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Research -- Completed Projects

Development of a real-time SAV management tool using RECON (2007-2008)

research boat and light sensor
Representation of the subsurface light field is a critical component of pelagic ecosystem models and for protection and restoration of SAV (Submerged Aquatic Vegetation) habitats. Four optical models were developed for and specifically tuned to the Caloosahatchee River and Estuary, San Carlos Bay and Pine Island Sound located in Southwest Florida during this project. Development of these tools provide local resource managers with a real-time assessment of estuarine conditions relevant to SAV by integrating seagrass light requirements with RECON. These tools are critical choosing appropriate SAV restoration sites and evaluating the effect of large scale everglades restoration projects, such as C-43 reservoir construction.

Related Publications: Final Report

Tape grass restoration (2008)

To help restore aquatic habitats in the Caloosahatchee River and Estuary, SCCF and partners launched an experimental project holding tapegrassto learn if tape grass planted upstream of the Franklin Lock and Dam (S-79 water control structure) on the Caloosahatchee River can help re-seed the estuary downstream. Beds of tape grass provide prime habitat for native juvenile blue crabs, fish and other species that spend early developmental stages in shallow estuaries where they can hide from large predators. SCCF scientists and research assistants planted tapegrass Vallisneria americana in circular beds at five locations in the Caloosahatchee River. The native wide-bladed grass typically grows in Florida’s fresh or mildly saline waters. By planting upstream of the Franklin Lock and Dam, the new plants will be less vulnerable to changes in salinity levels nearer the coast and so may continue providing seed stock to downstream areas. The multi-year rainfall deficit has dramatically reduced the amount of freshwater runoff and river flows available to help maintain the right salinity balance for tape grass to grow in the Caloosahatchee Estuary. Tape grass for the study was provided by Lee County Hyacinth Control District, which provided the plants at no costs. SCCF planted three beds at each locations, one was surrounded by a wire mesh cage to prevent turtles and fish from eating the fresh grass.
Read the report.

Mangroves of Sanibel-Captiva (2003-2008)

A conspicuous habitat on Sanibel and Captiva Islands are mangroves. Mangroves provide refuge for wading birds and provide storm and flood protection. Distributed throughout the islands are 27 study plots,approximately 36 feet in diameter. Within the plots, all large trees are permanently tagged and the number and of seedlings are measured.The health of mangrove habitats depends on tidal flushing, which has been altered over the course of human development of tropical coasts. Research on the factors contributing to degraded mangroves and the best way to improve or enhance mangroves is the subject of ongoing study. Further, restoration activities to increase high quality mangrove habitat on Sanibel and Captiva are led by SCCF marine laboratory.

Related Publications: Milbrandt et al 2006, Proffitt et al 2006

Clam Bayou Mangroves (2003-2008)

Despite repeated attempts to re-introduce tidal flooding to this mangrove-lined lagoon, Clam Bayou remained isolated from tidal clam bayou plantingflow resulting in severely degraded mangrove wetlands. All reproductively productive mangroves were now standing dead snags. The purpose of this research was to characterize mangrove, fish, and seagrass communities in Clam Bayou in addition to a reference embayment to provide benchmarks for measuring restoration success. A box culvert provided a permanent tidal connection and a restoration solution for Clam Bayou in 2006. Now that the communities are well-characterized,predictions about the pace and direction of recovery can be inferred.

Related Publications: Final report to City of Sanibel, Restoration and Creation Conference Proceedings 2006, Journal of Coastal Research (in press), co-authored with James Evans, City of Sanibel

Physiological Responses of Tape Grass (Vallisneria americana) to Light, Temperature and Salinity

Seagrasses and brackish water submersed aquatic vegetation (or SAV) like tapegrass (Vallisneria americana) are valuable components of estuarine ecosystems. These plants are not actually in the family of grasses, but are similarly monocots. All flowering plants are divided into dicots and monocots (the latter name most simplistically refers to the singleseed leaf produced by the embryo). A two year study (2006 to 2008) of physiological responses of tape grass to environmental parameters vallisneriasupported by the SFWMD, was just completed. A series of experiments measuring the growth and photosynthetic rates of tape grass at two salinities (0 and 10 ppt), and two light levels (42 and 331 µE m-2 s-1) at six different water temperatures were conducted in order to determine the relationship between the environmental parameters and photosynthetic rates and ultimately plant growth as a surrogate for tape grass health. The temperature ranges tested covered seasonally observed river temperatures (14 to 34ºC). Plant growth rate is known increase with temperature to an optimum temperature and then decline,and this optimum temperature was not known for local tape grass, and it could depend on light level and salinity. Photosynthesis vs. irradiance(P-I) curves were produced at each temperature for each treatment. Leaf elongation rates were close to zero at the lowest temperature (13°C),generally increased with temperature to an average of 1.3% per day at30°C, and were significantly lower in the high salinity treatments. The low light treatment leaves grew the fastest except at 13°C and 32°C,but the high light, low salinity plants had the largest biomass increase (including new shoots and roots). Longest average leaf lengths and highest elongation rates were obtained in the 30°C experiment. The highest maximum photosynthetic rates (Pmax) were at 30 and 32°C. The lethal temperature at 0 ppt was 36°C, which is a temperature that is reached in shallow areas where the water is dark from tannins. The results of these measurements will be used to provide information for formulating a tape grass model that can be used to predict response of tape grass growth to water management decisions affecting salinity.

