Delaware News

A walk in the park

Life finds a way beneath icy coating

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As a transitional month, you never really know what March will have in store.

So, with undefined expectations, I hit the park trails March 1, looking for who knows what. Although bird song filled the air -- notably that from northern cardinals -- and animal tracks told of wildlife movement within the parks, what really struck me at both Char-Mar Ridge and Shale Hollow preserves was the ice. There was ice on the trails, ice clinging to trees and rocks, and -- especially -- ice covering the streams, ponds and wetlands.

Sections of the streams were thick with opaque, white ice, while other sections were more translucent, affording peeks at water rushing underneath a frigid blanket. The pond at Char-Mar Ridge and the shallow little woodland wetlands -- with no running water to keep them aerated -- were frozen from edge to edge. All seemed devoid of life, as if every creature had packed its bags and gone away for the winter.

But appearances are deceiving. In reality, frozen streams and ponds are home to a multitude of creatures.

Fish, for example, do quite well in the winter, seeking out the lower levels of a pond where the water is warmest. Ponds freeze from the top down, and only the shallowest ponds freeze all the way through.

So generally, fish are safe in winter ponds. However, if thick layers of snow and ice prevent sunlight from reaching the water, their lives can be threatened by lack of oxygen.

Aquatic plants use the sunlight to produce this essential element, and deprivation will cause the plants to die and decompose, using up oxygen the fish need to survive. Even small cracks in the ice can let in just enough sunlight to ensure survival.

When warm weather arrives, we'll see painted turtles, red-eared sliders and other aquatic turtles sunning themselves on the logs in the Char-Mar pond. But right now, they are completing their hibernation, buried in mud at the pond edge. Their breathing and heartbeats are slow, their body temperature lowered -- all in an effort to conserve energy.

To me, the most interesting means of surviving winter belongs to some species of frogs, which literally freeze during the cold months and thaw out in the spring. A high concentration of glucose prevents the frogs' vital organs from freezing, even as ice crystals form in other parts of the body. These frogs live in suspended animation until warmer weather thaws their frozen parts and their hearts and lungs start up again.

Some insects use a similar substance -- glycerol, a sugar alcohol -- to achieve the same thing. Others, however, protect against exposure to ice by spinning waterproof cocoons or building up the waxy substance that surrounds their bodies. It doesn't take much warm weather before they are humming and buzzing around us again.

A few insects stay active all winter. Among them, nymphs of dragonflies and mayflies live in the wetlands, ponds and streams, including those that are frozen over. They feed and grow all winter, emerging in early spring as adults. And migrating aquatic birds appreciate them: As the ice breaks, the waterfowl take advantage, seeking out water insects that did not flee the winter weather.

As I walked through the parks on that cold day earlier this month, the watery environments did not easily give up their secrets. All were quiet and still. But just as the birds and other creatures know that spring is just ahead, I know that, too. And I look forward to the time when the streams, ponds and wetlands explode with life, filling the parks with energy and bright sounds.

Park visitors can don their waterproof boots and join in that springtime celebration during three upcoming wetlands programs set April 19, May 3 and May 24. All are free, but two of the programs require advance registration. Visit preservationparks.com for details.

The programs will be held at Gallant Woods Preserve, just northwest of Delaware. Here, Preservation Parks staff members have restored a number of wetlands that were drained when the park was part of a farm. In addition, woodland vernal pools fill up each spring, providing breeding grounds for countless amphibians and macroinvertebrates.

Sue Hagan is marketing and communications manager for Preservation Parks of Delaware County.

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