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1: Ecosystems and Populations

Amar Nayegandhi1, John Brock2, C. Wayne Wright3, and Monica Palaseanu-Lovejoy1

1 Jacobs Technology, Inc., Florida Integrated Science Center, St. Petersburg, Florida
2 U.S. Geological Survey, Reston, Virginia
3 U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida

The USGS Coastal and Marine Geology Program is supporting the creation of new capabilities for the synoptic remote sensing of coastal-marine and terrestrial environments based on aircraft and satellite sensors.  Special emphasis has been placed on the use of aircraft-mounted light detection and ranging (lidar) and multi-spectral imaging to map coral reef ecosystem geomorphology, topographic roughness, and habitats at spatial scales finer than 2 m.  Through partnerships with the National Aeronautics and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA), and National Park Service (NPS), these capabilities have been applied to create highly detailed benthic and submerged topography maps of portions of the Florida reef tract and the U.S. Virgin Islands.  In a similar collaboration between the USGS and NPS, aircraft lidar and color-infrared imaging have been acquired and processed to create high-resolution subaerial topographic maps of barrier island geomorphology and vegetated habitats for NPS Inventory and Monitoring Programs along the Northeast Atlantic and the Gulf Coast. The Experimental Advanced Airborne Research Lidar (EAARL) system, used in these data-acquisition efforts, is a unique waveform-resolving, green-wavelength lidar system capable of mapping subaerial and submerged topography simultaneously. The EAARL sensor records the time history of the return waveform within a small footprint (20-cm diameter at nominal flying altitude of 300 m) for each laser pulse, enabling characterization of vegetation canopy structure and “bare earth” topography under a variety of vegetation types. EAARL surveys conducted over coastal-vegetation communities at Gulf Islands National Seashore and Jean Lafitte National Park were used to develop and evaluate the capability of lidar waveform data to determine the vertical distribution of canopy characteristics across a diverse set of vegetation classes. 

In total, these new coastal remote-sensing, mapping, and point-monitoring tools constitute a unique integrated package of instrumentation and software that may be deployed in support of appropriately timed and scaled zoning decisions by management authorities in order to conserve and sensibly exploit nearshore coastal and marine ecosystems.

Contact Information: Amar Nayegandhi, U.S. Geological Survey, Florida Integrated Science Center, 600 4th Street, St. Petersburg, FL 33701; phone: 727-803-8474; email: anayegandhi@usgs.gov

Kenneth J. Sulak, April D. Norem, Kirsten E. Luke, Michael T. Randalland Jana M. Miller

