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2001 Progress Report: ECOHAB: Control of Harmful Algal Blooms using Clay
EPA Grant Number: R827090Title: ECOHAB: Control of Harmful Algal Blooms using Clay
Investigators: Anderson, Donald M. , Bricelj, V. Monica , Chapman, Peter , Greene, Richard M. , Lewis, Michael , Pierce, Richard
Current Investigators: Anderson, Donald M. , Bricelj, V. Monica , Greene, Richard M. , Lewis, Michael , Pierce, Richard
Institution: Woods Hole Oceanographic Institution , Mote Marine Laboratory
Current Institution: Woods Hole Oceanographic Institution
EPA Project Officer: Perovich, Gina
Project Period: November 23, 1998 through November 22, 2001 (Extended to November 22, 2002)
Project Period Covered by this Report: November 23, 2000 through November 22, 2001
Project Amount: $332,938
RFA: Ecology and Oceanography of Harmful Algal Blooms (1998)
Research Category: Aquatic Ecosystems , Water Quality
Description:
Objective:The objectives of this research project are to use laboratory cultures, aquaria, and mesocosms to: (1) determine the removal efficiencies of selected clays on three harmful algal bloom (HAB) species found in U.S. waters (the Florida red tide dinoflagellate Gymnodinium breve, the New York brown tide chrysophyte Aureococcus anophagefferens, and fish-killing Pfiesteria-like dinoflagellates); (2) determine the variability in cell removal efficiencies (RE) due to factors such as species differences, growth stage, and cell density; (3) determine whether cell RE can be improved by addition of alum or polymeric coagulants; (4) investigate changes in water chemistry following clay treatment, including the release or removal of nutrients such as phosphorus, nitrogen, radioactivity, trace metals, and other toxicants; (5) investigate toxin release and uptake by clays during the flocculation process; (6) investigate the use of clays to mitigate the impacts of aerosolized brevetoxins; (7) conduct larger scale aquarium and mesocosm studies to examine flocculation efficiencies on natural plankton assemblages, and assess the impacts of sedimented biomass and toxins on benthic organisms; (8) evaluate the engineering requirements, economic costs, and environmental clearances that must be addressed if this control strategy is to be applied to blooms in natural waters; and (9) design a pilot program for field application of this bloom mitigation strategy.
Progress Summary:Removal Efficiencies of Selected Clays (G. breve, A. anophagefferens, and Pfiesteria-like dinoflagellates). In the process of our investigation, we have tested more than 25 different clay minerals from domestic sources for their removal abilities against Karenia brevis (formerly G. breve), A. anophagefferens, and Pfiesteria piscicida. In general, clays such as montmorillonite and a polymer-treated (cationic) kaolinite were highly effective at removing K. brevis and P. piscicida from suspension, but not very efficient at removing A. anophagefferens. We found that by gently agitating the cell culture after the clay slurry was added, removal efficiency increased significantly. Further experiments revealed that by prolonging the flocculation time, and increasing the salinity of the medium, cell RE can be improved by a factor of two from the initial surveys. These latter findings have led us to speculate that the removal of this species with clay is limited by the encounter (or collision) rates between clays and cells in our quiescent system. Therefore, methods that introduce water motion, such as brief agitation, or by prolonging the time for flocculation in the static system, appeared to enhance overall cell removal.
In further experiments with K. brevis, the removal ability of clay minerals far exceeded those of several non-clay minerals (e.g., diatomaceous earth, apatite, and volcanic glass). Additional tests using phosphatic clays from various locations in central Florida, and from different processing stages, revealed slight variations of removal ability in the loading rate. This clay also showed the ability to kill cells from direct physical contact with the organism. Cell mortality increased with increasing clay loading and with longer contact with the algae.
Factors Affecting Cell Removal by Clays and the Mechanism of Clay-Cell Flocculation. Laboratory experiments were conducted to determine how factors such as particle concentration, particle size, surface chemical properties, cell swimming speed, and culture salinity can influence overall cell removal efficiency. From these empirical studies, a working understanding and a model of clay-cell aggregation can be formulated and tested.
In nearly all of our studies, removal of any given algal species from a wide range of taxa generally increases with increasing clay concentration for all types of clay minerals. However, these cell-removal trends varied from linear to sigmoidal or hyperbolic as loading increased. The case was not the same for increasing algal concentrations treated with a given clay mineral. In a survey using Florida phosphatic clay against a wide variety of algal species, cell removal showed increasing, decreasing, and constant trends as phosphatic clay loading increased. The result was species dependent. Finally, we determined that phosphatic clay can remove two species in a mixed culture differentially. When K. brevis (high RE) was mixed in different proportions with P. micans (low RE) and treated with phosphatic clay, K. brevis removal remained constantly high while P. micans remained low. In fact, the removal of K. brevis increased slightly in the presence of P. micans, which may indicate that even the slight removal of a co-occuring algae may influence how K. brevis is removed. Similar results were found with K. brevis mixed with Skeletonema costatum, a cosmopolitan diatom species.
