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The availability of dissolved inorganic and organic nutrients and their transformations along the fresh to marine continuum are being modified by various natural and anthropogenic activities and climate-related changes. Subtropical central and eastern Florida Bay, located at the southern end of the Florida peninsula, is classically considered to have inorganic nutrient conditions that are in higher-than-Redfield ratio proportions, and high levels of organic and chemically-reduced forms of nitrogen. However, salinity, pH and nutrients, both organic and inorganic, change with changes in freshwater flows to the bay. Here, using a time series of water quality and physico-chemical conditions from 2009 to 2019, the impacts of distinct changes in managed flow, drought, El Niño-related increases in precipitation, and intensive storms and hurricanes are explored with respect to changes in water quality and resulting ecosystem effects, with a focus on understanding why picocyanobacterial blooms formed when they did. Drought produced hyper-salinity conditions that were associated with a seagrass die-off. Years later, increases in precipitation resulting from intensive storms and a hurricane were associated with high loads of organic nutrients, and declines in pH, likely due to high organic acid input and decaying organic matter, collectively leading to physiologically favorable conditions for growth of the picocyanobacterium, Synechococcus spp. These conditions, including very high concentrations of NH4+, were likely inhibiting for seagrass recovery and for growth of competing phytoplankton or their grazers. Given projected future climate conditions, and anticipated cycles of drought and intensive storms, the likelihood of future seagrass die-offs and picocyanobacterial blooms is high.

Recent increases in global urea usage, including its incorporation in slow-release fertilizers commonly used in lawn care in Florida, have the potential to alter the form and amount of nitrogen inputs to coastal waters. This shift may, in turn, impact phytoplankton community diversity and nutrient cycling processes. An autonomous water quality monitoring and sampling platform containing meteorological and water quality instrumentation, including urea and phycocyanin sensors, was deployed between June and November of 2009 in Sarasota Bay, Florida. This shallow, lagoonal bay is characterized by extensive and growing urban and suburban development and limited tidal exchange and freshwater inputs. During the monitoring period, three high-biomass (up to 40 &micro, g chlorophyll-a&middot, L&minus, 1) phytoplankton blooms dominated by picocyanobacteria or picoeukaryotes were observed. Each bloom was preceded by elevated (up to 20 &mu, M) urea concentrations. The geolocation of these three parameters suggests that &ldquo, finger canals&rdquo, lining the shore of Sarasota Bay were the source of urea pulses and there is a direct link between localized urea inputs and downstream picoplankton blooms. Furthermore, high frequency sampling is required to detect the response of plankton communities to pulsed events.

Bivalves, from raw oysters to steamed clams, are popular choices among seafood lovers and once limited to the coastal areas. The rapid growth of the aquaculture industry and improvement in the preservation and transport of seafood have enabled them to be readily available anywhere in the world. Over the years, oysters, mussels, scallops, and clams have been the focus of research for improving the production, managing resources, and investigating basic biological and ecological questions. During this decade, an impressive amount of information using high-throughput genomic, transcriptomic and proteomic technologies has been produced in various classes of the Mollusca group, and it is anticipated that basic and applied research will significantly benefit from this resource. One aspect that is also taking momentum is the use of bivalves as a model system for human health. In this review, we highlight some of the aspects of the biology of bivalves that have direct implications in human health including the shell formation, stem cells and cell differentiation, the ability to fight opportunistic and specific pathogens in the absence of adaptive immunity, as source of alternative drugs, mucosal immunity and, microbiome turnover, toxicology, and cancer research. There is still a long way to go; however, the next time you order a dozen oysters at your favorite raw bar, think about a tasty model organism that will not only please your palate but also help unlock multiple aspects of molluscan biology and improve human health.

Nutrient pollution is altering the availability of nutrients for phytoplankton in waters throughout the world. The consequence is that many receiving waters are now not only enriched with nutrients, but these nutrients are in proportions that differ from those of decades past—and also diverge considerably from those that have long been associated with phytoplankton growth, namely, Redfield proportions. The classic focus on nutrient limitation and application of fixed kinetic models has created considerable confusion in the literature with respect to nutrient regulation of harmful algal blooms (HABs). Here, we underscore the dynamic nature of nutrient responses and the fact that nutrient ratios do, indeed, matter, whether nutrients are limiting or not. Understanding nutrient limitation of growth does not inform changes in biodiversity, including changes leading to HABs. Our concepts of nutrient regulation must be expanded to include an understanding of how nutrients can be regulating even in a nutrient-saturated, eutrophic environment. The complexity of management of anthropogenic nutrient loads is well recognized, but our practice of viewing responses through a single, limiting nutrient viewpoint has hampered progress of nutrient management in relation to HABs. Controlling one nutrient may control overall biomass, but it may have unintended consequences for community structure. The synergism complicating our understanding of the relationship between nutrients and HABs, and further negating the simple construct of nutrient-dose relationships, is the fact that for many HABs, acquisition of nutrients occurs not only in dissolved but also in particulate form. The balance between autotrophy and mixotrophy thus becomes another factor that can drive biodiversity changes. The synergism of phototrophy and heterotrophy in mixotrophs has important consequences for cell metabolism, especially the maintenance of cell stoichiometry. Mixotrophy not only is an important nutritional strategy in plankton that form toxic blooms, but it is this process that may allow blooms to be sustained in nutrient-enriched environments where both dissolved nutrients and prey are ample and may allow blooms to be sustained for longer periods than autotrophy alone would allow.

article Ammonium is a nutrient frequently preferred by microorganisms that photosynthesize at the base of the marine food web and remove atmospheric carbon dioxide via carbon fixation. Because their photosynthesis is concentrated in the ocean's thin euphotic zone, its nutrient concentrations are critical to oceanic carbon fixation. Identification of replacement processes for euphotic-zone ammonium thus becomes important. These processes were investigated in a two-experiment, Lagrangian field study that produced results consistent with an apparent inverse effect of wind forcing on upper-ocean ammonium concentrations. At low wind speeds (especially ≤4ms −1 ), continuoussea

Bacterial abundance, production, protein and nucleic acid synthesis, growth, and viral abundance were measured in waters associated with three bloom stages of the “red tide” dinoflagellate Karenia brevis along the south West Florida Shelf (WFS). Measurements were taken: (1) when no bloom was present; (2) during the initiation stage of a bloom; and (3) during the maintenance stage of a bloom. Results indicate that the bacterial community was nutrient limited in the non-bloom period, with highest abundance and production rates occurring near and within estuaries. Abundance of virus like particles (VLPs) was higher within estuaries, but we hypothesize VLPs were not a high source of bacterial mortality, possibly due to high decay rates due to UV degradation or extracellular nucleases. High bacterial production, balanced protein to nucleic acid synthesis, and statistically similar bacteria abundances measured on consecutive days within the initiating bloom suggest a highly productive community with equally high mortality. VLP abundance declined during the first 48 h within both bloom stages, suggesting that viral genomes were either within host cells (not evident in water column samples), or bacterial mortality was due to mixotrophic grazing by K. brevis . Using a conservative grazing rate of 1 bacteria K. brevis −1 h −1 , K. brevis grazing could account for >100% of bacterial mortality during an initiating bloom. Bacterial abundance and production were significantly decreased and protein to nucleic acid synthesis became unbalanced during the maintenance phase bloom. An increase in VLP abundance during the maintenance phase was most likely the cause of bacterial mortality as mixotrophic grazing could only account for ∼4% of the change in bacterial abundance. Together, these data suggest that the associated bacteria and viruses play a critical role in the formation and termination of K. brevis blooms.

