398 



study Description: 



Sediment samples for hydrocarbon analyses are collected 

 seasonally by removing the upper 1-2 cm of sediment from each 

 of three replicate 0.1 square meter grab samples collected at 

 M3 stations on or near Georges Bank. Epifauna samples for 

 hydrocarbon and trace metal tissue analyses are collected 

 by dredge and/or trawl at six stations: at the "mud patch," 

 the head of Lydonia Canyon, an upcurrent control station, and 

 at three sites near the exploratory operation. Special 

 consideration is given to commercially-important species 

 that are sufficiently abundant for analyses and, if possible, 

 to species representing different feeding mechanisms. 



The analyses of hydrocarbons in sediments are performed 



on each of three replicate grab samples from each of the four 



seasonal cruises at six of the 43 stations listed above. All 



other sediment samples are archived. Initial scanning for 



hydrocarbons is performed by ultraviolet fluorescence on 



the upper 1-2 cm of sediment. Samples with detectable unsaturated 



hydrocarbons are characterized for their origin (petrogenic 



or biogenic) by using glass-capillary gas chromatography on the 



aliphatic and aromatic fractions of the sample. Additional 



intensive analyses using gas chromatography/mass spectrometry 



are performed on a few samples to identify and characterize 



component compounds. 



Analyses of trace metals and hydrocarbons in benthic organisms 

 are performed on a maximum of three species, representing 

 at least three feeding types, whic will be collected seasonally 

 at the six stations described above. The amalyses of hydrocarbons 

 in biota follow the same analytical hierarchy as the sediment 

 samples. Tissue samples for trace metal analysis are prepared 

 by complete acid digestion. Samples are analyzed for eleven 

 trace metals: aluminum, mercury, chromium, zinc, lead, iron, 

 cadmium, copper, nickel, vanadium, and barium. Barium and 

 vanadium concentrations are measured by Instrumental 

 Neutron Activation Analysis. The remaining nine trace metals 

 are analyzed by flame or flameless atomic absorption. 



Information Use: 



The final report containing the results of the first year 

 of this study was submitted to MMS in November 1982. 

 The information from this study was presented to the Biological 

 Task Force to evaluate the effects of OCS exploratory 

 operations on the benthic communities of the Georges Bank area. 

 The information will be used in future pre- and post-sale 

 decisions related to environmental sensitivity of benthic 

 communities to OCS discharges, platform siting, discharge 

 requirements, and the adequacy of mitigating measures. 



