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SPARKS, Nev. – State wildlife officials are trying to figure out why all the fish have died in a northern Nevada marina where the stocked fishery has flourished since the man-made lake was created nearly 15 years ago.
As many as 100,000 trout, bass and catfish have died over the past month in the Sparks Marina along U.S. Interstate 80 east of Reno, apparently the result of a dramatic, unexplained drop in dissolved oxygen levels, Nevada Department of Wildlife spokesman Chris Healy said Wednesday...
Fish biologists confirmed low oxygen levels caused the death of an estimated 3,000 fish in one corner of the lake in mid-December but Healy said they thought at the time the event was localized and of limited impact. Since then, they've been unable to detect any live fish in the 77-acre lake...
"The 100,000 dead fish figure is something that is probably a pretty conservative guess," said Healy, who estimates they've stocked close to 1 million adult fish in the lake since they started in 1998.
"We don't know if any small fish have survived, but for all intents and purposes, the fishery doesn't exist anymore..."
Scientists say a bitter cold snap could have caused oxygen-poor waters to rise from the old rock quarry's bottom to the surface, but they don't understand what sparked the massive die-off...
...a boat survey on Monday found dissolved oxygen levels far too low to support the fish at 11 different sampling locations. Readings from an electronic fish-finder also revealed no fish swimming in the lake's depths.
Lakes like the marina consist of different layers of water temperatures, with the warmest water on top holding the highest oxygen content, Healy said. He said one theory is that the surface water may have chilled very quickly, sank toward the bottom of the lake and stirred up material on its floor, causing a "violent turnover" that could have sucked up additional oxygen...
Healy said testing earlier this week found dissolved oxygen levels in the range of 1.1 to 1.9 parts per million. Fish do best with levels in the range of 7 to 9 parts per million and typically can't survive when it drops below 5 parts per million, he said.
Michael Drinkwater, manager of the Truckee Meadows Wastewater Reclamation Facility which collects water from the lake, is awaiting results of new toxicity tests conducted last week but said routine testing has revealed no problems before...
burdman30ott6
Lake turnover happens alot, and usually with similar results as seen in this article. Often it only kills the largest fish, as the smaller guys don't need as much concentration of disolved O2 to survive, but in extreme cases it can completely kill a lake.
Bigburgh
But my gut still says solvent/fuel plant.
Edit: Helms gravel pit. I knew that name would come back to me.
ndep.nv.gov...
Bigburgh
It was just brought to my attention. From family that still reside there. Reno had a fairly sizable earthquake in the last 5 month. Around October.
In Reno there is a good fault that runs right down Virginia street.
This may have contributed in ground shifting releasing some of the chemicals...or other earth gasses..
Its not uncommon to have fish die offs around these events.
ikonoklast
reply to post by burdman30ott6
burdman30ott6
Lake turnover happens alot, and usually with similar results as seen in this article. Often it only kills the largest fish, as the smaller guys don't need as much concentration of disolved O2 to survive, but in extreme cases it can completely kill a lake.
I had only vaguely heard about lake turnover before and didn't know much about it. I found a number of interesting references, but I especially liked this excellent article for those who may want to learn more: Lake Turnover - how it works.
I'm not sure how often the really extreme cases of it completely killing a lake occur. I tried to get an idea of how often it might happen, but Google came back with mostly links to this particular fish kill and even to this ATS thread.
Bigburgh
ikonoklast
Lake Turnover - how it works.
...Thanks for replying back.
Thanks everyone for the stars. I feel like I actually contributed.
Edit: answered my own question. Helms gravel pit is very deep. At least 200 ft when it was just a gravel pit. So the water at the bottom could get to near freezing temps...enough to freeze from the bottom up...
Why doesn't water freeze at the bottom of a lake?...
A cubic metre of ice is less dense than a cubic metre of water. That means a given amount of water has to expand to form ice. The pressure at the bottom of the lake doesn't allow this expansion to take place...
Ice crystals have a nice hexagon type structure which occupies more space than the less ordered liquid - same number of molecules taking up more space means lower density - so ice floats. If the frozen bits float then the last bit to get frozen is right down at the bottom. The bottom of the lake can freeze but it will be the last bit to do so. It takes a lot of energy to unlock water molecules from ice - conversely it takes a lot of energy to turn water into ice - so conversion of water into ice soaks up a lot of 'cold' (must be a better way of putting that) and the ice forms a (fairly) good insulatiing layer between cold air and the water at the bottom of the lake...