An assessment of drilling disturbance on Echinus acutus var. norvegicus based on in-situ observations and experiments using a remotely operated vehicle (ROV)

Abstract

An industrial work-class remotely operated vehicle (ROV) carried out a video survey of epibenthic megafauna before and after physical disturbance caused by the drilling of a hydrocarbon exploration well in the North Sea, off Norway at 114 m water depth. Megafaunal density, in general, had declined one month after the drilling event. There were particular declines in the density of the numerically dominant echinoid, Echinus acutus var. norvegicus, in a 50 m zone around the drill site. The ROV was also used to carry out in-situ experiments to assay the effects of drilling disturbance (via sediment burial) on E. acutus and, in addition, to determine any consequence upon E. acutus of retrieval to the surface (due to decompression and temperature change). Changes in the expression of an inducible stress-70 protein in echinoid Aristotle's lantern muscle and intestine were evaluated using quantitative real-time PCR. Sediment burial caused a significant increase in the expression of a stress-70 gene from the echinoids' Aristotle's lantern muscle tissue. Repeated echinoid retrieval to the sea surface did not result in any significant alteration of stress-70 gene expression. These experiments show the utility of ROVs in linking ecological observations with real-time in-situ experimental manipulations, and that investigative gene expression techniques can be incorporated in the subsequent analysis of retrieved specimens.