Analysis Of Marine Biotoxins: Paralytic And Lipophilic Shellfish Toxins In Mussels (Mytilus Galloprovincialis) Along The Namibian Coastline

Abstract

The study was carried out along the Namibian coastline, this includes Henties Bay, Swakopmund, Bird Island, Walvis Bay and Lüderitz to assess presence of shellfish marine biotoxins in mussels, Mytilus galloprovincialis which are filter feeders and feed on some of the algal species that produces phycotoxins, that can negatively affect the mariculture industry and human health. Samples were analysed for Paralytic and lipophilic shellfish toxins; including environmental parameters and phytoplankton species composition. Samples were collected using randomized sampling techniques for the period of May 2012 to April 2013. Mussel toxin content was measured by liquid chromatography-mass spectrometry (LC-MS/MS) for lipophilic toxins and paralytic shellfish poisoning Mouse bioassay (PSP MBA). The diarrhetic shellfish poisoning (DSP) toxin profile was found to be primarily composed of Okadaic acid (OA) and dinophysistoxins-1 (DTX-1), with the highest concentration recorded at Walvis Bay area, each toxin accounted for at least 50% of the total toxin content, this is probably due to the Dinophysis species reported in this area during the sampling period. In addition, Yessotoxin (YTX) and its analogues 1a-Homoyessotoxin (homo-YTX) and 45- hydroxy-yessotoxin (45-OH-YTX) were all detected at concentrations below the regulatory limit of 1 mg YTX equivalents/kg with homo-YTX dominating at Swakopmund and Bird Island stations with the highest toxin content of 0.14 mg YTX equ./kg recorded at both stations. Furthermore, PSP toxin contents in mussels were only detected at Walvis Bay and Lüderitz, with highest toxin concentrations of 80 and 903 μg STX equivalents/100g respectively. This coincided with the time at which Alexandrium species cell concentration at Lüderitz were at maximum, and could be a source of the paralytic shellfish toxins (PST). Although the toxin content in mussels were generally low, it still highlights the

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importance of a continued monitoring of both shellfish toxicity and their causative phytoplankton species, in order to produce safe shellfish for both local and international consumers