Climate change threat to bottom of marine food chain: New Zealand study

Tiny plants that are critical to the marine ecosystem are prone to extinction during major climatic changes, according to a New Zealand study of marine plants around Antarctica out Tuesday.

Researchers at the government's Institute of Geological and Nuclear Sciences (GNS Science) and Victoria University studied phytoplankton fossil records from ocean sediments around Antarctica that date back 15 million years.

The single-celled plants formed the base of the marine food web, were a crucial element of the cycle of carbon dioxide, and account for about 50 percent of the total biological productivity on Earth, said the scientists.

"Over the past 15 million years phytoplankton in the Southern Ocean have experienced five major pulses of extinction that are linked with particularly big and sharp temperature swings from warm to cold," said GNS Science and Victoria University paleontologist Professor James Crampton.

"Climate does naturally vary a lot and there are swings in temperature over time, and phytoplankton communities can tolerate this general variability. But we found that past a certain threshold of environmental change phytoplankton are vulnerable, some species become extinct and others have to evolve."

The researchers figured out accurate times of origination and extinction of the species, and resolved what happened in a much finer timescale than was possible previously.

"These phytoplankton communities appear to be sensitive to major changes in the climate system and we suspect that a similar response may occur during intervals of relatively rapid warming," said Crampton.

"In the future we plan to look at the flow-on effects further up the marine ecosystem and food web, and if other species that depend on the phytoplankton to survive become vulnerable as well." Endit