All the organisms make their preparations for the slowing of activities, that is to follow. They do not know what is to follow, nor can they make plans for the future. They simply feel that the days are growing shorter and the nights cooler. They respond automatically with the built-in system that has assured the survival of their species through countless winters.
Autumn starts in the north and moves south during September and October. The grasses mature their seed heads. Some of the more adventurous aquatic animals of the marsh, worms and mud crabs turn toward the sea where the water never goes below freezing beneath its surface.
Birds
The birds fly south. The swallows start almost before summer is over. They hawk their way over the ribbon of marshes, feeding on insect swarms as they move along. The rails with their young migrate south, hiding their ungainly flight at night. The herons that feed on the small fish also go south to eat where the fish are still abundant in shallow water.
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When the marsh creeks get colder than the offshore waters, the high tides are warmed by waters coming from offshore. The fish move out and leave the marshes for the winter.
Plants
The plants die down. The remaining marsh animals burrow into the mud below the frost line and retreat toward the low water level. The living activities in the marsh slow and almost stop.
Ecosystem
Estuaries, (where the tide meets the current of the river), in general and salt marshes in particular are unusually productive places. Marshes are productive for several reasons, all of which are a result of the meeting of land and sea. The tides continually mix the waters and, by their rise and fall, water the plants. Harmful accumulations of waste products are diluted and removed. Nutrients are brought in continuously.
Clams, oysters and mussels help from the sediment which acts as a nutrient trap because of their method of feeding. They remove all the particles from a large volume of water as it passes over their gills and deposit most of them in neat pseudofeces bundles.
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Although marshes concentrate the nutrients, they do not create them. They must also be brought in from some place. Some of the necessary nitrate is actually extracted from the air by way of nitrogen-fixing blue-green algae that live on the marsh mud. Nutrient concentrations in soils are thousands of times greater than those in waters. As a result, plants growing in soils are more productive than those floating in the water.
Another reason for high marsh productivity is the quick rate of turnover of nutrients. The algae replace themselves in a matter of days and the abundant bacteria of the marsh in a matter of hours.
Finally, the marshes are productive because there is almost no time during the year, even in the north, when there is not some plant growth taking place. In the north, where the land plants and Spartina cease activity during the winter, the algae in the marshes continue to grow throughout the year.
The marsh plants are the most important consumers of the energy they capture from the sunlight.
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Bacteria are the next most important group and consume about one seventh as much as the plants. Moving down, animals are only about one seventh as important as the bacteria. When all this consumption is added together, however, we have account for only fifty-five percent of the energy that remained after we allowed for use by plants.
The tide giveth and the tide taketh away. It is the tide that makes the high production possible and the removes half of it before animals of the marsh get a chance to use it. But what is denied the animals of the marsh is given to the abundant animal life in the estuarine waters around the marsh.
The tides continually wash a part of the marsh production into the creeks and bays where fish and oysters lie in wait. Without the marsh, these animals could not survive.
The science textbook,
The New Exploring Science, Red Book
, Laidlaw Brothers, 1982 will be used as a part of this unit. Unit I, “Ecosystems”, pages 16-47, is used to reinforce the students’ understanding of the balance of nature, the many kinds of ecosystems and the food webs.
Marsh Plants
Listed below and briefly described are some of the plants of the salt marsh that will be identified and discussed (Figure 3).
Saltwater Cordgrass
(
Spartina alterniflora
).
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The tall form of this smooth grass ranges from three to seven feet in height and is restricted to the intertidal zone of the marsh. It is the most productive of the marsh grasses. The plants provide cover for many species of marsh birds and the rootstocks make up a large part of the diet of Canadian geese wintering along the shore.
Saltmeadow Cordgrass
(
Spartina patens
). This is the fine, twelve to eighteen inch high grass that often dominate the high marsh.
Spikegrass
(
Distichlis spicata
). This highly salt-tolerant plant, eight to fifteen inches in height, is a widely scattered species on the high marsh.
Blackgrass
(
Juncus gerardi
). This dark green, grass-like plant, ten to fifteen inches in height, is actually a rush. It grows most commonly near the upland. Blackgrass is less tolerant of high soil salinity than other marsh species such as spikegrass.
Salt-marsh Aster
(
Aster tenuifolius
). This straggly, few-flowered perennial aster has whitish or pale purple flowerheads and is found scattered in the saltmeadow cordgrass or in openings on the marsh where it is associated with sea lavender and purple gerardia. The plant flowers from late August into fall.
