To the average person a tidal marsh may appear as an uninviting and uninteresting expanse of wasteland. If you take a closer look, it reveals an intricate and fascinating community of plants and animals that adjust to an ever-changing environment. Their habitat is a complex one, one that includes some of the most productive acreage on earth. The tidal ebb and flow brings about interesting zones of plant life from the edge of the marsh to the upper borders that are occasionally inundated. Along with the many common grasses, some of the most striking wild flowers may be found there—sea lavender, marsh mallow, purple gerardia and sea goldenrod. One can observe spectacular water birds—herons, ducks, rails and many others that feed and nest in this habitat. Marshes serve as a vital resting and feeding area for migrating waterfowl, as well as a wintering sanctuary. These marshes also contribute to the productivity of adjacent waters by providing the basic nutrients that start the food chain that supports the large numbers of fish and shell fish in the area waters.
This fascinating world of plants and animals that are alternately flooded by seawater and exposed to air by the rise and fall of the tides opens up a new world to a unique ecosystem that involves a complex food web.
Course of Study
This unit is intended for use with 6th grade students throughout the school year as a part of the social studies unit on Connecticut. The first of many periodic observations at Lighthouse Point Park (Morris Creek) will take place in the early fall. During these visits, observations of salt water plants, bird, invertebrate and vertebrates will be made. Specimens will be collected and classified. The students’ observations will be illustrated on charts to show the varied life sustained during the different seasons. Photographs and slides available at the Yale-New Haven Teachers Institute will also be used to help students with the identification process prior to each first-hand observation.
Lighthouse Point Park
Lighthouse Point Park (Figure 1), at the mouth of New Haven Harbor with Morris Cove forming the northern boundary and Long Island as the southern boundary, will be the basic resource of the 6th grade amateur naturalists.
In 1958 a groin was constructed at the western end of the beach and rebuilt in 1977. For a number of years the wind and waves have carried the sand back on to the beach during the winter forming a dune along the front of the beach. In early spring each year, the city of New Haven bulldozes the beach and flattens it, basically, for the safety of swimmers. A seawall was built in the 1950’s at the eastern side of the beach. The mean tidal range in the New Haven area is 6.2 feet with slightly greater Spring tidal range of 7.1 feet.
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Morris Creek
Morris Creek that flows on the eastern side of the park will be examined and explored to better understand and appreciate the balanced and continuing life of the marsh. As one follows the creek from the mouth (eastern side of the seawall), the land on the left is elevated and on its upper borders is found Phragmites (Common Reedgrass) that is especially common where there has been a disturbance on the marsh such as tidal gates or dredge spoils. This plant will quickly replace the cordgrass that is restricted to intertidal zones of a marsh. This western side of the creek along with the wooded area of the park are a bird sanctuary. Directly across from this area is a marina (East Haven side). In this immediate area there are culverts that run off the creek to the east under the existing dirt roads and behind Shell Beach.
North of the marina can be found
Spartina patens
(Saltmeadow cord-grass) which often dominates the high marsh. It is this grass that formed the salt marsh hay that was harvested extensively by the early colonists and today is still mowed on some marshes.
Tide gates are farther up the creek. They are located west of Townsend Avenue (Rt. 142) on the Long lsland Sound side of this road. These gates prevent tidal water from getting into the airport and industrial park area that is just to the north. They also allow the fresh water flowing from the ponded area by the industrial park to flow down the Morris Creek.
The Morris Creek branches off and runs along the western side of the Tweed-New Haven Airport bounded by Dean Street in New Haven. This area is presently under study by the Coastal Area Management Program, Connecticut Department of Environmental Protection concerning the flooding of the creek in this area. The eastern branch of the creek goes along the eastern side of the airport and industrial area in East Haven. It is bounded on the east by Ora Avenue in East Haven. This area was a former salt marsh until the installation of the tide gates prevented the flow of salt water into the area. Dredge spoil material from the New Haven Harbor was at one time deposited in this Ora Avenue area and has naturally disturbed the area. It is now designated as an inland wetland. To the north is a fresh water ponded area that drains down the Morris Creek. Waters of this creek flow into Long Island Sound and are all part of the Southcentral Shoreline.
The inwelling or influx of sediment into the creek is caused by incoming tides, and wind and wave action. The adjacent upland is the principal source of the sediment that is accumulating. The Army Corps of Engineers at one time deposited dredge spoils behind dikes east of the airport. After a period of time the dikes broke and the sediment spilled into the creek.
The filling of salt marsh wetlands around the creek has also affected the creek. It has reduced the water capacity of the land. Since the land no longer can absorb as much of the water as it used to, it runs off into the creek carrying sediment with it.
Morris Creek as a Food Source
Morris Creek is a valuable natural oyster habitat. The oysters spawn in the creek during the summer months when the water is between 68°F-72°F. The male releases its sperm and the female releases its egg into the creek.
The egg is fertilized in the water and changes into a free swimming larva. It swims and drifts about for two to three weeks and then settles to the bottom on to a clean surface such as an oyster shell or shell fragment to begin growing. Some of the larvae go out of the creek and may settle on shell in the New Haven Harbor.
Planting of the oysters takes place north of the marina and south of the tide gates. This area is designated as a State Spawning Sanctuary.
If the shell base is covered with silt the larvae cannot settle on a shell. If this silt covers the oyster after it has settled on a shell it will suffocate.
Salinity is less conducive to long term growth of the oyster. Oysters prefer a salinity of 15 parts per thousand. At the mouth of the creek the salinity is about 25 parts per thousand.
