Weather | Sports | Forums | Comics | Classifieds | Calendar | Movies
Zoning in on coastal marine biology.
By MIKE SCARANTINO
© St. Petersburg Times, published January 4, 2003
Life in the littoral zone is hardship at best.
That intense little crease of land and space between the high and low tides is in a constant state of flux.
The natural struggle to survive is real in every way. From the highest high tide to the lowest low, all manner of life finds difficulty. It is among the cradles of the marine world. There can be no wonder that it's a tough place.
Think of a child during its infancy. Everything it learns is by challenge.
Now think how difficult life would be if that child was left to fend for itself. Evolution, with time, would equip it with the means to progress. Yet during that initial time frame, life is extreme. The littoral zone is the birthplace of numerous species of flora and fauna. From primal organisms to highly predatory creatures, even the stones and sediments play crucial roles in evolution.
In the cramped space from the shoreline out to 200 meters, the constant change that occurs so often creates hardships. There are three delineations that exist in the littoral area:
The supra-littoral or spray zone seldom is under water. Typically, this area is hit by the highest tides, making life of any kind a difficult process.
Organisms must be highly adaptive. Change comes in the form of altered salinity and water levels and temperature. Not much vegetation grows due to the conditions.
The intertidal zone partially is covered by water from wave action.
Many poorly-adapted creatures are dislodged or carried away. Some, such as clams, burrow into the sand to hold themselves in place. Others -- mussels and barnacles -- attach to rocks. The sublittoral zone mostly is covered by water. Only when extreme low tides occur do the residents need to adapt to the lack of water.
On top of these rough circumstances, there is the constant threat of predation.
When tides are high, predation comes in the form of fish and other marine species. Wading birds will feed as the tide begins to recede.
When the tide is out, threats come from other animals and, of course, man. Raccoons feed voraciously on shellfish during low tide. Birds will feed from small pools left from the dropping tide.
These pools often trap small fish, crabs and other minute organisms, making the water an opportune place to find a fast meal.
As the tides move, there are vertical dynamics involved in the littoral zone.
The supra-littoral also is known as the upper littoral, the splash and the barnacle belt. It is dry most of the time. Organisms other than barnacles that thrive include isopods, lichens, lice, limpets, periwinkles and whelks.
Next is the high-tide area, also referred to as the upper mid-littoral and the high intertidal zone. It gets flooded only by the high tides. It's perfectly suited for anemones, barnacles, brittle stars, chitons, crabs, green algae, isopods, limpets, mussels, sea stars, snails, whelks and some marine vegetation.
The middle tide zone, also known as the lower mid-littoral, is covered and uncovered twice a day by the high tide. The area is home to anemones, barnacles, chitons, crabs, green algae, isopods, limpets, mussels, sea lettuce, sea palms, sea stars, snails, sponges, and whelks.
The low tide zone or lower littoral is uncovered by only the lowest tides. Its resident organisms do not adapt well to long, harsh periods of dryness or extreme heat. The area has the largest diversity among its residents.
Some of the species that exist in this zone -- including many previously mentioned -- are abalone, anemones, sea cucumbers, urchins, shrimp snails, surf grass and tube worms. They co-exist with many fish.
Understanding these definitions and dynamics can lead to a higher degree of enjoyment of the natural resources. There is a delicate balance that must remain intact for these cradles of the sea to prosper.
Once they become unbalanced, there can be only degradation of the marine environment and an altering to the pool of species.
If you have a question or comment, call Capt. Mike Scarantino, (352) 683-4868.