Hydrocarbon contamination from the Deepwater Horizon oil spill affects long- and short-term oyster recruitment and succession

We studied how the 2010 Deepwater Horizon oil spill affected oysters (Crassostrea virginica) in Barataria Bay, Louisiana. Four study sites within the bay were selected: two control and two oiled, with a low- and high-salinity... [ view full abstract ]

We studied how the 2010 Deepwater Horizon oil spill affected oysters (Crassostrea virginica) in Barataria Bay, Louisiana. Four study sites within the bay were selected: two control and two oiled, with a low- and high-salinity location. Three approaches were used to determine long- and short-term effects of the oil spill. First, cement substrates were placed at each site in 2012, and retrieved after 6, 12, and 18 months to measure oyster reef succession. Oysters were smaller at oiled sites, and mussels (Ischadium recurvum), which only recruited to the low salinity sites, occurred at higher densities at the control site. Cement board tiles were placed at each site in 2012 and 2013 and oyster recruitment quantified monthly. In 2012, recruitment varied more with salinity than oil contamination, but in 2013 early summer salinity was lower, and recruitment only occurred at the control sites. Finally, tiles exposed to light crude oil were used to study the short-term effects of oil on oyster and barnacle recruitment in 2013. Recruitment was lower on oiled tiles but there was no difference in oyster size between treatments; there was a slight tendency for oil to increase barnacle (Balanus eburneus) recruitment. In general, our results suggest oil contamination may affect the density or size distribution of estuarine bivalves, and interact with other stressors like low salinity to lower oyster recruitment over the long-term. Thus, cleanup efforts immediately following an oil spill, and continuous monitoring efforts are necessary to maintain healthy oyster populations.