Identification and quantification of the nutrient sources supporting large, extended duration Karenia brevis blooms on the West Florida Shelf (WFS) in the eastern Gulf of Mexico are critical steps for effective bloom management and mitigation. Previous research had identified multiple (>12) potential nutrient sources available to K. brevis blooms on the WFS, which vary with bloom stage, location, biomass and bloom toxicity. This current study newly identified and quantified additional nitrogen (N) sources including water column nitrification, photochemical nutrient production, pelagic unicell N2 fixation by diazotrophs other than the colonial cyanobacterium Trichodesmium, and remineralization from seasonal Trichodesmium biomass decay and microzooplankton grazing (and estimated regeneration). Newly identified phosphorus (P) sources include remineralization from Trichodesmium biomass decay and microzooplankton grazing. In estuarine environments, benthic nutrient flux, mixotrophic consumption of picoplankton, nutrient release from zooplankton and microzooplankton grazing, photochemical nutrient production, and nitrification all can contribute up to 100% of the N and/or P requirements of small ( Given the complexity of K. brevis bloom dynamics, the multiple available nutrient sources on the WFS and the importance of regenerated N forms in supporting blooms, efforts to reduce potentially controllable nearshore nutrient inputs should be undertaken with the understanding that while they may lead to enhanced coastal water quality, they may not have an immediate impact on the frequency or magnitude of nearshore K. brevis blooms. Additionally, time lags in ecosystem responses or differences in the time scales on which various process operate may require multi-year assessments to determine how effective management practices are in relation to K. brevis blooms. Timely red tide related monitoring products that allow for effective focusing of monitoring needs for short-term prediction of impacts and targeted communication of scientific results to the public and stakeholders, remains the most effective means of K. brevis management.

To investigate nutrient release from decaying fish carcasses as a potential source fueling blooms of the toxic dinoflagellate, Karenia brevis (C.C. Davis) G. Hansen & O. Moestrup this study evaluated the type and quantity of nutrients (nitrogen (N), phosphorus (P), and carbon (C)) released from decaying fish using both wet chemistry and compound specific (Fourier transform ion cyclotron resonance mass spectrometry, FT-ICR MS) techniques. A 3 day bioassay experiment was then conducted to examine how eutrophic (Charlotte Harbor, CH) and oligotrophic (Blue Water, BW) microbial communities in the eastern Gulf of Mexico (GoM) respond to fish-derived nutrients (FDN) relative to other in situ N sources. Decaying fish released a suite of compounds, primarily in the form of ammonium (NH 4 + ); release rates ranged from 37.7 ± 12.6 to 102.3 ± 4.7 μmol N L −1 g −1 wet wt. d −1 . Phosphate release was 13.9 ± 2.8 to 21.4 ± 2.9 μmol P L −1 g −1 wet wt. d −1 . A total of 3515 organic compounds were produced, which were dominated by lipid and protein-like compounds. In the bioassay, FDN were utilized by microbial communities collected from both CH and BW, with complete drawdown of fish-derived NH 4 + in the CH treatment in conjunction with a 3-fold increase in Chl a . FDN provided the necessary nutrients to alleviate P limitation in the BW treatment, resulting in a 13-fold increase in Chl a . Results from this experiment indicate FDN are important N and P sources to the microbial community along the eastern GoM and have important implications for maintenance of associated ichthyotoxic K. brevis blooms.

The West Florida Shelf (WFS) encompasses a range of environments from inshore estuarine to offshore oligotrophic waters, which are frequently the site of large and persistent blooms of the toxic dinoflagellate, Karenia brevis. The goals of this study were to characterize the nitrogen (N) nutrition of plankton across the range of environmental conditions on the WFS, to quantify the percentage of the plankton N demand met through in situ N regeneration, and to determine whether planktonic N nutrition changes when high concentrations of Karenia are present. In the fall of 2007, 2008, and 2009 we measured ambient nutrient concentrations and used stable isotope techniques to measure rates of primary production and uptake rates of inorganic N (ammonium, NH4+, and nitrate, NO3−), and organic N and carbon (C; urea and amino acids, AA) in estuarine, coastal, and offshore waters, as well as coastal sites with Karenia blooms present. In parallel, we also measured rates of in situ N regeneration – NH4+ regeneration, nitrification, and photoproduction of NH4+, nitrite and AA. Based on microscope observations, ancillary measurements, and previous monitoring history, Karenia blooms sampled represented three bloom stages – initiation in 2008, maintenance in 2007, and late maintenance/stationary phase in 2009. Nutrient concentrations were highest at estuarine sampling sites and lowest at offshore sites. Uptake of NH4+ and NO3− provided the largest contribution to N nutrition at all sites. At the non-Karenia sites, in situ rates of NH4+ regeneration and nitrification were generally sufficient to supply these substrates equal to the rates at which they were taken up. At Karenia sites, NO3− was the most important N substrate during the initiation phase, while NH4+ was the most important N form used during bloom maintenance and stationary phases. Rates of NH4+ regeneration were high but insufficient (85 ± 36% of uptake) to support the measured NH4+ uptake at all the Karenia sites although nitrification rates far exceeded uptake rates of NO3−. Taken together our results support the “no smoking gun” nutrient hypothesis that there is no single nutrient source or strategy that can explain Karenia's frequent dominance in the waters where it occurs. Consistent with other papers in this volume, our results indicate that Karenia can utilize an array of inorganic and organic N forms from a number of N sources.

This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis to date as it encompasses natural populations sampled during three different bloom years in addition to cultured strains under controlled conditions. Nitrogen (N) uptake kinetics for ammonium (NH 4 + ), nitrate (NO 3 − ), urea, an amino acid mixture, individual amino acids (glutamate and alanine), and humic substrates were examined for the toxic red tide dinoflagellate, K. brevis , during short term incubations (0.5–1 h) using 15 N tracer techniques. Experiments were conducted using natural populations collected during extensive blooms along the West Florida Shelf in October 2001, 2002, and 2007, and in cultured strains (CCFWC 251 and CCFWC 267) obtained from the Florida Fish and Wildlife Institute culture collection. Kinetic parameters for the maximum uptake velocity ( V max ), half-saturation concentration ( K s ), and the affinity constant ( α ) were determined. The affinity constant is considered a more accurate indicator of substrate affinity at low concentrations. K. brevis took up all organic substrates tested, including N derived from humic substances. Uptake rates of the amino acid mixture and some NO 3 − incubations did not saturate even at the highest substrate additions (50–200 μmol N L −1 ). Based upon the calculated α values, the greatest substrate preference was for NH 4 + followed by NO 3 − ≥ urea, humic compounds and amino acids. The ability of K. brevis to utilize a variety of inorganic and organic substrates likely helps it flourish under a wide range of nutrient conditions from bloom initiation in oligotrophic waters offshore to bloom maintenance near shore where ambient nutrient concentrations may be orders of magnitude greater.

Blooms of Karenia brevis plague the West Florida Shelf (WFS) region in the Gulf of Mexico (GOM) where they exert harmful effects on aquatic biota and humans. Because productivity on the WFS is N limited, new N inputs into the region are thought to trigger blooms of K. brevis. Here we examine the potential for new N inputs via N2 fixation by Trichodesmium and other diazotrophic plankton to contribute to the N demand of K. brevis. Because of possible methodological biases, we also compared N2 fixation rates by cultured Trichodesmium using the 15N2 bubble addition method and the 15N2 saturated seawater. Both methods yielded identical results in 12 and 24 h incubations; however, there was more variability in rate estimates made using the bubble addition method. Pelagic N2 fixation rates by other planktonic diazotrophs ranged from 0 to 13.6 nmol N L−1 d−1, comparable to or higher than rates observed in oligotrophic gyres. These rates should be considered conservative estimates because they were made using the bubble addition method. Integrating over our study area, we estimate that new inputs of N to the WFS via N2 fixation are on the order of 0.011 Tmol N annually. Further, we measured directly the trophic transfer of recently fixed N2 to co-occurring plankton that included K. brevis and found that up to 47% of N2 fixed was transferred to non-diazotrophic plankton even in short (

The toxic HAB dinoflagellate Karenia brevis (Davis) G. Hansen & O. Moestrup (formerly Gymnodinium breve) exhibits a migratory pattern atypical of dinoflagellates: cells concentrate in a narrow (∼0–5 cm) band at the water surface during daylight hours due to phototactic and negative geotactic responses, then disperse downward at night via non-tactic, random swimming. The hypothesis that this daylight surface aggregation behavior significantly influences bacterial and algal productivity and nutrient cycling within blooms was tested during a large, high biomass (chlorophyll a >19 μg L−1) K. brevis bloom in October of 2001 by examining the effects of this surface layer aggregation on inorganic and organic nutrient concentrations, cellular nitrogen uptake, primary and bacterial productivity and the stable isotopic signature (δ15N, δ13C) of particulate material. During daylight hours, concentrations of K. brevis and chlorophyll a in the 0–5 cm surface layer were enhanced by 131% (±241%) and 32.1% (±86.1%) respectively compared with an integrated water sample collection over a 0–1 m depth. Inorganic (NH4, NO3+2, PO4, SiO4) and organic (DOP, DON) nutrient concentrations were also elevated within the surface layer as was both bacterial and primary productivity. Uptake of nitrogen (NH4+, NO3−, urea, dissolved primary amines, glutamine and alanine) compounds by K. brevis was greatest in the surface layer for all compounds tested, with the greatest enhancement evident in urea uptake rates, from 0.08 × 10−5 ng N K. brevis cell−1 h−1 to 3.1 × 10−5 ng N K. brevis cell−1 h−1. These data suggests that this surface aggregation layer is not only an area of concentrated cells within K. brevis blooms, but also an area of increased biological activity and nutrient cycling, especially of nitrogen. Additionally, the classic dinoflagellate migration paradigm of a downward migration for access to elevated NO3− concentrations during the dark period may not apply to certain dinoflagellates such as K. brevis in oligotrophic nearshore areas with no significant nitricline. For these dinoflagellates, concentration within a narrow surface layer in blooms during daylight hours may enhance nutrient supply through biological cycling and photochemical nutrient regeneration.

Dissolved organic nitrogen (DON) produced by the nitrogen-fixer Trichodesmium sp. has the potential to serve as a nitrogen source for the red tide dinoflagellate Karenia brevis. Dis- solved organic matter (DOM) from laboratory cultures of Trichodesmium sp. was isolated, concen- trated and then supplied as a nutrient source to K. brevis cells collected from the Gulf of Mexico. K. brevis abundance increased immediately after Trichodesmium sp. cellular exudate (TCE) addition, allowing the population to double within the first 24 h. There was rapid and complete utilization of the TCE DON as well as ~89% of the TCE dissolved organic phosphorus (DOP). Additionally, ter- minal restriction fragment length polymorphism (TRFLP) was used to assess the bacterial commu- nity response to the addition of TCE . The number of bacterial operational taxonomic units (OTUs) initially increased after the TCE DOM addition, but decreased as K. brevis reached its maximum abundance. Electrospray ionization mass spectrometry (ESI-MS) and Fourier transform ion cy- clotron resonance mass spectrometry (FT-ICR MS) were used to chemically characterize the DOM. Approximately 25% of compounds disappeared within the first 24 h, corresponding to the greatest increase in K. brevis abundance. Using FT-ICR MS, 391 DON and 219 DOP potentially bioavailable compounds were characterized. The bioavailable DON compounds were highly re- duced and 44% had molar ratios indicative of lipid or protein-like compounds. The changes in DON concentration and compound composition show that Tricho desmium sp. provides a sufficient source of nitrogen to directly or indirectly support K. brevis blooms.

Within the context of ubiquitous overfishing of piscivores, recent consequent increments of jellyfish and clupeids have occurred at the zooplanktivore trophic level in the eastern Gulf of Mexico (GOM), after overfishing of one of their predators, i.e. red snapper. Initiation of a local trophic cascade thence led to declines of herbivore stocks, documented here on the West Florida shelf. These exacerbating world-wide trophic cascades have resulted in larger harmful algal blooms (HABs), already present at the base of most coastal food webs. Impacts on human health have thus far been minimal within nutrient-rich coastal regions. To provide a setting for past morbidities, consideration is given to chronologies of other trophic cascades within eutrophic, cold water marine ecosystems of the Scotian Sea, in the Gulf of Alaska, off Southwest Africa, within the Barents, White, and Black Seas, in the Gulf of Maine, and finally in the North Sea. Next, comparison is now made here of recent ten-fold increments within Florida waters of both relatively benign and saxitoxic HABs, some of which are fatal to humans. These events are placed in a perspective of other warm shelf systems of the South China and Caribbean Seas to assess prior and possible future poison toxicities of oligotrophic coastal habitats. Past wide-spread kills of fishes and sea urchins over the Caribbean Sea and the downstream GOM are examined in relation to the potential transmission of dinoflagellate saxitoxin and other epizootic poison vectors by western boundary currents over larger “commons” than local embayments. Furthermore, since some HABs produce more potent saxitoxins upon nutrient depletion, recent decisions to ban seasonal fertilizer applications to Florida lawns may have unintended consequences. In the future, human-killing phytoplankton, rather than relatively benign fish-killing HABs of the past, may be dispersed along the southeastern United States seaboard.

In 2002, the Florida Department of Environmental Protection began discharging phosphate-processing effluent into Bishop Harbor, an estuary within Tampa Bay. Because of concerns that the effluent would serve as a nutrient source for blooms of the toxic dinoflagellate Karenia brevis, a field monitoring program was established and laboratory bioassays were conducted. Several harmful algal bloom (HAB) species, including Prorocentrum minimum and Heterosigma akashiwo, were observed in bloom concentrations adjacent to the effluent discharge site. Blooms of diatoms were widespread throughout Bishop Harbor. K. brevis was observed with cell concentrations decreasing with increasing proximity to the effluent discharge site. Bioassays using effluent as a nutrient source for K. brevis resulted in decreased cell yields, increased growth rates, and increased time to log-phase growth. The responses of HAB species within Bishop Harbor and of K. brevis to effluent in bioassays suggested that HAB species differ in their response to phosphate-processing effluent.

Blooms of Karenia brevis co-occur with populations of the N 2 fixing cyanobacterium Trichodesmium on the West Florida shelf where iron (Fe) and phosphorus (P) supplies have been shown to control the growth potential of these cyanophytes. Historical data records of Trichodesmium presence and abundance (1960-2008) were analyzed in relation to the nutrient requirements of annually coincident K. brevis blooms, focusing on the potential direct supply of nitrogen (N) via N 2 -fixation with subsequent excretion of recently fixed N 2 as NH 4 + and dissolved organic nitrogen and indirect transfer from Trichodesmium biomass (as particulate N and P) during cell death. While release of "new" N from biological N 2 - f ixation can supply up to 40% of the 2001 large red tide (9.5 × 10 6 cells L -1 ), estimates of the total N available, including the regeneration of additional nutrients supplied from particulate stocks aggregated within surface populations of observed Trichodesmium biomass during cell death, suggest that up to 100% of N and P requirements of such large blooms can be met from N 2 -fixation sources.

