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November 19th, 2013

Marine Sampling II: The Outfall

by Steve Sweet

 

Today the weather is really nice, we expect a high of 30 degrees and it is clear and sunny this morning.  On the way to our next transect Mary noticed a really beautiful mirage where the mountains meet the ice across McMurdo Sound, such a great scenery on the way to work! 

The next transect is closer to the Station with the mid depth site located where the sewage outfall discharges into the ocean.  Over the years, the conditions have dramatically changed.  When we first started sampling here in 2000 the Station’s sewage was discharged directly into the sea without any treatment, this made the site very different from any other site in the area.  With time the tertiary treatment plant was constructed and by 2003 it was placed in service.  Ten years after the plant was put in operation the conditions on the bottom are significantly different which makes sampling here much more pleasant for both the divers during collection and for us when we process the samples in the dive hut.  Even though conditions have improved here, when the divers come out of the water they are sprayed with disinfectant just to be on the safe side.

The effluent pile before 2003

 

The effluent pile in 2011 (There was no plume today)

Steve and Rob worked the deep site first. Our two most experienced divers are needed since the collection times at 120 feet are about 12 minutes per diver.  It is very challenging to collect eight large cores, three smaller cores, marine organisms, and to photograph the site in less than 24 minutes! 

Some starfish/seastars from the bottom

A gross nemertean worm (they get up to a meter long

Terry took care of collecting sediments and critters from the middle site (at 80 feet) like a seasoned pro now (only his third dive of the year).  I guess he got the short straw since he had sample right next to the pile at the end of the effluent pipe, even though there haven’t been any additions to the pile in a decade, there still is a hill of material below the pipe.  When we were putting the sediments into our sample containers at this site it was still a little bit of a smelly job.

Terry emerging from the dive hole

Terry out of the hole

Our newest diver, Martin, was up next and photographed the middle site, added to our organism collection, and proceded to the shallow site.  He was able photograph the site and collected almost all of the sediment samples when his regulator began to free-flow and he had to stop and come back to the surface.  Sometimes ice will form in the regulator making it malfunction. Because he was diving with a surface supply he didn’t have to worry about using too much air during his ascent to the surface.  Not to worry, we will finish up this site on Wednesday before going to the next transect.  After another successful day of sampling, we ate dinner and finished processing the samples in the Crary Lab.  I was sure tired after such a productive day and went to bed early.

Waiting while Martin is diving

Sectioning a core of sediment