Caloosahatchee Estuary Seagrass / SAV Monitoring

monitoring savUnder a contract with SFWMD, SCCF monitored submersed vegetation from upriver near Beautiful Island to San Carlos Bay from 2004 until spring 2008.This monitoring project was designed to detect changes in seagrass health and coverage in response to water quality changes. The data show a dramatic response to long period of high volume river discharges of dark water. During this period, turtle grass coverage declined by 70%at Pine Island Sound sites. Subsequently, shoal grass recovered rapidly to coverage greater than before the releases. Plants throughout the main stem of the river never fully recovered from the dark water releases thought light levels were usually suitable at a depth of 1meter and widgeon grass was lost from two sites. During 2006, a drought caused salinities to increase at the upstream sites to levels higher than the tolerance level for tape grass. These salinities remained high until 2008’s rainy season, and the tape grass will need to be replaced since there is no seed bank. The data from this monitoring program will be used to judge the ecosystem effects of water quality changes(success of Everglades RECOVER restoration efforts). The data is also being used to calibrate and validate seagrass simulation models. These models can be used, for example, to predict seagrass response to changes in salinity at different light levels and temperatures.

Mangrove Restoration at Shell Point (2005)

A large mangrove die-off area within the protected coastline managed dead mangrovesby Estero Bay Aquatic Buffer Preserve was targeted as a demonstration of new restoration techniques. Within the die-off area, black mangrove seedlings were thriving in circular patches of saltwort (Batis maritima). To test the prediction that saltwort surved as a nurse species to black mangrove seedlings, survivorship of black mangroves was determined in saltwort patches and outside. No surviving black mangroves were left after two months, while half of those planted in saltwort survived.

Related Publications: Final report to SFWMD, Hydrobiologia 2005, co-authored with Megan Tinsley, Audubon of Florida

Blue Crab Populations in the Caloosahatchee (2005-2007)

blue crabBlue crab landings data were compiled and analyzed to develop management targets related to the freshwater inflow to the Caloosahatchee estuary. Landings, effort and catch-per-unit effort of the blue crab landings were analyzed relative to environmental conditions within and around the Caloosahatchee River/Estuary. Major findings of this study are a correlation between the Secchi disk measurement and the catch per unit effort (CPUE) of crabs caught in the Caloosahatchee River. When Secchi disk readings were high (water was clearer), the CPUE was higher. Other water quality parameters, including flow rate did not correlate with landings.

Related Publications: Final report to SFWMD.

Ecological and Geographical Extent of Lake Okeechobee Releases to the Caloosahatchee Estuary (2005-2006)

Above-average hurricane activity and rainfall forced multiple releases of large volumes of freshwater into the Caloosahatchee milbrandtEstuary in 2005 and 2006. The purpose of this research was to characterize the optical properties of water from the lake and basin sources and determine whether releases were responsible for light limitation in seagrass populations. Seagrass growth rate near the mouth of the Caloosahatchee River was significantly lower than other stations in the lower estuary. Lake releases were typified by high total suspended solids (TSS) and high colored dissolved organic matter (CDOM). Basin freshwater releases were high in CDOM. Mass spectrometry of dissolved organic matter (DOM) indicated that UV and bacterial degradation was occurring as DOM from freshwater sources significantly differed from DOM in the estuary.

Related Publications: Final report to SFWMD, Milbrandt, in prep, Estuaries and Coasts.

Macroalgae and seagrass monitoring during spring and summer of 2006.

As a consequence of large watershed influxes of nutrients and turbid water following several hurricanes, seagrass coverage was reduced and algal biomass was high.
diverMacroalgal biomass, Karenia spp. cell density, and seagrass characteristics and growth rate in the water surrounding Sanibel were recorded in the spring and summer of 2006. Average macroalgal biomass in July in water surrounding Sanibel was high (M = 215 g d wt m-2) compared to other estuaries such as Biscayne Bay, and indicative of eutrophic conditions. At sites near the river, turtle grass percent cover was more than 70% lower than it was in 2005. Turtle grass abundance and growth were higher at sites farther from the river mouth, though epiphytic algal coverage was often high at all sites. Light attenuation underneath dense algal mats averaged less than 7% of surface irradiance, which is below the level required by seagrasses for growth.

Identification of Microbes Critical to the Enhancement of Seagrass Restoration (2007)

measuring seagrassA greenhouse experiment was designed to repeat an experiment in the field. Seagrasses were transplanted with autoclaved sediments and 10 mM sodium sulfide to determine whether rhizome associated bacteria were moderating toxic effects from sulfide intrusion. The highest growth rates were recorded in untransplanted seagrasses, followed by seagrasses transplanted in native soils and the lowest growth was observed in seagrasses transplanted with autoclaved sediments. Subsequent analysis of DNA from the rhizome bacterial community was largely inconclusive.

Relevant Publications: Milbrandt, in press, Botanica marina. Final report to Charlotte Harbor National Estuary Program .

Repair and Maintenance of Seagrass Meadows in Charlotte Harbor (2007)

Propeller scarring of seagrass beds is a widespread problem in Charlotte Harbor. Shallow water and inexperienced boaters cause thousands of scars every year. New techniques for restoration of these propeller scars were monitored to determine feasibility of prop scar restoration in Southwest Florida. Injections of prop scars and bringing scars back to grade were monitored relative to targets and unmanipulated scars. While no significant differences were observed, there were greater growth rates in injected scars over the one year monitoring period. Differences among treatments was thought to be masked by heavy macroalgal biomass at the study site. Additional monitoring of the study site, plus additional restoration of propeller scars is planned.

Relevant Publications: Final report to West Coast Inland Navigation District.