Nutrient Loading: Typhoons often bring heavy rainfall and flooding, which can wash nutrients from the land into coastal waters. These nutrients, such as nitrogen and phosphorus, serve as essential fertilizers for algae, promoting their rapid growth and proliferation.
Upwelling: As typhoons pass over the ocean, they generate strong winds that cause upwelling—a process where deeper, nutrient-rich waters rise to the surface. This upwelling brings essential nutrients into the sunlit surface layer, where they can be readily utilized by phytoplankton, microscopic algae that form the base of the marine food web.
Mixing and Resuspension: The intense winds and waves associated with typhoons can result in vigorous mixing of the water column. This mixing brings nutrients from deeper waters to the surface and also resuspend sediments, releasing additional nutrients into the water. The increased nutrient availability fuels algal growth and facilitates the formation of blooms.
Light Penetration: Typhoons can influence light penetration in coastal waters by stirring up sediments and increasing turbidity. This reduced light penetration can benefit certain algal species that are adapted to low-light conditions, allowing them to outcompete other phytoplankton and form dense blooms.
Changes in Salinity: The heavy rainfall and freshwater runoff associated with typhoons can significantly reduce the salinity of coastal waters. This sudden decrease in salinity can stress or kill marine organisms, including predators that would normally feed on algae. The reduction in grazing pressure can further enhance algal growth and bloom formation.
These factors, acting together or in combination, create favorable conditions for coastal algal blooms to develop and persist after typhoons.
