Certain types of plankton have adapted themselves to living in water with low oxygen content, so they can hide away from fish when digesting [through anaerobic glycolysis] and meanwhile suppressing their metabolism. Only at night, when in search for food, the plankton moves to the surface to re-enter oxygen-richer waters, having to accept the risk of a deadly encounter.

Climate hypoxia

We recently reported on the increase of hypoxic and anoxic zones in the world’s oceans, as a contributing factor to marine biodiversity decline. These are waters that lack sufficient oxygen to support complex marine life, like fish. Although – especially in the deep seas – such zones are a natural phenomenon, the total volume of oxygen-deprived water is likely on the increase due to climate change, as oceans get warmer and warm water can (chemically) contain less oxygen.

Shallow feeding zone

This especially means the boundary between oxygen-rich water and hypoxic water will move upwards – meaning the first zone may become shallower.

In some places it may become so shallow, the plankton would be cramped together while fish could frenzy on them. This may lead to a disturbed food chain equilibrium and collapsing populations, warned University of Rhode Island doctoral student Leanne Elder yesterday, during her research presentation at the annual conference of the Society for Experimental Biology in Glasgow, Scotland.

© Rolf Schuttenhelm | www.bitsofscience.org