Study of Clay as a Control Technique for Karenia brevis: Water Chemistry Dynamics and Physiological Impacts on Benthic Invertebrates
Clay-based compounds are currently being investigated as a technique to manage harmful algal blooms of Karenia brevis in Florida. In a series of laboratory experiments, we tested cell and toxin removal efficiency of a PAC-modified kaolinite clay, evaluated water chemistry dynamics, and measured physiological responses in blue crab (Callinectes sapidus), sea urchin (Lytechinus variegatus), and hard clam (Mercenaria campechiensis).
In these experiments, clay treatment significantly reduced cell concentrations but did not reduce toxin concentrations in the water column. We found no notable impacts of clay treatment to mortality, reflexes, respiration rates, or internal toxin content for either of our three species. Among other chemical effects, we found clay significantly reduced dissolved phosphorus from the water column, indicating this treatment may provide an additional benefit of reducing nutrients that can contribute to algal growth.
Overall, this formulation of clay did not appear to induce any significant measured effects on our model species within the observed time frames of these experiments. We recommend that clay compounds be considered for additional laboratory and field tests, with the goal of obtaining further information on potential ecological impacts, so that managers and researchers can make informed decisions on the use of bloom control technologies in Florida waters.
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