In relation to the ocean, the Long Island Sound is rather young. Figures 3a and b give some idea of the possibility that a freshwater lake preceded the formation of the Sound. The glacier that covered this region left water, sand and gravel in the basin that had previously been formed by erosion from streams and rivers. The shores of the lake were formed by the two long ridges of sediment called moraines. These were formed at two different times. They intersect down in the Norwalk area and also up near Madison. The small islands off these areas are the remains of the moraines. The eastern side of the lake was bounded by another ridge in the area of Mattituck on the Long Island side running across to the Old Saybrook Moraine on the Connecticut side. This is now covered by the waters of the Sound. Most of our shore is covered with the glacial sediments. However, it is easy to see bedrock pushing up through the glacial debris.
figure available in print form.
About 8,000 years ago, the sea level began to rise as the glacier was melting. Salt water entered
the region left open when the Mattituck ridge was covered. Sand and sediment were free to enter; an estuary was formed with the mixing of the salt and fresh waters. The study of the bottom sediments of the oceans and other water bodies can reveal much about the earth’s history.
The Sound is a very dynamic body of water. There has been a steady, but minute, rise in the sea level for the past 8,000 years. According to scientific information, we have nearly reached a maximum for a midglacial period.
When the Sound became attached to the sea, it also developed increased wave activity and tidal currents. This shifted sands and outwash from the river sediment —called deltas—and formed beaches. This process is continually changing our shoreline.
Twice a day the Sound experiences high tides followed by low tides. These tides help to determine the character of the coast. Tides show the effect on the waters of the gravitational attraction between the sun and moon and between both bodies and the earth. It is apredictable rhythm. Ina similar way, the’position of the moon in relation to the earth informs us when the highest and lowest tides will occur. At both full moon and new moon the combined pull of the position of the sun and moon will be felt. These are called spring tides; they come twice a month. It is then that the greatest tidal rangesfrom very high to very low tides—take place. When the sun and moon are at right angles to each other the tides are not as high. These are called neap tides and occur twice a month. Some animals’ life and reproductive cycles depend on instinctively knowing when these events will occur.
Every 24 hours and 52 minutes, there are two high tides or flood tides followed by two low or ebb tides. There is a strange current phenomenon that occurs in the waters that enter and leave the eastern end called the Race. The ebb current flows to the east from Long Island Sound and west going from the bays off the Vineyard and Nantucket. Off Newport the two ebbing currents join and flow south. The opposite situation occurs during flood tide current as it flows west down the Sound. All seamen are well acquainted with the strong currents at the Race; if they use the proper navigational procedures, they can turn this situation to their advantage,
The salinity of the Sound varies from east to west.
expected, the salinity is higher in the eastern end, which is nearer the ocean. The salinity also varies vertically) as the lighter fresh water floats on top of the saltier water. This condition is typical of estuaries; plant and animal life must adjust to these everchanging conditions.
Long Island Sound and its shores contain several varied environments. They shall be considered separately. However, there is almost always a mingling of the features of the different areas. They all share the problems or stresses due to tides, currents, winds, waves, storms, salinity, temperature, pressure, erosion and the unnecessary factor—pollution. This last factor puts the greatest stress on any organism, as the plant or animal must adapt quickly or die. Eventually, no time is left for generations to adapt and live to maintain the species. Whole populations can be wiped out this way.
There are significant differences in the shorelines that are evident at high and low tides. There is a progression of plants and animals living and making their habitat in strips or belts, which are known as zones. Sometimes these zones are difficult to distinguish, but with careful observation they can be identified.
Rocky shore environments can easily be found along the Connecticut coast. Life found here must be able to adapt to drying, fresh rain water, cold and the power of waves. The animals have developed either threads to fasten themselves to rocks or astrong glue to’ hold their coverings in place, like mussels and barnacles. The plants present have evolved strong holdfasts and air bladders to keep them in place, like Eucus. Some animals have evolved devices for retaining the water within their soft tissues so that they don’t dry out. Periwinkles have a little operculum that can close, shutting bits of seaweed and salt water inside. Little sponges can be found at the bases of rocks; they are protected by the toughness of their outer covering. Limpets are well constructed for their life in the middle of the tidal zone. Each limpet has a powerful grasping foot, which gives it the very descriptive name of Chinaman’s Hat. Animals that look more like plants are firmly attached by their basal discs. They are exciting to watch feeding; they are found in water left by the ebbing tide—a tidal pool. Many hours of fascinating study are in store if you will observe some scraping from pilings or look into a tidal pool with a magnifying instrument. This is a difficult habitat to live in, but an exciting one to observe . We can learn how these organisms carry on their life functions and how they help one another to survive.