Soft clams (steamers), blue mussels and hard clams (quahog), are abundant at the mouth of the creek. Ribbed mussels are found further up the creek.
Eastern Flyway
Lighthouse Point Park is very important to birds migrating along the Eastern flyway. From the end of August through October the second largest number of hawks migrate over the coastal area along the Eastern flyway. The two most common hawks in migration over Lighthouse are the Sharp-shinned Hawk and Kestral Falcon.
Ten or more other species fly over and all are listed below in 5 groups.
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I. Accipiters—all bird hawks, with short wings, long tails and are basically woodland hawks
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A. Sharp-shinned Hawk
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B. Kestral Falcons
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C. Cooper’s Hawk
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D. Goshawk
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II. Buteo Hawks—wide wings, wide tail, and are basically inland migrants
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A. Broadwinged Hawk
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B. Red tail Hawk
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C. Red shouldered Hawk
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III. Falcons—long tails and long wings
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A. Kestral Hawk
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B. Merlin Falcon—endangered species
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C. Northern Harrier—third most common bird going over marsh
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D. Marsh Hawk
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IV. Eagles
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A. Bald Eagle—Endangered species
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V. Others
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A. Osprays (common migrant)
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B. Turkey Vultures (Occasional, rare on coast)
Lots of song birds also come through during the spring and fall migration.
Mr. Frank Gallo, Edgewood Park Ranger with the Department of Parks, Recreation and Trees is a registered bird bander and coordinator of the Bird Banding-Migration Program. The classroom activities include a discussion on migration and the basic concepts of bird banding. A week later the children go to Lighthouse Point Park and participate in net-lanes, bird-banding and hawk-watching. This program will be incorporated into this unit as the first activity in the early fall.
Objectives
Upon completion of the unit the students should be able to: 1) understand what a salt marsh is, 2) identify some of the salt water plants, 3) identify some of the birds of the salt marsh, 4) identify some of the invertebrates that inhabit the salt marsh, 5) identify some of the vertebrates that inhabit the salt marsh, 6) to understand and appreciate that many forms of life can only live because of the presence of other forms of life, 7) understand the importance of the marsh to marine animals in Long Island, 8) identify some ways in which man is destroying the productive lands of the salt marshes, 9) use aerial photographs of Morris Creek and compare with topographical maps.
Salt Marshes
Salt marshes are grass-dominated tidal wetlands that fringe the land-water interface of many temperate regions throughout the world.
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The New England tidal marshes are relatively recent land forms that have developed in the last 3000-4000 years. Their development is the result of interactions of tidal marsh vegetation and a gradually rising sea level. As the post-glacial rise in sea level slowed to about one millimeter per year approximately 4000 years ago, sediment deposition within stands of salt water cordgrass was able to keep pace with the rise and thus marsh development.
Once established, a marsh may maintain its position near mean high water level and may shift gradually landward if sea level rises. During the rise of water level, the thickness of salt peat may increase by upward growth.
Geological Aspects
The coast of Connecticut has been enormously influenced in its later geologic history by the advances of a continental glacier with concomitant lowering of sea level.
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The advancing glacier, which reached southward to Long Island laid down a carpet of unsorted material called till which ranges in grain size from clay to huge boulders. The southern margin of the retreating glacier had moved considerably northward before the sea gained access to the depression that is now occupied by the waters of Long Island Sound about 8000 years ago. Valleys which probably had been deepened and enlarged by glacial erosion were then occupied by meltwater streams which drained southward away from the glacier. After the sea entered the Sound and continued to rise, the gradients of these meltwater streams were progressively lowered, and the deep bedrock valleys were filled by sand and gravel. In addition, waves began to work on the carpet of till and to sort out the finegrained components. These were put into suspension and carried away by currents. Some of it found its way via the tide into coastal indentations, where it eventually formed mudflats on which salt marshes grew. The coarser components of the till remained in place as a washed lag residue of sand and gravel.
After coastal salt marshes were established on the mudflats, they encroached landward as sea level rose. The marshes locally covered the earlier-formed stream deposits of sand and gravel which originated during still earlier phases of sea level rise.
If the rise in sea level is slower, the rise in the surface of the marsh will be slower or temporarily stop. If sea level rises slightly faster than the plant growth can add to the surface of the marsh, the surface will be flooded more frequently with sediment-laden waters. The accumulation of mud on the surface will increase and keep the marsh level in harmony with sea level.
If the high tides do not flood the marsh regularly, there will be periods without rains when the mud will dry out.
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The salinity will increase, due to the concentration of salts, as the water evaporates. The marsh plants will die and no longer hold the mud in place. Subsequent rains or extra high tides will reduce the level of the marsh again, by increased erosion, until it is about at the level of mean high tide.
It is common to find this kind of balance struck between the forces of the environment and the plants that live in that environment, each modifying the effects of the other.
Zones
Typically, salt marshes will contain three zones of flowering plants and their associated communities.
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At the lowest levels a sparse growth of a few species forms the pioneer zone or low marsh. This intergrades at higher levels with the richer flora of the mature zone of middle marsh. Finally, the species of the mature zone are partially replaced at the highest level of the salt marsh or high marsh by species of nonsaline habitats or facultative halophytes which can only withstand brief and infrequent submergence in sea water (Figure 2).
Seasonal Changes
The moderation of climate produced by the sea results from the slowness of the water temperature to change with the seasons.
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The moderation of the water temperature makes abrupt changes in marsh temperature when the tide rises and falls. All animal life in the marsh must adjust to these changes. It adjusts by physiological, chemical and structural adaptations, as well as behavioral adaptations made to cope with the seasonal changes.
