GEORGES BANK STUDIES 



Two stations on the bank, close to exploratory drilling rigs, were 

 sampled quarterly for 3 years, with 29 stations in a ring pattern around one 

 rig, and 3 stations near a second rig. The sites were both on the south flank 

 of the bank, one in 80-m water depth, the other at 140 m. Chemical analyses 

 by Bothner showed five- to seven-fold increases in barium concentrations in 

 the bulk sediment, much higher in the fine fraction, and some drill cuttings. 

 There was a tendency for the barium to migrate as a result of reworking and 

 resuspension of sediments. There was little or no evidence of hydrocarbon 

 accumulation. 



Biological effects were examined down current from the rigs. At the 

 shallower station, a strong seasonal signal was found in both diversity and 

 abundance, but no real biological impacts were attributable to the discharges. 

 At the deeper site, there was a smaller seasonal signal, but no other 

 discernible change occurred except a gradual increase over time in both 

 diversity and species abundance. The increase was attributed to an accident 

 of timing, as it was also seen at the control sites. Two species of amphipods 

 virtually disappeared when drilling began, but that was attributed to a severe 

 winter storm. In short, if there were any effects at all, they were small and 

 transitory. 



DISCUSSION 



Several questions concerned the laboratory experiments. Vild asked about 

 signs of stress in lobsters; there was slight elevation in mortality and 

 slight decreases in growth. Ray asked for barium concentrations in the 

 aquaria sediments; they were field muds from Gulf of Mexico rigs, and barium 

 concentrations were increased above background by 5,000 to 10,000 ppm. Cooper 

 noted that lobsters are very vulnerable to zinc and copper; Neff responded 

 that those metals are in forms that are not bioavailable. 



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