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  • Writer's pictureLynn

Saba Bank sink holes: what lies beneath the surface!

Excerpts and images thanks to Wageningen University & Research article

Most divers have heard of the famous Blue Hole in Belize, but it took until 2019 to realize the Saba Bank is home to more than 20 blue holes (otherwise known as sink holes) that are the deepest and largest sinkholes in the world! Saba's deepest blue hole is nearly 70 meters deeper than China's Dragon Hole, previously having claim to being the world's deepest with Belize now in 3rd place.

Sinkholes are a geological phenomenon that occur when underground cavities or voids collapse, creating depressions or holes at the Earth's surface. These cavities are typically formed through various natural processes, such as the dissolution of limestone or other soluble rocks by water, or the collapse of underground mines or tunnels. Sinkholes can vary in size from small depressions to massive craters, and they are found all over the world.

So why do we care about blue holes? Not only are they deep, but they have stories to tell! In December 2019, an expedition was planned to the Saba Bank with specific goals: "The aim is to find out more about the nature of the calcareous algae turrets and the environmental factors that influence their growth. How does the exchange of water between the sinkholes and the flowing water above work, and which biological communities and nutrients such as bacteria are present? This research will provide insights into why these turrets occur at some sinkholes but not others."

The sinkholes on the Saba Bank, which is a submerged atoll in the Caribbean Sea, are of particular importance due to their unique characteristics. The Saba Bank is located just 6 miles off of the island of Saba and covers more than 2400 km2 or nearly 1500 sq miles and is therefore, the largest protected nature area in the Netherlands. The Bank is an extensive area of shallow marine habitat, and the 21 "blue holes" are significant for several reasons:

1. Biodiversity: The sheltered and nutrient-rich conditions within these sinkholes support a thriving marine community, including corals, sponges, fish, and other organisms.

2. Scientific Research: Scientists are drawn to the sinkholes on Saba Bank because they offer a window into the past. Sediment layers in the sinkholes can provide valuable information about past climate conditions and changes in sea level. Additionally, researchers study the unique adaptations of the species that inhabit these sinkholes to better understand how life can thrive in extreme environments.

3. Conservation: The conservation of Saba Bank's blue holes is crucial for maintaining the health of the wider Caribbean marine ecosystem. Protecting these sinkholes helps preserve the biodiversity and connectivity of marine species in the region. It also contributes to understanding the overall resilience of coral reefs, which face numerous threats.

4. