Wednesday, October 15, 2008

Choking the Sound: Conditions in '08 Were Worse Than Usual

Conditions in Long Island Sound, as defined by concentrations of dissolved oxygen, were bad this summer, and they were bad for a long time. Using 3.5 milligrams of dissolved oxygen per liter as the point at which hypoxia starts (which is Connecticut's standard), the Connecticut DEP found:

...the maximum area affected by hypoxia was observed ... between 20 and 22 August and encompassed 360 square miles .... The aereal extent was the highest since 2003. ...

The duration of this year's hypoxic event concluded on our about 20 September after approximately 83 days. The duration of this year's hypoxic event is greater than the 16-year (1991-2007) average of 68 days.

Three hundred and sixty square miles is about 30 percent of the Sound.

Using 3.0 mg/L as the standard (which is what the Long Island Sound Study does), the duration was 79 days (as compared to an average of 57 days and the maximum extent was 181 square miles (the report the DEP sent out late yesterday didn't provide information on the average number of square miles affected.

Of course no one ever knows why conditions are more or less bad -- maybe the weather, maybe the rainfall, maybe the fact that New York City, Great Neck and Westchester County haven't completed their sewage treatment plant upgrades yet. Of course the fish don't really care. All they know is that they can't live there. And if it gets really low, like the 0.14 mg/L it sank to in mid-August off Great Neck, any fish that haven't fled probably will die.

The DEP puts its hypoxia maps online here, although this year's aren't up yet.



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