Karenia brevis is a toxic marine dinoflagellate species that blooms almost every year in the Gulf of Mexico. These blooms have had devastating effects on local economies, as well as on the fauna of the area. The ECOHAB:Florida project was founded to study the population dynamics and trophic impacts of K. brevis. The project included a series of monthly hydrographic offshore research cruises, as well as monthly surveys of a transect along the 10-meter isobath of the West Florida Shelf. This study focused on data from the alongshore transect over a three-year period (1999-2001). Physical parameters (temperature, salinity, and density) and chemical parameters (particulate carbon, nitrogen, and phosphorus; dissolved inorganic nitrogen and phosphorus) of the West Florida Shelf were analyzed. The amount of chlorophll a and the location and amount of K. brevis cells present were also examined. Clear spatial, seasonal, and interannual patterns in the hydrographic parameters, particulate matter (C, N, P), dissolved inorganic nutrient (nitrite, nitrate, and phosphate), and chlorophyll a concentrations were found. At various times throughout the study, the location of K. brevis blooms was influenced by all of these factors except for the amount of dissolved inorganic nutrients. There were differences in particulate matter ratios present in bloom and non-bloom periods. No clear-cut differences in dissolved inorganic nutrients between bloom and non-bloom periods were found. Finally, relationships between the biological indicators of blooms (i.e., chlorophyll a) and the aforementioned physical and chemical parameters were found.

Optical research has shown that Karenia brevis has distinct spectral characteristics, yet most studies have focused exclusively on absorption and chemical properties, ignoring the size, shape, internal structure, and orientation, and their effect on scattering properties. The application of a new spectral interpretation model to K. brevis is shown to provide characterization of unique spectral information, not previously reported, through the use of scattering and absorption properties. The spectroscopy models are based on light scattering and absorption theories, and the approximation of the frequency-dependent optical properties of the basic constituents of living organisms. The model uses the process of mathematically separating the cell into four components, while combining their respective scattering and absorption properties, and appropriately weighted physical and chemical characteristics. The parameters for the model are based upon both reported literature values, and experimental values obtained from laboratory grown cultures and pigment standards. Measured and mathematically derived spectra are compared to determine the adequacy of the model, contribute new spectral information, and to establish the proposed spectral interpretation approach as a new detection method for K. brevis. Absorption and scattering properties of K. brevis, such as cell size/shape, internal structure, and chemical composition, are shown to predict the spectral features observed in the measured spectra. This research documents for the first time the exploitation of every spectral feature produced by the interaction of light with the cellular components and their contribution to the total spectrum of a larger (20-40 µm) photosynthetic eukaryote, K. brevis. Overall, this approach could eventually address the detection deficiencies of current optical detection applications and facilitate the understanding of K. brevis bloom ecology.

Harmful algal blooms (HABs, or "red tides") of the brevetoxin-producing dinoflagellate Karenia brevis occur periodically along Florida's Gulf coast. Mass mortalities of marine birds have long been associated with these blooms, yet there are few data documenting the accumulation of brevetoxins (PbTx) in the tissues of birds. Post-mortem evaluations were performed on 185 birds representing 22 species collected from October 2001 through May 2006 during red tide and non-red tide events to quantify their body burdens of brevetoxins. A variety of tissues and organs were selected for brevetoxin analysis including blood, brain, heart, fat, stomach or gut contents, intestinal contents or digestive tract, muscle, lung, liver or viscera, kidney, gonads, gallbladder and spleen. Brevetoxin levels in avian tissues ranged from K. brevis which may amass in various tissues of the body. As a consequence, the birds may exhibit acute brevetoxicosis during red tide events or show chronic accumulation effects during non-red tide events.

Thermal stratification occurs in shallow water bodies because solar energy separates the water column into an upper warm layer, a lower cold layer, and an intermediate layer between the upper and lower layers. In general the intermediate layer exhibits a significant thermal gradient over depth. Because cold water is heavier than warm water, this temperature structure produces a stable stratification, thereby inhibiting circulation from the bottom to the surface. This stable stratification results in a deficit of dissolved oxygen in the lower layer leading to water quality problems. Hence understanding the thermal structure and vertical circulation in shallow water bodies is important for water quality and its management. In this research, a numerical code is developed to examine the three-dimensional flow structure in shallow water bodies. This numerical code is used to solve the governing equations : the Reynolds averaged Navier-Stokes equations for three velocities and pressure, the depth-averaged continuity equation for free surface movement, the equations for turbulence closure, the scalar transport equation for temperature, and the international equation of state for density variation due to temperature. These equations are solved simultaneously using a finite difference method. The mathematical equations are transformed into a generalised coordinate system which allows flexibility for irregular boundaries and the allocation of vertical grid points every time step depending on free surface movements. In order to overcome possible numerical instabilities because of the small vertical length scale in shallow water bodies, an implicit method is used in the vertical direction. Several test cases involving free surface movement are used to verify the numerical code, and numerical solutions compare favourably against analytical solutions and measured data. The numerical code has been applied to the Torrens Lake in Adelaide, South Australia, where algal blooms occur frequently in summer due to thermal stratification. Typical thermal structures have been obtained from the model and these are compared with field data. The current code has been developed to improve upon existing commercial models which may not adequately address shallow water flows because of the high computational burden required to resolve free surface movements and consequential difficulties encountered for models with a small vertical length scale. / Thesis (Ph.D.)--School of Mathematical Sciences, 2007.

