Abstract
Across the European Atlantic Arc (Scotland, Ireland, England, France, Spain, and Portugal) the shellfish aquaculture industry is dominated by the production of mussels, followed by oysters and clams. A range of spatially and temporally variable harmful algal bloom species (HABs) impact the industry through their production of biotoxins that accumulate and concentrate in shellfish flesh, which negatively impact the health of consumers through consumption. Regulatory monitoring of harmful cells in the water column and toxin concentrations within shellfish flesh are currently the main means of warning of elevated toxin events in bivalves, with harvesting being suspended when toxicity is elevated above EU regulatory limits. However, while such an approach is generally successful in safeguarding human health, it does not provide the early warning that is needed to support business planning and harvesting by the aquaculture industry. To address this issue, a proliferation of web portals have been developed to make monitoring data widely accessible. These systems are now transitioning from “nowcasts” to operational Early Warning Systems (EWS) to better mitigate against HAB-generated harmful effects. To achieve this, EWS are incorporating a range of environmental data parameters and developing varied forecasting approaches. For example, EWS are increasingly utilizing satellite data and the results of oceanographic modeling to identify and predict the behavior of HABs. Modeling demonstrates that some HABs can be advected significant distances before impacting aquaculture sites. Traffic light indices are being developed to provide users with an easily interpreted assessment of HAB and biotoxin risk, and expert interpretation of these multiple data streams is being used to assess risk into the future. Proof-of-concept EWS are being developed to combine model information with in situ data, in some cases using machine learning-based approaches. This article: (1) reviews HAB and biotoxin issues relevant to shellfish aquaculture in the European Atlantic Arc (Scotland, Ireland, England, France, Spain, and Portugal; (2) evaluates the current status of HAB events and EWS in the region; and (3) evaluates the potential of further improving these EWS though multi-disciplinary approaches combining heterogeneous sources of information.
Highlights
Phytoplankton provide key ecosystem services to humans by providing food for marine life, oxygen and sequestering CO2 (Billett et al, 1983; Smetacek, 1999; Irigoien et al, 2004)
We describe typical patterns of HAB shellfish closures using as examples a northern (Ireland) and southern region (Portugal) since other countries around them follow similar patterns: In Ireland, it is not unusual to have site closures due to toxins above regulatory levels from all four main toxin groups Amnesic Shellfish Toxins (ASTs), AZAs, Diarrhetic Shellfish Toxins (DSTs) and Paralytic Shellfish Toxins (PSTs) (Table 2)
This study describes the range of toxin-producing phytoplankton, their associated toxins, the impact they can have on shellfish aquaculture in the Atlantic arc countries and the various Early Warning Systems (EWS) that are being developed to safeguard the industry and human health
Summary
Phytoplankton provide key ecosystem services to humans by providing food for marine life, oxygen and sequestering CO2 (Billett et al, 1983; Smetacek, 1999; Irigoien et al, 2004). Some naturally occurring phytoplankton species can produce a range of marine biotoxins that accumulate in shellfish tissues through filter feeding (Vale et al, 2008; Wang, 2008) Blooms of these harmful algal species (HABs) can negatively impact fisheries and aquaculture (Smayda, 1990; Berdalet et al, 2016; Sanseverino et al, 2016; FAO, 2018). The risk of intoxication causes significant economic losses for the aquaculture industry due to the temporary suspension of harvesting when toxin concentrations exceed the permissible regulatory limits as laid down in regulation EU853/2004 (Rodríguez-Rodríguez et al, 2011; Mardones et al, 2020; Martino et al, 2020) These temporary suspensions in harvesting cannot be prevented, but Early Warning Systems (EWS), such as bulletins issued to local harvesters to warn them of upcoming HAB events, aim to forecast their occurrence and reduce their socio-economic impact. According to Regulation (EC) No 854/2004 (Annex II, Chapter II, B, 7) and Articles 59 and 61 in EC 627/2019, plankton samples for regulatory monitoring purposes are to be TABLE 1 | Summary of toxins typically analyzed in Europe with the analytical methods and the regulatory limits (maximum quantities allowed in bivalve molluscs placed on the market)
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