Nucleic acid sequence-based amplification (NASBA) is an isothermal method used to amplify RNA and has been used for clinical, environmental, and food testing applications. Quantification of RNA by realtime NASBA occurs by comparing time to positive (TTP) fluorescence values, similar to threshold cycle (Ct) values in PCR, of unknown samples to a standard curve of known RNA titers. Incorporation of an internal control RNA molecule (IC-RNA) has been used to increase precision and accuracy of real-time NASBA and also serves as an indicator of NASBA inhibition. A real-time IC-NASBA assay was developed targeting the ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO) large-subunit gene (rbcL )o f the harmful algal bloom (HAB) causing dinoflagellate Karenia mikimotoi. This assay is sensitive to one K. mikimotoi cell and 1 � 10

Using shipboard data collected from the central west Florida shelf (WFS) between 2000 and 2001, an optical classification algorithm was developed to differentiate toxic Karenia brevis blooms (>104 cells l−1) from other waters (including non-blooms and blooms of other phytoplankton species). The identification of K. brevis blooms is based on two criteria: (1) chlorophyll a concentration ≥1.5 mg m−3 and (2) chlorophyll-specific particulate backscattering at 550 nm ≤ 0.0045 m2 mg−1. The classification criteria yielded an overall accuracy of 99% in identifying both K. brevis blooms and other waters from 194 cruise stations. The algorithm was validated using an independent dataset collected from both the central and south WFS between 2005 and 2006. After excluding data from estuarine and post-hurricane turbid waters, an overall accuracy of 94% was achieved with 86% of all K. brevis bloom data points identified successfully. Satisfactory algorithm performance (88% overall accuracy) was also achieved when using underway chlorophyll fluorescence and backscattering data collected during a repeated alongshore transect between Tampa Bay and Florida Bay in 2005 and 2006. These results suggest that it may be possible to use presently available, commercial optical backscattering instrumentation on autonomous platforms (e.g. moorings, gliders, and AUVs) for rapid and timely detection and monitoring of K. brevis blooms on the WFS.

Annual blooms of the toxic dinoflagellate Karenia brevis in the eastern Gulf of Mexico represent one of the most predictable global harmful algal bloom (HAB) events, yet remain amongst the most difficult HABs to effectively monitor for human and environmental health. Monitoring of Karenia blooms is necessary for a variety of precautionary, management and predictive purposes. These include the protection of public health from exposure to aerosolized brevetoxins and the consumption of toxic shellfish, the protection and management of environmental resources, the prevention of bloom associated economic losses, and the evaluation of long term ecosystem trends and for potential future bloom forecasting and prediction purposes. The multipurpose nature of Karenia monitoring, the large areas over which blooms occur, the large range of Karenia cell concentrations (from 5 × 103 cells L−1 to >1 × 106 cells L−1) over which multiple bloom impacts are possible, and limitations in resources and knowledge of bloom ecology have complicated K. brevis monitoring, mitigation and management strategies. Historically, K. brevis blooms were informally and intermittently monitored on an event response basis in Florida, usually in the later bloom stages after impacts (e.g. fish kills, marine mammal mortalities, respiratory irritation) were noted and when resources were available. Monitoring of different K. brevis bloom stages remains the most practical method for predicting human health impacts and is currently accomplished by the state of Florida via direct microscopic counts of water samples from a state coordinated volunteer HAB monitoring program. K. brevis cell concentrations are mapped weekly and disseminated to stakeholders via e-mail, web and toll-free phone numbers and provided to Florida Department of Agriculture and Consumer Services (FDACS) for management of both recreational and commercial shellfish beds in Florida and to the National Oceanic and Atmospheric Administration (NOAA) for validation of the NOAA Gulf of Mexico HAB bulletin for provision to environmental managers. Many challenges remain for effective monitoring and management of Karenia blooms, however, including incorporating impact specific monitoring for the diverse array of potential human and environmental impacts associated with blooms, timely detection of offshore bloom initiation, sampling of the large geographic extent of blooms which often covers multiple state boundaries, and the involvement of multiple Karenia species other than K. brevis (several of which have yet to be isolated and described) with unknown toxin profiles. The implementation and integration of a diverse array of optical, molecular and hybrid Karenia detection technologies currently under development into appropriate regulatory and non-regulatory monitoring formats represents a further unique challenge.

Toxic Florida red tides of the dinoflagellate Karenia brevis have downstream consequences of 500–1000 km spatial extent. Fish stocks, shellfish beds, and harmful algal blooms of similar species occupy the same continental shelf waters of the southeastern United States, amounting to economic losses of more than 25 million dollars in some years. Under the aegis of the Center for Prediction of Red tides, we are now developing coupled biophysical models of the conditions that lead to red tides and impacted coastal fisheries, from the Florida Panhandle to Cape Hatteras. Here, a nitrogen isotope budget of the coastal food web of the West Florida shelf (WFS) and the downstream South Atlantic Bight (SAB) reaffirms that diazotrophs are the initial nutrient source for onset of red tides and now identifies clupeid fish as the major recycled nutrient source for their maintenance. The recent isotope budget of WFS and SAB coastal waters during 1998–2001 indicates that since prehistoric times of Timacua Indian settlements along the Georgia coast during 1075, ∼50% of the nutrients required for large red tides of >1 μg chl l −1 of K. brevis have been derived from nitrogen-fixers, with the other half from decomposing dead sardines and herrings. During 2001, >90% of the harvest of WFS clupeids was by large ichthyotoxic red tides of >10 μg chl l −1 of K. brevis , rather than by fishermen. After onset of the usual red tides in summer of 2006 and 2007, the simulated subsequent fall exports of Florida red tides in September 2007 to North Carolina shelf waters replicate observations of just ∼1 μg chl l −1 on the WFS that year. In contrast, the earlier red tides of >10 μg chl l −1 left behind off West Florida during 2006, with less physical export, are instead 10-fold larger than those of 2007. Earlier, 55 fish kills were associated with these coastal red tides during September 2006, between Tampa and Naples. Yet, only six fish kills were reported there in September 2007. With little export of red tides and their fish prey during the former year, the computed larger nutrient-sated, fish-fed growth rates of the model’s dinoflagellates also replicate satellite-observed daily increments of K. brevis during fall maintenance in 2006, compared to simulated smaller fish-starved growth rates of decanted red tides during fall 2007. During the last few decades, K. brevis has remained a “prudent predator” of some clupeids, i.e. Spanish sardine, whereas humans have now overfished other Florida stocks of both thread herring and Atlantic shad. Thus, future operational forecasts of the land falls and durations of Florida red tides, from Louisiana to North Carolina, as well as prudent management of regional fisheries of the southeastern United States, require consideration of negelected fish losses, at intermediate trophic levels, to algal predators. Some clupeids are harvested by K. brevis , but these fish are separately supported by a longer parallel diatom-based food chain of calanoid copepods, feeding the zooplanktivores and thence other piscivore fish predators, while intersecting the shorter food chain of just diazotrophs and red tide dinoflagellates, poorly grazed in turn by harpactacoid copepods. The distinct phytoplankton functional groups, different herbivores, as well as zoophagous and piscivore fishes, must all be formulated as explicit state variables of the next set of complex ecological models, cued by satellite data and driven by nested circulation models, within an ecosystem-based management paradigm of commercial and sport harvests of biotic marine resources at higher trophic levels of the WFS and SAB.

