Oceans worldwide have darkened significantly over the past two decades, raising concerns about the impact on marine life and ecosystems, according to a recent study.
Oceans around the globe have become darker over the last two decades, prompting researchers to express growing concern for marine ecosystems. A study led by Professor Thomas Davies from the University of Plymouth, published in the journal Global Change Biology, highlights the alarming trend observed in satellite data.
According to data from NASA’s Ocean Color Web, 21% of the planet’s oceans have darkened between 2003 and 2022. This change poses a significant threat to marine life, particularly in the photic zones of the ocean, where light penetrates sufficiently to support vital photobiological processes.
The photic zone extends to depths of about 200 meters and is crucial for sustaining global nutrients and carbon budgets that underpin the world’s fisheries. Marine organisms that inhabit this zone depend on both sunlight and moonlight for essential activities such as hunting, mating, and reproduction.
As the oceans darken, species that rely on light may be forced to migrate closer to the surface, potentially leading to overcrowding in these vital habitats. The upper layers of the ocean are home to microscopic organisms and various types of plankton, which are foundational to the marine food web.
Using satellite data and an algorithm to measure light attenuation in seawater, Davies assessed the depth of photic zones globally. The findings revealed that in areas where the oceans have darkened, 9% of the photic zones have become 50 meters shallower, while 3% have decreased by 100 meters.
The reasons behind the darkening of oceans, particularly in offshore areas, remain unclear. However, the study suggests that global warming and changes in ocean currents may play a role in this phenomenon. Interestingly, despite the overall trend of darkening, approximately 10% of the oceans, covering around 37 million square kilometers, have actually become lighter over the past two decades.
Coastal areas, in particular, have experienced an increase in light; however, this does not equate to a net reduction in the depth of photic zones near shorelines. Davies warns that the implications of ocean darkening could be severe, affecting marine food webs, global fisheries, and the balance of carbon and nutrient budgets.
These findings underscore the urgent need for further research and monitoring to understand the full impact of changing ocean conditions on marine life and ecosystems, according to Fox News.