Grantee Research Project Results
2000 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. , Greene, Richard M. , Bricelj, V. Monica , Lewis, Michael , Chapman, Peter , Pierce, Richard
Current Investigators: Anderson, Donald M. , Greene, Richard M. , Bricelj, V. Monica , Lewis, Michael , Pierce, Richard
Institution: Woods Hole Oceanographic Institution
EPA Project Officer: Packard, Benjamin H
Project Period: November 23, 1998 through November 22, 2001 (Extended to November 22, 2002)
Project Period Covered by this Report: November 23, 1999 through November 22, 2000
Project Amount: $332,938
RFA: Ecology and Oceanography of Harmful Algal Blooms (1998) RFA Text | Recipients Lists
Research Category: Water Quality , Harmful Algal Blooms , Water , Aquatic Ecosystems
Objective:
The general objectives of this project are to use laboratory cultures, aquaria, and mesocosms to: (1) determine the removal efficiencies of selected clays on three 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 due to such factors as species differences, growth stage, and cell density; (3) determine whether cell removal efficiencies 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 and nitrogen, release of 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 to access 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:
Considerable progress has been made during the second year of this project. With support from the EPA ECOHAB grant, we are pleased to report the following progress.1. Removal efficiencies of selected clays on three HAB species found in U.S. waters (Gymnodinium breve, Aureococcus anophagefferens, and Pfiesteria-like dinoflagellates).
Last year, we reported that a variety of clays had been tested and results showed that Florida phosphatic clay, a by-product of the Florida phosphorus mining industry, and a kaolinite (HDP clay) were the most effective (>90 percent) against G. breve and Pfiesteria piscicida. However, relatively low (<30 percent) removal efficiency was achieved for Aureococcus anophagefferens when using the same clay loading (0.25 g/L) and flocculation time (2.5 hours). Results of these studies suggest that the effectiveness of a clay to remove an algal species is not only determined by its mineral type, but is also influenced by the ambient chemical and physical environment.
2. Mesocosm studies to examine flocculation efficiencies on natural plankton assemblages.
A series of mesocosm experiments were conducted near Great South Bay, Long Island, to determine the removal efficiency of Huber kaolinite DP-1010 (H-DP) against Aureococcus anophagefferens. Various parameters, including cell number, chlorophyll, dissolved inorganic nutrients, and other chemical properties (e.g., dissolved organic carbon and oxygen) and physical properties (e.g., salinity, temperature, and turbidity) were measured. Results from these experiments were not conclusive as relatively low removal efficiency (<50 percent) against the target species was achieved. Low removal efficiency might be attributed to the duration for flocculation and settling, which was only 2.5 hours?perhaps not long enough for full cell/floc removal. Further experiments with a longer settling time (e.g., >7 hours as indicated in laboratory experiments) and use of the flocculant polyaluminum chloride (PAC) are needed.
3. Use of coagulants to enhance cell removal in mesocosm tanks using clays.
After a number of trials of alternative dispersal strategies, we obtained the best results using highly diluted PAC dissolved in seawater. Studies with this approach were then conducted using natural plankton assemblages in 6 tanks with a volume of 530 L each. The results are very promising. With only 4 ppm (mg/L) of PAC added, followed by 95 ppm (mg/L) of IMCP clay, dinoflagellate removal efficiency was up to 81 percent. Several similar experiments were conducted to test this method using these large tanks with low cell abundance. Samples for inorganic nutrient adsorption/release during these clay treatments were also collected and are currently being analyzed in our laboratory.
Overall, the advantage of the PAC is clear?we can significantly reduce the amount of clay needed through the addition of an environmentally benign flocculant in ppm concentrations. PAC is accepted for drinking water clarification.
4. Examination of changes in water chemistry following clay treatment, including the release or removal of nutrients such as phosphorus and nitrogen, release of radioactivity, trace metals and other toxicants.
An important step towards understanding the possible environmental impacts of clay application is to examine the change in biological oxygen demand (BOD) in the water column and the sediments following clay deposition. This term refers to the amount of oxygen required by organisms, primarily microbes, to oxidize organic material. We are interested in this measure because we predict that the settling flocs will contain a large amount of organic material from the captured cells, which, in turn, can stimulate microbial activity, leading to the depletion of dissolved oxygen in the system and mortalities of bottom-dwelling animals. Our intention is to collect sedimented material to determine its biological oxygen demand (BOD). To accomplish this, we tested several methods for BOD measurement using laboratory cultures treated with clay.
