Population dynamics and toxicity of harmful microalgae in Ship Harbour, Nova Scotia

Prediction of toxic algal blooms has become increasingly important on a global scale, largely driven by concern for their effects on public health as well as their potentially detrimental impact on the aquaculture industry. Phytoplankton enumeration and identification in conjunction with phycotoxin monitoring is an efficient strategy for identifying known toxic events and predicting new ones. In order to investigate methods for the early detection of toxic algal blooms, a threeyear project was implemented in Ship Harbour, Nova Scotia, which is an important site for mussel aquaculture. The water column was routinely monitored in situ from spring to fall, (2004-2006) for phycotoxins using solid phase adsorption toxin tracking (SPATT) bags and for phytoplankton composition. Over the three-year period, annual patterns in species succession were observed. Several potentially toxic species were found to occur including Alexandrium tamarense and Alexandrium ostenfeldii. These species were most abundant from late May-July. Gonyaulax spinifera (prox) was observed in early fall (Sept-Oct) for the past two years. Pseudonitzchia seriata peaked in July each year. Several species of Dinophysis were most abundant in June and August but occurred in lower numbers throughout the entire season. Phycotoxins can accumulate in shellfish tissue and cause toxic incidents if not detected prior to shellfish harvesting. Toxins were quantified and correlated with cell concentrations of toxin-producing species. Temporal observations of species succession and population structure displayed reoccurring patterns throughout the three-year project. Concurrent measurements of toxin concentration and population dynamics provide an accurate assessment of toxic algal events. This study demonstrates the effective use of this type of monitoring program in the prediction of toxic algal blooms.NRC publication: Ye