The Diverse Creatures of the Deep May Be Starving
William J. Broad
The New York Times
June 1, 1999
Hordes of creatures living in the hidden depths of the deep sea are in danger of starving to death, scientists report. This remote part of the planet is believed to harbor millions of undiscovered species, an unknown number of which may be in crisis.
A study of food supply and demand miles down in the North Pacific between 1989 and 1996 found that creatures of the seabed suffered from growing food shortages. A likely culprit, scientists say, is a documented increase in sea surface temperatures during the same period.
"If the food deficit continues, it is going to change the configuration of the deep-sea communities," said Kenneth L. Smith Jr., a biologist at the Scripps Institution of Oceanography in San Diego and a co-author of the report, which was published recently in Science. "Some species will die out while those that can survive on a very low food supply will still be able to maintain themselves."
Little is known about the creatures of the darkness, much less about fluctuations in their diets and fortunes.
The sea's inky depths, which dwarf the planet's land masses in overall size, have been found to support fish, snails, worms, slugs, barnacles, corals, crabs, prawns, sponges, sea anemones, brittle stars, sea cucumbers, sea urchins, feather stars and sea lilies. Scientists estimate the diversity at up to 10 million species -- far more than the 1.4 million varieties of land dwellers that have been described and named.
Most animals of the deep rely on a food chain that begins in the sea's lighted realms, where sunlight is captured by the microscopic plants known as phytoplankton. The plants in turn nourish a riot of sea life. Leftovers from the feast, including dead plants and animals, as well as fecal droppings, produce a constant rain of organic matter that falls into the depths and feeds the bottom dwellers.
Dr. Smith and Ronald S. Kaufmann, a former Scripps post-doctoral researcher now at the University of San Diego, found that the rainfall of food in the North Pacific had declined over seven years.
About 135 miles off the central California coast, in a region more than two and a half miles deep, they measured the rain in sediment traps, cone-shaped devices that catch falling particles. The traps were suspended off the bottom at elevations of roughly 150 and 2,000 feet. Trapped particles were collected periodically over the seven-year study period and analyzed to determine organic carbon content.
The amount of sinking particulate matter (a measure of food supply) was compared to oxygen consumption by marine creatures in the seabed (a measure of food demand). The scientists reported that between 1989 and 1996 the ratio decreased by more than 50 percent.
"The findings of Smith and Kaufmann will have far-reaching implications," Ellen R. M. Druffel of the University of California at Irvine and Bruce H. Robison of the Monterey Bay Aquarium Research Institute, in Moss Landing, Calif., said of the research in a Science commentary. "We used to think of the deep sea as a highly stable, steady-state system."
Dr. Smith and Dr. Kaufmann said the decline in the food supply might be related to an increase in surface temperatures during the same period. The ocean warming, they said, may have prompted a decline in zooplankton -- tiny creatures that eat the tiny plants of the sea and in turn become food for a vast web of life. And their diminishment in turn may have cut the total amount of food that falls into the depths.
"A long-term reduction in surface productivity," Dr. Kaufmann said in a Scripps statement, "could severely impact the amount of food delivered to the deep ocean."
Copyright 1999 The New York Times Company