See Earth’s toxic algae from SPACE: Phytoplankton blooms cover 12.1 MILLION square miles of ocean

Incredible satellite images show how toxic algal blooms are now growing in at least 12.1 million square miles (31.47 million square kilometers) of ocean, thanks to human activity.

A study by researchers at the Southern University of Science and Technology in China found that the total area affected by phytoplankton growth has increased by 13.2 percent since 2003.

When nutrients from fertilizers, sewage, air pollution and animal manure find their way into water sources, phytoplankton will feed on their nutrients and grow.

The researchers also found that rising sea temperatures have increased the frequency of algal blooms over the past two decades, as warmer water extends the length of the bloom season.

They wrote, “Many algal blooms are beneficial, sequester carbon at the base of the food chain and support fisheries and ecosystems worldwide. But proliferations of harmful algae, called harmful algal blooms, have become a major environmental problem worldwide.’

An algal bloom is a rapid increase in the algae population in a water system and can occur in both freshwater and marine water.

Blooms can cause discoloration of the water at the surface, turning it yellow, red or bright green, as seen in the new satellite images.

They are often the result of eutrophication – when bodies of water become enriched with nutrients such as phosphates and nitrates, which provide food for algae and other green plants, allowing them to grow.

The phytoplankton become harmful when they use up all the dissolved oxygen in the water, leading to the suffocation of fish and aquatic insects, which in turn become food sources themselves.

Some species of algae also produce biotoxins that can have serious consequences for wildlife, contributing to these ‘dead zones’ where aquatic life cannot survive.

For the study, published today in Naturescientists used 760,000 photos taken by NASA satellites from 2003 to 2020 to calculate the global ocean area covered by algae each year and the bloom frequency.

They then compared this data to sea surface temperatures (SSTs) and how much the temperature changes per meter, or the “spatial SST gradient.”

A large temperature difference between two adjacent areas in the ocean, or a large spatial SST gradient, may indicate poor water circulation.

This is because hotter water is less dense than colder water and reduces sinking in the natural ‘conveyor belt’ motion of the current.

As a result, nutrients become less evenly distributed throughout the water column and phytoplankton can grow in areas where they are highly concentrated, usually those closer to the surface.

Large temperature differences between adjacent parts of the ocean can also create turbulence and draw more nutrients from deeper waters to further encourage algal growth.

The maps showed that coastal phytoplankton blooms increased by 3.97 million square kilometers over the observed period.

In 2020, they covered 8.6 percent of the global ocean area.

The average annual number of flowers observed was also found to increase by 59.2 percent between 2003 and 2020 — the equivalent of 2.19 percent per year.

This increasing bloom frequency correlated significantly with ocean temperature, suggesting that “bloom-favorable seasons in these temperate seas are extended in warmer temperatures.”

Bloom frequency also increased with the spatial SST gradient in many areas, including California, the Gulf Steam and the Canary Current.

This suggests that the weak ocean currents caused by rising sea temperatures contribute to algae growth.

In China, Iran, Vietnam and the Philippines, the researchers also noted an increase in fertilizer use over the study period, which likely contributed to the uptick in phytoplankton.

The same can be said of the intensified aquaculture industry in Finland, China, Algeria, Guinea, Vietnam, Argentina, Russia and Uruguay.

The researchers hope their maps and data will help understand the mechanisms that drive and displace coastal phytoplankton blooms.

This can inform policymakers about the risk of harmful algal blooms and decide on strategies to help reduce their occurrence.

“Many flowers are beneficial, especially in terms of their positive effects on ecosystems and on wild and farmed fisheries,” the authors wrote.

‘The results here can also contribute to policy and management actions that maintain that beneficial bloom.’