From: Forschungsverbund Berlin e.V. (FVB)
Published October 4, 2017 08:39 AM

In Times of Climate Change: What a Lake's Colour Can Tell About Its Condition

With the help of satellite observations from 188 lakes worldwide, scientists at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) have shown that the warming of large lakes amplifies their colour. Lakes which are green due to their high phytoplankton content tend to become greener in warm years as phytoplankton content increases. Clear, blue lakes with little phytoplankton, on the other hand, tend to become even bluer in warm years caused by declines in phytoplankton. Thus, contrary to previous assumptions, the warming of lakes tends to amplify their richness or poverty of phytoplankton.

Lake specialist Dr. Benjamin Kraemer and his team used freely accessible NASA satellite images to test for associations between temperature and phytoplankton content in 188 of the world's largest lakes from 2002 to 2016.

Based on experiments performed by others, the scientists expected that warming would decrease phytoplankton biomass in the world’s lakes. In contrast to their assumption, however, warm years were rather associated with higher phytoplankton biomass in most (68 per cent) of the lakes in their analysis. Kraemer explains that, “warming could increase phytoplankton content by expanding the growing season or by reducing the abundance of animals which feed on phytoplankton.”

Read more at Forschungsverbund Berlin e.V. (FVB)

Image: Satellite image showing a global Chlorophyll_a map that the team used for its analyses. Blue and green indicate a low phytoplankton biomass whereas red stands for a high phytoplankton biomass. (Credit: NASA's OceanColor Web)

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