Energy for life among the waves.

Energy for life among the waves

The thunderous crash of a large wavebreaking on an ocean beach is a vivid reminder of the sizable amount of energy that such a wave dissipates. Although marine plants and animals can't harness this energy directly, it now appears that wave energy probably contributes in a variety of ways toward enhancing the productivity and diversity of organisms that live on wave-beaten shores between low and high tide.

"The intertidal zones of rocky weathercoasts receive far more energy from the waves than from the sun,' say Egbert G. Leigh Jr. of the Smithsonian Tropical Research Institute in Balboa, Panama, Robert T. Paine of the University of Washington in Seattle, and their colleagues. This abundant wave energy allows marine organisms in places such as the coast of Washington state "to maintain exceptionally high productivity,' the researchers say. Their report appears in this month's PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

The researchers base their conclusionon a detailed study of the quantity and type of organisms, such as algae, sea palms and mussels, produced at several exposed and sheltered sites around Tatoosh Island, off Washington state. They discovered that two species of algae that grow only on wave-beaten shores are the most productive algae at Tatoosh. Beds of these algae often produce twice the dry weight of organic matter generated by an equal area of rain forest. Even more surprising was the finding that some intertidal mussel beds are as fruitful (also measured as dry weight) as any plant community on earth.

"Animals and plants shouldn't beequally productive,' says Paine. "This is a rather remarkable phenomenon that's not easily addressed without asking questions about the kinetic energy impinging on the shore.'

The researchers list several possiblereasons for the presence of lush, diverse plant and animal communities in turbulent water. They suggest that on exposed shores, the stirring action of breaking waves increases the capacity of resident algae to collect nutrients and use sunlight. Waves also protect intertidal inhabitants by knocking away their enemies or by preventing potential predators and grazers from feeding. Even devastating winter storms help by clearing away patches of old material to allow fresh, vigorous growth.

Wave energy, says Paine, "is an importantcontributor to the overall richness of this type of environment.' Similar effects can be seen along other wave-battered shores or on the margins of coral reefs where waves pound hardest.