The Great Ocean Elevator: How Eastern Boundary Upwelling Systems Feed the Sea

The Banquet Table and the Invisible Hand

Imagine a massive banquet table where the tablecloth is constantly being yanked away by an invisible hand. As the cloth disappears off the edge, new fabric rushes up from underneath the table to replace it, bringing fresh plates of food with it. This is not magic. It is physics. In the ocean, the wind acts as that invisible hand. If the wind blows along the coast in a specific direction, the rotation of the Earth pushes the surface water away from the land. Nature abhors a vacuum. Consequently, cold, nutrient-rich water from the deep ocean rises to fill the gap. This process creates what scientists call Eastern Boundary Upwelling Systems (EBUS).

These systems are the engines of marine life. They turn a watery desert into a bustling metropolis of biodiversity.

Comparing the Mauritanian and Benguela Eastern Boundary Upwelling Systems

A recent study looked at two of these vital zones: the Mauritanian Upwelling (MU) and the Benguela Upwelling System (BUS). While they operate on the same mechanical principle, the researchers found distinct differences in the guests attending the banquet. The team identified over 40 species of pelagic crustaceans—shrimp-like creatures that serve as essential snacks for larger fish—in each region.

The difference lay in the size. In the Mauritanian system, the upwelling is permanent and perhaps more stable. Here, the study measured the highest abundance of life, and notably, the crustaceans were large. Individuals larger than 100 mm² were frequently found. It seems that when the 'elevator' bringing food up is steady, the diners have time to grow fat and happy.

The Benguela system told a different story.

In the BUS, the smallest organisms (0–20 mm²) dominated the scene. Why the discrepancy? The authors suggest that the intensity of the upwelling in the Benguela region creates a turbulent, high-energy environment. If the water is churning violently, being big is a disadvantage. You get tossed around. Being small allows these organisms to ride the chaotic currents rather than fighting them.

The Stowaway from the East

The mechanics of the ocean do not exist in isolation. The study also highlighted how these systems interact with neighbouring currents. In the oxygen-rich waters of the southern Benguela system, the team identified a stranger: Thysanopoda tricuspidata. This tropical euphausiid does not typically belong there.

Its presence suggests it was kidnapped and transported by the Agulhas Current, moving from the Indian Ocean into the Atlantic. This proves that Eastern Boundary Upwelling Systems are not closed loops; they are porous borders where local physics meets global circulation. Understanding these mechanical differences—stable versus intense, local versus imported—is vital for predicting how these food webs might cope as climate patterns shift the wind.