Zooplankton's small but mighty impact

Zooplankton are the smallest animals in the sea and a vital link in marine life, yet scientists know next to nothing about them.

A deep-sea trawl by scientists has come up with hundreds of species of zooplankton - from tiny shrimp-like creatures and swimming worms to flying snails and pulsing jellyfish.

In the Sargasso Sea of the North Atlantic they catalogued about 500 species of zooplankton living at depths of between 800m to 4.5km.

Their investigation was designed to capture some of the most important, but overlooked, creatures of the oceans that play a vital role in both the food chain and the carbon cycle.

"We're trying to really make a census of what actually lives in the ocean," said Dr Peter Wiebe, a senior scientist at the Woods Hole Oceanographic Institution in Massachusetts.

"To say anything about how climate change affects the ocean we really need to know who is living there."

The research is part of the international Census of Marine Life and was designed to explore the little-known area of the Atlantic between the southeast American coast and the mid-Atlantic ridge, which runs like a spine along the ocean floor.

"Among the 1000 individual organisms identified at sea, our team of 28 found what appear to be several undescribed species that may be new to science," Wiebe said.

"With the zooplankton chart, we can assess what changes - manmade and natural - are taking place in the largest habitat on the planet."

Many zooplankton feed on the plant plankton that absorb carbon dioxide from the sea surface where it has dissolved from the atmosphere.

Through the zooplankton, much of this carbon gets deposited deep in the ocean where it can remain for many thousands of years - acting as an important "sink" for atmospheric carbon dioxide.

The zooplankton had to be gently trapped in fine-mesh nets before being brought to the surface, where organism DNA "barcodes" could be analysed.

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