Linda F. Malanson
(figure available in print form)
North and south of the tropics, saltwater swamps give way to tidal marshes. These wetlands form a grassy fringe near river mouths, in bays, and along coastlines protected from the open ocean. They are dominated by grasses and are alternately flooded and exposed by the movement of the tides. Tidal creeks carrying fish and tiny plants crisscross them.
Of the ecosystems available for human use, tidewater basins are among the richest in plant and animal life. The grasses provide food and shelter for shellfish, fish, amphibians, and other animals. Wading birds and other animals feed on the vegetation and abundant insects. Tidal salt marshes make ideal nurseries for the young of many animals that live in the ocean as adults.
ACTIVITY
For children living near the sea coast, a small marine aquarium may be the best capstone to a trip to a beach or tidal flats. In the interest of conservation, no more than one or two small specimens of the common species, such as clams, hermit crabs, sea anemones, starfish, scallops, and some salt-water fish, should be collected to stock the aquarium.
The salt-water tank should be clean, leak-free, and located in a cool place. Cover the bottom with sea sand and a few barnacled rocks. Water may be brought from the ocean or be synthetic brine. Sea salts in cloth bags (available from scientific supply houses) should be dissolved according to directions. Avoid contact between brine and brass, copper or zinc.
Tidepool animals will not survive overnight without an aerator. Common aerators for fresh-water tanks are suitable if more than one per tank (usually two) is used. Specimens will survive for a considerable period in a cool, aerated tank.
Even a superficial consideration of sea life will suggest comparisons with life in a pond—that is, communities within a community.
Life in a tidepool is very different from the plant and animal life on a sandy beach or life along a muddy shore or tidal estuary. The offshore shallow also represent a different community. Children should be led to see that transitions between saltwater communities are sharper than those between freshwater life zones.
Because of the rigorous conditions, animal forms, being more adaptable, predominate over plant forms in marine zones. Observation of this phenomenon can lead to discussion and research into the world’s population explosion and food problems. With respect to the latter problem, the sea is achieving great prominence as a source of protein. The production of fish protein is less costly because of the extensiveness of the sea and its countless beds of algae and animal plankton which need no cultivation or irrigation.