A preliminary study on mercury levels in the soft tissues of the Guiana dolphin (Sotalia guianensis) and edible fish from southern Lake Maracaibo, Venezuela

Abstract

Coastal ecosystems around the world are facing increasing mercury pollution from various anthropogenic activities, which are affecting many aquatic mammals such as dolphins. Lake Maracaibo receives discharges of industrial water, wastewater, pesticides and herbicides from runoff, and constant oil spills; these discharges include several contaminants. In this paper, we highlight the extent of mercury accumulation in the soft tissues of Guiana dolphins and some fish species from southern Lake Maracaibo. A total of 17 fish species were analyzed. All but one of the species had traces of mercury, but only the mercury level in Gobioides broussonnetii (mean ± standard deviation = 0.9209 ± 0.0134 mg kg-1 wet weight (ww)) exceeded the limit established as safe for human consumption. In Guiana dolphins, mercury levels in four of six individuals exceeded the maximum limit considered safe for human consumption (0.5 mg kg-1 ww), with the highest level of 2.9611 ± 0.1637 mg kg-1 ww in the liver of one individual, suggesting biomagnification through diet and possible adverse effects in this species. It is important to note that the dolphins from which samples were collected were juveniles. There is evidence of a correlation between mercury accumulation and the size and age of dolphins, emphasising the ecological risks posed by anthropogenic pollutants. The wider ecological impacts, including threats to endangered fish species and public health risks associated with mercury-contaminated marine resources are also discussed. This study emphasises the urgent need for comprehensive management strategies to reduce mercury pollution and to protect coastal ecosystems and public health.