What is an example of a desert in the ocean?

The Sargasso Sea is a prime example of what biologists often refer to as a "biological desert" in the ocean.

The Sargasso Sea: An Oceanic "Biological Desert"

The Sargasso Sea is a unique region in the North Atlantic Ocean, famously known for its vast expanses of still waters and dense mats of free-floating seaweed called Sargassum. While it might seem rich with vegetation, biologists classify it as an oceanic desert due to a critical ecological characteristic highlighted in the provided reference:

• Lack of Plankton: The Sargasso Sea is largely devoid of plankton. Plankton, microscopic organisms that drift in water, form the fundamental basis of the marine food web. They serve as the primary food supply for small organisms and fishes.

This scarcity of plankton means there's limited food available to support a diverse and abundant array of marine life, leading to an ecosystem with lower productivity compared to most other ocean regions.

Why Plankton Deficiency Matters

The absence of abundant plankton directly impacts the entire food chain within the Sargasso Sea:

• Limited Food Source: Without a rich plankton base, there's insufficient food to sustain large populations of small fish and invertebrates.
• Impact on Higher Trophic Levels: Consequently, larger marine animals that feed on these smaller organisms, such as tuna, whales, and seabirds, are also less common in this area compared to more productive waters. This scarcity mirrors the conditions found in terrestrial deserts, where limited water (analogous to plankton in the ocean) restricts plant and animal life.

Unique Characteristics of the Sargasso Sea

Despite its "desert" classification in terms of productivity, the Sargasso Sea possesses several distinctive features:

• Still Waters: As mentioned, the sea remains notably still. This is due to its location within the North Atlantic Gyre, a large system of circulating ocean currents that creates a calm, central area where water does not mix much with nutrient-rich currents from other parts of the ocean.
• Floating Sargassum Seaweed: This unique ecosystem is named after the Sargassum seaweed that floats freely on its surface, forming vast mats. Unlike most seaweeds, Sargassum does not attach to the seafloor. These mats provide a crucial habitat for a variety of specialized marine species, offering shelter and a place to spawn, even in a nutrient-poor environment.
• Nutrient-Poor Environment: The lack of strong currents and upwelling means that deep-sea nutrients are not brought to the surface, further contributing to the low plankton levels.

The table below summarizes the key differences between the Sargasso Sea and more productive ocean regions:

In conclusion, the Sargasso Sea serves as an excellent example of an "oceanic desert" because its unique oceanographic conditions lead to a significant scarcity of plankton, the very foundation of marine life, despite the presence of its characteristic floating seaweed.