Filenews 24 May 2024
The oceans are huge, covering more than 70% of the Earth's surface. They play a critical role in regulating the planet's climate, supporting marine ecosystems and providing livelihoods for millions of people.
Recently, however, scientists have noticed that their color is changing, a phenomenon closely linked to climate change, as global temperatures rise.
Although this change in colour is not visible to the naked eye, satellite studies are able to map it, with the recent European State of the Climate Report, published in April 2024 by the European Union's Copernicus Climate Service, revealing just how big the change is taking place in the ocean. Understanding these changes is essential to understanding the wider implications for the environment and human life.
What color are the oceans?
The color of the ocean is mainly influenced by how sunlight interacts with water and what is in it. In the open ocean, water appears blue because it absorbs colors in the red part of the light spectrum and reflects and scatters blue light. However, the presence of other substances, such as phytoplankton, can change this color.
Phytoplankton, in turn, consists of microscopic marine algae that form the basis of the oceanic food web. They are vital to life on Earth, as they perform photosynthesis, like plants on land, and produce about half of the planet's oxygen. Phytoplankton contain chlorophyll, which they use to bind sunlight for photosynthesis. Chlorophyll absorbs blue and red wavelengths of light and reflects green, causing areas with high concentrations of phytoplankton to appear greenish.
Changing color
Recent research shows that climate change significantly affects the distribution and abundance of phytoplankton, thereby changing the color of the oceans. More specifically, experts found that chlorophyll – the photocellular pigment found in phytoplankton and plants that gives them their green hue – was 200-500% higher than average in the Norwegian Sea and Atlantic Ocean north of the UK in April 2023, while it was 60-80% lower in the ocean west of the Iberian Peninsula. In the Mediterranean Sea, forage levels were 50-100% higher than average in June 2023.
The main culprit of these changes is, according to scientists, rising ocean temperatures. The connection is simple: as global temperatures rise, so do ocean temperatures. Thus, warmer waters can lead to changes in phytoplankton populations. Some species thrive in warmer conditions, while others may decline, leading to changes in dominant phytoplankton types in different regions. These shifts can change the color of water, as different species have different concentrations of chlorophyll and reflect light differently.
In addition, increased levels of carbon dioxide (CO₂) in the atmosphere not only warm the planet but are also absorbed by the oceans, causing acidification. This change in pH can affect the growth and distribution of phytoplankton, further affecting the color of the oceans.
Effects of ocean color change
But changing the color of the oceans, while understandable, is more than just a visual phenomenon, as it has profound ecological and climate implications.
Phytoplankton is therefore the foundation of marine food webs. Changes in its populations can permeate the ecosystem, affecting fish, marine mammals, birds and ultimately us, as a shift in phytoplankton species can affect the entire food chain, potentially leading to a decline in commercially important fish species. In addition, phytoplankton plays a vital role in the carbon cycle by absorbing CO₂ during photosynthesis. Changes in their abundance and distribution can affect the ocean's ability to sequester carbon, affecting the regulation of global climate.
So although changes in the color of the ocean do not have a direct negative impact on ourselves, they can ultimately affect everything from climate patterns to the animal kingdom, changing the food chain with dramatic impact. Ultimately, this change is another stark example that reminds us how connected everything in nature is and how fragile its balance is. If that doesn't call us to action, then what?
