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Experimental Ecology


Often in nature, the things with the least-impressive appearance prove to be the most significant. Take the case of the tiny Anopheles mosquito. At a fraction of an inch in length, it appears far less threatening to humans than, say, a great white shark or a grizzly bear. But appearances can be deceiving. Perhaps no other organism on Earth has had a greater impact on human civilization than the Anopheles—the mosquito responsible for the spread of malaria and the deaths of more than one million people each year.

Isolated temporary ponds certainly do not look very impressive either. In fact most people are probably unaware these naturally occurring wetlands are even referred to as anything other than “puddles.” But what many look upon as nothing more than mosquito breeding grounds, biologists and ecologists view as valuable resources for the study of biological diversity.

Dr. David Chalcraft, assistant professor of biology at East Carolina University, is an expert in the ecology of temporary ponds. These ponds are water-filled depressions in forests or fields independent of existing lakes, rivers, or streams. They are temporary because they eventually dry out, a key characteristic because it prevents the establishment of predatory fish species. Fish tend to be voracious predators, and their presence in temporary ponds would hinder the pond's ability to spawn life. Temporary ponds are flush with diverse species of amphibians, aquatic insects, and plants. Their isolation from larger waterways makes them essentially closed ecosystems and easier to study than larger wetlands like rivers, lakes, or oceans.

Chalcraft is currently operating a laboratory at West Research Campus comprising hundreds of artificial isolated temporary ponds. He uses the artificial ponds to learn what factors control the biological diversity in an ecosystem and the consequences of changing that biodiversity within the system. The artificial ponds give Chalcraft complete control over the ecosystems and allow him to study specific scenarios based on things such as the introduction of predatory species into the ponds, an increase or decrease in plant life within the ponds, or the effects of commonly occurring pollutants such as pesticides or fertilizers.

“One of the goals of my research is to see how a change in the biological diversity of amphibians in those ponds influences a variety of ecosystem functions that operate in those ponds,” said Chalcraft. “Some of these functions include the rate at which plants produce energy for food webs, rates of decomposition, and rates of energy flow between aquatic and terrestrial ecosystems.”

Chalcraft has based a large portion of his research on the amphibian populations that thrive in temporary ponds. Amphibians, he says, represent a diverse group of organisms and they make excellent research subjects because they are readily available in nature. Also, their small size makes them amenable to experimental research without being so small as to require special tools to study them. He is quick to point out the importance of amphibians not only to the ponds they call home, but also to the ecology of the planet as a whole.

“Amphibians are often really good bioindicators in the environment. They are susceptible to toxins and pesticides that people may be putting out in the environment intentionally or unintentionally. Because amphibians are particularly sensitive to environmental pollutants, we can actually see how these pollutants may be influencing the environment on a short time scale and potentially how these pollutants may come back and have some negative impact on humans as well,” he said.