It takes about two thousand years to build up a salt marsh through the steady deposit of mud and sediment brought in by the tides. Marshes are formed by the growth of certain grasses and changes in sea levels. When the first settlers came to the New England coast, they harvested marsh grass. (This plant is commonly called salt hay; biologists call it Spartina patens.) Plants and animals have evolved delicate mechanisms to control the salinity of their habitat; these make interesting study material. Too many people think of a tide marsh as a wasteland; but in truth, these marshes have a definite role in the balance of nature. Marshes are the nursery for life. In these shallow and protected waters food and game fish spend much of their lives. There are great numbers of animals living in close association with the plants. It is a beautiful and highly productive ecosystem that must be preserved. There is a great deal of literature available to inspire people to help protect this vital land.
At first glance, a sandy beach may seem barren of animal life. The gulls and terns seem to own the beach. A gleam from the scales of a minnow might be the target for a swooping tern. The beach grass is what holds it all together. This grass is the first to grow, making the land more stable for other plants. Animals here have adapted by acquiring digging techniques. The Mole crab is a master of this. It can be found running down a slope of receding water, moving its sievelike antennae to catch plankton, the tiny plant and animal forms in the water. Color adaptation is necessary for these animals to hide from their predators by blending into the sand. At the tide line live the burrowers—the clams, the crabs and the sand dollars. One of the greatest enemies of these animals is the tremendous heat generated by pollutants and industrial waste.
A fourth kind of habitat is the benthos or sea bottom. Some animal specimens are adapted to lie on the sea floor. The flounder has adapted by lying on its side; the former bottomside eye has moved to the upper side of its head. New Haven Harbor is quite heavily populated with benthic animals because its shallow bottom ensures the availability of oxygen and food. Many of these animals live on dead material or detritus. Detritvores, as these animals are called, are a great link in the food chain; they recycle the temporarily “dead” energy of detritus, making it available to other organisms.
Some of the benthic animals burrow into the sediment. Surface dwellers are called epifauna; infauna is the name given to the animals that live in the sea sediment. The most numerous of the infauna are the twoshelled mollusks or bivalvesthe clams and oysters. Most of the infauna feed by filtering the sediment; they often ingest pollutants and turn poisonous. This is killing the local oyster industry.
There is another group of benthic organisms that can carry on life without oxygen. These are bacteria that help break up organic matter for reuse.
The last habitat to consider is the constantly moving water, where freely swimming organisms of fairly good size can be found. The minute organisms—both plants and animals—collectively called plankton, swim or float in this area that is not far from the sun’s rays. It is the phytoplankton—tiny plant plankton—which convert chemicals with the aid of sunlight into the important first food in a long food chain. The fish you eat is ultimately dependent upon animals that have eaten this food. The stresses that disturb or destroy this environment and all its inhabitants are all of human origin. A few of these are sewage, oil, and the excess heat generated and pumped into the water by the electric companies.
These are the ocean habitats that we can find around Connecticut. Some of these ecosystems can be simulated in the classroom. If field trips are impossible either for classes or for individual students, slide presentations or movies can be effective substitutes. Your students will then be able to see what they are reading about.
With a little instruction, both a tide pool and parts of a marsh can be set up for a real “hands on” approach. The marine aquarium can be simply a gallon jar containing small plant and animal organisms. (A word of caution: Never have any seaweed but the green lettuce of the sea, the Ulva, because other seaweed can produce substances that are antibiotic. Ulva is the best oxygenator.)
The following information might be helpful in setting up an aquarium. The aquarium must not be made of metal or have any metal introduced into it. Leftover bits of food should be removed. The water should be kept as cool as possible, between 15° and 25°C. Try to keep the temperature as near to the collection site of the animal as is possible. When the water level in the tank goes down, add only distilled water to the original level. Also, keep the tank well aerated by using an underground filter. Check the pH and specific gravity daily. Don’t place the
tank in direct sunlight. And last, don’t overcrowd the tank.
Classroom aquaria can help students to see and to appreciate the ecology of these organisms. Watching the behavior of a specific organism is really rewarding. Controlled experiments in pollutants can be recorded and analyzed. Questions can be asked. The kind of aquarium you set up is limited only by your sophistication and budget. There is plenty of material to help you get started; some of this is included in the bibliography.