The relationship between Pseudo-nitzschia (Peragallo) and domoic acid in Scottish shellfish

Area of Science:

• Marine Ecology
• Ecotoxicology
• Phycology

Background:

• The diatom Pseudo-nitzschia is a known producer of domoic acid (DA), a toxin causing amnesic shellfish poisoning.
• Pseudo-nitzschia blooms are prevalent in Scottish waters, posing a risk to marine ecosystems and human health.
• Understanding toxin dynamics in commercially important shellfish is crucial for food safety and environmental monitoring.

Purpose of the Study:

• To investigate the relationship between Pseudo-nitzschia cell densities and domoic acid (DA) concentrations in blue mussels (Mytilus edulis) and king scallops (Pecten maximus).
• To compare the rates of DA uptake and depuration in these two commercially important shellfish species.
• To assess the potential of M. edulis and P. maximus as bioindicators for DA contamination.

Main Methods:

• A two-year field study was conducted at two sites in Scotland.
• Monitoring of Pseudo-nitzschia cell densities in the water column.
• Quantification of DA concentrations in whole tissue and gonad tissue of M. edulis and P. maximus.

Main Results:

• M. edulis exhibited rapid DA uptake and depuration, clearing toxins weekly.
• P. maximus showed significantly slower DA depuration, with gonad tissue retaining toxins for up to 12 weeks.
• Correlations between Pseudo-nitzschia cell counts and DA levels were weak to moderate in mussels and weak in scallops.
• Higher DA toxicity was associated with summer/autumn blooms, particularly when Pseudo-nitzschia australis was present.

Conclusions:

• There are marked differences in DA accumulation and elimination kinetics between M. edulis and P. maximus.
• The rapid depuration in mussels suggests they may not be reliable long-term indicators of DA exposure.
• The slow depuration in scallops indicates potential for prolonged toxin accumulation, but their weak correlation with cell density requires further investigation for bioindicator use.