Oceans worldwide have darkened significantly over the past two decades, raising concerns about the impact on marine life and ecosystems, according to a new study.
Oceans around the globe have experienced a notable darkening over the last two decades, prompting serious concerns from researchers regarding the health of 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 based on satellite data.
Data from NASA’s Ocean Color Web indicates that 21% of the planet’s oceans have darkened between 2003 and 2022. This change poses a significant threat to marine life, particularly those species that inhabit the photic zones of the ocean. These zones, which extend to depths of approximately 200 meters, are crucial for photobiological processes that sustain marine ecosystems.
The photic zone is vital for the health of global fish markets, as it is where light penetrates the water, allowing for the existence of various marine organisms. Many ocean inhabitants depend on both moonlight and sunlight for essential activities such as hunting, mating, and reproduction.
As the oceans darken, researchers predict that creatures reliant on light may begin to migrate closer to the surface. This shift could lead to overcrowding in these upper layers of the ocean, potentially disrupting the delicate balance of marine life.
Using satellite data and an algorithm to assess light attenuation in seawater, Davies was able to determine the depth of photic zones worldwide. The study revealed that in areas where the oceans have darkened, 9% of photic zones have become shallower by 50 meters, 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 alterations in ocean currents could be contributing factors.
Interestingly, despite the overall trend of darkening, approximately 10% of the oceans, equating to about 37 million square kilometers, have become lighter over the past two decades. Coastal regions, in particular, have seen an increase in light levels. Nevertheless, this increase does not lead to a net reduction in photic zone depth along shorelines.
Davies warns that the implications of ocean darkening could be severe, affecting marine food webs, global fisheries, and the carbon and nutrient budgets that are essential for maintaining ecological balance.
As researchers continue to study these changes, the potential consequences for marine life and ecosystems worldwide remain a pressing concern.
Source: Original article