1 (A brief recess was taken.) 



2 DR. BUTMAN: The final thing I tried to do was list a few of the 



3 limitations of available data and we have actually covered a number of 



4 these already in the discussion this morning. 



5 I thought it was important to try to list what we do know, what we 



6 did know and what we do know. This is a partial listing of things which 



7 we don't know and some sort of qualifications to things that we know. 



8 First, we have made the point already this morning that much of 



9 the process work has been confined to depths really in the heads of the 



10 canyons, 500 to 1,000 meters and really only one or two canyons. I 



11 think that's probably all right because the focus here is for 



12 canyonheads. 



13 In terms of a large-scale box model and a bigger picture of the 



14 canyons, I think that is an important limitation we have to keep in 



15 mind. 



16 We talked also about the stripping of pollutants from the water 



17 column as indicated by the lead-210 observations. It seems like what 



18 that efficiency is is an important question which we don't know about. 



19 Third, we have talked a lot about resuspension and accumulation 



20 and transport in a few places. I suggested this hypothesis of a leaky 



21 system where there is some local accumulation but there may be some 



22 transport of material. Even though there is some accumulation, there is 



23 also some transport out of the system. 



24 Actually, John brought this up yesterday in our discussion, that 



25 the rates is really a critical issue. We have a good idea about some of 



26 the processes but not necessarily some of the rates. I think the rates 



27 are going to be critical in trying to assess what some of the 



28 implications are for drilling. 



29 We also talked this morning about hypotheses for the species 



30 abundance and diversity that are actually seen in the canyon. Joe and 



31 Barbara talked about variable substrates. We talked about limited 



32 exploitation in terms of direct fishing or dragging. We had a little 



33 bit of a discussion about temperature, but there may be others. 



210 



