The water at Area 51 experienced immense turbulence and probably had material that was discharged by local streams and municiple sewage treatment facilities mixed in it. There is a lot of dead algea still in the water due to the high Lake Erie temperatures that are record breaking. That might be the black material washing up on the shoreline.
Last week I was looking at the Buffalo River Keepers web page for e coli testing in streams and creeks that flow into Lake Erie and the Niagara River. Some of these bodies of water in Buffalo, New York are very dangerous to fall into. The water is so polluted. In my opinion this is just a micro sampling of how bad the water is that flows in all the Great Lakes in both the United States of America and Canada.
Take a look at this information and get ready to see sadness:
http://www.bnriverkeeper.org/programs/riverwatch/e.coli.htm