The oceans are no plankton
The abundance of phytoplankton or plant plankton, the first element of the food chain in the oceans, decreased markedly over the last century, as confirmed by a comprehensive study by Dalhousie University in Halifax (Canada).
The study, published by the journal Nature, finds that the reduction was approximately 1% per year since 1900, albeit with a higher trend since 1950, likely as a result of climate change and higher surface temperatures of ocean waters, say the authors.
Threat to the marine food chain
The phytoplankton, consisting of microscopic organisms that live suspended in water, is the staple food of zooplankton both as large mammals (cetaceans), numerous seabirds and the most fish. “They are the fuel of the marine ecosystem. Their fall affects the entire food chain and humans, “write Daniel Boyce, Marlon Lewis and Boris Worm, the three principal authors of the research.
The trend is particularly strong in the tropics and in the most polar, especially in the Pacific, while the southern Indian surprising behaves in the opposite direction, “the study.
Data from 1899
The team from Dalhousie University has combined historical data since 1899 by research vessels and the latest supplied by satellites since 1979. The database totals more than half a million phytoplankton analysis.
Scientists have found a correlation between the reduction of phytoplankton and increased surface temperatures of the sea. The decline was accelerated from 1950 with a cumulative decline of 40% since then.
Small agencies
Phytoplankton is made especially by cyanobacteria, diatoms and other photosynthetic organisms. “Phytoplankton plays a crucial role in the ecosystem of the planet. Produces 50% of the oxygen we breathe, reduce carbon dioxide and is important for the fishing industry. A sea with less phytoplankton works differently, “continues Worm.
The increase in water temperature is correlated with lower growth of phytoplankton. Microscopic algae need light and food to grow, actually, but the more heat the water, the less the amount of food that manage to reach the surface. Phenomena such as El Niño also have a clear impact. Previous studies had also linked the decline of phytoplankton in polar regions to the weakening of the ozone layer and increased ultraviolet radiation.
Temperature and biodiversity
The surface temperature has a crucial influence on marine biodiversity, says another study published in the magazine. The team led by Derek Tittensor, also of Dalhousie University, examined the relationship between environmental parameters and distribution of 11,000 species belonging to 13 major groups (zooplankton, plants, invertebrates, fish, mammals …). The study suggests that “warming of the oceans could alter the distribution of life in its waters.”
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