have been attributed to human activities in the region, and efforts are underway to restore the Everglades to a more pristine state. Restoration plans include alteration of the present levee and canal system that controls water flow throughout southern Florida and changes in agricultural and land development activities. However, can we be sure that the observed changes are related to human practices rather than representing an extreme in the natural variability of the system? This question should be answered before changing current land-use practices to alleviate environmental concerns. To address this question, it is necessary to look at patterns of floral and faunal change over the last century as well as over the last few millennia. This project aims to reconstruct floral and faunal composition at selected time intervals throughout southern Florida to determine: 1) detailed biotic changes over the last 150 years; 2) the natural range of biotic variability over the last few thousand years; and 3) determine whether any cause-and-effect relationships exist between biotic and environmental changes. Such questions are being addressed by scientists in the South Florida Initiative of the Ecosystem Program at the U.S. Geological Survey.

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USGS1999

Sedimentation, sea-level rise and circulation in Florida Bay

Issue Recent algal blooms and seagrass mortality have raised concerns about the water quality of Florida Bay, particularly its nutrient content (nitrogen and phosphorus), hypersalinity, and turbidity. Water quality is closely tied to sediment transport processes because resuspension of sediments increases turbidity, releases stored nutrients, and facilitates sediment export to the reef tract. Over decades to centuries, bathymetric changes due to erosion or sediment deposition affect water circulation and hypersalinity. The effect on circulation depends on the interplay between sediment accumulation and sea-level rise. The goal of this U. S. Geological Survey project is to document and quantify short- and long- term processes associated with sediment transport so that the influence of sediments on water quality can be better defined and later integrated with numerical modeling efforts conducted by cooperating agencies.

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USGS1999

Color infrared digital orthophoto quadrangles for the South Florida ecosystem area

The South Florida Ecosystem Restoration Program is an intergovernmental effort to reestablish and maintain the ecosystems of south Florida. One element of the restoration effort is the development of a firm scientific basis for resource decision making. The U.S. Geological Survey (USGS) is one of the agencies that provides scientific information as part of the South Florida Ecosystem Program (SFEP). The program, which was begun in fiscal year (FY) 1995, provides multidisciplinary hydrologic, cartographic, geologic, and biologic data that relate to the mainland of south Florida, the Florida Bay, and the Florida Keys and Reef ecosystems.

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USGS1999

South Florida ecosystems; changes through time

Ecosystems are communities of organisms, often including humans, and the associated physical and chemical environments in which they live. Ecosystems are a complex natural resource that need to be understood, carefully managed, and prudently conserved. Human modification of the environment, such as changing water drainage patterns and introducing pollutants (such as mercury) and nutrients (such as nitrates and phosphates), has altered critical ecosystems around the globe, and the south Florida region is now considered to be one of the most threatened ecosystems in the Nation. The south Florida ecosystem has both a land component, the Everglades (including all fresh-water wetlands south of Lake Okeechobee), and an estuarine component, Florida Bay. The two components are closely linked by hydrologic cycles and the plants and animals that live within the ecosystem.

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USGS1999

Geology and evolution of lakes in north-central Florida

Fluid exchange between surficial waters and groundwater in karst environments, and the processes that control exchange, are of critical concern to water management districts and planners. High-resolution seismic data were collected from 30 lakes of north-central Florida. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: (1) karstification or dissolution of the underlying limestone, and (2) the collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phases: (1) active subsidence or collapse phase (young); (2) transitional phase (middle age); (3) baselevel phase (mature); and (4) polje (drowned prairie) – broad flat-bottom that have one or all phases of sinkhole. Using these criteria, Florida lakes can be classified by size, fill, subsurface features, and geomorphology.

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USGS1999

Water-use patterns of woody species in pineland and hammock communities of South Florida

Rockland pine forests of south Florida dominated by Pinus elliottii var. densa characteristically have poor soil development in relation to neighboring hardwood hammocks. This has led to the hypothesis that Everglades hammock trees are more reliant on soil moisture derived from local precipitation whereas pineland plants must depend more on groundwater linked to broader regional hydrologic patterns. Because soil moisture sources are likely to vary more than groundwater sources, we hypothesized that hammock plants would exhibit correspondingly higher levels of dry season water stress. This was examined by measuring predawn water potentials, and by analyzing water uptake in representative hammock and pineland woody species using stable isotopes of plant water and that of potential sources during wet and dry seasons. Two species typical of each of the two communities were selected; a fifth species which was found in both communities, Lysiloma latisiliqua Benth., was also analyzed. Water content of soils in both communities decreased from wet to dry season. Consistent with our hypothesis, the change in predawn water potentials between the wet and dry season was less in pineland species than that of hammock species. Water potential changes in L. latisiliqua in both communities resembled that of hammock species more than pineland plants. Isotopic data showed that pineland species rely proportionately more on groundwater than hammock species. Nevertheless, unlike hammock species in the Florida Keys, mainland hammock species utilized a substantial amount of groundwater during the dry season.

