Tiny Plankton Power in South Africa's St Helena Bay

In the sunny waters of St Helena Bay, South Africa, tiny plankton, known as nano-picoplankton, rule the post-upwelling period. These tiny guys are the main producers of food for marine life. Yet, we don't fully understand how they behave over short periods or what kind of community they form. Scientists gathered samples over five days in March 2018 from different depths in the bay: 1 meter, 25 meters, and 50 meters. They found that the diversity and functions of these microorganisms varied greatly with depth. At the surface (1 meter and 25 meters), there were more diverse eukaryotes, with higher numbers of Syndiniales and Bacillariophyta. Deeper down, critters involved in nitrogen cycling were more abundant, like nitrifiers and denitrifiers. The surface water was packed with light-loving microorganisms, while deeper waters hosted those involved in nutrient processing. The amount of ammonia nutrient transporters also showed clear depth differences, indicating varying uptake rates. What drives these tiny plankton? Light, nutrients, carbon, and oxygen levels. Their roles help keep St Helena Bay's ecosystem healthy, stressing the need to keep an eye on these small but mighty creatures.