Epsilon Archive for Student Projects

Abstract

With climate change-induced increases in water temperatures, cyanobacteria and their toxins are becoming increasingly prevalent in the Baltic Sea. Using mussels as a bioindicator, this thesis assesses the seasonality of cyanotoxin production and examines the accumulation of cyanotoxin in mussel tissue. Samples were collected from March to October bi-weekly and weekly, yielding a high temporal resolution from a submerged mussel farm close to Stockholm, at both 3 m and 10 m depth. Mussel tissue was analysed using both enzyme-linked immunosorbent assay (ELISA) analysis and liquid chromatography mass spectrometry (LC-MS) analysis for their microcystin and nodularin concentrations. The ELISA results were unusable due to interference either from the solvent or from dissolved mussel tissue. When analysing the extracted mussel tissue using LC-MS instead, microcystins were under the limit of detection. Nodularins had a base line concentration of around 4μg/kg of mussel tissue, with levels rising in initial tandem with rising levels of the cyanobacteria Nodularia spumigena. The toxin levels in mussels were however not linearly related to the N. spumigena population, but were affected by both accumulation and depuration. Even though Sweden does not have regulation on cyanobacterial toxins in mussels, we can look at those globally available. The mussels collected from the 3 m “surface depth” exceeded the Australian threshold value for safe consumption of 51μg/kg on two occasions during summer. The deep samples were always well below this safety limit. In conclusion, if mussels are harvested between October and May, they would be below the suggested limit for consumption with regards to microcystins and nodularins.