In January 2003, the US Environmental Protection Agency sponsored a “roundtable discussion” to develop a consensus on the relationship between eutrophication and harmful algal blooms (HABs), specifically targeting those relationships for which management actions may be appropriate. Academic, federal, and state agency representatives were in attendance. The following seven statements were unanimously adopted by attendees based on review and analysis of current as well as pertinent previous data: 1) Degraded water quality from increased nutrient pollution promotes the development and persistence of many HABs and is one of the reasons for their expansion in the U.S. and the world; 2) The composition – not just the total quantity – of the nutrient pool impacts HABs; 3) High biomass blooms must have exogenous nutrients to be sustained; 4) Both chronic and episodic nutrient delivery promote HAB development; 5) Recently developed tools and techniques are already improving the detection of some HABs, and emerging technologies are rapidly advancing toward operational status for the prediction of HABs and their toxins; 6) Experimental studies are critical to further the understanding of the role of nutrients in HAB expression, and will strengthen prediction and mitigation of HABs; and 7) Management of nutrient inputs to the watershed can lead to significant reduction in HABs. Supporting evidence and pertinent examples for each consensus statement is provided herein.

Coastal waters of the United States (U.S.) are subject to many of the major harmful algal bloom (HAB) poisoning syndromes and impacts. These include paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), ciguatera fish poisoning (CFP) and various other HAB phenomena such as fish kills, loss of submerged vegetation, shellfish mortalities, and widespread marine mammal mortalities. Here, the occurrences of selected HABs in a selected set of regions are described in terms of their relationship to eutrophication, illustrating a range of responses. Evidence suggestive of changes in the frequency, extent or magnitude of HABs in these areas is explored in the context of the nutrient sources underlying those blooms, both natural and anthropogenic. In some regions of the U.S., the linkages between HABs and eutrophication are clear and well documented, whereas in others, information is limited, thereby highlighting important areas for further research.

During July 2006, 2 distinctly different harmful algal blooms (HABs), one dominated by the pelagic red tide dinoflagellates Karenia spp. and the other by the benthic cyanobacterium Lyngbya majuscula, occurred simultaneously in the coastal embayments surrounding Sanibel and Captiva Islands, Florida, USA. The co-occurring HABs were investigated using in situ bioassays with additions of nitrogen (N) and phosphorus (P) alone and in combination to assess nutrient controls of these ‘dueling’ toxin-producing species. Photosynthetic, biomass (chlorophyll a), and (in L. majuscula) nitrogen fixation responses to nutrient enrichment were examined over 4 d. Primary productivity in Karenia spp. was consistently stimulated by N additions, while P additions failed to show stimulation. When added in combination with N, P did not lead to additional stimulation above N alone. Similar patterns of chlorophyll a stimulation were observed. These patterns were observed at 2 d, after which the cells fell out of suspension. Nutrient stimulation of L. majuscula metabolic activities as well as biomass production was smaller and much slower, relative to controls, than responses observed in Karenia spp. After the demise of Karenia spp., L. majuscula was able to continue utilizing subsequent nutrient additions, and it responded most strongly to the N+P additions after 4 d. This study confirms previous estuarine and coastal studies that indicated that when non-N₂-fixing HABs co-occur with N₂-fixing cyanobacterial HAB species, both N and P inputs need to be carefully considered and, in all likelihood, controlled.

The availability of iron within the surface waters of the broad, oligotrophic West Florida Shelf (WFS) controls periodic blooms of the pelagic marine cyanobacterium Trichodesmium. Summer delivery of Saharan dust provided adequate iron (Fe) to shift limitation of growth to the availability of phosphorus (P). Florida's rivers drain Miocene phosphorus deposits to provide the WFS with freshwater nutrient supplies at molar dissolved inorganic nitrogen/phosphate (DIN/PO4) ratios of

Identifying nutrient sources, primarily nitrogen (N) and phosphorus (P), sufficient to support high biomass blooms of the red tide dinoflagellate, Karenia brevis, has remained problematic. The West Florida Shelf is oligotrophic, yet populations >106 cells L−1 frequently occur and blooms can persist for months. Here we examine the magnitude and variety of sources for N and P that are available to support blooms. Annual average in situ or background concentrations of inorganic N in the region where blooms occur range 0.02–0.2 μM while inorganic P ranges 0.025–0.24 μM. Such concentrations would be sufficient to support the growth of populations up to ∼3×104 cells L−1 with at least a 1 d turnover rate. Organic N concentrations average 1–2 orders of magnitude greater than inorganic N, 8–14 μM while organic P concentrations average 0.2–0.5 μM. Concentrations of organic N are sufficient to support blooms >105 cells L−1 but the extent to which this complex mixture of N species is utilizable is unknown. Other sources of nutrients included in our analysis are aerial deposition, estuarine flux, benthic flux, zooplankton excretion, N2-fixation, and subsequent release of organic and inorganic N by Trichodesmium spp., and release of N and P from dead and decaying fish killed by the blooms. Inputs based on atmospheric deposition, benthic flux, and N2-fixation, were minor contributors to the flux required to support growth of populations >2.6×104 cells L−1. N and P from decaying fish could theoretically maintain populations at moderate concentrations but insufficient data on the flux and subsequent mixing rates does not allow us to calculate average values. Zooplankton excretion rates, based on measured zooplankton population estimates and excretion rates could also supply all of the N and P required to support populations of 105 and 106 cells L−1, respectively, but excretion is considered as “regenerated” nutrient input and can only maintain biomass rather than contribute to “new” biomass. The combined estuarine flux from Tampa Bay, Charlotte Harbor, and the Caloosahatchee River can supply a varying, but at times significant level of N and P to meet growth and photosynthesis requirements for populations of approximately 105 cells L−1 or below. Estimates of remineralization of dead fish could supply a significant proportion of bloom maintenance requirements but the rate of supply must still be determined. Overall, a combination of sources is required to maintain populations >106 cells L−1.

Blooms of the toxic dinoflagellate Karenia brevis are common in the Gulf of Mexico, yet no in situ studies of zooplankton and K. brevis have been conducted there. Zooplankton abundance and taxonomic composition at non-bloom and K. brevis bloom stations within the Ecology of Harmful Algal Blooms (ECOHAB) study area were compared. At non-bloom stations, the most abundant species of zooplankton were Parvocalanus crassirostris, Oithona colcarva, and Paracalanus quasimodo at the 5-m isobath and P. quasimodo, O. colcarva, and Oikopleura dioica at the 25-m isobath. There was considerable overlap in dominance of zooplankton species between the 5 and 25-m isobaths, with nine species contributing to 90% of abundance at both isobaths. At stations within K. brevis blooms however, Acartia tonsa, Centropages velificatus, Temora turbinata, Evadne tergestina, O. colcarva, O. dioica, and P. crassirostris were dominant. Variations in abundance between non-bloom and bloom assemblages were evident, including the reduction in abundance of three key species within K. brevis blooms.

Karenia brevis , a toxic dinoflagellate that blooms regularly in the Gulf of Mexico, frequently causes widespread ecological and economic damage and can pose a serious threat to human health. A means for detecting blooms early and monitoring existing blooms that offers high spatial and temporal resolution is desired. Between 1999 and 2001, a large bio-optical data set consisting of spectral measurements of remote-sensing reflectance ( R rs ( λ )), absorption ( a ( λ )), and backscattering ( b b ( λ )) along with chlorophyll a concentrations and K. brevis cell counts was collected on the central west Florida shelf (WFS) as part of the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) and Hyperspectral Coastal Ocean Dynamics Experiment (HyCODE) programs. Reflectance model simulations indicate that absorption due to cellular pigmentation is not responsible for the factor of ∼3–4 decrease observed in R rs ( λ ) for waters containing greater than 10 4 cells l −1 of K. brevis . Instead, particulate backscattering is responsible for this decreased reflectivity. Measured particulate backscattering coefficients were significantly lower when K. brevis concentrations exceeded 10 4 cells l −1 compared to values measured in high-chlorophyll (>1.5 mg m −3 ), diatom-dominated waters containing fewer than 10 4 cells l −1 of K. brevis . A classification technique for detecting high-chlorophyll, low-backscattering K. brevis blooms is developed. In addition, a method for quantifying chlorophyll concentrations in positively flagged pixels using fluorescence line height (FLH) data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) is introduced. Both techniques are successfully applied to Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and MODIS data acquired in late August 2001 and validated using in situ K. brevis cell concentrations.