Sea Lavender
(
Limonium carolinianum
). This is one of the most beautiful of the tidal marsh plants. Its tiny, funnel-shaped flowers are pale purple and occur in many one-sided clusters. It is frequently found on the high marsh in association with arrow-grass and seaside plantain.
Arrow-grass (Triglochin maritima
). This is a grass-like plant with long, sword-like leaves which are a foot or more in length. Its small flowers are scattered along a flowering stalk that rises above the leaves. It is frequently associated with depressions on the high marsh and found with sea lavender and seaside plantain.
Narrow-leaved Cattail
. This species is found in brackish marshes. It has narrow leaves and a gap between the yellow male flowers (stamens) toward the top of the spike and the female flowers (pistils) below. The starchy rootstocks of these plants are edible and were ground into meal by Indians and early colonists.
Common Reedgrass
(
Phragmites australis
). This tall grass has a distinctive feathery flower that is initially reddish, then silver, and finally tan in color. In viable marsh it is found along the upper border, especially where there has been disturbance. With the installation of tidal gates or other restrictions to tidal flooding this aggressive plant can replace the cordgrasses.
Marsh Mallow: Swamp Rose Mallow
(
Hisbiscus palustris
). This tall, coarse plant blooms from late July to September with large showy pink flowers and is most typical along the upland edge of the marsh.
Birds of the Salt Marsh
Of all the wildlife associated with the marsh, birds are the most conspicuous. Listed below are some of the most common birds that the students will discuss and identify (Figure 4).
Clapper Rail (Rallus longirostris
). The rails are narrow birds uniquely adapted for slipping between the dense vertical stems of the grasses and reeds. Its long, slender bill is used for probing for worms in the mud or fetching out snails and insects from the dense marsh grass. It is found in salt and brackish marshes.
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Song Sparrow
(
Melospiza melodia
) and
Sharp-Tailed Sparrow
(
Ammospiza Caudacuta
). The periphery of the tidal marsh provides an ideal habitat for the song sparrow. It has heavy streaking on the breast and side.
The sharp-tailed sparrow can be found among the Spartian grasses and mosquito ditches. It is rather shy and usually allows no more than a quick glimpse of itself.
It generally nests in higher portions of the marsh where salt marsh hay and spike grass predominate and tidal flooding does not frequently occur.
Great Blue Heron
(
Ardea herodias
). Its color is more steel-grey than blue, with a buff neck and streaked throat. A black crown patch on the predominantly white head of the adult usually bears a few ornate plumes.
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This bird is often seen by the grassy edges of the tidal creek or wading in the shallows waiting for a stray fish.
Northern Harrier
(
Circus Cyaneus
). These are agile birds with long wings “V” shape and the bird frequently rocks from side to side as it glides over the marsh. Relying on sound as well as sight, they pounce on unsuspecting prey from just a few feet.
Herring Gull
(
Larus Argentatus
). In adult plumage this species sports a grey mantle (back and wings) with black wing tips. The heavy yellow bill is marked with a red spot on the lower mandible.
Red-winged Blackbird
(
Agelaius phoeniceus
). This bird is black with orange-red shoulder patches (epaulets) bordered by yellow or buff. Males rely not only on their song to proclaim territory, but depend on visual effects as well. The classic rediving stance is to perch at the edge of its territory while singing, thrusting out its shoulders to expose the bright epaulets.
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Invertebrates of the Salt Marsh
Listed below and briefly described are some of the invertebrates that will be identified and discussed (Figure 5).
Mud Snail
(
Nassarius obsoletus
). On the tidal mud flats of the estuaries bordering the marshes and in muddy tidal creeks and mosquito ditches the mud snail is often very abundant. This snail has a conical shell of dark gray or brown or black, and is often covered with a slippery layer of algal growth and debris. Mud snails leave groove-like trails behind them as they travel through the mud, and wave their siphons back and forth as they search for their odors.
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Rough Periwinkle
(
Littorina Saxatiks
). This snail is most frequently found in the saltwater cordgrass of the low marsh. It carries its eggs in a brood pouch until the young are fully formed and able to meet the demanding conditions of marsh life.
Salt Marsh Snail
(
Melampus bidentatus
). This is one of the most abundant and interesting high marsh animals. The shells of the young are always shiny and vary in color from light to dark brown. There are from one to six transverse bands. The shell is ovoid, with a short conical spire.
Its usual habitat is the saltmeadow grass or spikegrass of the high marsh, between the mean high water level of neap tides and the mean high water level of spring tides. Adult snails are not aquatic since they possess an air sac and must breathe air in order to survive. Therefore, they cannot be submerged for long periods of time.
