Wednesday, September 04, 2013

Mosquitoes and Toppled-Tree Ponds

Part of the legacy of Hurricane Sandy, and other severe storms that have buffeted Princeton in recent years, is a lot of new mini-ponds in the woods. Each uprooted tree leaves a depression in the ground where its root ball had been.

Is this minipond megapuddle a mosquito haven or a mosquito trap? Well, that depends.

Depending on the underlying hydrology, one minipond will last much longer than another. Some dry out after a rain, and if it happens within a few days, any mosquito larvae there won't survive to adulthood. In such circumstances, the minpond serves as a trap, luring adult mosquitoes to lay eggs, then pulling the plug on the resulting wigglers.

Other miniponds in the forest will stay filled all summer if there's no drought. They may be in a floodplain with a high water table, or receive steady seepage from a slope. These also can serve as mosquito traps, because their stable conditions allow predators of mosquitoes to get established, like this frog at Herrontown Woods, and the water beetle

floating half submerged nearby.

Water striders that walk on water (not much luck with the photo) are also able predators of mosquito larvae.

The ponds that offer a haven for mosquitoes are the ones that neither stay full long enough to attract and sustain a food chain, nor drain quickly enough. The only way to figure out which is which is to resist the reflexive association of standing water with mosquitoes, and take a closer look.

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