SYDNEY, July 26 (Xinhua) -- A global study involving Australian scientists has uncovered dramatic shifts at the base of the Antarctic food web, with experts warning of a fundamental reorganization of life in the region.
The 26-year investigation is the most comprehensive analysis to date of marine phytoplankton in the Southern Ocean, said a statement released Friday by the Australian Antarctic Program Partnership (AAPP) at the University of Tasmania.
The study documents a significant shift in the species of marine phytoplankton -- the microscopic single-celled algae that are the first link in the ocean food chain.
Scientists from Denmark, Australia, New Zealand, Spain and the United States, analyzing nearly 15,000 water samples from 1997 to 2023, found that energy-rich diatoms, the main food for krill, are declining and being replaced by smaller, less nutritious phytoplankton -- haptophytes and cryptophytes.
The implications of a shift from diatoms towards haptophytes and cryptophytes mean less food for krill. This threatens the Antarctic ecosystem reliant on krill as food for predators like penguins, seals, and baleen whales, according to the study published in the journal Nature Climate Change.
Plant-like phytoplankton absorb carbon dioxide through photosynthesis. Diatoms -- with dense silicon skeletons -- sink quickly and drag carbon into the deep ocean. Haptophytes and cryptophytes do not sequester carbon to the same extent.
Rising ocean temperatures, lowered iron levels, and changes in sea ice, especially the sharp sea ice loss since 2016, have driven a shift in phytoplankton communities, signaling a climate-related regime change, said the AAPP statement.
Researchers warn this shift may have broad impacts on Antarctic wildlife and global climate, as the new dominant phytoplankton sequester less carbon than diatoms, potentially increasing CO2 release into the atmosphere.
"Our research documents an ecological system change in the southern polar ocean caused by climate change, which could itself influence the climate through a feedback mechanism," said the study's co-author, sea-ice scientist Pat Wongpan with the AAPP in the island state of Tasmania. ■