Ribbed Mussel
(
Modiolus demissus
). This gets its name from the many radiating ribs on the shell and is abundant in the mud of the low marsh and along the banks of mosquito ditches. Several mussels are usually found clumped together, attached to each other with byssal threads which are secreted by the foot. The shell of this bivalve is dark blue or greenish-blue in color. It can only feed when submerged and therefore is found only in areas which are covered by water for part of each day.
Blue Crab
(
Callinectes sapidus
). The blue crab is found only in the tidal creeks and mosquioto ditches except during periods of high tides when it invades the area of the high marsh which are submerged. They are active and pugnacious predators. Their diet includes small living bivalves and crabs, live plants, and dead animal material.
Green Crab
(
Carcinus maenas
). It is often found in the tall saltwater cordgrass areas of the low marsh. It is even more common in the tide pools or hidden in the seaweed of the intertidal areas along rocky shores.
It is chiefly a scavenger and feeds on any dead animal material.
Fiddler Crabs
(
Uca pugnax
). This crab is very abundant on Connecticut tidal marshes. The truly distinguishing feature of these crabs is the very large first claw of the male. The claw is used during breeding season to attract the female to threaten and fight other males.
These fiddler crabs generally dig their burrows in the mud of the tall saltwater cordgrass areas of the low marsh and along the mosquito ditches, but they will also excavate burrows among any other type of marsh vegetation where soft mud occurs. The crabs remain inactive in these burrows during periods of high tides but emerge to feed at low tides. They are most active during the night or during the early morning hours. This activity pattern affords them some protection from predators and from the higher daytime temperature which they cannot tolerate.
Spiders
. All spiders feed on living prey. On the tidal marshes they are probably the chief predators on small invertebrates. In turn, they are eaten by birds, some kinds of insects, and by other spiders.
Vertebrates of the Salt Marsh
The vertebrates are the major predators on the smaller animals and form an important part of the marsh food chain. These are the American eel, the common mummichog, and the diamond-back terrapin(Figure 6).
American Eel
(
Anguilla rostrata
). The small eels found in the upper reaches of tidal creeks and in the mosquito ditches of Connecticut salt marshes are immature American eels. Although a few immature eels can be found in intertidal salt waters, the majority work their way up the brackish tidal creeks and mosquito ditches and on to fresh water streams and ponds.
Common Mummichog
(
Fundulus heteroclitus
). The mummichog is abundant in the tidal creeks and mosquito ditches of Connecticut salt marshes. They prefer brackish water, but appear to tolerate both the high salinities and low oxygen levels found in shallow tidal pools left behind by outgoing tides.
Northern Diamond-Back Terrapin (Malaclemys terrapin terrapin)
. It is a relatively small turtle. It can apparently tolerate waters of varying salinities and is often found quite far up rivers.
Protection of Marsh Land
Tidal marshes are valuable to us as an indirect source of food as a stabilizing protection to our eroding shoreline, as open space enjoyed by millions of boating, fishing, hunting and birding enthusiasts and as an important part of our aesthetic heritage.
Within the last half century Connecticut’s tidal marshes have been disappearing at an average rate of about one percent per year. This rate of attrition gives every indication of accelerating in the face of increasing population pressure. If this destruction continues we can look forward to their total loss early in the next century. Once a piece of tidal marsh has been destroyed, it is gone forever. It cannot be restored. An effective conservation program is needed to prevent or reduce further loss.
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Immediate steps need to be taken to get as much of the land as possible into the hands of suitable organizations and agencies. The State Board of Fisheries and Game, a nature preservation and governmental agency, owns the largest acreage of tidal marshes in Connecticut.
Private land owners can be alerted to the problem and appealed to to cooperate in various ways in a conservation program. Action must be taken to protect acreage in public ownership. This includes state land and land to be acquired for park purposes. Marshes adjacent to the beaches must be preserved. Parking areas must be located on the higher ground.
Town-owned land must also be given attention. All too frequently dumps, sewage disposal works and other encroachments are permitted by aldermen who do not understand the vital importance of tidal marshes. A small dump may exert far-reaching effects upon adjacent marshland.
Action should be taken to control the dredging and filling of the marshes. The dredging of privately-owned marshes for small marinas will continue to be a most difficult problem as the pressure for increased boating facilities continues to grow. This problem might be solved by conservation agencies acquiring these private wetlands.
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Tidal marshes should be zoned against real estate development. It is in the public interest to keep housing and factories out of low-lying areas that are subject to periodic flooding by hurricane tides.
It should be evident that our salt marshes are one of our most valuable resources and should be preserved wherever possible.