Abstract
The NW coast of the Iberian Peninsula is dominated by extensive shellfish farming, which places this region as a world leader in mussel production. Harmful algal blooms in the area frequent lead to lengthy harvesting closures threatening food security. This study developed a framework for the detection of Pseudo-nitzschia blooms in the Galician rias from satellite data (MERIS full-resolution images) and identified key variables that affect their abundance and toxicity. Two events of toxin-containing Pseudo-nitzschia were detected (up to 2.5 μg L−1 pDA) in the area. This study suggests that even moderate densities of Pseudo-nitzschia in this area might indicate high toxin content. Empirical models for particulate domoic acid (pDA) were developed based on MERIS FR data. The resulting remote-sensing model, including MERIS bands centered around 510, 560, and 620 nm explain 73% of the pDA variance (R2 = 0.73, p < 0.001). The results show that higher salinity values and lower Si(OH)4/N ratios favour higher Pseudo-nitzschia spp. abundances. High pDA values seem to be associated with relatively high PO43, low NO3− concentrations, and low Si(OH)4/N. While MERIS FR data and regionally specific algorithms can be useful for detecting Pseudo-nitzschia blooms, nutrient relationships are crucial for predicting the toxicity of these blooms.
Highlights
Pseudo-nitzschia Peragallo is a chain-forming diatom genus that is widespread in all oceans of the world [1]
Analysed time series of Pseudo-nitzschia spp. abundance between 1999 and 2000 and concluded that Pseudo-nitzschia spp. blooms were mainly recorded in high salinity values (> 35)
The final generalised additive mixed models (GAMMs) fitted to the Pseudo-nitzschia spp. abundance includes linear relationship with chla. [8,36,37] pointed out that there is higher probability for Pseudo-nitzschia spp. blooms when chla concentration is high
Summary
Pseudo-nitzschia Peragallo is a chain-forming diatom genus that is widespread in all oceans of the world [1]. A number of these diatom species of this genus are known producers of a neurotoxic amino acid, domoic acid (DA), which when accumulated via trophic transfer in the food-web can have deleterious (amnesic shellfish poisoning, ASP) and even fatal effects to several marine organisms and less frequently to humans [2–4]. Pseudo-nitzschia is the only diatom genus among 27 dinoflagellates and 1 raphidophyte species that is listed as responsible for harmful algal events in upwelling regions [5]. Understanding the relationships between the abundance of these diatoms, DA, and the characteristics of the environment will provide valuable information on the variable(s) that might determine their growth, distribution, and DA production.
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