In situ surveys (1997–2002) of Karenia brevis distribution on the west Florida shelf were used to explain spectral remote sensing reflectance, chlorophyll- a concentration, and backscattering coefficient estimates derived using SeaWiFS satellite data. Two existing approaches were tested in an attempt to differentiate K. brevis blooms from other blooms or plumes. A chlorophyll-anomaly method used operationally by the National Oceanic and Atmospheric Administration (NOAA) sometimes correctly identified K. brevis blooms but also generated false positives and false negatives. The method identified approximately 1000 km 2 of high chlorophyll-anomalies (>1 mg m −3 ) off southwest Florida between the 10 and 50-m isobaths nearly every day from summer to late fall. Whether these patches were K. brevis blooms or not is unknown. A second method used a backscattering:chlorophyll- a ratio to identify K. brevis patches. This method separated K. brevis from other blooms using in situ optical data, but it yielded less satisfactory results with SeaWiFS data. Spectral reflectance ( R rs ) estimates for K. brevis blooms, diatom blooms, and coastal river plumes are statistically similar for many cases. Large pixel size, shallow water, and imperfect algorithms distort satellite retrievals of bio-optical parameters in patchy blooms. At present, a combination of chlorophyll- a , chlorophyll-anomaly, backscattering:chlorophyll- a ratio, RGB composites, MODIS fluorescence data, as well as time-series analysis and ancillary data such as winds, currents, and sea surface temperature can improve K. brevis bloom assessments. Progress in atmospheric correction and bio-optical inversion algorithms is required to help improve capabilities to monitor K. brevis blooms from space. Further, satellite sensors with improved radiometric capabilities and temporal/spatial resolutions are also required.

Brevetoxins produced by the marine dinoflagellate Karenia brevis (C. C. Davis) G. Hansen et Moestrup cause neurotoxic shellfish poisoning (NSP) in human consumers and also endanger a variety of coastal wildlife. In the eastern Gulf of Mexico the presence and abundance of this species have traditionally been monitored using light microscopy (LM) observations of whole water samples. Various molecular probe methods now enable detection of multiple species from a single sample, allowing rapid sample analysis. We describe the development of sandwich hybridization assays (SHAs) for Karenia brevis, K. selliformis Haywood, Steid. et L. MacK., K. mikimotoi (Miyake et Kominami ex M. Oda) G. Hansen et Moestrup, K. papilionacea Haywood et Steid., the Karlotoxin-producer Karlodinium veneficum (D. Ballant.) J. Larsen (=K. micrum), and Gymnodinium aureolum (Hulburt) G. Hansen, comb. nov. The assays require no nucleic acid purification and use LSU rRNA-targeted probes and a semiautomated, 96-well plate format. Probes tested in matrix format were specific relative to rRNAs of all nontarget species used. The response of the SHA for a constant number of K. brevis cells per unit volume of homogenate depended on the growth status of a culture, decreasing for senescent cells relative to actively growing cells. The results of preliminary field tests of the K. brevis SHA indicated that cells collected from natural populations tended to return a lower signal than those harvested from laboratory cultures, but these results are nonetheless very encouraging. These preliminary field studies show that robust standards are required for cell identification and enumeration, with which new methods can be compared.

During May 2003, the dry season, the southwest Florida shelf was surveyed for nutrient concentrations and phytoplankton community composition concurrently with plankton nutritional and physiological status (tracer techniques, enzyme assay, and biomass response bioassays). Inorganic nitrogen concentrations were low throughout the region, while dissolved organic nitrogen (DON) was elevated (.30 mmol N L21) nearshore. Conversely, PO 3{ 4 and dissolved organic phosphorus concentrations were high only in northern coastal areas adjacent to estuarine outflows. Nitrogen : phosphorus (N : P) ratios in the particulate material; gradients in NO { and urea uptake rates; urease and alkaline phosphatase activities; and bioassay responses were indicative of a strong gradient from N to P limitation of plankton biomass from north to south. Nitrogen limitation was apparent in the northern region (N : Pparticulate , 8, Tampa to Sanibel), where PO 3{ 4 and DON inputs dominated; balanced nutrient conditions were evident in the mid-region (N : Pparticulate 5 8–24, Sanibel to Shark River); and P limitation was evident south of the Shark River (N : Pparticulate . 24), where inorganic N input was greatest. Phytoplankton community composition varied along the same gradient, from a cyanobacteria and dinoflagellate community in the north, to a cyanobacteria-dominated community in the mid-region, and to a diatom community in the southern region. Percentages of NO { uptake and diatoms in the total phytoplankton community were positively related, as were percentages of urea uptake and cyanobacteria. Inorganic and organic N and P fractions in the nearshore shelf region reflect longitudinal gradients in regional watershed characteristics, and their relative availability thus appeared to control both phytoplankton community composition and its physiological status.

During a 3-yr study in the Gulf of Mexico, we measured dinitrogen (N 2 ) fixation and nitrogen (N) release by Trichodesmium and compared these rates with water column N demand and the estimated N necessary to support blooms of Karenia brevis, a toxic dinoflagellate that severely affects the West Florida shelf. Net and gross N 2 fixation rates were compared in simultaneous incubations using 15 N 2 uptake and acetylene reduction, respectively. The difference between net and gross N 2 fixation is assumed to be an approximation of the rate of N release. Results demonstrate that Trichodesmium in the Gulf of Mexico are fixing N 2 at high rates and that an average of 52% of this recently fixed N 2 is rapidly released. Calculations suggest that observed densities of Trichodesmium can provide enough N to support moderately sized K. brevis blooms. Based on other studies where 15 N 2 and acetylene reduction were compared directly, it appears that N release from Trichodesmium is common but varies in magnitude among environments. In addition, carbon (C) and N-based doubling times for Trichodesmium vary among studies and environments. Comparing gross N 2 fixation and C fixation directly, C-based doubling times exceeded N-based doubling times, which suggests an imbalance in elemental turnover or a failure to fully quantify Trichodesmium N use.

Subtropical estuaries have received comparatively little attention in the study of nutrient loading and subsequent nutrient processing relative to temperate estuaries. Australian estuaries are particularly susceptible to increased nutrient loading and eutrophication, as 75% of the population resides within 200 km of the coastline. We assessed the factors potentially limiting both biomass and production in one Australian estuary, Moreton Bay, through stoichiometric comparisons of nitrogen (N), phosphorus (P), silicon (Si), and carbon (C) concentrations, particulate compositions, and rates of uptake. Samples were collected over 3 seasons in 1997–1998 at stations located throughout the bay system, including one riverine endmember site. Concentrations of all dissolved nutrients, as well as particulate nutrients and chlorophyll, declined 10-fold to 100-fold from the impacted western embayments to the eastern, more oceanic-influenced regions of the bay during all seasons. For all seasons and all regions, both the dissolved nutrients and particulate biomass yielded N:P ratios

While the global increase in the use of nitrogen-based fertilizers has been well recognized, another change in fertilizer usage has simultaneously occurred: a shift toward urea-based products. Worldwide use of urea has increased more than 100-fold in the past 4 decades and now constitutes >50% of global nitrogenous fertilizer usage. Global urea usage extends beyond agricultural applications; urea is also used extensively in animal feeds and in manufacturing processes. This change has occurred to satisfy the world's need for food and more efficient agriculture. Long thought to be retained in soils, new data are suggestive of significant overland transport of urea to sensitive coastal waters. Urea concentrations in coastal and estuarine waters can be substantially elevated and can represent a large fraction of the total dissolved organic nitrogen pool. Urea is used as a nitrogen substrate by many coastal phytoplankton and is increasingly found to be important in the nitrogenous nutrition of some harmful algal bloom (HAB) species. The global increase from 1970 to 2000 in documented incidences of paralytic shellfish poisoning, caused by several HAB species, is similar to the global increase in urea use over the same 3 decades. The trend toward global urea use is expected to continue, with the potential for increasing pollution of sensitive coastal waters around the world.

