Climate Wire | As ocean temperatures warm and circulation patterns change, blue-green algae are growing larger and more frequently around the world.
Climate change is likely one cause of changes that boost phytoplankton growth, according to a new study published in . Nature.
Whether that’s good or bad is an ambiguous question. Algae are an important food source for many marine animals, and large-scale algae can be beneficial to marine ecosystems and fisheries.
However, some blue-green algae release toxins into the water and pollute the environment. Also, when the flowers die and begin to decompose, the oxygen levels in the water are depleted, which can harm ecosystems.
With both positive and negative consequences, experts closely monitor algal blooms around the world.
A new study uses satellite data to track algal blooms around the world between 2003 and 2020. Researchers focused on 153 coastal states and 54 large marine ecosystems.
Blue-green algae increased in size by about 13%, or 1.5 million square miles, during the study period. Also, the frequency he increased by 59%.
Trends varied by region. The greatest flowering was seen in Europe and North America, with the most frequent flowering in Africa and South America.
The largest increases in frequency over time occurred in major coastal current systems, such as the Oyashio Current in the western North Pacific, the Alaska Current, the Malvinas Current off Patagonia, the Canary Current, and the Benguela Current off the southern coast of Africa. , and the Gulf Stream.
Some places have actually seen algal blooms weaken over time, including the California Current, parts of the northeastern North Atlantic, and the Sea of Okhotsk in the North Pacific.
Just as trends vary from place to place, so can causes. The researchers looked at many factors that may contribute to algal blooms, including sea temperature, ocean circulation patterns, and runoff from fertilizers and other nutrients.
Increased water temperature may have affected some regions of the world, especially in high-latitude regions such as the Alaska Current and the Oyashio Current.
Climate change may also play a role in altering the course of ocean currents. These changing circulation patterns can alter the flow of nutrients and how they mix in the water, leading to increased flowering in certain areas and decreased in others.
The researchers suggest that this type of change may have played a role in reducing algal blooms in the California Current, while increasing in places like the Canary and Benguela Currents.
On the other hand, the blue-green algal blooms that occurred in some areas did not appear to be clearly related to changes in seawater temperature or circulation patterns.
For example, declines in the Arabian Sea and increases around China may be the result of changes in fertilizer use patterns. Increased aquaculture in countries such as Finland, China, Algeria, Argentina and Russia may also be driving algal blooms in these regions, the researchers suggest.
Reprinted from E&E News with permission of POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environmental professionals.