Our results with simple BOD bottles show that the BOD of clay-treated samples with cells was slightly lower than that of untreated samples with only cells, yielding an oxygen demand of around 4mg/L after 5 days. When cultured G. breve cells were added to acrylic columns containing both sediments and seawater, the oxygen consumption in the clay treatment was again significantly lower than with cells alone. The lower BOD may be due to inhibition of respiration of the Gymnodinium breve cells and associated bacterial activity by the clay. More importantly, we now have a method to obtain an important measurement of our flocs that can be compared to other organic loadings to bottom sediments (e.g., natural bloom deposition). These data, as they are collected in subsequent experiments, will define the oxygen consumption of our flocs under different conditions, allowing an assessment of potential impacts.
A total of 10 Florida phosphatic clay samples were collected, and the contents of heavy/toxic metals and particle sizes are currently being analyzed. Experiments have been conducted to examine kinetics of inorganic nutrient adsorption/release by these clays. Experiments to investigate release of radioactivity from these clays are currently being conducted at WHOI.
5. Investigation of toxin release and aerosolized brevetoxins uptake by clays during the flocculation process.
Laboratory studies were conducted to determine the effects of clay flocculation on the removal of brevetoxin in seawater. Additional studies were conducted to determine the reduction of brevetoxin in aerosols produced in the presence of clay. Results from these experiments are promising, as we found that the presence of clay reduced the amount of aerosolized toxin by 75 ? 64 percent.
These results demonstrate that the IMCP clay is a very efficient means for removing dissolved brevetoxins from seawater. It has already been shown to be highly effective in removing intact G. breve cells. Studies are continuing to test various combinations of clay and PAC, and combinations of G. breve cells and toxins to assess optimum ratios of clay/PAC for brevetoxin removal.
6. Examination of impacts of clay/PAC treatments on benthos.
Experiments have been conducted to identify potential lethal and sublethal
effects of clay additions on the juvenile hard clam. These experiments were run
in a recirculating flume with 6 cm deep coarse sand as sediment bed for juvenile
Mercenaria mercenaria. The non-toxic dinoflagellate Prorocentrum micans was
added at 1000 cells/ml for cell flocculation while phosphatic clay was added at
a loading of 1 g/L. Results indicated that even under extremely high clay
loading (1 g/L) there was no mortality in any of the trials within an 11 day
period. It was also found that clams could quickly recover siphon contact with
the overlying water column during and following sedimentation. In one case,
significant growth in shell length and soft tissue occurred in control and
treatment; however, in another case, treatment effects were evidenced by reduced
shell growth by 51 percent and reduced soft tissue growth by 52 percent. Further
tests are ongoing to address this inconsistency and to better characterize the
effects of clay/cell floc on bivalves.
A series of invertebrate and
vertebrate toxicity studies were also conducted to examine the background
toxicity of a clay/coagulant (PAC) mixture alone and as an applied treatment to
lysed and intact cells of Gymnodinium breve. Four species of organisms,
including Leptocheirus plumulosus, Ampelisca abdita, Palaemonetes pugio, and
Cyprinodon variegates, were used for the tests of the impacts of PAC and clay
treatments on their survival, growth, and reproduction. When there were no toxic
G. breve cells in the treatments and controls, the primary results indicated
that these four species were not significantly impacted by the addition of PAC
(up to 70 ppm), clay alone (0.25 g/L), and a mixture of PAC with clay. However,
the results for the fish and Leptocheirus showed that the unlysed G. breve cells
which were settled with clay/PAC were toxic, and the lysed G. breve cells
settled with clay/PAC were also toxic, but to a lesser extent. Further
experiments are currently being conducted to expand upon these results.
Overall, significant progress has been made on this project and results continue to be encouraging. We are grateful for the continued support of the EPA grant and look forward to reporting continued progress.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 34 publications | 14 publications in selected types | All 14 journal articles |
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Type | Citation | ||
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Li A, Sengco MR, Anderson DM. Controlling harmful algal blooms through clay flocculation. JOURNAL OF EUKARYOTIC MICROBIOLOGY 2004;51(2):169-72 |
R827090 (1999) R827090 (2000) |
Exit |
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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 |
Supplemental Keywords:
ecological effects, cellular, population, biology, modeling, Florida, New York, FL, NY., RFA, Scientific Discipline, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, Ecosystem/Assessment/Indicators, Ecosystem Protection, State, Environmental Microbiology, Ecological Effects - Environmental Exposure & Risk, algal blooms, Biochemistry, Ecology and Ecosystems, Ecological Risk Assessment, Environmental Engineering, marine ecosystem, ecological exposure, ecological effects, bloom dynamics, dinoflagellates, fish kills, sustainable fisheries, brevetoxins, harmful algal blooms, nutrient kinetics, phytoplankton, control of algal blooms, biotoxin risk, ECOHAB, water quality, Florida, benthic algae, FLA, New York (NY), clay, G. breve red tidesProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.