INVESTIGATING THE TOXIC AND ACIDIFYING EFFECT OF SCRUBBER EFFLUENT ON STRONGYLOCENTROTUS DROEBACHIENSIS LARVAE

Abstract

To meet the new environmental requirements of reduced sulfur emissions from ships, many shipowners have installed an open-loop scrubber to clean the exhaust. In this scrubbing process, seawater is pumped from the ocean and combined with the emission gas, creating an acidic and toxic effluent that is directly discharged into the ocean, potentially damaging the marine environment. This study aims to understand the effects of different concentrations of scrubber effluent (toxicant mixtures, pH and alkalinity decrease) on green sea urchin larvae (Strongylocentrotus droebachiensis). The central hypothesis was that the combination of toxins and low pH/alkalinity in scrubber effluent would negatively impact survival, growth, and morphology of sea urchin larvae. Moreover, it was hypothesized that part of the negative effect driven by low pH and low alkalinity could be minimized by correcting these parameters using a strong base. However, some negative effects would still be observed due to the toxins present in the scrubber effluent. The experiment was conducted at the Kristineberg Marine Research Station. Larvae were cultured for 14 days in different concentrations of scrubber effluent in filtered seawater. In the treatments with highest concentrations, pH and alkalinity were corrected to a similar level as filtered seawater to only evaluate the effect of the mixture of toxicants. We found severe effects on body length growth rate and development caused by the scrubber effluent in the treatment with the highest concentration (10% ~ pH 7.3). When corrected for pH and alkalinity (10%AT ~ pH 7.9), we observed a decrease of the harmful effects enabling the larvae to develop and grow. However, toxins hindered the larvae from reaching the same growth rate as the larvae in the water without scrubber effluent. In conclusion, the scrubber effluent harms the green sea urchin larvae development and growth. While this effect can be reduced by treating the effluent for its increased acidity, sea urchin larvae still suffer from toxicity of the chemical cocktail.