U.S. Geological Survey, Florida Integrated Science Center, Gainesville, Florida

This study represents the first quantitative analysis of the fauna associated with Lophelia reefs in the Gulf of Mexico, and generally in the western North Atlantic. It also provides the first evidence of a distinctive mineralogical regime on Viosca Knoll. The biology and geology of Lophelia pertusa coral reefs and associated hard-bottom biotopes were investigated at two depth horizons (325m and 500m depth) on Viosca Knoll in the northern Gulf of Mexico. Megafauna was quantified from high-quality submersible digital video frame grabs using Coral Point Count software. Megafaunal assemblages classified by multivariate analyses of video data were used to characterize and differentiate the key biotopes used by fishes as either Lophelia coral ‘Thicket’, ‘Rock’ (3-D), ‘Plate’ (2-D), ‘Plate/Chemo’ (chemo-seeps) or ‘Open’ (soft substrate). Basal reef rock was analyzed for mineralogy via x-ray diffraction. Reef sand collected was analyzed to identify major biotic contributors to reef substrate. In striking contrast to Lophelia reefs in the Atlantic, ‘Rubble’ biotope was essentially absent in this study. Lophelia coral ‘Thicket’ biotope was extensively developed on the 500 m site. Mixed species oases comprised of Lophelia, black corals, sponges and other taxa occurred primarily on the 325 m site. Among structured biotopes, species richness was highest for ‘Rock’ biotope, and lowest on Lophelia ‘Thicket’. Thus, contrary to expectations, Lophelia biotope in the northern Gulf of Mexico does not support a particularly rich megafaunal. Indeed, rarefaction analysis suggests species richness is highest on “Open’ biotope, again contrary to expectations. The Viosca Knoll fish fauna consisted of at least 54 species, dominated by sit-and-wait and hover-and-wait carnivores and generalized mesocarnivores. Only one specialized microcarnivore, Grammicolepis brachiusculus, appears to be highly associated with Lophelia reefs. Radiometric determinations indicate an age of <400 yrs for contemporary Lophelia reefs, and of 25.0-26.0 ky for the overall Lophelia ecosystem in the northern Gulf of Mexico. These findings indicate that reefs flourished during the low sea-level stand of the Pleistocene Wisconsonian Glaciation. From the young age of contemporary reefs, relative to the much greater age of sub-fossil Lophelia, it may be hypothesized that reef-building has occurred episodically over geological time. X-ray diffraction of the typical black substrate rock revealed unexpected goethite mineralogy, whereas methanogenic carbonates had been anticipated in the area of methane seeps. The atypical rock substrate mineralogy, and the exclusive occurrence in the Gulf of Mexico of well-developed Lophelia reefs on Viosca Knoll suggest a uniquely favorable environmental context for reef development. The absence of coral mounds and of extensive rubble fields indicates a distinct difference relative to Lophelia reefs elsewhere in the world ocean. Soft substrates found on Viosca Knoll are biogenic sands, comprised predominantly of the eroded calcium carbonate shells, spines, and skeletons of reef inhabitants. Thus, Lophelia reefs do create a unique sedimentary regime very different from that of the surrounding abiogenic fine sediment of the open slope.

Contact Information: Kenneth J. Sulak, U.S. Geological Survey, Florida Integrated Science Center, 7920 NW 71st Street, Gainesville, FL, 32653, USA, Phone: 352-264-3500, Email: ksulak@usgs.gov

Jeremy D. Decker1, Eric D. Swain1, Brad M. Stith2, and Catherine A. Langtimm2

1 U.S. Geological Survey, Florida Integrated Science Center, Ft. Lauderdale, Florida
2 U.S. Geological Survey, Florida Integrated Science Center, Gainesville, Florida

The Picayune Strand Hydrologic Restoration Project (PSRP), which is part of the larger Comprehensive Everglades Restoration Plan (CERP), is focused on restoring an over-drained, 85-mi2 rural area in western Collier County, Florida. The ultimate goals of the project are to reestablish predevelopment hydrologic patterns and to improve the downstream coastal flows. To fulfill these goals, proposed changes include the removal or modification of existing roads and canal networks, as well as the construction of several pumping stations and spreader canals. The purpose of the current study is to determine whether the proposed changes will adversely affect the primary habitats of West Indian manatees and other temperature- and salinity-sensitive species in the region.

With the addition of Heat transport capabilities within the FTLOADDS (Flow and Transport in a Linked Overland Aquifer Density Dependant System) coupled hydrodynamic, 2-D surface-water and 3-D ground-water modeling code, model simulations can now be used to predict changes in both temperature and salinity caused by hydrologic alterations. This formulation has most recently been applied to the Ten Thousand Islands (TTI) area in southwestern Florida where the PSRP is planned. The model was initially constructed to represent existing conditions, with several north-south oriented canals that connect to the Port of the Islands marina, and then to the coast. Alterations were incorporated to represent the proposed restoration changes, which include (1) filling in or plugging canals, (2) creating spreader canals, and (3) building levees and pump stations.

Simulation results demonstrate how freshwater flows may be redistributed as well as potential changes to seasonal inundation patterns. Salinity differences appear to be greatest in coastal areas west of the Port of the Islands marina, and there is evidence of substantial salinity and temperature differences within the marina itself, which could adversely affect the manatee habitat. Simulation results have also been compared to specimen tracking locations to determine how environmental changes may affect animal behavior during high thermal stress periods. The results for both current and post-restoration conditions have been integrated into ecological models, including a nodal network model that can be used to predict manatee responses to environmental changes.

