Scientists Concerned by the Drastic Change Noted in One-Fifth of the Oceans in the World Over the Past Two Decades
Oceans have undergone a lot of damage over the years for various reasons. A new study has detected a massive change in one-fifth of the oceans, which could hugely impact marine life, according to Phys.org. This study was published in the journal Global Change Biology.
The change in question is ocean darkening, which has been observed in waters spanning an area of around 75 million square km. This phenomenon typically alters the optical properties of the ocean. This, in turn, reduces the depth of photic zones in the ocean. Photic zones are essentially the regions of water bodies that allow the light needed by organisms for their life processes to pass through. These areas are vital as 90% of all marine life exists here, and they also serve as the site of ecological interactions facilitated by sunlight and moonlight.
Researchers claim that this change took place in the span of two decades, according to The Guardian. The team took into consideration satellite data as well as numerical modeling for the study. Experts noted that from 2003 to 2022, the band of water containing life dependent on sunlight and moonlight significantly reduced. This finding concerns many experts, like Dr. Thomas Davies, a marine conservationist at the University of Plymouth. Dr. Davies believes the far-reaching consequences of ocean darkening could impact not only marine ecosystems and global fisheries but also the quantity of critical carbon and nutrients provided by the oceans.
The upper band of water impacted by ocean darkening is where microscopic plant-like organisms called phytoplankton photosynthesize. These beings are a crucial part of almost all the marine food webs and are responsible for the production of half the oxygen present on the planet. Many marine beings, as well as other creatures, hunt, reproduce, and feed in the warmer waters of the photic zones, as food is most abundant in these sections. Hence, the disappearance of these areas will massively alter the life cycles of several beings.
In order to calculate the depths of photic zones worldwide, the team combined satellite data with an algorithm that could measure light in seawater, according to Oceanographic Magazine. The alterations in the photic zones were calculated using data gathered by NASA’s Ocean Color Web. This appliance breaks down the global ocean into several 9km pixels. Satellite data allowed scientists to observe the change that took place on the ocean surface on each of these pixels. Later, an algorithm was used to measure the amount of light in seawater, which indicated the depth of photic zones in each location.
The results indicated that 21% of the global ocean underwent darkening until 2022. This phenomenon caused photic zones to become 50 meters shallower in 9% of the oceans. The study notes that the zones turned 100 metres shallower in 2.6% of the ocean. The most prominent change in photic zone depth was observed in the open ocean at the top of the Gulf Stream and waters surrounding the Arctic and Antarctic. These areas are also known to be the most impacted due to climate change. Darkening was noted more in coastal regions and enclosed seas like the Baltic Sea.
As far as the cause is concerned, scientists are not exactly sure. The team speculates that agricultural runoff and increased rainfall could be contributing factors. However, they believe the widespread changes can be pinned to alterations in plankton communities. The study clarifies that it is not just ocean darkening that has occurred within the water bodies over the past two decades. The study showcased that around 10% of the ocean had also become lighter, meaning their capability of absorbing light increased.
Dr. Davies, in his statement, reiterated that it was important that these changes be further analyzed and, if possible, improved upon. “We also rely on the ocean and its photic zones for the air we breathe, the fish we eat, our ability to fight climate change, and for the general health and well-being of the planet. Taking all of that into account, our findings represent genuine cause for concern,” he said.