Abstract: This study investigated the extent to which deep-dwelling, infaunal foraminifera bias modern and fossil distributions in the subtropical mangroves of the Everglades (southwest Florida), and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. Typically, these studies are based on modern analogs from the upper 1 to 2 cm of sediments, as most benthic foraminifera live in the surface 1 cm, but in tropical mangrove environments, deep-dwelling infaunal foraminifera may be more common. The vertical distributions of live assemblages in cores from a mudflat and three mangrove sites were investigated. To examine the preservation potential of dead tests, distributions of wall types and inner test linings were recorded. The living depths of benthic foraminifera showed a landward deepening from 1 to 3 cm in mudflats and low mangroves and from 7 to 10 cm in middle and high mangroves, possibly due to a landward increase in oxygenation of the subsurface sediments. Modern assemblages from the top 2 cm included species common in the deep infauna and contained, on average, 36% of the total standing crop. Additions to total assemblages at greater depths by subsurface production were negligible. Thus, the upper 2 cm of the sediment column would be sufficient as a modern analog for paleoenvironmental studies in the southwestern Everglades. Preservation of dead tests is influenced by a landward increase in the degradation of agglutinated taxa through oxidation/bacterial breakdown of organic cements. Fortuitously, calcareous taxa preserve well in the carbonate-buffered sediments of the Everglades.

Southeast Florida's beaches, which are heavily developed and imperiled by rising sea level, continue to be seriously mismanaged and uneconomically maintained and to generate increasing environmental stress for adjacent marine habitats. Broward County heads the list of counties that stretch from St. Lucie southward to Miami-Dade. Five serious problems plague the stability of these barrier-island shorelines: inlet disruption of littoral drift; beach management that enhances shore erosion (lack of shore vegetation, inappropriate vehicular traffic, and structural protections that enhance erosion); historically very poor-quality renourishment sediment (in size and durability); strong resistance by coastal engineering and dredging firms and counties to embrace an understanding of sandy shore dynamics; and a philosophy that renourishment projects are a solve-all management approach to maintaining beaches and protecting infrastructure. This has led to seriously destabilized beaches, overly aggressive beachfront development, major economic waste, and severe environmental degradation to adjacent marine waters and associated valuable sandy bottom and hard-bottom communities. Many of these sandy shorelines may well not survive this global warming century of rapidly rising sea level. It is economically and environmentally critical for both the future risks to be understood and for lessons from the repeated failed history of beach management to be learned. Continued mismanagement will shorten the inhabitable lifetime of this developed sandy coast by decades and at great economic and environmental cost.

A new method is proposed to estimate porosity within heterogeneous karst aquifers using techniques borrowed from remote sensing and geospatial analysis. High-resolution borehole images are classified into binary images consisting of pixels designated as either rock matrix or pore space. Two-dimensional porosity is calculated by summing the total area occupied by pores within a rectangular sampling window placed over the binary image. Small sampling windows quantify the heterogeneous nature of porosity distribution in the aquifer, whereas large windows provide an estimate of overall porosity. Applying this procedure to imagery taken from the Biscayne aquifer of south Florida yields a porosity of ∼40%, considerably higher than the ∼28% mean porosity measured in the laboratory from recovered core samples. Geospatial analysis, using geographic information systems, may provide the more reliable estimate, because it incorporates large solution cavities and conduits captured by the borehole image yet not recovered in core samples. The representative elementary area (REA) is estimated from borehole images by varying the size of sampling windows around prominent conduits and evaluating the change in porosity as a function of window size. Average porosities decrease systematically with increasing sampling window size, eventually converging to a constant value of ∼40% for a window height of ∼5 m. The representative elementary volume (REV) for porosity in this section of the Biscayne aquifer is thus estimated as ∼125 m 3 .

Combined analyses of cores, borehole geophysical logs, and cyclostratigraphy produced a new conceptual hydrogeologic framework for the triple-porosity (matrix, touching-vug, and conduit porosity) karst limestone of the Biscayne aquifer in a 0.65 km 2 study area, SE Florida. Vertical lithofacies successions, which have recurrent stacking patterns, fit within high-frequency cycles. We define three ideal high-frequency cycles as: (1) upward-shallowing subtidal cycles, (2) upward-shallowing paralic cycles, and (3) aggradational subtidal cycles. Digital optical borehole images, tracers, and flow meters indicate that there is a predictable vertical pattern of porosity and permeability within the three ideal cycles, because the distribution of porosity and permeability is related to lithofacies. Stratiform zones of high permeability commonly occur just above flooding surfaces in the lower part of upward-shallowing subtidal and paralic cycles, forming preferential groundwater flow zones. Aggradational subtidal cycles are either mostly high-permeability zones or leaky, low-permeability units. In the study area, groundwater flow within stratiform high-permeability zones is through a secondary pore system of touching-vug porosity principally related to molds of burrows and pelecypods and to interburrow vugs. Movement of a dye-tracer pulse observed using a borehole fluid-temperature tool during a conservative tracer test indicates heterogeneous permeability. Advective movement of the tracer appears to be most concentrated within a thin stratiform flow zone contained within the lower part of a high-frequency cycle, indicating a distinctly high relative permeability for this zone. Borehole flow-meter measurements corroborate the relatively high permeability of the flow zone. Identification and mapping of such high-permeability flow zones is crucial to conceptualization of karst groundwater flow within a cyclostratigraphic framework. Many karst aquifers are included in cyclic platform carbonates. Clearly, a cyclostratigraphic approach that translates carbonate aquifer heterogeneity into a consistent framework of correlative units will improve simulation of karst groundwater flow.

The regional Floridan aquifer system has been dewatered and otherwise altered extensively throughout much of Florida and coastal Georgia by groundwater pumpage (mining). An increasing threat to this karst aquifer system is structural mining of aquifer formations, primarily to produce fertilizers, titanium products, construction materials, and pet food supplements. These excavations often include mechanical dewatering to facilitate shallow and deep extraction of the aquifer formations. All include reduced aquifer levels, dewatering of the aquifer system, and altered hydroperiods at and surrounding the excavated pits, due to increased void space and evapotranspirative losses (nonmechanical dewatering). Only mechanical dewatering is considered by regulatory agencies during evaluations of applications for structural mining of the aquifer system. Despite refuting data, open pits resulting from these excavations increasingly are portrayed as subsurface “reservoirs” that create new or enhanced sources of water in areas where natural groundwater supplies have been depleted. Four permits and sites were evaluated for excavated and proposed pits in SE, NW, SW, and east-central Florida's natural areas used for groundwater supply. The combined surface area for pits under those four permits will result in ∼237,000 m 3 /d (∼62.7 million gallons per day [Mgd]) of induced discharge from the regional Floridan aquifer system due to nonmechanical dewatering. This volume is more than twice the reported pumpage from the combined three municipal supply wells at the Miami-Dade West Well Field. The ∼123 ha (∼308 ac) SW Florida mine, most recently excavated in an area designated as critical habitat for the federally listed Florida panther, will result in induced aquifer discharge of ∼1505 m 3 /d (0.4 Mgd) due to nonmechanical dewatering. This loss is equivalent to ∼5% of all water used by domestic supply wells in that county in 1990. That recently initiated excavation in SW Florida revealed environmental damage extending beyond the mine boundaries, to surrounding private property, and is the first documented case of such damage solely from aquifer formation mining and nonmechanical dewatering of the aquifer system. A federal court ruled on 22 March 2006 that the U.S. Army Corps of Engineers and U.S. Fish and Wildlife Service had failed to carry out their duty to protect the federal wetlands and protected species by issuing permits for mining in the SE case-study area.