Recent research indicates that warming ocean waters are causing notable changes in the colors of the sea, a phenomenon that may have significant implications for human activities.
A study published in the journal Science reveals that satellite data shows ocean waters are becoming greener at the poles and bluer towards the equator.
These changes are primarily due to alterations in the concentrations of chlorophyll, a green pigment produced by phytoplankton, according to Haipeng Zhao, the lead author of the study.
Phytoplankton are vital photosynthetic marine organisms that give waters their green hue due to the pigments they reflect.
Susan Lozier, a co-author of the paper and dean of the College of Sciences at the Georgia Institute of Technology, explained that when phytoplankton are absent, the water appears blue.
To arrive at their conclusions, researchers analyzed satellite data from open oceans collected by a NASA instrument from 2003 to 2022.
This instrument monitors light wavelengths every two days, providing insights into chlorophyll levels in various parts of the ocean.
The presence of chlorophyll is a key indicator of phytoplankton biomass, and the researchers found that chlorophyll concentrations have shifted significantly over time.
In particular, the subtropics are experiencing a decline in chlorophyll levels, while high-latitude regions are becoming greener.
The research team noted that green areas, especially in the northern hemisphere, are increasing in greenness while blue regions are becoming bluer.
The researchers adopted concepts from economics, such as the Lorenz curve and Gini index, to analyze changes in chlorophyll distribution.
Nicolas Cassar, from Duke University’s Nicholas School of the Environment, explained how these concepts were applied to assess whether the ocean’s chlorophyll distribution has evolved over time.
They also examined how various factors—like sea surface temperature, wind speed, light availability, and mixed layer depth—affected their findings.
The researchers found a correlation between warming seas and changing chlorophyll concentrations, but noted that other variables did not show significant associations.
Despite the compelling findings, the authors cautioned that the changes observed cannot be attributed solely to climate change, as the research period was not long enough to rule out recurring climate phenomena.
Lozier remarked on the relatively short history of satellite technology, which limits comprehensive long-term ocean observation.
Zhao shared that his insights into high-latitude oceans inspired him to explore whether similar color transformations were evident in other regions.
Lozier emphasized that as ocean temperatures continue to rise, understanding the biological consequences becomes increasingly crucial.
While previous studies have documented greening trends on land since the 1990s, capturing similar changes in the ocean remains challenging.
Satellite images provide surface data on chlorophyll production, but the overall picture remains incomplete, according to the researchers.
The implications of this trend are significant, as marine food webs could be disrupted.
Given that phytoplankton serve as the foundation of the marine food chain, their decline could affect fish populations.
The research highlighted the potential for a persistent decline in phytoplankton near the equator to result in a shift in the location of fisheries.
This could have dire consequences for low to middle-income nations, particularly in the Pacific Islands, which depend heavily on commercial fishing for food and economic stability.
image source from：abcnews
