Toxic effects of drilling fluid on the embryos and prelarvae of Ruissian sturgeon Acipenser guelenstaedtii

Abstract

The active development of oil and gas production on the sea shelf negatively affects aquatic organisms, leading to deterioration of their existence and reduced viability. The early stages of development of marine organisms are particularly sensitive to pollutants, which disrupt their survival rate, growth, and development. The researchers studied the impact of a drilling fluid component (an aqueous solution of hemicellulase) at concentrations of 0.1, 0.5, 1, 5, and 10 mg/L on the survival of embryos and prelarvae of the Russian sturgeon, Acipenser gueldenstaedtii (Brandt & Ratzeberg, 1833), in a saline environment (salinity 5 ‰). No differences were observed in the survival of embryos in solutions containing a toxicant at a concentration of 0.1–1 mg/l. However, when the concentration increased to 5 mg/l and higher, there was a significant (p<0.01) decrease in survival rate and delayed hatching of prelarvae. An average correlation (r=0.53) between embryo survival and substance concentration was found. The hatching of larvae in the control groups was the highest and it did not differ significantly in fresh and salty water. A concentration of 1 mg/L of the substance had no effect on fish embryos survival. Various mechanisms of the negative impact of drilling fluid on developing fish embryos are considered, including habitat deterioration, sedimentation of solid particles on the surface of eggs leading to delayed hatching, and direct toxic effects caused by the presence of toxicants, especially heavy metals, in the composition of the drilling fluid. The potential use of fish eggs to assess the ecological status of coastal marine areas in the regions of intensive oil and gas production is discussed.