Predicting the Effects of Climate Change on the Occurrence of the Toxic Dinoflagellate Alexandrium catenella Along Canada’s East Coast

Abstract

Alexandrium catenella produces paralytic shellfish toxins that affect marine fisheries and aquaculture as well as ecosystem and human health worldwide. This harmful algal species is extremely sensitive to environmental conditions and potentially to future climate change. Using a generalized additive mixed model (GAMM) we studied the potential effects of changing salinity and temperatures on A. catenella bloom (≥1000 cells L–1) occurrence along Canada’s East Coast throughout the 21st century. Our GAMM was applied to two high greenhouse gas emissions scenarios (RCP 8.5) and one mitigation scenario (RCP 4.5). Under present-day conditions, our model successfully predicted A. catenella’s spatio-temporal distribution in Eastern Canada. Under future conditions, all scenarios predict increases in bloom frequency and spatial extent as well as changes in bloom seasonality. Under one RCP 8.5 scenario, A. catenella bloom occurrences increased at up to 3.5 days per decade throughout the 21st century, with amplified year-to-year variability. Blooms expanded into the Gulf of St. Lawrence and onto the Scotian Shelf. These conditions could trigger unprecedented bloom events in the future throughout our study region. In all climate scenarios, the bloom season intensified earlier (May–June) and ended later (October). In some areas of the Gulf of St. Lawrence, the thermal habitat of A. catenella was exceeded, thereby locally reducing bloom risk during the summer months. We conclude that an increase in A. catenella’s environmental bloom window could further threaten marine fauna including endangered species as well as fisheries and aquaculture industries on Canada’s East Coast. Similar impacts could be felt in other coastal regions of the globe where warming and freshening of waters are intensifying.

Variability patterns and phenology of harmful phytoplankton blooms off southern Portugal: Looking for region-specific environmental drivers and predictors

“…GAMs are empirical-statistical models, that establish relationships between a dependent response variable and multiple predictors (independent variables; Wood, 2017). Since GAMs do not assume a particular type of response function, allowing both non-linear and linear relationships, they are considered a flexible, computing cost-effective modeling approach for assessing the responses of plankton communities (e.g., Irwin and Finkel, 2008;Llope et al, 2009;Otto et al, 2014), specifically HABs (e.g., Matus-Hernández et al, 2019;Ajani et al, 2020;Boivin-Rioux et al, 2021, to environmental factors. The basic GAM model structure can be defined as follows (Eq.…”

Changes in Canada's Phosphorus Cycle 1961–2018: Surpluses and Deficits

“…Since only about 4% of its land is arable, Canada relies heavily on agrochemicals, including P fertilizers, to maintain its elevated level of food production (Malaj et al., 2020). Yet the excess P discharged into the environment has caused serious eutrophication in Canada's rivers and lakes (Boivin‐Rioux et al., 2021; Bunting et al., 2016; Seewer, 2015). Environment Canada (2011) indicated that from 2005 to 2007, 32% of surface water quality monitoring sites in Canada exceeded P guidelines more than half the time.…”

Use of valvometry as an alert tool to signal the presence of toxic algae Alexandrium catenella by Mytilus edulis

“…Indeed, both temperature (Clements et al, 2018;Clements et al, 2021) and salinity are reported to affect valve gaping behaviour in bivalves but with more of closures contrary to our results who shown less of closure. However, A. catenella development in the Lower St. Lawrence Estuary is also associated with these physico-chemical parameters, in particular salinity and water temperature (Fauchot et al, 2005;Navarro et al, 2006;Aguilera-Belmonte et al, 2013;Starr et al, 2017;Boivin-Rioux et al, 2021). The optimal temperature for the development of this algae is ≈14°C (Boivin-Rioux et al, 2021), a temperature only present during summer in the St. Lawrence Estuary.…”

“…The experiment was conducted over three days at 18°C, an intermediate temperature between the optima for mussels (20°C; Almada-Villela et al, 1982) and 14°C for A. catenella (Boivin-Rioux et al, 2021). Following the 30-day acclimatation period (as described above), 24 mussels were connected to valvometry monitoring systems described in Nagai et al (2006) and Comeau (2014) (see Section 2.5 below for details).…”

“…In addition to the controlled laboratory experiment, a 90-day in situ experiment was conducted with unfiltered natural seawater at the Maurice-Lamontagne Institute (DFO, Mont-Joli, Quebec, Canada) from June to September 2019a period in which A. catenella blooms are known to occur in the St. Lawrence Estuary (Parkhill and Cembella, 1999;Boivin-Rioux et al, 2021). The natural seawater experiment was performed with M. edulis collected in a mussel lease in St Peter's Bay, Prince Edward Island in 2019.…”