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USGS1999

The distribution of, and relation among, mercury and methylmercury, organic carbon, carbonate, nitrogen and phosphorus, in periphyton of the south Florida ecosystem

Periphyton samples from Water Conservation Areas, Big Cypress National Preserve, and Everglades National Park in south Florida were analyzed for concentrations of total mercury, methylmercury, nitrogen, phosphorus, organic carbon, and inorganic carbon. Concentrations of total mercury in periphyton decrease slightly along a gradient from north‐to‐south. Both total mercury and methylmercury are positively correlated with organic carbon, nitrogen and phosphorus in periphyton. In horizontal sections of periphyton mats, total mercury concentrations tend to be largest at the tops and bottoms of the mats. Methylmercury concentrations tend to be the largest near the bottom of mats. These localized elevated concentrations of methylmercury suggest that there are “hot spots”; of methylmercury in periphyton.

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USGS1999

Using multiple-polarization L-band radar to monitor marsh burn recovery

Aircraft L-band VV-, HH-, and VH-polarizations were examined as tools for monitoring burn recovery in a coastal marsh. Significant relationships were observed between time-since-burn (difference between burn and image collection dates; 550-900 days after burn) and returns related to all polarizations. As marsh burn recovery progressed, VV returns decreased while HH and VH returns increased. Radar returns extracted from control sites adjacent to each burn-simulated nonburn marsh and were not individually or in combination significantly related to the timesince-burn. Normalized by the control data, VH-polarization explained up to 83% of the total variations. Overall, the L-band multipolarization radars estimated time-since-burn within ±59 to ±92 days.

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USGS1999

Effectiveness of an existing estuarine no-take fish sanctuary within the Kennedy Space Center, Florida

Approximately 22% of the waters of the Merritt Island National Wildlife Refuge, which encompasses the Kennedy Space Center, Florida, have been closed to public access and fishing since 1962. These closed areas offer an opportunity to test the effectiveness of “no-take” sanctuaries by analyzing two replicated estuarine areas. Areas open and closed to fishing were sampled from Nov 1986 to Jan 1990 with 653 random trammel-net sets, each enclosing 3,721 m 2 . Samples from no-fishing areas had significantly (P < 0.05) greater abundance and larger fishes than fished areas. Relative abundance (standardized catch per unit effort, CPUE) in protected areas (6.4 fish/set) was 2.6 times greater than in the fished areas (2.4 fish/set) for total game fish, 2.4 times greater for spotted seatrout Cynoscion nebulosus , 6.3 times greater for red drum Sciaenops ocellatus, 12.8 times greater for black drum Pogonias cromis , 5.3 times greater for common snook Centropomus undecimalis , and 2.6 times greater for striped mullet Mugil cephalus . Fishing had the primary effect on CPUE, independent of habitat and other environmental factors. Salinity and depth were important secondary factors affecting CPUE, followed by season or month, and temperature. The importance of specific factors varied with each species. Median and maximum size of red drum, spotted seatrout, black drum, and striped mullet were also significantly greater in the unfished areas. More and larger fish of spawning age were observed in the unfished areas for red drum, spotted seatrout, and black drum. Tagging studies documented export of important sport fish from protected areas to fished areas.

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USGS1999

Florida Bay: A history of recent ecological changes

Florida Bay is a unique subtropical estuary at the southern tip of the Florida peninsula. Recent ecological changes (seagrass die-off, algal blooms, increased turbidity) to the Florida Bay ecosystem have focused the attention of the public, commercial interests, scientists, and resource managers on the factors influencing the structure and function of Florida Bay. Restoring Florida Bay to some historic condition is the goal of resource managers, but what is not clear is what an anthropogenically-unaltered Florida Bay would look like. While there is general consensus that human activities have contributed to the changes occurring in the Florida Bay ecosystem, a high degree of natural system variability has made elucidation of the links between human activity and Florida Bay dynamics difficult. Paleoecological analyses, examination of long-term datasets, and directed measurements of aspects of the ecology of Florida Bay all contribute to our understanding of the behavior of the bay, and allow quantification of the magnitude of the recent ecological changes with respect to historical variability of the system.

