Seasonal Phytoplankton Blooms in Al-Wajh Lagoon Reveal Unique Dynamics

Phytoplankton blooms, a key indicator of marine ecosystem health, exhibit an intriguing seasonal pattern in the Al-Wajh lagoon, differing significantly from the blooms in the adjacent Red Sea. Researchers from KAUST, collaborating with international teams, have uncovered how regional water dynamics and nutrient availability influence these distinct bloom cycles.

The Al-Wajh lagoon, part of Saudi Arabia’s Red Sea Project conservation zone, is home to diverse marine ecosystems. Phytoplankton, which form the foundation of the ocean’s food web, are vital for the health of these ecosystems. While most tropical oceans experience phytoplankton blooms during winter and early spring, the team found that Al-Wajh's blooms peak during August and September—an unexpected shift.

Using satellite imagery and a remote-sensing ocean-color algorithm developed specifically for the Red Sea, the researchers tracked chlorophyll concentrations, providing insights into phytoplankton abundance. They also built a high-resolution ocean model to understand the bloom mechanisms.

The study revealed that the unique timing of the Al-Wajh lagoon’s blooms is due to the region’s hydrodynamic conditions. In autumn, when the Red Sea is nutrient-poor and highly stratified, colder seawater flows into the lagoon, mixing with warmer water and bringing nutrients from the lagoon floor. This triggers the bloom. In contrast, early spring conditions see the lagoon’s cooler waters prevented from mixing, halting nutrient upwelling and postponing the bloom.

KAUST’s Ibrahim Hoteit emphasizes the significance of understanding these biophysical dynamics, as they are crucial for the conservation and management of lagoon ecosystems, which are often vulnerable to environmental changes.

🔗 Read more on KAUST Discovery

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