Connecticut Water Trails Program

Estuaries

Coastal Marshes In Depth

A common estuarine habitat found around the world is coastal marshes. Coastal marshes along the oceans are called salt marshes, or tidal marshes. Salt marshes prefer cool, temperate climates (winter temperatures near or below 10° C). They occur in areas that are directly affected by tidal waters.

Many different types of plants such as marsh grasses, rushes and sedges grow in salt marshes. These different types of plants require different water levels, oxygen content and salinity. These requirements determine where they grow in the lower, middle or upper marsh. Salt marsh plants are highly tolerant of the salty waters. They absorb the estuary waters through their roots and special plant cells concentrate the salt ions, freeing up freshwater to be used by the plant.

Salt marshes can filter small amounts of pollutants and runoff. The marsh grass also filters and traps silt. However, too much nutrient or sediment input will create an unbalanced situation causing the health of the marsh to decline.

Salt marshes provide important protection and nursery areas for fish, shellfish and crustaceans. Small fish and other animals live in the shallow waters and dense grasses and hide here from predators. Salt marshes also trap decaying organic matter (detritus) that is used as food by some estuarine animals. Salt marshes provide food, fresh water and shelter for migrating birds on their long journey between nesting and wintering habitats.

Salt marsh plants have strong root systems that help them withstand surges of water that come from storms. Many winding creeks and channels snake through salt marshes. They carry detritus and deposit sediment, replacing what storms, floods and tides flush out. Salt marshes develop in low energy waters, meaning that there is usually only a small amount of wave action in the area. Decaying plants, fish, and animals are broken down by bacteria and fungi helping produce the ripe, rotten egg smell common in salt marsh mudflats.

In The Zone

There are usually three zones in an estuary. The first zone is where the river begins to meet the saltwater. It has more fresh water than saltwater. Next is a middle zone where there is an almost equal mix of fresh and saltwater. The last zone is where the water begins to flow into the ocean, and is mostly saltwater.

Tidal Zones

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