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. 2023 Jun 13;15(6):395.
doi: 10.3390/toxins15060395.

Dissolved Algal Toxins along the Southern Coast of British Columbia Canada

Ryan B Shartau  1   2 , Lenora D M Turcotte  2 , Julia C Bradshaw  2 , Andrew R S Ross  3 , Blair D Surridge  4 , Nina Nemcek  3 , Stewart C Johnson  2
Affiliations

Dissolved Algal Toxins along the Southern Coast of British Columbia Canada

Ryan B Shartau et al. Toxins (Basel). .

Abstract

Harmful algal blooms (HABs) in coastal British Columbia (BC), Canada, negatively impact the salmon aquaculture industry. One disease of interest to salmon aquaculture is Net Pen Liver Disease (NPLD), which induces severe liver damage and is believed to be caused by the exposure to microcystins (MCs). To address the lack of information about algal toxins in BC marine environments and the risk they pose, this study investigated the presence of MCs and other toxins at aquaculture sites. Sampling was carried out using discrete water samples and Solid Phase Adsorption Toxin Tracking (SPATT) samplers from 2017-2019. All 283 SPATT samples and all 81 water samples tested positive for MCs. Testing for okadaic acid (OA) and domoic acid (DA) occurred in 66 and 43 samples, respectively, and all samples were positive for the toxin tested. Testing for dinophysistoxin-1 (DTX-1) (20 samples), pectenotoxin-2 (PTX-2) (20 samples), and yessotoxin (YTX) (17 samples) revealed that all samples were positive for the tested toxins. This study revealed the presence of multiple co-occurring toxins in BC's coastal waters and the levels detected in this study were below the regulatory limits for health and recreational use. This study expands our limited knowledge of algal toxins in coastal BC and shows that further studies are needed to understand the risks they pose to marine fisheries and ecosystems.

Keywords: SPATT; aquaculture; domoic acid; harmful algae; marine phycotoxins; microcystin; okadaic acid.

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Conflict of interest statement

The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Location of sampling sites in British Columbia, Canada. Outlined labels indicate farm sites: Concepcion (Concep.), Saranac Island (Saranac), Millar Island (Millar), Raza Island (Raza), Ahlstrom (Ahls), Dixon Bay (Dixon), and Brennan Island (Brennan). SOG—Strait of Georgia, WCVI—west coast Vancouver Island.
Figure 2
Figure 2
Toxin concentrations for each site over the time period collected for SPATT (A) and discrete water samples (B). SPATT (A): microcystin (MC; ng MC/g resin (dry weight)/day) (i); domoic acid (DA; pg DA/g resin dry weight/day) (ii); dinophysistoxin-1 (DTX-1; ng DTX-1/g resin dry weight/day) (iii); okadaic acid (OA; ng OA/g resin dry weight/day) (iv); pectenotoxin-2 (PTX-2; ng PTX-2/g resin dry weight/day) (v); yessotoxin (YTX; ng YTX/g resin dry weight/day) (vi). Discrete water: MC (ng MC/L) (i); OA (ng OA/L) (ii). Data are mean ± SEM; different letters indicate significant differences (p < 0.05) in toxin concentration between sites; see text for details.
Figure 3
Figure 3
Microcystin (MC) concentration in SPATT (ng MC/g resin dry weight/day) (A) and water samples (ng MC/L) (B) from June 2017–September 2019 at sites along the west coast of Vancouver Island and the Strait of Georgia in British Columbia.
Figure 4
Figure 4
Okadaic acid (OA) concentration in SPATT (ng OA/g resin dry weight/day) from June 2017–April 2019 (A) and water samples (ng OA/L) from June 2017–September 2018 (B) at sites along the west coast of Vancouver Island and the Strait of Georgia in British Columbia.
Figure 4
Figure 4
Okadaic acid (OA) concentration in SPATT (ng OA/g resin dry weight/day) from June 2017–April 2019 (A) and water samples (ng OA/L) from June 2017–September 2018 (B) at sites along the west coast of Vancouver Island and the Strait of Georgia in British Columbia.
Figure 5
Figure 5
Domoic acid (DA) concentration in SPATT (pg DA/g resin dry weight/day) from June 2017–August 2018 at sites along the west coast of Vancouver Island and the Strait of Georgia in British Columbia.
Figure 6
Figure 6
Concentrations of co-occurring toxins found in SPATT at Miller (A), Saranac (B), Raza (C), and Ahlstrom (D) at selected dates during 2017 and 2018 (Day Month Year). Dinophysistoxin-1 (DTX-1; ng DTX-1/g resin dry weight/day), pectenotoxin-2 (PTX-2; ng PTX-2/g resin dry weight/day), and yessotoxin (YTX; ng YTX/g resin dry weight/day) were measured using LC-MS/MS. Reproducibility was evaluated for LC-MS/MS by running a test sample 7 times, which yielded relative standard deviation (RSD) values of 14.2, 13.1 and 19.0%, respectively, for DTX1, PTX2, and YTX; standard deviation for each sample was calculated using RSD to produce error bars for these toxins. Okadaic acid (OA; ng OA/g resin dry weight/day), microcystin (MC; ng MC/g resin dry weight/day), and domoic acid (DA; ng DA/g resin dry weight/day) were measured using ELISA; error bars could not be calculated for individual samples measured using ELISA.
Figure 7
Figure 7
Correlation of microcystin (A) and okadaic acid (B) in SPATT and water samples. SPATT values were ng toxin/g of dry weight of SPATT resin/ day of deployment time; these were compared to toxin concentration in water (ng toxin/L) collected at the same time SPATT bags were collected.
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