Standard and experimental drilling fluids’ effect on the response of the larvae of bivalve Hiatella sp.

Abstract

Behavior of the larvae of common genus of marine bivalve mollusk Hiatella sp. was tested at the presence of the standard drilling fluid and the water-based drilling fluid containing brown alga Saccharina latissima as biodegradable component. Standard drilling fluid (based on polyanionic cellulose and xanthan gum) is currently used at Prirazlomnaya offshore ice-resistant oil platform. A series of experiments have been performed with live larvae (young and elder stages, ~250 µm and ~350 µm, respectively) at 6.7 and 20 mL/L concentrations of the drilling fluids and in control. Larvae tended to spend more time with closed valves when exposed to standard drilling fluid. Larvae exposed to drilling fluid with Saccharina latissima extract were characterized by significantly higher activity comparing both to control group and to standard drilling fluid solution. Elder larvae were more sensitive to standard drilling fluid, being under stress from the very beginning of the experiment (3 hours of exposure) to the end (48 hours of exposure + 24 hours in native sea water). Young larvae tend to be more resistant both to standard drilling fluid and drilling fluid with Saccharina latissima extract; this may promote their better survival. Possible biological consequences of using natural and environmentally friendly extract of brown algae on pelagic larvae of benthic species is discussed.