Global oceans are darkening, disrupting life beneath the surface: Study

Study by Plymouth researchers shows 21 per cent of the ocean has dimmed in two decades, endangering life dependent on natural light.

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(Indian Express) Climate change is not only causing irreversible damage to the green cover, they are equally impacting marine life.

A new study seems to suggest that more than one-fifth of the global ocean has considerably darkened in the last two decades. This alarming state of the oceans has been brought to light by the study, Darkening of the Global Ocean, conducted by researchers from University of Plymouth.

The study by Dr Thomas Davies, Professor Tim Smyth, and team, suggest that ocean darkening at this scale is not only the latest ecological crisis, but one that comes with grave implications for marine life and overall planetary health.

Darkening of the ocean is essentially shrinking of the photic zones or those layers of water where sunlight can pass and induce the process of photosynthesis which is key to all biological processes. The photic layers can go down to about 200 meters and they also act as a base for nearly 90 per cent of the world’s marine life. This layer is responsible for increasing the productivity of the ocean which also involves regulating climate and even supporting global fisheries or related activities.

As part of the study, Davies and Smyth used satellite data along with sophisticated modelling techniques to analyse changes in how the oceans have absorbed light in the last two decades. The duo tracked the changes using the diffuse attenuation coefficient (Kd 490), a measure of how rapidly light fades as it passes through seawater.