You are here:
MITIGATION OF HARMFUL ALGAL BLOOMS IN THE UNITED STATES USING CLAY: RESEARCH PROGRESS AND FUTURE PERSPECTIVES
Citation:
Anderson, D. M., M. R. Sengco, R. H. Pierce, M. S. Henry, V. M. Bricelj, M. Archambault, J. Grant, M A. Lewis, AND R M. Greene. MITIGATION OF HARMFUL ALGAL BLOOMS IN THE UNITED STATES USING CLAY: RESEARCH PROGRESS AND FUTURE PERSPECTIVES. Presented at HABTECH 2003 Workshop Conference, Nelson, NEW ZEALAND, November 26 - 30, 2003.
Impact/Purpose:
Workshop abstract
Description:
Throughout the United States, red tides and harmful algal blooms (HABs) pose a serious and recurrent threat to marine ecosystems, fisheries, human health, and coastal aesthetics. Here we report results from a research program investigating the use of clay dispersal for bloom control. This strategy is based on the interaction (e.g. aggregation) of clays and cells, leading to the formation of large, rapidly sinking particles (floc) that eventually settle to the ocean floor. The outcome is the physical removal of HAB species from the water column and the reduction of their deleterious impacts. The goal of the project was to evaluate clay dispersal as a control or mitigation strategy for several types of HABs, starting with laboratory cultures and moving to flume and mesocosm tests using model organisms or mixed natural communities to evaluate environmental effects. Experiments were conducted to assess impacts that might arise during treatment, such as those due to nutrients, trace metals or radioisotopes released from the clay, as well as the fate and impact of deposited and suspended clay and cells on benthic macrofauna. Other laboratory studies examined the uptake of dissolved toxin (brevetoxins produced by Karenia brevis) by clay. Flume studies were conducted to determine settling and resuspension characteristics of particulates, as well as their potential impacts on suspension feeding bivalves. Initial studies used a commercially important species, the hard clam, Mercenaria mercenaria, as a test organism. These and other experiments will be summarized. Overall, this investigation revealed the ability of several domestic clays to remove HAB cells from suspension, and highlighted the physicochemical and hydrodynamic conditions that can influence cell removal and sedimentation. Compared to other clay minerals, Florida phosphatic clays were among the most effective. There are concerns, however, regarding: 1) the release of inorganic phosphorus and certain trace metals into the marine environment with clay treatment; 2) changes in the sediment composition and oxygen demand from settled materials; 3) the impacts on suspension-feeding benthos in areas where prolonged, in situ suspension of clay might occur; 4) the reduced sedimentation of cells and clay in higher flow; and 5) the fate and trophic transfer of sedimented toxins. Results remain promising in many respects, but possible negative impacts merit further, careful investigation before a commitment to a large-scale field application is attempted.
Will be oral presentation.