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USGS1999

Reconstructing the history of eastern and central Florida Bay using mollusk-shell isotope records

Stable isotopic ratios of carbon and oxygen (δ 13 C and δ 18 O) from mollusk shells reflect the water quality characteristics of Florida Bay and can be used to characterize the great temporal variability of the bay. Values of δ 18 O are directly influenced by temperature and evaporation and may be related to salinity, δ 13 C values of δ 13 C are sensitive to organic and inorganic sources of carbon and are influenced by productivity. Analyses of eight mollusk species from five short-core localities across Florida Bay show large ranges in the values of δ 13 C and δ 18 O, and reflect the variation of the bay over decades. Samples from southwester Florida Bay have distinct δ 13 C values relative to samples collected in northeastern Florida Bay, and intermediate localities have intermediate values. 13 C values of δ 13 C grade from marine in the southwest bay to more estuarine in the northeast. Long cores (>1m), with excellent chronologies were analyzed from central and eastern Florida Bay. Preliminary analyses of Brachiodontes exustus and Transenella spp. from the cores showed that both δ 13 C and δ 18 O changed during the first part of the twentieth century. After a century of relative stability during the 1800s, δ 13 C decreased between about 1910 and 1940, then stabilized at these new values for the next five decades. The magnitude of the reduction in δ 13 C values increased toward the northeast. Using a carbon budget model, reduced δ 13 C values are interpreted as resulting from decreased circulation in the bay, probably associated with decreased freshwater flow into the Bay. Mollusk shell δ 18 O values display several negative excursions during the 1800s, suggesting that the bay was less evaporitic than during the twentieth century. The isotope records indicate a fundamental change took place in Florida Bay circulation early in the twentieth century. The timing of the change links it to railroad building and early drainage efforts in South Florida rather than to flood control and water management measures initiated after World War II.

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USGS1999

Historical trends in salinity and substrate in central and northern Florida Bay: A Paleoecological Reconstruction using modern analogue data

Understanding the natural spatial and temporal variability that exists within an ecosystem is a critical component of efforts to restore systems to their natural state. Analysis of benthic foraminifers and molluscs from modern monitoring sites within Florida Bay allows us to determine what environmental parameters control spatial and temporal variability of their assemblages. Faunal assemblages associated with specific environmental parameters, including salinity and substrate, serve as proxies for an interpretation of paleoecologic data. The faunal record preserved in two shallow (<2 m) cores in central Florida Bay (Russell Bank and Bob Allen Bank) provides a record of historical trends in environmental parameters for those sites. Analysis of these two cores has revealed two distinct patterns of salinity change at these sites: 1) a long-term trend of slightly increasing average salinity; and 2) a relatively rapid change to salinity fluctuations of greater frequency and amplitude, beginning around the turn of the century and becoming most pronounced after 1940. The degree of variability in substrate types at each locality limits interpretations of substrate trends to specific sites. A common sequence of change is present in the Russell Bank and Bob Allen Bank cores: from mixed grass and bare-sediment indicators at the bottom of the cores, to bare-sediment dwellers in the center, to a dominance of vegetative-cover indicators at the top of the cores. Changes in interpreted salinity patterns around the turn of the century are consistent with the timing of the construction of the Flagler Railroad from 1905 to 1912, and the Tamiami Trail and the canal and levee systems between 1915 and 1928. Beginning around 1940, the changes in the frequency and amplitude of salinity fluctuations may be related to changes in water management practices, meteorologic events (frequent hurricanes coupled with severe droughts in 1943 and 1944), or a combination of factors. The correspondence of these changes in Florida Bay with changes in the terrestrial Everglades suggests factors affecting the entire ecosystem are responsible for the salinity and substrate patterns seen in Florida Bay.

