Lipophilic marine toxins in sediments from Arra<acute accent>bida marine protected area, Portugal (NE Atlantic)

During the development and senescence of harmful algal blooms (HAB), most of the algae cells not ingested by grazers or filter-feeding organisms sink to the bottom, making sediments important reservoirs of algae toxins. In this study, lipophilic marine toxins were determined in the sediments collected from depths ranging from 5 to 145 m depth in the marine protected area of Arra<acute accent>bida (southwest Portuguese coast). Sediments were characterized in terms of granulometry, water and organic matter content. The toxins were determined by liquid chromatography with tandem mass spectrometry. Okadaic acid (OA), dinophysistoxin-2 (DTX2), and azaspiracid-2 (AZA2), reaching concentrations up to 3.4, 1.3, and 0.13 ng/g, respectively, were found. A trend in the occurrence of DTX2 and AZA2 with sediment water and organic matter content was observed, as well as with AZA2 and depth. This study highlights the need to further investigate sediment deposition of toxins and their availability for bottom-dwelling organisms and its contamination.