Near real-time data from the MODIS satellite sensor was used to detect and trace a harmful algal bloom (HAB), or red tide, in SW Florida coastal waters from October to December 2004. MODIS fluorescence line height (FLH in W m− 2 μm− 1 sr− 1) data showed the highest correlation with near-concurrent in situ chlorophyll-a concentration (Chl in mg m− 3). For Chl ranging between 0.4 to 4 mg m− 3 the ratio between MODIS FLH and in situ Chl is about 0.1 W m− 2 μm− 1 sr− 1 per mg m− 3 chlorophyll (Chl = 1.255 (FLH × 10)0.86, r = 0.92, n = 77). In contrast, the band-ratio chlorophyll product of either MODIS or SeaWiFS in this complex coastal environment provided false information. Errors in the satellite Chl data can be both negative and positive (3–15 times higher than in situ Chl) and these data are often inconsistent either spatially or temporally, due to interferences of other water constituents. The red tide that formed from November to December 2004 off SW Florida was revealed by MODIS FLH imagery, and was confirmed by field sampling to contain medium (104 to 105 cells L− 1) to high (> 105 cells L− 1) concentrations of the toxic dinoflagellate Karenia brevis. The FLH imagery also showed that the bloom started in mid-October south of Charlotte Harbor, and that it developed and moved to the south and southwest in the subsequent weeks. Despite some artifacts in the data and uncertainty caused by factors such as unknown fluorescence efficiency, our results show that the MODIS FLH data provide an unprecedented tool for research and managers to study and monitor algal blooms in coastal environments.

Blooms of the dinoflagellate Prorocentrum minimum often occur in coastal regions characterized by variable salinity and elevated concentrations of terrestrially derived dissolved organic carbon (DOC). Humic, fulvic and hydrophilic acid fractions of DOC were isolated from runoff entering lower Narragansett Bay immediately after a rainfall event and the influence of these fractions upon P. minimum growth, cell yield, photosynthesis and respiration was examined. All organic fractions stimulated growth rates and cell yields compared with controls (no organic additions), but the extent of stimulation varied with the fraction and its molecular weight. Greatest stimulations were observed with humic and fulvic acids additions; cell yields were more than 2.5 and 3.5 times higher than with hydrophilic acid additions while growth rates were 21 and 44% higher, respectively. Responses to additions of different molecular weight fractions of each DOC fraction suggest that growth rate effects were attributable to specific molecular weight fractions: the >10,000 fraction of humic acids, both the >10,000 and 10 μm ml−1. Low concentrations (5–10 μg ml−1) of humic acid had no statistically significant effect upon production, but exposure to concentrations >25 μg ml−1 resulted in a 30% decrease in O2 evolution, probably due to light attenuation by the highly colored humic acid fraction. Respiration rates ranged from 1.2 to 2.7 pg O2 cell−1 h−1 and were elevated upon exposure to both fulvic and hydrophilic acids, but not to humic acid. These results demonstrate that terrestrially derived DOC fractions play an active role in stimulation of P. minimum growth via direct effects upon growth, yield and photosynthesis as well as via indirect influences such as interactions with nitrogen and effects upon light attenuation.

Prorocentrum minimum (Pavillard) Schiller, a common, neritic, bloom-forming dinoflagellate, is the cause of harmful blooms in many estuarine and coastal environments. Among harmful algal bloom species, P. minimum is important for the following reasons: it is widely distributed geographically in temperate and subtropical waters; it is potentially harmful to humans via shellfish poisoning; it has detrimental effects at both the organismal and environmental levels; blooms appear to be undergoing a geographical expansion over the past several decades; and, a relationship appears to exist between blooms of this species and increasing coastal eutrophication. Although shellfish toxicity with associated human impacts has been attributed to P. minimum blooms from a variety of coastal environments (Japan; France; Norway; Netherlands; New York, USA), only clones isolated from the Mediterranean coast of France, and shellfish exposed to P. minimum blooms in this area, have been shown to contain a water soluble neurotoxic component which killed mice. Detrimental ecosystem effects associated with blooms range from fish and zoobenthic mortalities to shellfish aquaculture mortalities, attributable to both indirect biomass effects (e.g., low dissolved oxygen) and toxic effects. P. minimum blooms generally occur under conditions of high temperatures and incident irradiances and low to moderate salinities in coastal and estuarine environments often characterized as eutrophic, although they have been found under widely varying salinities and temperatures if other factors are conducive for growth. The physiological flexibility of P. minimum in response to changing environmental parameters (e.g., light, temperature, salinity) as well as its ability to utilize both inorganic and organic nitrogen, phosphorus, and carbon nutrient sources, suggest that increasing blooms of this species are a response to increasing coastal eutrophication.

The abundance and productivity of benthic microalgae in coral reef sediments are poorly known compared with other, more conspicuous (e.g. coral zooxanthellae, macroalgae) primary producers of coral reef habitats. A survey of the distribution, biomass, and productivity of benthic microalgae on a platform reef flat and in a cross-shelf transect in the southern Great Barrier Reef indicated that benthic microalgae are ubiquitous, abundant (up to 995.0 mg chlorophyll (chl) a m−2), and productive (up to 110 mg O2 m−2 h−1) components of the reef ecosystem. Concentrations of benthic microalgae, expressed as chlorophyll a per surface area, were approximately 100-fold greater than the integrated water column concentrations of microalgae throughout the region. Benthic microalgal biomass was greater on the shallow water platform reef than in the deeper waters of the cross-shelf transect. In both areas the benthic microalgal communities had a similar composition, dominated by pennate diatoms, dinoflagellates, and cyanobacteria. Benthic microalgal populations were potentially nutrient-limited, based on responses to nitrogen and phosphorus enrichments in short-term (7-day) microcosm experiments. Benthic microalgal productivity, measured by O2 evolution, indicated productive communities responsive to light and nutrient availability. The benthic microalgal concentrations observed (92–995 mg chl a m−2) were high relative to other reports, particularly compared with temperate regions. This abundance of productive plants in both reef and shelf sediments in the southern Great Barrier Reef suggests that benthic microalgae are key components of coral reef ecosystems.

Frequent blooms of the toxic dinoflagellate, Karenia brevis, along the west coast of Florida are of considerable concern to state resource managers due to numerous ecological and health impacts. With the availability of remotely sensed ocean color imagery from SeaWiFS, a regional algorithm that compensates for the scattering of sediments in coastal waters can be applied to accurately estimate chlorophyll concentrations in coastal areas of Florida. Chlorophyll anomalies of 1 μg l−1 based on a 60-day running mean are currently used along the Panhandle and west Florida coast, to detect K. brevis blooms exceeding 100,000 cells l−1. This is the first step in an early warning system to forecast K. brevis blooms in the eastern Gulf of Mexico. A retrospective analysis was performed on imagery acquired from 1999, 2000 and 2001 to determine the accuracy of this technique in detecting K. brevis blooms in this region. During the K. brevis bloom season from August through April, chlorophyll anomalies accurately identified K. brevis blooms along the Florida Panhandle, from Tampa Bay to Cape Romano and Key West >83% of the time. Frequent chlorophyll anomalies were falsely observed in the spring and early summer, prior to the beginning of the K. brevis bloom season. Areas rich in colored dissolved and particulate matter were prone to anomalies that falsely identify K. brevis blooms; however, blooms rarely originate in these areas.

