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ENVIRONMENT: What Are Zooplankton? (And Why You Should Care)

Stephen Leahy

BROOKLIN, Canada, May 5 2006 (IPS) - Scientists probing the depths of the Sargasso Sea have discovered new species and learned more about the vital role of its smallest animals, zooplankton.

“We found a large number of species, including a number that may be new to science, at depths of one to five kilometres,” said Larry Madin, a senior scientist at the Woods Hole Oceanographic Institute, located on the U.S. northeast coast.

“Despite inhospitable conditions of permanent darkness, crushing pressure and 4 degree C temperatures, the deep oceans are not devoid of life,” Madin told IPS.

Using a specially designed capture net, the Census of Marine Life expedition spent three weeks sampling the southern Sargasso Sea in the Caribbean region near Bermuda. The expedition’s goal is to simply find out what lives in this largely unexplored region.

Little is known about life in seas below 1,000 metres, even though 75 percent of the volume of the world’s oceans lies in this realm, he said, adding that, “We need to understand the whole ocean ecosystem.”

The 20-day cruise, completed Apr. 30, is part of an ambitious global inventory of zooplankton by 2010, a Census of Marine Life initiative that sheds light on some important global ecosystem processes, including the ocean’s function as Earth’s largest carbon sink and the impact ocean acidification may have on life in the seas.

“By 2010, the research conducted by this project will provide a baseline against which future generations can measure changes to the zooplankton and their provinces, caused by pollution, over-fishing, climate change, and other shifting environmental conditions,” says Ann Bucklin, lead scientist and head of the University of Connecticut Marine Sciences Department.

Zooplankton species – tiny shrimp-like creatures, worms, snails and jellyfish – provide a fundamental link in the food chain between ocean plant life and predators from fish to whales.

By one rough estimate, 10,000 pounds of plant plankton is needed to feed 1,000 pounds of small zooplankton, which in turn support 100 pounds of larger zooplankton, which supports 10 pounds of small fish species (like herring or anchovies), which support 1 pound of a larger fish species, such as those harvested for human consumption.

Several bird and whale species depend directly on zooplankton; others rely on zooplankton-eating fish higher in the food chain.

Surprisingly, zooplankton also help moderate the global climate. They travel up and down the water column feeding on the plant plankton that absorbs carbon dioxide from the sea surface, where it has dissolved from the atmosphere. “In the deepest waters, zooplankton don’t move much, they just wait for food to drift down from above or eat each other,” Madin said.

Huge volumes of carbon end up being transported to the ocean depths thanks to zooplankton, where it remains for many thousands of years and thus helps regulate the amount of carbon dioxide in the atmosphere.

However, rising levels of carbon dioxide in the atmosphere from human emissions of fossil fuels are making the oceans more acidic, making it difficult for some species of zooplankton like snails to form shells, he said.

That in turn may affect how much atmospheric carbon dioxide ends up going to the bottom of the ocean.

During the expedition, a team of 28 experts from 14 nations eagerly examined thousands of fish and zooplankton brought up from the depths using traditional taxonomic tools and a new way of sequencing DNA onboard the ship.

Hundreds of species were found of the tiny shrimp-like animals, called copepods, that sustain commercial fish stocks, plus six species of ostracods – another shrimp relative – thought to be new to science. Special sampling brought up comb jellies, jellyfish, and their meters-long chain-forming relatives in good enough shape to be identified and DNA sequenced.

“Although there are many fewer creatures living two or three kilometres deep, we were surprised by the diversity of species we found,” said Madin.

Over 120 fish species were brought to the surface including a possible new species of black dragonfish, known as the great swallower, extremely large and in near perfect condition with its own light-producing organ, and several rare male anglerfishes.

“We are just starting to realise how little we know about species variety,” said Bucklin.

In sampling unique marine environments, the zooplankton census is enlarging human understanding of the pattern, flow, and development of life in the sea, she adds.

“This research is fundamental to our knowledge of the oceans and the basic processes sustaining life on Earth,” says Ron O’Dor, chief scientist for the Census of Marine Life (www.CoML.org), a 10-year, independent and unprecedented global scientific collaboration, started in 2000, to inventory biodiversity throughout the seas.

“In half a century, humans have transformed the ecosystems they are dependent upon for survival,” said Peter Neill, director of World Ocean Observatory, global clearinghouse of ocean information.

Celebrating and expressing concern for our oceans on Jun. 8, the 14th World Oceans Day, is just a first step said Neill said in a statement.

“Understanding the ocean’s impact on human survival must become a daily concern. The sea connects us all.”