Hello, ladies and gentlemen. I'm the "Environmental Bank" with all the worldwide environmental issues. Today, weโll take a closer look at the topic "Is the ocean getting darker?"
What is the issue?
A new study found that over the last 20 years, more than 21% of the global ocean has become darker. This change reduced the depth of the photic zones, where 90% of marine life resides and where sunlight and moonlight drive ecological interactions.
The decrease in light in the photic zones might also further affect the humans who depend on the ocean.
How was the study conducted?
To track changes in light levels, the researchers used NASAโs Ocean Colour Web satellite data, which divides the ocean into 9 km-wide pixels for detailed analysis. An algorithm was then combined with satellite, solar, and lunar models to estimate the depth of the photic zone in each pixel.
Then, is the Ocean Really Getting Darker?
In many regions around the globe, the depth of sunlight penetration in seawater is indeed decreasing. In some areas, the photic zone has shrunk by more than 100 metres.
- From 2003 to 2022, over 75 million square kilometres, or 21% of the global ocean, experienced reduced light penetration.
- 9% of the ocean lost more than 50 metres of photic depth.
- 2.6% lost over 100 metres.
However, not all areas darkened. During the same period, about 10% of the ocean, or 37 million square kilometres, actually became lighter.
This variation reflects the complexity of ocean systems and the many factors that affect water clarity, according to the study's authors.
Why Is the Ocean Getting Darker?
The causes vary by region.
- In coastal areas, runoff of sediments and nutrients from agriculture, as well as increased rainfall due to climate change, are likely culprits. These pollutants stimulate plankton blooms that reduce water clarity.
- In the open ocean, darkening is thought to be related to shifts in plankton populations caused by changes in sea surface temperature and nutrient levels.
Where Is Ocean Darkening Most Severe?
Some of the most significant changes were observed in:
- The Arctic and Antarctic regions
- Areas influenced by the Gulf Stream
- Enclosed seas like the Baltic, where river runoff brings in sediments and nutrients, further reducing light penetration
What Does This Mean for Marine Life?
As the photic zone shrinks, animals may be forced closer to the surface, where competition for resources increases. Moreover, entire ecosystems could be reshaped as a result.
Wrap-up
Since the causes of photic zone reduction attribute to the climate change, we can clearly see the impact of climate change on our environment, including the ocean. It is time for us to take an action to prevent the further increases in global temperature.
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