Abstract
Annual and interannual dynamics of shellfish toxins and associated harmful algal species (HAS) were analyzed from 2015 to 2020 in Tortolì Lagoon (Sardinia, west Mediterranean Sea). Analysis of seasonal occurrence of different harmful algae, such as Dinophysis spp., Prorocentrum spp., Pseudo-nitzschia spp. and Alexandrium minutum, was performed. The species Dinophysis acuminata and Dinophysis sacculus were responsible for the accumulation of lipophilic toxins belonging to the okadaic acid group (OAs) and pectenotoxins2 (PTX2) in bivalve mollusks. The highest HAS detection was recorded in the winter months; in particular, Dinophysis spp. was mostly present in January–February. Out of 1090 analyzed mollusk samples, 39 were non-compliant, exceeding the legal limits (160 μg OA eq/kg e.p.) reported in Regulation 853/2004 of the European Commission. A statistical analysis related to the presence of OA and PTX2 in mollusks with various environmental parameters (pH, water temperature, dissolved oxygen, algal density) was implemented, proving a clear winter seasonality. The present study highlights the necessity to better understand the different factors able to influence the production and accumulation of toxins in bivalve mollusks bred in an important Sardinian production area. The contribution of this research is important not only from an environmental and productive point of view but also from the view of implementing management in order to mitigate any harm to human health.
Highlights
Some exceptions were observed: in June 2016 (Figure 2b), there was the highest suite of different harmful algal species (HAS) (Pseudo-nitzschia spp., D. acuminata, D. caudata, D. sacculus, P. mexicanum, P. lima)
Temperature showed negative correlations with okadaic acid (OA) (−0.33), PTX2 (−0.09) and algal abundance (−0.14), suggesting that when the temperatures decrease, the amount of algae and toxins significantly increases (p < 0.001). This could be explained by the presence of HAS in farmed water, where they may determine the intake of OA by bivalve mollusks reared in that area
Our results show that species of the Dinophysis genus
Summary
About 300 harmful algal species (HAS) can generate negative events [1], 100 of which produce natural toxins that could be noxious to humans and animals [2]. The term “HAB” was initially coined to describe a toxic event able to impact humans but has recently evolved to include negative ecological impacts [3]. Sometimes, this event creates only an esthetic annoyance (e.g., discoloration of water or red tides by Dinoflagellates); in the worst cases, toxins eventually produced by HAS may be accumulated by filter-feeding organisms such as bivalve mollusks. Phenomena of human intoxication by aerosols such as those produced by Ostreopsis ovata have been reported [4]
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