NASA's Aqua: Algal bloom trends finally spotted thanks to space view

The size and frequency of coastal phytoplankton blooms rose between 2003 and 2020, according to a study published in Nature on March 1. 

The results are significant since previous research has struggled to accurately characterize bloom patterns due to infrequent sampling and the diversity of particular ecosystems in which they occur.  

Now, this map of bloom patterns on a global scale provides a valuable resource for assessing these events, which could inform environmental policymaking. 

Phytoplankton blooms from space 

By analyzing 760,000 photos taken by NASA's Aqua satellite between 2003 and 2020, Lian Feng and colleagues created a detailed map of the distribution and trends of blooms this century.

They document that the total bloom-affected area in 2020 was 31.47 million kilometers² (8.6 percent of the global ocean area). This was an increase of 3.97 million km² (13.2 percent) from 2003. Moreover, a 59.2 percent increase in global median frequency was seen during the observational period.

The authors also found a strong connection between mean bloom frequency, changes in ocean circulation, and changes in sea surface temperature, with greater temperatures associated with the prevalence of blooms in some areas.

Researchers can better grasp how coastal phytoplankton blooms arise and break down because of specific information on their size and frequency. The authors suggest that this information might be used to evaluate the dangers and advantages of blooms and could help develop plans to reduce their incidence or adverse effects.

Are phytoplankton good or bad?

Did you know a teaspoon of ocean water can contain over a million plankton? In a balanced ecosystem, these microscopic creatures (zooplankton) and plants (phytoplankton) float with the ocean's currents and are essential components of many ocean systems. 

Better yet, according to scientific estimates, phytoplankton photosynthesis generates nearly 50 percent of the world's oxygen.

Phytoplankton blooms can form in the surface layer of freshwater and marine habitats. These blooms can serve as a source of food and nutrition for other organisms. 

Still, they can also have unfavorable consequences, including the creation of toxins that can build up in food webs. An increase in them can also result in oxygen depletion, producing oxygen-free "dead zones" in previously stable ecosystems.

Blooms tend to occur due to ocean water change, sometimes caused by an overabundance of nutrients such as nitrogen or phosphorus from fertilizer runoff, sewage treatment plants, and other land-based sources. Human activities are anticipated to cause such changes, resulting in blooms occurring more frequently worldwide.