Abstract
In British Columbia (BC), harmful algal blooms (HABs) regularly cause severe economic losses through finfish mortalities and shellfish harvest closures due to toxin accumulation, gill damage, or hypoxia. As there is no routine governmental monitoring of HAB phenomena in BC, HAB variability, and its potential links to environmental drivers are not well understood. Here we present results from a well-managed citizen science program which collected an unprecedented 4 year, high-resolution (∼bi-monthly, ∼80 stations) dataset of harmful algae (HA) concentrations and corresponding physical and chemical properties of seawater throughout the Strait of Georgia (SoG), BC. Analysis of this dataset revealed statistically significant interannual and seasonal relationships between environmental drivers and the most common HA taxa: Rhizosolenia setigera, Dictyocha spp., Alexandrium spp., Heterosigma akashiwo, Chaetoceros convolutus, and C. concavicornis. HABs exhibited significant interannual variations; specifically, no HABs were found during the summer of 2015, blooms of Dictyocha occurred in 2016 and 2017, and dense blooms of Heterosigma and Noctiluca occurred in 2018. In addition, HA prevalence corresponded with negative effects observed in local aquaculture facilities where higher toxins concentrations (causing Paralytic and Diarrhetic Shellfish Poisonings) in shellfish flesh were detected during years with greater abundance of Alexandrium and Dinophysis. Furthermore, salmon mass mortality at fish farms corresponded to years with high concentrations of Heterosigma and Dictyocha. As such, these results highlight the need for long-term data to evaluate the potential role of HA as a stressor on the SoG ecosystem.
Highlights
The public health and economic impacts of harmful algal blooms (HABs) in the coastal ocean have increased in frequency, intensity, and distribution in recent years (Hallegraeff, 2004; Heisler et al, 2008), and it is accepted that “global expansion” of HAB phenomena is real (e.g., Smayda, 1990; Anderson et al, 2012)
This study aims to analyze this dataset to advance our limited understanding of HAB ecology and provide insights useful to fisheries management in the entire Strait of Georgia
Seasonal variations in surface salinities were similar across years, with the lowest salinities usually observed in June (∼23.3 g/kg) and the highest in October (∼27.4 g/kg); surface salinities in late spring and summer of 2016–2018 were noticeably lower compared to that of 2015 (∼27.6 g/kg) (Figure 2B)
Summary
The public health and economic impacts of harmful algal blooms (HABs) in the coastal ocean have increased in frequency, intensity, and distribution in recent years (Hallegraeff, 2004; Heisler et al, 2008), and it is accepted that “global expansion” of HAB phenomena is real (e.g., Smayda, 1990; Anderson et al, 2012). Harmful Algae and Oceanographic Conditions losses through finfish/shellfish mortalities and shellfish harvest closures due to toxin accumulation, gill damage, or hypoxia (Horner et al, 1997; Whyte et al, 1997; Taylor and Harrison, 2002; Rensel and Whyte, 2004; Haigh and Esenkulova, 2011, 2014; Bates et al, 2020). Chaetoceros convolutus and C. concavicornis are known to kill fish as a result of gill damage (Albright et al, 1993; Taylor and Harrison, 2002; Hallegraeff et al, 2004) and have caused fish losses in coastal BC (Albright et al, 1993; Haigh and Esenkulova, 2014). Other species known to cause HABs in BC coastal waters include Chrysochromulina spp., Margalefidinium fulvescens, Noctiluca scintillans, Prymnesium spp., Pseudochattonella verruculosa, Pseudo-nitzschia spp. (Whyte et al, 1997, 2001; Haigh and Esenkulova, 2011; Haigh et al, 2014)
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