Macrobenthic community response to Hebei spirit oil-spill in the sandy beaches of Korea

Abstract

The M/T Hebei Spirit released an estimated 3.25 million gallons of crude oil on December 7, 2007. Over 100 miles of coastline were impacted, with the heaviest concentrations of oil in Taean County and points 30 miles to the north. Macrobenthos studies on sandy tidal flat were carried out from January 2008 to January 2010 to assess the impact of the spill on macrobenthic community. The studies were conducted seasonally at two of oil-impacted areas, Shinduri and Mallipo, and at two control areas, Yeonpo and Mongsanpo. A total of 244 macrobenthos appeared on a sandy intertidal area during the sampling periods, and the mean density was 1,129 ind./㎡. A year after the oil spill, the number of species, density and biomass of macrobenthos in the impacted area increased significantly, but diversity did not show a definite change. The number of species in the oil-impacted area was less by two folds than that in the unpolluted area. On the other hand, the density in the oil-impacted area increased more than in the unpolluted area by October, 2009. The most dominant species, Felaniella sowerbyi, did not appear in the unpolluted area, but only appeared in the affected area. Cluster analysis showed that the macrobenthic community in the oil-impacted area was similar to the community in the unpolluted area; however, after January 2009, the affected area was distinct from the unpolluted area. In addition, the communities in the oil-impacted area were further divided into two groups, namely, Shinduri and Mallipo, which showed variation in sediment grain size and total organic carbon. An increase in the number of opportunistic species was observed as well. We suggest that long term monitoring is needed to assess the recovery of the macrobenthic community in the impacted area.