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

Aude Boivin-Rioux,Joël Chassé,Michael Scarratt,William Perrie,Michel Starr,Zhenxia Long

doi:10.3389/fmars.2020.608021

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.

Highlights

Harmful algal blooms (HABs), as defined by the UNESCO, designate proliferations of microalgae that are detrimental to public health, local marine fauna, fisheries and the aquaculture industry
Data of A. catenella abundances for biological model fitting were obtained from the DFO/IML harmful algae monitoring program (DFO-HAB) spanning the period, 1994–2017, at 12 recurrent coastal monitoring stations located across the EGSL on the Canadian East Coast (Figure 1)
We used combinations of remaining variables to fit an ensemble of generalized additive mixed model (GAMM) that we evaluated through cross-validation as described in Albouy-Boyer et al (2016)

Summary

Introduction

Harmful algal blooms (HABs), as defined by the UNESCO, designate proliferations of microalgae that are detrimental to public health, local marine fauna, fisheries and the aquaculture industry. The worldwide socio-economic threat posed by HABs is often linked to marine dinoflagellates, such as Alexandrium spp. PSTs bioaccumulate in tissues of shellfish and zooplankton, making filter-feeding invertebrates highly neurotoxic to marine fish, mammals and birds when ingested (Shumway, 1990; Bricelj and Shumway, 1998; Cembella et al, 2002; Landsberg, 2009; Starr et al, 2017). Bioaccumulation of PSTs prevents human consumption of contaminated shellfish, such as the economically valuable blue mussel Mytilus edulis (Etheridge, 2010). Bloom events often lead to mussel farm and aquaculture closures in affected areas (Blasco et al, 2003; Díaz et al, 2019). Aquaculture sites along Canada’s East Coast are affected by A. catenella when favorable environmental conditions occur (Bates et al, 2020; McKenzie et al, 2020)

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Results

Discussion

Conclusion