Aquatic toxicity

Aquatic toxicity is the ability of a substance spilled into the water to cause damage to marine organisms. Chemicals carried by ships may be released and dissolve or disperse into the water, after which they present a hazard to marine organisms. The degree of solubility and turbulence in the water column determine whether significant levels of toxicity occur in the water phase. As such products dissolve, a plume will develop in the water phase, which will disperse under the action of turbulence. The prevailing current will transport plumes of this type. Compounds dissolved in aqueous solution mainly cause toxic effects of marine organisms. The effect of these compounds in the dispersed from is less significant.

The GESAMP hazard profile lists two types of aquatic toxicity: Acute Toxicity in category B1 and Chronic Toxicity in category B2.

An indicator for acute aquatic toxicity is the LC50 (or EC50 or IC50). The LC50 (Lethal Concentration) is the concentration that causes death in 50% of the test organisms during a certain exposure time. A low LC50 means a substance is extremely toxic as it is lethal in low concentrations.

Chronic toxicity is best indicated by the NOEC (No Observed Effect Concentration). The NOEC is the highest concentration tested which showed no negative effect on the test organisms over a longer period of time.