In further studies with P. piscicida, changing the salinity of initial culture medium and the initial clay slurry produced changes in the overall cell removal. In both cases, cell removal declined drastically. One explanation may be that higher salinity led to higher clay-clay flocculation, which then influenced their sinking rates and loss from the system. As the clays sink from the culture more quickly, they have less opportunity to interact with the organisms.
Use of Coagulants and Flocculants To Enhance Cell Removal in Mesocosm Tanks Using Clays. Chemical coagulants and flocculants are used in water and waste water treatment to promote the aggregation and settling of very fine particles. We tested these additives in combination with clays to determine whether they can further enhance cell removal by increasing the "stickiness" of clays. Of the chemicals tested, polyaluminum hydroxy-chloride showed the best results in combination with the most effective clays used with K. brevis, P. piscicida, and A. anophagefferens, respectively.
In further trials, the experiments were run in larger volumes. Unfortunately, the polyaluminum chloride (PAC)-treated clay rapidly flocculated with itself, forming large, baseball-size aggregates that fell rapidly to the bottom. Within the first few minutes, all of the clays were deposited, and cell removal was predictably low. After a number of repeated trials using alternative dispersal strategies, the best results were obtained by using highly diluted PAC dispersed in seawater, which was first added to the culture and allowed to diffuse through the upper water column before the clays were added. The improvement in RE using this method was confirmed during a series of mesocosm experiments conducted in Corpus Christi, TX, during an actual K. brevis bloom. These results are very promising.
Resuspension properties of untreated phosphatic clay and PAC-treated clay also were tested in flow using a racetrack flume at Woods Hole Oceanographic Institute. Suspension organisms and phosphatic clay were placed in a fenced portion and allowed to settle over the test bed. Results indicated that the longer the material is allowed to consolidate, the higher the flow speed required for resuspension. Moreover, the addition of PAC lowered these values, suggesting that the material becomes easier to resuspend. The addition of PAC appeared to make the flocs more porous and readily moved by water motion.
Investigation of Toxin Release and Aerosolized Brevetoxin Uptake by Clays During the Flocculation Process. At the Mote Marine Laboratory, controlled experiments focusing on the effect of clay treatment on intracellular and extracellular toxins have been completed. Briefly, results showed that the brevetoxins were removed with high efficiency. The addition of PAC did not significantly improve toxin removal with clay alone. Other results found that the presence of clay reduced the amount of aerosolized toxin by 75 percent. These observations underscore the potential applicability of clay at mitigating the toxins alone. However, the strong affinity of these toxins for clay particles argues for the need to investigate the fate (e.g., permanence, degradation) and effects (e.g., bioavailability, potential for trophic transport) of brevetoxins associated with clay in the water column, and especially in the benthos.
Mesocosm Studies To Examine Flocculation Efficiencies on Natural Plankton Assemblages. A series of experiments were conducted in Corpus Christi, TX, during a large K. brevis bloom in the region. Removal experiments were performed using untreated and PAC-treated phosphatic clays. Cell removal was determined over a range of clay loadings, cell concentrations, and PAC concentrations. With each run, changes in water quality and chemistry were monitored, including turbidity, temperature, salinity, dissolved oxygen, pH, inorganic nutrients, toxins, chlorophyll a, and total suspended solids. Samples also were taken for cell counts and plankton identification before and after treatment. Briefly, cell removal rates were comparable from laboratory trials, given the combination of clay loading and cell concentrations. Likewise, PAC treatment increased cell removal. Turbidity increased predictably by a factor of three, as clay was added, and remained high throughout the short time period of the experiment. There was no change in salinity, pH, and dissolved oxygen due to clay addition. Adsorption of nitrate/nitrite was observed, while ammonia appeared to be released and absorbed. As expected, some release of phosphate was found. There was no significant difference in the silicate concentration before and after clay addition. Finally, differential cell removal was observed among the four dominant species in the water in one set of replicated experiments: K. brevis, Bacillaria sp., and Skeletonema sp. were removed at about the same level, while Prymnesium sp. was not removed.
Examination of Impacts of Clay/PAC Treatments on Benthos. A series of
experiments were conducted at the National Research Council of Canada to determine
the impact of fully sedimented and resuspended clay-cell aggregates on the survival
and growth of juvenile hard clams, Mercenaria mercenaria. Experiments
were performed in a recirculating flume using the nontoxic dinoflagellates Heterocapsa
triquetra, Prorocentrum micans, and phosphatic clay (no PAC). Flow
regimes simulated two extreme conditions, representing end members of a continuum
expected in the field: (1) where low flow allowed complete settling and formation
of a sediment layer; and (2) where high flow maintained complete particle resuspension.
