TOXICITY DRIVERS IN CHEMICAL MIXTURES FROM THE SWEDISH WEST COAST – EFFECTS ON PELAGIC COMMUNITIES

Sammanfattning: Human society benefits from a range of ecosystem services provided by the oceans, such as oxygen production, carbon storage, and fishing. However, these services are relying on the ecosystem’s functional and structural integrity, which are correlated to its biodiversity. The increasing amount of chemicals that pollute the marine environment, particularly coastal areas, threaten to impact this integrity. A monitoring study conducted at the Swedish west coast showed high levels of chemical contamination at all sampled sites, but mixture toxicity prediction regarding copepods and actual chemical mixture testing on the copepod genus Pseudocalanus regarding the chemical mixtures produced contradicting results. The toxicity prediction resulted in an underestimation of the mixtures toxicity, raising the concern that the environmentally present concentration levels negatively impact the natural copepod communities. Therefore, I tried identifying toxicity drivers in the chemical mixtures present at the Swedish west coast by ranking the detected chemicals according to their contributory toxicity by using ecotoxicological data from US EPA for three different organism groups. The considered groups were mesozooplankton, microalgae, and bacteria, including cyanobacteria. The highest-ranking chemicals in toxicity for mesozooplankton and microalgae, formetanate hydrochloride and Spinosyn A, respectively, were selected for further ecotoxicological testing on natural copepod, algal and bacterial communities. The results of my study showed that neither Spinosyn A nor formetanate were the toxicity drivers in the mixtures as environmental concentrations caused no significant effects in all selected endpoints. Furthermore, the calculated contributory toxicity to the overall mixture toxicity seemed to be accurate regarding formetanate. However, the success of the toxicity driver identification was heavily impacted by the low amount of ecotoxicological data available, excluding the majority of detected chemicals. Therefore, this study further highlights the need for additional data collection when it comes to chemicals present in the environment, especially regarding marine organisms.