In addition to the model described above, a secondary, 3-D sub-model of the Port of the Islands marina is being constructed using the EFDC (Environmental Fluid Dynamics Code) modeling tool. Incorporating output from the larger (TTI) model as boundary conditions, the refined 3-D model will be used to study the passive thermal refuge present within the Port of Islands marina due to vertical stratification of temperature and salinity. Proposed alterations can then be modeled to determine their potential effects on this critical manatee habitat.

Contact Information: Jeremy D. Decker, U.S. Geological Survey, Florida Integrated Science Center, 3110 SW 9th Avenue, Ft. Lauderdale, FL 33315; phone: 954-377-5962; email: jdecker@usgs.gov

Robert K. Bonde, U.S. Geological Survey, Florida Integrated Science Center, Gainesville, Florida

Manatees have had an uncanny ability to establish new populations within their subtropical range, as evidenced by their evolutionary history and genetic traits. Although vicariance separated the taxa over time, the vagility of this unique group of aquatic mammals enabled populations to disperse through deliberate migration or stochastic events. This phenomenon of population expansion is characteristic when the core population is large enough to act as a source to populate new habitats. Although these adjacent habitats are not always biologically suitable, the sirenians have persisted due to their ability to adapt to the new surroundings. For example, specific but subtle morphological characteristics have evolved within each species/subspecies. Florida is an example of a more recently established population (within the last 20,000 years) and the northwest Florida group of manatees that overwinters at Crystal River is an example of a new subpopulation. Within Florida there are several distinct habitat types that require different survival strategies for the resident manatees.

Previous analyses have examined the genetic diversity of the Florida population. Early studies using allozymes and nuclear microsatellites suggest that Florida manatees have low to average genetic variation and are a relatively homogeneous population. Mitochondrial DNA analyses also suggest low genetic diversity among Florida manatees, which may have been caused by inbreeding, a bottleneck event, or the founder effect.

The Crystal River manatee population is well established and has increased in numbers over the last 30 years. Long-term data sets (over 35 years) using photo-identification of distinct individuals (n=417) from Crystal River exist for this well-studied winter population of manatees; furthermore, an aerial survey recorded the highest count of 438 manatees in this region in 2006. Although an increase in this subpopulation has occurred in recent decades, the possible genetic impacts of the accelerated growth of such a homogeneous subspecies may affect the well-being of the Florida population as a whole. Genetic connectivity and pedigree studies can provide information on breeding among different population units. Knowledge of the genetic composition of this group will determine whether breeding with parapatric populations is occurring, and may play a role in understanding the population structure by complementing efforts to model various life history strategies. To date, 700 samples (550 from calves and 150 from adults) have been collected from the Crystal River winter resident manatee population, providing a good base for future fine-scale genetic applications. This effort will allow for inferences about Florida manatee life history and population structure, including reproductive and breeding potential, migration and movements, and overall population size.

Contact Information: Robert K. Bonde, U.S. Geological Survey, Florida Integrated Science Center, 2201 NW 40th Terrace, Gainesville, FL 32605; phone: 352-264-3555; email: rbonde@usgs.gov

Colette C. Jacono, U.S. Geological Survey, Florida Integrated Science Center, Gainesville, Florida

Scleria lacustris is an introduced sedge initially discovered in south central Florida wetlands in 1988. Growing to two meters in height, this nonnative plant has invaded and dominated large portions of local wetland communities. Unlike dominant native species, it is annual in habit, dying at the end of the growing season and depending on seed for repopulation. Occurrence of this species appears to be restricted to natural areas that have maintained, or are managed for, surface water fluctuation. Seed banks and their function in seedling regeneration are crucial in the perseverance of annual species, regardless of their status as weeds or rare plants. Seed banks may interact with the hydrologic regime of particular wetlands and influence standing plant composition. Researchers consider hydrologic fluctuation to be a type of natural disturbance, important in maintenance of biological communities. However, in Florida the function of seed banks within wetlands characterized by hydrologic change is only beginning to be understood. I present evidence that supports the hypothesis that the seasonal wet/dry hydrologic cycle of Florida wetlands controls the incidence of an invasive species by selecting for strategies integral to seed dormancy break, seed bank longevity, and seedling regeneration.

