Effects of the Iron Barren oil spill - impact and recovery of sub tidal reefs

Abstract

The impact of the Iron Baron oil spill on subtidal reef communities in Bass Strait was assessed by quantitatively censusing plant and animal populations after the spill and comparing these data with information obtained using similar techniques prior to the spill. Natural changes at control sites were of a similar magnitude to changes in reef assemblages following the spill at sites with moderate and heavy oil contamination on nearby shores. Any effects of the oil spill on subtidal reef assemblages were therefore considered to be minor. By contrast, the grounding of the hull at Hebe Reef caused complete destruction of plant and animal life within a localised zone extending for z 170 m by 20 m. The fish population within this disturbed zone largely recovered to predisturbance levels within three months of the impact whereas very little recovery of invertebrate and virtually no recovery of macroalgal populations occurred during this time period. Given the lack of significant impact of the oil spill on coastal reefs, further monitoring of reef communities is not considered necessary. Limited monitoring of the impact zone and two nearby control sites on Hebe Reef is recommended in order to identify the timescale required for assemblages in this region to recover.