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Tidal Wetlands
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Tidal Wetlands

The Sound shoreline includes rocky terrain, tall bluffs, sandy beaches, and a wonderful collection of tidal wetlands built up by accumulation of sand, soil, and organic sediment. Between the normal high and low tide levels is the intertidal zone - land that is alternately covered with water and exposed to the air.

Tidal flats

At the low-tide border of the intertidal zone lie tidal flats. Here, the land is under water most of the time. At first glance, the flats look barren of life. No grasses or other rooted plants are visible - they cannot put down roots in the shifting sands nor live submerged in seawater for much of the day. Plant life in the tidal flats is limited to microscopic algae that form brown or green films on the surface.

Close inspection of tidal flats, however, shows that the initial impression of lifelessness couldn't he farther from the truth. An army of worms and small shellfish live just below the surface in the sediment, where they feed on algae and organic debris washed down from the shore and carried in by the tide from the coastal waters.

At low tide, birds arrive to dine on the permanent residents of the flats. Herons, egrets, and other wading birds do most of their feeding here. Ducks, gulls, and terns also pause on the flats to supplement their diets of fish. During the winter, waterfowl that do not migrate and many shorebirds as well take advantage of the resources of the tidal flats.

At high tide, shrimp, crabs, and young flatfish move in to feed in the shallow, protected environment where they are safe from predators and swift currents. Many commercially important species of fish depend on the flats for survival in early stages of their life cycle.

Salt marshes and the food web

Higher up in the intertidal zone, where the land remains under water for less time than in the flats, are the salt marshes. They are incredibly productive and valuable habitats. An acre of Long Island Sound salt marsh can produce over 2.7 tons of grasses, algae, and other organic matter each year, compared to 1.5 ton per acre of wheatfield. Organic matter not consumed by resident's of the salt marshes is washed into the Sound, where fish and bottom dwellers feed on it. It is estimated that two-thirds of our edible fish and shellfish depend on salt marshes for their food.

To grasp the essential role of the salt marshes requires looking at the food web in Long Island Sound. Food production begins with microscopic algae, seaweeds (which are larger algae), grasses, and other plants that live in abundance in the marshes. Only plants can utilize the energy of sunlight to convert carbon dioxide and soluble nutrients into food that can be consumed by animals. Microscopic animals, shellfish, and finfish that feed on plant matter are consumed, in turn, by other finfish that never feed on plants.

The food web is completed by decomposers - bacteria in the water and bottom sediments that break down dead plants, dead animals, and organic wastes. As the decomposers do their job, nutrients are returned to the surrounding waters where they are again accessible to plants. It's important to note that decomposers, like other organisms, require oxygen to survive. Later in the Soundbook you'll see that the use of oxygen by decomposers plays an important role in one of the major problems facing Long Island Sound today - hypoxia, or low concentrations of dissolved oxygen in the water.

Salt marsh vegetation is dominated by various kinds of grasses that grow in different regions according to their tolerance for time under saltwater. The division of a marsh into low marsh, high marsh, and upper border is defined by the kinds of grasses that grow in each zone.

The salt marshes are far more than farmland for the fishes, however. Crabs, barnacles, snails, and other shellfish live there, as well as small animals such as shrews, mice, diamondback turtles, snapping turtles, and muskrats. Racoons, red foxes, and weasels hunt there.

Salt marshes also provide food, shelter, and breeding grounds for many species of birds. The Connecticut coast is part of the Atlantic Flyway for migrating shorebirds and waterfowl, and in the spring and fall plovers, sandpipers, osprey, marsh hawks, and many kinds of songbirds can be seen stopping by in the marshes and tidal flats. Large flocks of ducks and geese, including mallards, black ducks, scaup, mergansers, brant, and Canada geese, winter along the salt marshes, while herring gulls and song sparrows frequent the marshes year-round.

The physical presence of marshes at the border between the land and the water is also of great value in protecting our environment. The marshes absorb water and provide storm and flood buffers for the upland. They also trap sediment and pollutants, and can greatly purify runoff water before it returns to the Sound.

The list of benefits provided by tidal wetlands is long and it should be obvious that the remaining wetlands of Long Island Sound must be protected from loss due to development and from overwhelming pollution. Since the 1950s, the major causes of wetlands loss in Connecticut and New York have been miscellaneous fill operations, waste disposal, housing and industrial construction, and the building of bridges, roads, and recreational areas. Wetlands are also vulnerable to damage when seawalls, bulkheads, and groins along the shore alter sediment deposition patterns.

Today, only about two-thirds, or 17,500 acres, of the estimated 26,500 acres of tidal wetlands present in Connecticut in 1916 remain. Since the passage of Connecticut's Tidal Wetlands Act in 1969, the rate of wetland loss from permitted activity has dropped dramatically-to one-half acre per year. Loss continues, however, from illegal activity and deterioration due to pollution.

On Long Island, where there were once 50,000 acres of tidal marshes, 34,000 acres remained in 1954, and this has diminished to about 25,000 acres today. As in Connecticut, wetland loss due to permitted activity has slowed since protective legislation was passed in 1972 in New York state.

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