As human populations increase along coastal watersheds, the understanding and monitoring of Harmful Algal Blooms (or red tides) is an increasingly important issue. A consistent method for accurately detecting red tides using satellite measurements would bring tremendous societal benefits to resource managers, the scientific community and to the public as well. In the West Florida Shelf, blooms of the toxic dinoflagelate Karenia brevis are responsible for massive red tides causing fish kills, massive die-offs of marine mammals, shellfish poisoning, and acute respiratory irritation in humans. In this work, for the first time a long-term dataset (2002~2006) the MODerate Resolution Imaging Spectroradiometer (MODIS) is compared (i.e., matched-up) to an extensive data set of in situ cell counts of K. brevis; provided by the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute. The pairing of remote sensing data with near-coincident field measurements of cell abundance was successfully used to derive the basis for the development of an alternative ocean color based algorithm for detecting the optical signatures associated with blooms of K. brevis in waters of the West coast of Florida. Conclusions are geographically limited to the Central West Florida Shelf during the boreal Summer-Fall (i.e., the K. brevis blooming season). The new simpler Empirical approach is compared with other two more complicated published techniques. Their potential is verified and uncertainties involved in the identification of blooms of K. brevis are presented. The results shown here indicate that the operational NOAA method for detecting red tides in the Gulf of Mexico (Stumpf et al., 2003; Tomlinson et al., 2004) performs less accurately than the other two algorithms at identifying K. brevis blooms. The sensitivity and specificity of the Bio-optical (Cannizzaro, 2004; Cannizzaro et al., 2008) and Empirical algorithms are simultaneously maximized with an optimization procedure. The combined use of these two optimized algorithms in sequence provides another new monitoring tool with improved accuracy at detecting K. brevis of blooms. The ability of this Hybrid scheme ranges about 80% for both sensitivity and specificity; and the capability at predicting a correct red tides is 70%, and ~85% for non-blooms conditions. The spatial and temporal knowledge of K. brevis blooms can improve the direction of field monitoring to areas that should receive special attention, allowing better understanding of the red tide phenomenon by the scientific community. The relevant agencies can also develop more appropriate mitigation action plans, and public health guidance can be improved with the enhancement of sustainable costal management strategies.

The Laurentian Great Lake, Lake Erie is an invaluable global resource and its watershed is home to over 11 million people. The pressures placed on the lake because of this high population caused Lake Erie to experience numerous environmental problems, including seasonal hypoxia and harmful algal blooms. While these topics have been widely studied in Lake Erie for over 40 years a more nuanced understanding of the interaction between phytoplankton and nutrient is needed to properly address the problems continuing to face the lake. In this study we combine classical limnological and cell growth experiments with modern molecular biological techniques and microscopy to more completely describe the aquatic microbial ecology of the lake. We used an oxalate rinse technique to examine the surface absorbed P pool of the toxic cyanobacterium Microcystis aeruginosa grown under a range of P conditions, as well as the general Lake Erie plankton assemblage. Our results suggest that while Microcystis is plastic in its cellular P needs, the ratio of intracellular to extracellular P remains stable across growth conditions. We describe the effect of the phosphonate herbicide glyphosate on the Lake Erie phytoplankton community using laboratory cell growth studies, field microcosm experiments and PCR amplification of a gene implicated in the breakdown of this compound from the environment. Results from these experiments suggest that the presence of glyphosate can affect community structure in multiple ways and may explain areas of unexplained phytoplankton diversity in coastal areas of Lake Erie. We also show heterotrophic bacteria are likely critical to the breakdown of glyphosate and further illustrate that understanding the context of the larger microbial community is critical to understanding the ecology of the constituent members of the community. Finally, we investigate the activity of the phytoplankton community in winter months with a focus on diatoms abundant in Lake Erie under the ice. We show these diatoms are active and that the winter bloom is a likely source of carbon important to seasonal hypoxia formation. Together, these studies significantly enrich our understanding of how phytoplankton influence important ecological processes in Lake Erie.

