Oceans are turning green with climate change (and that’s not good news)

The waters of the oceans are not always the same. They may seem calmer, more moved, more transparent or turbid, but they can also change colour, because their composition changes, in particular the plankton communities change. So much so that if you look back you could see how, over the last twenty years, the surface waters of the oceans have become progressively greener. And, needless to say, climate change would be to blame.

In fact, so says a group of researchers scattered between the United Kingdom and the United States who have analyzed just how the nuances of the oceans have changed over the years. In reality, as they explain from the pages of Nature, they have not directly studied this. More precisely, they used the Modis instrument of the Aqua satellite, a spectroradiometer which, by analyzing visible and infrared radiation, provides information on vegetation or snow cover. It can also see fires or detect traces of chlorophyll in the oceans, NASA said. Thus, thanks to Modis – and in particular to the reflectance data – the researchers have collected information attributable to changes in surface ocean ecosystems, and therefore also in plankton, over the course of twenty years. In fact, the Aqua satellite has been orbiting in space for more than twenty years. In this way it was possible to observe changes in reflectance over time in more than half of the ocean waters, especially near the equator. Thanks to a simulation, the researchers therefore calculated those that would have occurred as a result of climate change, observing a correspondence with the experimental data, both for areas and for quantity.

Overall, the data collected show that ocean waters at low latitudes are becoming greener. However, the reason has to do with phytoplankton (at least not directly) and is not very clear: perhaps debris particles or zooplantcon are increasing, the authors write, or perhaps the amount of light entering the oceans is changing. What is certain is that there is a change: the light conditions in the surface waters are changing and this will necessarily have, or has already had, changes also on the phytoplankton, which feed on light (in fact, they are photosynthesizing organisms). And all this consequently will have repercussions on the trophic chain, on the water’s ability to store carbon, and cannot, the authors conclude, be ignored when it comes to conservation.