An In-Depth Look at the Plankton Bloom Phenomenon: The Crisis of Ocean Discoloration and Its Impact on Marine Ecosystems.

During the rainy season, starting in May, one natural phenomenon that often occurs in the sea is a plankton bloom. As plankton in the sea rapidly increase in number, they can cause the sea surface to change color. At night, plankton may also produce beautiful bioluminescence in various colors, including green, blue, and red. However, did you know? Beneath the beautiful light on the sea surface, there may be danger greater than you think.

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Plankton bloom, also known as a discoloration or the whale excrement phenomenon, occurs when the number of small organisms increases rapidly, causing them to accumulate and float on the water’s surface. These organisms can be both plant and animal. When their numbers increase significantly, they can accumulate near the water's surface, causing the water to change color. The visible color varies depending on the type and composition of the organisms. The phenomenon mentioned above can occur in both freshwater and saltwater and is often found in coastal areas during the rainy season.

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Environmental factors that contribute to plankton growth include several key factors, such as high sea surface temperature, relatively calm water currents, and the amount of nutrients in the water, such as phosphorus, which is an important nutrient for plankton growth. When these factors occur together, some types of plankton can grow rapidly.

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Meanwhile, rising sea temperatures are another key factor contributing to plankton blooms. In addition, the climate change and global warming that the Earth is currently experiencing are causing sea surface temperatures to rise. As a result, average sea temperatures are showing an increasing trend. These changes may increase the likelihood of plankton blooms in some areas.

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Many people may wonder: What are the impacts of plankton blooms? At night, some types of plankton may glow beautifully, creating a fascinating sight for those who witness it. However, what is more concerning is the potential damage and danger that plankton blooms may cause to the underwater ecosystem. If a plankton bloom occurs on a large scale, the dense accumulation of plankton may block sunlight from reaching the seabed. This can result in insufficient light for marine plants, causing stress and preventing them from photosynthesizing fully. This, in turn, may affect aquatic animals, potentially leading to a shortage of food sources for their survival.

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Furthermore, an increase in plankton can lead to a decrease in oxygen levels in the water, especially when plankton die and decompose. This can affect marine life. If marine animals consume certain types of plankton, they may accumulate toxins and die. These toxins can also be passed along the food chain and eventually affect humans. In addition, plankton blooms can make seawater cloudy and more viscous, as well as produce unpleasant odors. Besides affecting the environment, plankton blooms can also impact tourism activities and the use of coastal areas.

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Due to the potential impacts mentioned above, on July 19, 2026, a plankton bloom was detected along the coastal areas of three provinces: Samut Prakan, Phetchaburi, and Prachuap Khiri Khan. The Natural Resources Division of the Geo-Informatics and Space Technology Development Agency (GISTDA) interpreted and analyzed satellite imagery to detect and monitor the plankton bloom, analyze the situation, and report the results in map format. The analysis used imagery from the Sentinel-2 satellite's MSI system, along with models to assess potentially affected areas and the duration of the plankton bloom.

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Currently, the application of satellite technology combined with geospatial data analysis enables continuous monitoring and tracking of the situation, allowing for proactive planning rather than waiting to address problems after they occur. This includes examining the extent of the plankton bloom and analyzing the expansion of affected areas at various stages using buffer analysis. The information can support planning and management by relevant agencies and local authorities, as well as help prepare for potential future impacts on marine ecosystems.

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For those interested, more information can be found at: https://marineportal.gistda.or.th/