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 36-40)

Inflows affect water quality, food web dynamics, and even the incidence of harmful algal blooms. It may be that inflows can be manipulated to create refuge habitat for biota trying to escape poor environmental conditions, such as fish populations in lakes during times of toxic Prymnesium parvum blooms. Water availability sometimes can be an issue, especially in arid climates, which limits this approach to management. Utilizing source water from deeper depths to displace surface waters, however, might effectively mimic inflow events. I test this notion by conducting in-lake mesocosm experiments with natural plankton communities where I manipulate hydraulic flushing. Results show that P. parvum cell density is reduced by 69%, and ambient toxicity completely ameliorates during pre-bloom conditions in the lake. During conditions of bloom development, population density is reduced by 53%, toxicity by 57%, and bloom proportions are never reached. There is minimal effect of these inflows on total phytoplankton and zooplankton biomass, and little effect on water quality. Shifts toward more rapidly growing phytoplankton taxa are observed, as are enhanced copepod nauplii. In other words, while inflows using deep waters suppress P. parvum bloom initiation and development, they are benign to other aspects of the lower food web and environment. The results from using deep lake water to suppress harmful algal blooms indicate this may be a promising management approach and further studies are recommended to test whether this mitigating effect can translate to a large-scale in-lake treatment.

<em>Cladophora glomerata</em> is a filamentous green alga that currently forms extensive blooms in nearshore areas of Lake Ontario, eastern Lake Erie, Lake Michigan, and isolated locations in Lake Huron. The biomass, areal coverage, algal bed characteristics, and tissue phosphorus concentrations of <em>Cladophora glomerata</em> were measured at 24 nearshore rocky sites along the northern shoreline of Lake Erie?s eastern basin between 1995-2002. Midsummer areal coverage at shallow depths (&le;5m) ranged from 4-100 %, with a median value of 96%. Peak seasonal biomass ranged from <1 to 940 g m^-2 dry mass (DM), with a median value of 171 g m^-2 DM. Tissue phosphorus varied seasonally, with initial high values in early May (0. 15 to 0. 27 % DM; median 0. 23 % DM) to midsummer seasonal low values during peak biomass (0. 03 to 0. 23 % DM; median 0. 06 % DM). A numerical <em>Cladophora</em> growth model (CGM) was revised and field-tested at 5 sites in eastern Lake Erie during 2002. The CGM is useful for: 1) Predicting <em>Cladophora</em> growth, biomass, and tissue phosphorus concentrations under non-point source P loading with no depth restrictions; 2) providing estimates of the timing and magnitude of the midsummer sloughing phenomenon; 3) determining the contribution of <em>Dreissena</em> invasion to the resurgence of <em>Cladophora</em> in eastern Lake Erie; and 4) developing management strategies for <em>Cladophora</em> abatement. The CGM was applied to investigate how the spatial and temporal patterns of <em>Cladophora</em> growth were influenced by the natural variability in environmental parameters in eastern Lake Erie. Seasonal patterns in <em>Cladophora</em> growth were strongly influenced by temperature, and peak depth-integrated biomass was strongly influenced by both available light and phosphorus. The photosynthetic capacity of field collected <em>Cladophora</em> was a poor predictor of the mid-summer sloughing phenomenon. The CGM, however, predicted that self-shading within the dense <em>Cladophora</em> mats would have caused negative growth rates at the base of the dense mats for 14 days prior to the sloughing event. The metabolic imbalances at the base of the <em>Cladophora</em> mats were driven primarily by the availability of light and were exacerbated by intermediate water temperatures (~23°C). The excellent agreement between model simulations and field data illustrates the ability of the CGM to predict tissue P and growth over a range of sites and depths in eastern Lake Erie and suggests potential for the model to be successfully applied in other systems.

The environment of bivalve Sanguinolaria rostrata growth and reproduction is affected by temperature, salinity and algal concentration.The growth and fattening of the bivalves is closely associated with filter-feeding. Hence, the present work was to investigate the effect of temperature, salinity and algal concentration on the filter-feeding of the bivalves. The salinity ranging from 5 to 30 at the interval of 5 psu, four temperatures at 20¢X, 25¢X, 27¢X and 30¢J, and three algal concentrations of each Isochrysis galbana and each Chaetoceros gracilis, 104 , 105 and 106 cells/ml, were used. Algal concentration was measured each hour and each test run last for 6 hours. A peak appeared at the salinity of 20 psu in each clearance rate vs salinity curve and clearance rate decreased with increasing algal concentration; a peak also appeared at the salinity of either 15¡ã20 psu in the ingestion rate vs salinity curve; and ingestion rate and the amount of pseudofaeces increased with increasing algal concentration. Under the conditions of algal concentration 104 cells/ml and temperature range 20¢X~30¢J, a peak appeared at 25¢J in each clearance rate and each ingestion rate vs temperature curves, and the greatest peak of clearance rate was 1.13 l/h; and the amount of pseudofaeces was the greatest at 25¢J and 20 psu. The bivalves fed with Isochrysis galbana have greater clearance and ingestion rates but less amount of pseudofaeces, compared to those fed with Chaetoceros gracilis.