An On-Farm Workflow for Predictive Management of Paralytic Shellfish Toxin-Producing Harmful Algal Blooms for the Aquaculture Industry.

Abstract

Paralytic shellfish toxins (PSTs) produced by marine dinoflagellates significantly impact shellfish industries worldwide. Early detection on-farm and with minimal training would allow additional time for management decisions to minimize economic losses. Here, we describe and test a standardized workflow based on the detection of <i>sxtA4</i>, an initial gene in the biosynthesis of PSTs. The workflow is simple and inexpensive and does not require a specialized laboratory. It consists of (1) water collection and filtration using a custom gravity sampler, (2) buffer selection for sample preservation and cell lysis for DNA, and (3) an assay based on a region of <i>sxtA</i>, DinoDtec lyophilized quantitative polymerase chain reaction (qPCR) assay. Water samples spiked with <i>Alexandrium catenella</i> showed a cell recovery of >90% when compared to light microscopy counts. The performance of the lysis method (90.3% efficient), Longmire's buffer, and the DinoDtec qPCR assay (tested across a range of <i>Alexandrium</i> species (90.7-106.9% efficiency; <i>r</i>² > 0.99)) was found to be specific, sensitive, and efficient. We tested the application of this workflow weekly from May 2016 to 30th October 2017 to compare the relationship between <i>sxtA4</i> copies L^-1 in seawater and PSTs in mussel tissue (<i>Mytilus galloprovincialis</i><i>)</i> on-farm and spatially (across multiple sites), effectively demonstrating an ∼2 week early warning of two <i>A. catenella</i> HABs (<i>r</i> = 0.95). Our tool provides an early, accurate, and efficient method for the identification of PST risk in shellfish aquaculture.