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USGS1999

Variations in water clarity and bottom albedo in Florida Bay from 1985 to 1997

Following extensive seagrass die-offs of the late 1980s and early 1990s, Florida Bay reportedly had significant declines in water clarity due to turbidity and algal blooms. Scant information exists on the extent of the decline, as this bay was not investigated for water quality concerns before the die-offs and limited areas were sampled after the primary die-off. We use imagery from the Advanced Very High Resolution Radiometer (AVHRR) to examine water clarity in Florida Bay for the period 1985 to 1997. The AVHRR provides data on nominal water reflectance and estimated light attenuation, which are used here to describe turbidity conditions in the bay on a seasonal basis. In situ observations on changes in seagrass abundance within the bay, combined with the satellite data, provide additional insights into losses of seagrass. The imagery shows an extensive region to the west of Florida Bay having increased reflectance and light attenuation in both winter and summer begining in winter of 1988. These increases are consistent with a change from dense seagrass to sparse or negligible cover. Approximately 200 km 2 of these offshore seagrasses may have been lost during the primary die-off (1988 through 1991), significantly more than in the bay. The imagery shows the distribution and timing of increased turbidity that followed the die-offs in the northwestern regions of the bay, exemplified in Rankin Lake and Johnson Key Basin, and indicates that about 200 km 2 of dense seagrass may have been lost or severely degraded within the bay from the start of the die-off. The decline in water clarity has continued in the northwestern bay since 1991. The area west of the Everglades National Park boundaries has shown decreases in both winter turbidity and summer reflectances, suggestive of partial seagrass recovery. Areas of low reflectance associated with a major Syringodium filiforme seagrass meadow north of Marathon (Vaca Key, in the Florida Keys) appear to have expanded westward toward Big Pine Key, indicating changes in the bottom cover from before the die-off. The southern and eastern sections of the Bay have not shown significant changes in water clarity or bottom albedo throughout the entire time period.

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USGS1999

Vegetation and hydrology of land-margin ecosystems: the mangroves of South Florida in relation to disturbance, global change and response to restoration

The USGS Florida Caribbean Science Center's Restoration Ecology Branch and Florida International University is conducting research on disturbance, global change and restoration of land margin ecosystems of South Florida. Criticial research for the restoration of these systems involves understanding the responses of mangrove forests to changes in the quality, quantity, timing and distribution of freshwater inflows, response to global change (e.g. sea level rise) and catastrophic disturbances such as hurricanes.

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USGS1999

USGS Science for Restoration of South Florida: The South Florida Ecosystem Program

As land and resource managers see the value of their resources diminish, and the public watches the environments they knew as children become degraded, there are increasing calls to restore what has been lost, or to build productive ecosystems that will be healthy and sustainable under the conditions of human use. The U.S. Geological Survey's (USGS) Placed-Based Studies Program was established to provide sound science for resource managers in critical ecosystems such as South Florida (fig. 1). The program, which began in south Florida in 1995, provides relevant information, high-quality data, and models to support decisions for ecosystem restoration and management. The program applies multi- and interdisciplinary science to address regional and subregional environmental resources issues.

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USGS1999

Canal and wetland flow transport interaction; coupling models for canal and wetland interactions in the South Florida ecosystem

Introduction The U.S. Geological Survey is one of several agencies participating in the scientific effort to provide knowledge that can help protect and preserve the ecosystem of south Florida. One project of the intergovernmental South Florida Ecosystem Program (SFEP) is focused on developing a computer model to simulate the flow of water and analyze the transport of waterborne chemical constituents between canals and wetlands. Quantification of dynamic flows within the south Florida ecosystem is vital to understanding the implications of the residence time of water, potentially nutrient-enriched (with nitrates or phosphates) or contaminant-laden (with metals or pesticides), that can alter plant life and affect biological communities. Nutrients carried in the water conveyed by canals draining agricultural areas and dispersed into wetlands by canal discharges, by levee overflows, or by seepage are considered to be a major contributor to changes in the types of vegetation found in the Everglades. Freshwater inflows, typically of varying magnitudes and durations, not only influence the salinity of Florida Bay but also potentially carry toxic substances that can affect and alter the Bay's aquatic biota. The simulation capability being developed within the SFEP can be useful for identifying approaches to alleviate adverse impacts of excessive or deficient flows and transported constituents. Through strategic use of a simulation model, cause-and-effect relations between discharge sources, flow magnitudes, transport processes, and changes in vegetation and biota can be investigated. The effects of driving forces on nutrient cycling and contaminant transport can then be quantified, evaluated, and considered in the development of remedial management plans.

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