In 2004, within-population random sampling of the S. lacustris seed bank and its seedlings was conducted at a lakefront marsh south of Kissimmee and at a depression marsh west of Vero Beach (VB). Results indicated that S. lacustris created an extensive soil seed bank with a high viability which, though shallowly buried and resulting in significant transition to seedlings, persisted beyond one year.

The 2004 findings were fundamental in testing the influence of seasonal hydrology on S. lacustris seed bank function and regeneration. In 2005 and 2006 seed bank and vegetation evaluations were conducted along three transects of the VB marsh gradient. Results from field sampling in conjunction with greenhouse trials, demonstrated that specific hydrologic conditions were required for seed bank survival and seedling regeneration. Regeneration of S. lacustris was restricted to bare, drained soils following surface water dry down in spring. Recent lower than average rainfall and receding water tables likely exacerbated the spring recession of surface water and promoted colonization from seed banks. Seed storage experiments clarified the significant influence of wet season flooding on both dormancy break and seed bank survival. Furthermore, seedling regeneration, seedling survival and adult productivity were significantly different along the marsh gradient as indicated by an uphill cut off from the optimum conditions provided in the previously flooded zone. The unique specificities required by this species at crucial life stages were shown to be met by the fluctuating wet/dry environment of the seasonal marsh, explaining in part the advantage of this annual sedge to proliferate in wetlands of Florida.

Contact Information: Colette C. Jacono, U.S. Geological Survey, Florida Integrated Science Center, 7920 NW 71st Street, Gainesville, FL 32653; phone: 352-264-3484; email: cjacono@usgs.gov

Donald L. DeAngelis, U.S. Geological Survey, Florida Integrated Science Center, Fort Lauderdale, Florida

Models used in applied aspects of ecology, such as dealing with specific questions of environ-mental conservation, assessment, and restoration, are usually far different from models used to elucidate theoretical issues. Temporal variability and spatial heterogeneity characterize the environments of most real ecological problems, whereas theoretical models tend to avoid such complexities and are kept as simple as possible to reveal theoretical insights. However, as ecological theory is extended to more and more complex phenomena in which spatial hetero-geneity and temporal fluctuations play a role, its potential applications to real ecosystems and to specific applied issues are increasing. In this paper, we develop a model, Greater Everglades Fish Model (GEFISH), for the dynamics of the small fish community in the freshwater Ever-glades that can be used in both applied and theoretical frameworks.

This model is part of the Across Trophic Level Systems Simulation (ATLSS) set of models, but is designed to examine fish dynamics on sub-regions within the Greater Everglades, rather than the entire South Florida Water Management Model region. We examine the dynamics of a small food web in which nutrients are recycled. The members of the food web include primary producers, detritus, invert-ebrate detritivores, several fish species including fish consumers of detritivores and periphyton as well as piscivores, and nutrients. The local food web model is contained in every cell of a two-dimensional topography 10,000 cells (100 x 100 grid), in which water levels rise and fall sinusoidally through the year. The fish are assumed to be migratory in that they follow the advancing wetting front when water levels increase, and move to areas that are still flooded when water levels decrease. In the model some of the fish are allowed to move up the elevation gradi-ent during rising water and down the gradient during falling water.

The model is used to show how details of hydrology can affect both biodiversity of the fish community and its productivity over the year. For example, decreases in water level fluctuations below the natural levels can lead to exclusion of some species that are strongly adapted to seasonal dispersal. If water level fluctuations are too low, biomass production of many of the small fishes may decline, as the area over which they forage decreases. The model is applied to specific areas of the Everglades for which monitoring data on small fishes are available. These include research sites (e.g., Dr. J. C. Trexler of FIU) in Water Conservation Area 3 and in Shark River Slough.

Contact Information: Donald L. DeAngelis, U.S. Geological Survey, Florida Integrated Science Center, Department of Biology, University of Miami, Coral Gables, FL 33124; phone 305-284-1690; email: don_deangelis@usgs.gov