No clam mortalities occurred in either treatment. The fully sedimented treatment
produced by a single clay application showed no significant differences in shell
or tissue growth compared to controls, and clams rapidly resumed siphon contact
with the overlying water. In contrast, a significant growth effect occurred
in trials with clay maintained in suspension for 2 weeks. These results suggest
that clay applications in the field likely are more detrimental to clams under
flow conditions leading to prolonged in situ resuspension of clay rather
than under conditions that promote rapid sedimentation. The magnitude of impacts
is thus dependent on the flow regime and the duration of exposure to resuspended
clay.
The experiments at the U.S. Environmental Protection Agency (EPA) Gulf Breeze Laboratory, FL, have been completed. The objective of these studies was to use standard EPA sediment toxicology procedures to determine acute and chronic toxicities of clay/cell flocs following treatment of K. brevis. Toxicity of phosphatic clay, with and without PAC, was assayed using four benthic organisms in 4 to 28 day exposures. The organisms tested were Ampelisca abdita (infaunal amphipod), Cyprinodon variegatus (sheepshead minnow), Leptocheirus plumulosus (infaunal amphipod), and Palaemonetes pugio (grass shrimp). Several tests also were conducted in the presence of intact and lysed cells of K. brevis. Clay and flocculant alone were not lethal to these juvenile fish and epibenthic and infaunal invertebrates following both acute or chronic exposures. Furthermore, the chronic and acute toxicities of the settled clay/flocculant/K. brevis cell aggregates were not significantly different from the toxicity of the K. brevis cells alone, suggesting that the use of this bloom control method may not result in toxicity to these types of organisms above those naturally occurring during a red tide event.
Engineering Requirements/Economic Costs/Environmental Clearances. As we continue to increase the scale of our experiments, particularly in mesocosms and limno-corrals in the field, we have become more aware of the engineering challenges associated with the transportation and handling of larger amounts of clay, the preparation of clay slurry, clay dispersal, and monitoring environmental and water quality changes. Aside from what we have learned from our own experiences, we have begun to establish contacts with Korean colleagues and domestic clay producers regarding the economic cost and feasibility of clay applications. We have begun to accumulate data on the cost of various clay types and their transport. We also have investigated existing clay dispersal methods (e.g., from Korea) using specially designed sprayers, as well as discussing new designs with local manufacturers. Finally, we also have made inquiries regarding the permit process and the pertinent legislation that must be addressed.
Future Activities:The investigators plan to continue accumulating data on the cost of various clay types and their transport. Investigators also plan to continue investigating existing clay dispersal methods using specially designed sprayers.
Journal Articles on this Report: 4 Displayed | Download in RIS Format
| Other project views: | All 34 publications | 14 publications in selected types | All 14 journal articles |
| Type | Citation | ||
|---|---|---|---|
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Archambault MC, Bricelj VM, Grant J, Anderson DM. Effects of clay used to control harmful algal blooms, on juvenile hard clams, Mercenaria mercenaria. Journal of Shellfish Research. |
R827090 (2001) |
not available |
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Beaulieu SE, Sengco MR, Anderson DM. Using clay to control harmful algal blooms: deposition and resuspension of clay/algal flocs. Harmful Algae 2005;4(1):123-138 |
R827090 (2001) |
not available |
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Li A, Sengco MR, Anderson DM. Flocculation and removal of Pfiesteria piscicida (Dinophyceae) using clays. Journal of Plankton Research. |
R827090 (2001) |
not available |
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Sengco MR, Li AS, Tugend K, Kulis D, Anderson DM. Removal of red- and brown-tide cells using clay flocculation. I. Laboratory culture experiments with Gymnodinium breve and Aureococcus anophagefferens. Marine Ecology-Progress Series 2001;210():41-53 |
R827090 (1999) R827090 (2000) R827090 (2001) R827090 (Final) |
not available |
ecological effects, cellular, population, biology, modeling, Florida, FL, New York, NY. , Ecosystem Protection/Environmental Exposure & Risk, Water, Geographic Area, Scientific Discipline, RFA, Ecosystem/Assessment/Indicators, Ecological Risk Assessment, algal blooms, Biochemistry, Environmental Engineering, Environmental Microbiology, Hydrology, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Ecology and Ecosystems, State, marine ecosystem, nutrient kinetics, water quality, biotoxin risk, phytoplankton, harmful algal blooms, benthic algae, dinoflagellates, sustainable fisheries, New York (NY), FLA, bloom dynamics, oceanography, ecological exposure, clay, brevetoxins, G. breve red tides, Florida, ECOHAB, ecological effects, fish kills
Progress and Final Reports:
1999 Progress Report
2000 Progress Report
Original Abstract
Final Report