Changes in marine dinoflagellate and diatom abundance under climate change

Hinder SL, Hays GC, Edwards M, Roberts EC, Walne AW, and Gravenor MB

Imagine looking at your garden one morning and finding that the grass had suddenly been replaced by bushes. Far fetched ? You might think so but changes of this magnitude have recently been reported in the biology of the North Atlantic with a dramatic switch in the prevalence of dinoflagellates and diatoms, two groups that include many of the microscopic planktonic plants that lie at the base of the food chain.

The findings, published in Nature Climate Change by a team of researchers from Swansea University and the Sir Alister Hardy Foundation for Ocean Science, show that this shift from dinoflagellates to diatoms is partly driven by increases in water temperature which are a well known part of global warming. But more unexpected was the discovery that the plankton shift is also strongly driven by an increase in the windiness in the North Atlantic region over the last 50 years. This increase in windiness is something that is often overlooked.

In the ocean, windiness promotes vertical mixing of the water, which in turn has profound impacts on surface nutrients levels and the vertical distribution of plankton. In general, windier conditions seem to favour diatoms over dinoflagellates. The new patterns show major shifts in the distribution of economically important species known to cause harmful effects through toxin poisoning. The wider implication of this discovery are not fully known, but the switch from dinoflagellates to diatoms is likely to have propagated up the food chain to impact much larger animals such as fish and whales.