Florida Bay, a shallow, seagrass-dominated bay in southern Florida, USA, receives significant nutrient inputs and has experienced seagrass losses and microalgal blooms within the last several decades. Inorganic nutrient inputs have been well characterized, but the role of organic nutri- ents, specifically of dissolved organic nitrogen (DON) and organic phosphorus (DOP), in supporting microbial processes in the bay is unknown. In this study various techniques were used to assess the importance of these nutrients along a transect in Florida Bay when a cyanobacterial bloom occurred in the central region in November 2002. These techniques included measurements of ambient particu- late and dissolved nutrients, enzyme (urease and alkaline phosphatase) activities, and experiments to determine rates of 15 N uptake (nitrate, ammonium, urea, and amino acids over a period of 0.5 h) and long-term (48 h) changes in microbial biomass and 15 N natural abundance in enrichment bioassays. The cyanobacterial bloom in central Florida Bay was associated with the highest concentrations of DON and DOP, whereas the microflagellate- and diatom-dominated eastern bay region was associ- ated with the highest concentrations of inorganic nutrients. The zeaxanthin:chlorophyll a ratio (an indicator of the relative contribution of cyanobacteria to phytoplankton biomass) was positively corre- lated with the rate of uptake of urea, and negatively correlated with the rate of uptake of inorganic nitrogen. The opposite pattern was observed for the fucoxanthin:chlorophyll a ratio (indicative of relative diatom biomass) and the peridinin:chlorophyll a ratio (indicative of relative photosynthetic dinoflagellate biomass), suggesting that different algal groups were using different N substrates. Bio- mass responses in the bioassay experiments showed that phytoplankton (as chlorophyll a) responded to DON additions in the western region and to DOP additions in the eastern region, but heterotrophic bacteria, in contrast, responded to DOP additions in the west and DON additions in the east. These findings thus demonstrate the potential for different sources of N, including DON, to stimulate differ- ent components of the algal community, and for the phytoplankton and bacteria to respond differently to N and P.

A simple ecological model, coupled to a primitive equation circulation model, is able to replicate the observed alongshore transport of the toxic dinoflagellate Karenia brevis on the West Florida shelf during a fall red tide in 1979. Initial land fall of these populations at the coast in our model matches shoreline data sets as well. The simulated vertical movement of K. brevis, in response to light-cued migration and nocturnal mixing, also mimics these aspects of the next fall red tide in 1980, suggesting that sunrise populations may provide the strongest surface signal, for detection of red tides by remote sensors aboard aircraft and satellites. Once a mature red tide is formed, a light-regulated maximal growth rate of 0.15 day−1, reflecting nutrient-limitation, and no other loss processes may be an adequate description of population dynamics above the 30–40 m isobaths, where blooms of K. brevis originate. Within shallow waters at the 10-m isobath, however, an apparent larger growth rate of 0.80 day−1—as a presumed consequence of frontal aggregations—must be offset by unknown processes of algal mortality. Likely candidates for cumulative, biomass-dependent losses are UV-B irradiation, microbial-induced lysis, and unselective grazing pressure from copepods, protozoans and heterotrophic dinoflagellates.

Prior laboratory studies of Trichodesmium have shown a high iron requirement that is consistent with the biochemical demand for iron in the enzyme nitrogenase. Summer delivery of iron, in the form of Saharan dust, may provide an explanation for Trichodesmium blooms observed in offshore waters of the West Florida shelf over the last 50 yr. During ecology and oceanography of harmful algal blooms (ECOHAB) field studies, background iron levels (0.1‐0.5 nmol kg 21

Significant natural and aquaculture fish deaths in Kuwait Bay occurred from September to October of 1999 and were attributed to a bloom of the dinoflagellate Gymnodinium sp. A chronology of the bloom event suggests that a period of low winds and stable water-column structure preceded the bloom. Maximum cell concentrations of Gymnodinium sp. (>6 × 10 6 cells l -1 ) were also immediately preceded by a more than 20-fold increase in mean inorganic nitrogen concentrations (up to 60 µM) and elevated inorganic phosphate concentrations. This, combined with elevated inorganic and or- ganic nutrient concentrations within the bloom, suggests that coastal nutrient eutrophication was likely to have contributed significantly to bloom development and support. Termination of the Gymno- dinium sp. bloom coincided with a bloom of the non-toxic ciliate Mesodinium rubrum, which appeared as large red patches in Kuwait Bay. While no adverse human health effects were associated with the bloom, closure of shellfish and selected finfish (largely mullet Liza macrolepis) markets resulted in sig- nificant economic losses to the region. The occurrence of this toxic algal bloom event, the first within the Arabian Sea, highlights the need for monitoring and research programs in the Arabian Sea and Kuwait Bay that focus on nutrients and eutrophication, in addition to oil related pollution issues.

Marine viruses have been shown to affect phytoplankton productivity; however, there are no reports on the effect of viruses on benthic microalgae (microphytobenthos). Hence, this study investigated the effects of elevated concentrations of virus-like particles on the photosynthetic physiology and community composition of benthic microalgae and phytoplankton. Virus populations were collected near the sediment surface and concentrated by tangential flow ultrafiltration, and the concentrate was added to benthic and water column samples that were obtained along a eutrophication gradient in the Brisbane River/Moreton Bay estuary, Australia. Photosynthetic and community responses of benthic microalgae, phytoplankton and bacteria were monitored over 7 d in aquaria and in situ. Benthic microalgal communities responded to viral enrichment in both eutrophic and oligotrophic sediments. In eutrophic sediments, Euglenophytes (Euglena sp.) and bacteria decreased in abundance by 20 to 60 and 26 to 66%, respectively, from seawater controls. In oligotrophic sediments, bacteria decreased in abundance by 30 to 42% from seawater controls but the dinoflagellate Gymnodinium sp. increased in abundance by 270 to 3600% from seawater controls, The increased abundance of Gymnodinium sp. may be related to increased availability of dissolved organic matter released from lysed bacteria. Increased (140 to 190% from seawater controls) initial chlorophyll a fluorescence measured with a pulse-amplitude modulated fluorometer was observed in eutrophic benthic microalgal incubations following virus enrichment, consistent with photosystem II damage. Virus enrichment in oligotrophic water significantly stimulated carbon fixation rates, perhaps due to increased nutrient availability by bacterial lysis. The interpretation of data from virus amendment experiments is difficult due to potential interaction with unidentified bioactive compounds within seawater concentrates. However, these results show that viruses are capable of influencing microbial dynamics in sediments.

A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 106 cells L−1 through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 104 cells L−1 in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11–15 ng PbTx-3 equivalents (g dry wt sediment)−1 in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6–18 ng (g dry wt epiphytes)−1. The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)−1. In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent.

Over the years, numerous outreach strategies by the science community, such as FAQ cards and website information, have been used to explain blooms of the toxic dinoflagellate, Karenia brevis that occur annually off the west coast of Florida to the impacted communities. Many state and federal agencies have turned to funded research groups for assistance in the development and testing of environmental outreach products. In the case of Florida red tide, the Fish and Wildlife Research Institute/Mote Marine Laboratory (MML) Cooperative Red Tide Agreement allowed MML to initiate a project aimed at developing innovative outreach products about Florida red tide. This project, which we coined “The Art of Red Tide Science,” consisted of a team effort between scientists from MML and students from Ringling College of Art and Design. This successful outreach project focused on Florida red tide can be used as a model to develop similar outreach projects for equally complex ecological issues.