Research Document - 2016/024
Use of hydrated lime to control Styela clava in the PEI mussel farming industry: industry practises and potential effects on non-target invertebrates
By L.E Burridge and L.A. Comeau
Abstract
Mussel culture in Prince Edward Island must contend with infestations of tunicates particularly the clubbed tunicate, Styela clava. Periodically, aquaculture leases are treated with hydrated lime (Ca(OH)2) in order to control these infestations and ensure minimal loss of the mussel crop. Treatment may take several forms but all involve dipping or spraying mussels sleeves with a 4% suspension of hydrated lime. Excess lime from these treatments may be released directly into the surrounding aquatic environment raising questions about the potential biological effects on non-target indigenous species. We herein review the current state of knowledge regarding treatment, chemistry and biological effects of hydrated lime and its post-treatment by-products. Treatment with hydrated lime results in a significant, yet short-lived, increase in pH and the conversion of Ca(OH)2 to carbonate which may precipitate into the environment. Lab-based studies have characterised the hazard associated with elevated pH and the presence of particulate carbonate. Field studies have shown that exposure to hazardous pH or particulate carbonate is unlikely to last more than several minutes and elevated pH is only observed for distances of several metres from the treatment operation. These data lead us to conclude that under current operating conditions lethal effects on non-target organisms resulting from use of hydrated lime are unlikely to occur.
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