WELLS — While there have been numerous efforts across the country and in Maine to preserve and restore salt marshes, there is little scientific data explaining how they work.

"We don't really know how salt marshes in Maine function," said Richard MacKenzie, a scientist at the Wells National Estuarine Research Reserve.

There is especially little data, he says, on what happens on the surface of the high marsh, the land area that is above the tidal creeks, and the pools on the surface, called pannes.

To find out how the organisms in the marsh interact and how the food chain in the marsh works, MacKenzie and other scientists have launched a study in the Webhannet and Ogunquit River estuaries.

The study, funded by the University of Maine Sea Grant Program, is important because most of the research that has been conducted on salt marshes has occurred in marshes south of Cape Cod.

"This is basic ecological science," MacKenzie said. "But this study is the first of its kind in Maine."

Organizers hope the data collected from the two-year project will add valuable information that will help shape management policies for the marshes.

For example, one management technique that has been used in recent years involves closing off mosquito ditches. These ditches were constructed in the 1930s to drain water off the marsh surface and redirect it back to a water source. It was thought that draining the water off the marsh surface would destroy breeding sites for mosquitos.

The theory behind plugging them up is that water would be returned to the marshes that have grown so high, only the strongest high tides can completely inundate the marsh with water.

But, MacKenzie says, the problem is that researchers aren't even sure how natural pannes work, and what are the negative effects of creating pannes.

One possible downside to plugging up the ditches, he says, is that the marsh vegetation is killed off by the pannes because the natural balance of the marsh has been thrown off.

Developing sound policies for the marshes is a high priority for many reasons, according to Linda Woodard, director of the Scarborough Marsh Nature Center.

"Marshes are important as a nursery for fish, for birds and a lot of different animals," Woodard said. "Seventy percent of the fish food we eat depends on the marsh in some way."

Besides providing a habitat to many different fish, birds, insects and other creatures, marshes also help protect land from flooding by absorbing water from storms.

For many years, marshes were simply drained or built over because they were thought to be useless. Although there are many conservation programs in place today, the marshes are still threatened by development and pollution.

Typically, the marsh moves with the ocean. As the sea level rises, the marsh either builds itself higher, or tries to move back from the water. But because there are many developments abutting the marshes, there is nowhere to go, and the natural growth upward can't keep up.

In the study, MacKenzie and Michele Dionne, another researcher with the reserve, chose 12 pannes to study in the Webhannet salt marsh off Harbor Road.

A number of fish, insects and other organisms live in the pannes. When the high tides flood the marsh, the animals are able to leave the pannes temporarily to feed off the marsh vegetation and other organisms that live on the marsh surface.

These sites are divided into three groups. In one, fish, crabs and other animals that live in the panne are restricted to living in the panne. In the second, they are able to move only a short distance beyond the panne. The third grouping is a control group, where the animals have no restrictions on movement.

To chart which animals eat what, the sites have been sprayed with a nitrate that leaves a trace on each organism that can be detected through a spectrometer.

The isotope is like a dye that leaves a different color on every animal it touches. When an animal like a fish is analyzed, scientists will be able to trace what it ate by the different "dyes" that have been left in its system. "Basically, you are what you eat," MacKenzie said.

It's complicated science, MacKenzie admits, but the results of it will be a great asset to scientists and conservationists.

"Marshes are very dynamic systems," he said. "This study is important because we're trying to manage and protect these systems, but there's so much out there we don't know about yet."

Staff Photo by Fred J. Field

Research associate Jum Dochtermann tosses a fish trap into a panne at the Webhannet salt marsh in Wells as Richard MacKenzie prepares to take a sediment sample.

Staff Photo by Fred J. Field

Richard MacKenzie, right, and Jim Dochtermann collect sediment from a panne, or surface pool, at the Webhannet marsh.  Researchers aren't sure how pannes work, MacKenzie says.