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 across the globe have experienced a notable decline in brightness over the last two decades, prompting alarm among researchers regarding the potential consequences for marine life. A study led by Professor Thomas Davies from the University of Plymouth, published in the journal Global Change Biology, highlights this growing concern for the health of marine ecosystems.
Utilizing satellite data from NASA’s Ocean Color Web data portal, the research reveals that 21% of the planet’s oceans have darkened between 2003 and 2022. This change poses a significant threat to the photic zones of the ocean, which are crucial for sustaining marine life.
The photic zone extends to about 200 meters deep and is vital for many marine organisms, as it is where sufficient light penetrates to support photobiological processes. This zone is essential for the global nutrients and carbon budgets that underpin the world’s fisheries.
Marine species that inhabit these upper layers of the ocean depend on both sunlight and moonlight for various critical activities, including hunting, mating, and reproduction. As the oceans darken, creatures that rely on light may be forced to migrate closer to the surface, potentially leading to overcrowding in these vital habitats.
Professor Davies employed satellite data alongside an algorithm to assess the attenuation of light in seawater, enabling him to measure the depth of photic zones worldwide. The findings indicate that in areas where the ocean has darkened, 9% of the photic zones have become shallower by 50 meters, while 3% have decreased in depth by 100 meters.
The reasons behind the darkening of oceans, particularly in offshore regions, remain somewhat unclear. However, the study suggests that global warming and shifts in ocean currents may play a role in this phenomenon.
Interestingly, despite the overall trend of darkening, approximately 10% of the oceans, equating to about 37 million square kilometers, have actually become lighter over the past 20 years. Coastal areas, in particular, have seen an increase in light levels. Nevertheless, this increase does not result in a net reduction in photic zone depth near shorelines.
Professor Davies warns that the implications of ocean darkening could be severe, potentially disrupting marine food webs, impacting global fisheries, and affecting the carbon and nutrient budgets that are critical for ocean health.
These findings underscore the urgent need for further research and monitoring of oceanic changes to better understand their impact on marine ecosystems and to develop strategies for mitigating these effects, according to Fox News.