[MARINE_BIOLOGY_INTERNATIONAL] DIE-OFF, FISH - USA: (TEXAS) LAKE INVERSION SUSPECTED

DIE-OFF, FISH - USA: (TEXAS) LAKE INVERSION SUSPECTED
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Date: Mon 17 Sep 2012
Source: kristv.com [edited]
<http://www.kristv.com/news/6-investigates-mass-fish-death/>

We have new information about the fish kill we reported at Lakeview Park yesterday [16 Sep 2012]. The Texas Department of Parks and Wildlife met 6 News at the site this morning [17 Sep 2012] after we called them. They took samples of the water to test it and see what may have caused this large fish kill.

So far, officials have concluded that the fish died due to a lack of oxygen in the water. However, until their tests are fully complete, they won't know exactly what caused the low oxygen levels.

We talked with Dr Larry McKinney, a marine biologist at Texas A&M Corpus Christi about the fish kill. He offered up several possible explanations as to what may have happened to these fish. He says the most likely cause may be something called lake turnover.

Lake turnover occurs in ponds and lakes. Typically, in a climate like Corpus Christi's, ponds and lakes have warm water on top with high levels of oxygen and cold water at the bottom with low levels of oxygen. When a cold front comes through, like the rain we've just had, the water levels mix. That causes the overall oxygen level to drop and the fish can't breath.

"It's likely a natural phenomenon. When the temperature gets right and the conditions are right, these things do happen," Dr McKinney says.

He added that other possibilities include pollution from runoff into the waterway and diseases spreading from fish to fish.

Whatever the reason, regular visitors to the park are stunned. A local man has been coming to the pond for 30 years and can't believe what's happened. He had just one question. "What's really wrong with the water? I've never seen it like this," he says.

Texas Parks and Wildlife officials hope to have more answers to that question soon.

[Byline: Andrew Ellison]

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[A naturally occurring temperature inversion might bring an oxygen-depleted layer of water from the bottom of a lake close to its surface. The density of water depends on its temperature, and water is at its densest at around 4 deg C (39.2 deg F). Water that is colder or warmer than 4 degrees will be 'lighter', and will tend to move upwards. This property of water makes it tend to form into layers.
There is less oxygen in deeper layers. In a lake, the interface between those layers is known as a thermocline. If water at the surface changes, approaching 4 deg C, it will sink downwards.

A map of the affected area can be accessed at <http://healthmap.org/r/3vBj>. - Mod.PMB]

[Thermocline diagram:
<http://www.fishingreports.com/wp-content/uploads/2012/05/thermocline-fishing.jpg>.
- Mod.JW]

[see also:
Die-off, fish - Canada: (ON) lake inversion susp 20120909.1287307 Die-off, fish - USA (06): (OH) RFI 20120827.1266581 Die-off, fish - USA (02): (GA) comment 20120601.1153265 Die-off, fish - USA: (GA) pollution susp. 20120531.1152141
2011
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Undiagnosed die-off, fish - USA (02): (GA) columnaris 20110528.1641 2010
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Undiagnosed fish die-off - USA (04): (WV, OH, PA) columnaris 20100610.1946] .................................................sb/pmb/mj/jw/ll
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