Stunning satellite images show how toxic algae is now growing in at least 31.47 million square kilometers (12.1 million square miles) of the world’s oceans thanks to human activities.
A study by scientists from the Southern University of Science and Technology in China found that the total area affected by phytoplankton growth has increased by 13.2% since 2003.
When nutrients from fertilizers, sewage, air pollution, and livestock manure enter water sources, phytoplankton will feed on those nutrients and grow.
The researchers also found that rising sea temperatures have increased algal blooms over the past two decades, as warmer waters have lengthened the bloom season.
They write: “Many algal blooms are beneficial, fixing carbon at the base of the food chain and supporting fisheries and ecosystems around the world. However, harmful algal blooms, referred to as harmful algal blooms, have become a major environmental problem worldwide.” .
An algal bloom is a rapid increase in the number of algae in an aquatic system that can occur in both freshwater and marine environments.
Blooms could cause water at surface level to change color to yellow, red or bright green, new satellite imagery suggests.
This is often the result of eutrophication (water eutrophication or eutrophication), when water bodies are enriched with nutrients such as phosphate and nitrate, which feed algae and other green plants to grow.
Coastal phytoplankton blooms increased in Both their size and their frequency between 2003 and 2020. This card of bloom patterns on A global scale provides valuable resource for evaluating these events that could inform the environment policy manufacturing: https://t.co/kNfS3yMuvK
— Springer Nature (@SpringerNature) March 1, 2023
Phytoplankton become harmful when they use up all the oxygen dissolved in the water by choking on fish and aquatic insects, which in turn become nutrients themselves.
Some species of algae also produce biotoxins that can have a severe impact on wildlife and contribute to these “dead zones” where aquatic life cannot survive.
In a study published in the journal Nature, researchers used 760,000 images taken by NASA satellites from 2003 to 2020 to calculate the area of the world’s oceans annually covered by algae and the frequency of blooms.
They then compared this data with sea surface temperature (SST) as well as the amount of temperature change per meter or “spatial gradient in sea surface temperature.”
A large temperature difference between two adjacent ocean regions or a large spatial gradient in sea surface temperature may indicate poor water circulation.
This is because hotter water is less dense than cold water and sinks less in the natural movement of currents along the “conveyor belt”.
As a result, nutrients are unevenly distributed throughout the water column, and phytoplankton can thrive in areas of greatest concentration, typically those closest to the surface.
A large temperature difference between adjacent regions of the ocean can cause disturbances and lead to an increase in nutrients from deeper waters, further encouraging algae growth.
The maps showed that coastal phytoplankton blooms increased by 1.53 million square miles (3.97 million square kilometers) over the observed period.
In 2020, it covered 8.6% of the total area of the World Ocean.
It was also found that the average annual number of observed flowers increased by 59.2% between 2003 and 2020, which is 2.19% per year.
The higher frequency of blooms was largely related to ocean temperatures, suggesting that “the favorable seasons in these temperate seas continued at higher temperatures.”
Bloom frequency has also increased with the spatial gradient of sea surface temperature in several regions including California, Steam Bay and the Canary Stream.
This indicates that weak ocean currents caused by rising sea temperatures are promoting algae growth.
In China, Iran, Vietnam, and the Philippines, the researchers also observed an increase in fertilizer use during the study period, which likely contributed to phytoplankton blooms.
The same can be said for intensive aquaculture in Finland, China, Algeria, Guinea, Vietnam, Argentina, Russia and Uruguay.
The researchers hope their maps and data will help to better understand the mechanisms that cause and disperse coastal phytoplankton blooms.
Source: Daily Mail
