The oceans are becoming increasingly dark. These are the disturbing results of a study published on Global Change Biologywhich thanks to a combination of satellite data and IT models shows how a fifth of the entire ocean surface has “darkened” in the last twenty years, with consequences on ecosystems which are still difficult to understand.
But what does it mean that “oceans are darker”?
The problem of the Fotica area. The oceans are rich in life, the 90% of which, however, is concentrated in a very restricted band of the water column. It is the so -called Fotic area, the one in which the light of the sun manages to arrive and therefore to feed the Photoplankton photosynthesisand consequently feed the entire ecosystem. On average, the Fotica area reaches about 200 meters deep, after which The sunlight no longer penetrates and the environment changes radically.
Well, the study of the University of Plymouth shows that we have a depth problem. Originally, the research was born to study the impact of night artificial lights on coastal ecosystems. Two decades of observations, however, has shifted attention to natural light, and on the fact that In the last twenty years it no longer comes in depth as it once was.
Why are the oceans darken? The figures are frightening: 21% of all oceans have seen a reduction in the depth of the Fotica area. In 9% of cases, This reduction is 50 metersWhile In 2.6% of cases it reaches and exceeds 100 meters: in practice, The space available for life forms that depend on the sunlight has halved.
But why are the oceans get darker? It is the result of a combination of factors, the most important of which, according to the authors, is the change in planktonic communities; But we humans also contributed directly, entering large quantities of sediments in the waters of the oceans and stirring them. Not to mention the fact that the surface temperatures of the oceans themselves are raising, and the light penetrates worse where it is hottest.
