Abstract
Abstract ShellBond is a patented material derived from high temperature treatment of calcareous materials, including oyster shells, yielding a unique form of calcium hydroxide, Ca(OH)2. Previous work with ShellBond showed effects on ammonium and phosphate concentrations in natural waters as well as significant effects on phytoplankton biomass measured as chlorophyll a. The ability of oyster ShellBond to regulate phytoplankton growth in natural waters was investigated in laboratory experiments in order to determine the likely mechanism of action. Experimental investigation of indirect ShellBond effects on phytoplankton growth mediated by effects on nutrient availability (as ammonium and phosphate) revealed no evidence for a plausible mechanism. The direct effect of ShellBond on the pH of the medium was sufficient, however, to suggest that ShellBond acted to limit availability of dissolved CO2 to primary producers; ShellBond amendments at 200 mg L−1 were sufficient to raise pH to >10.5. Dose-response experiments demonstrated an effect of ShellBond concentration on pH and phytoplankton growth, but without complete mortality. These results suggest that ShellBond dosing may have promise for algal bloom remediation, justifying field scale investigations.
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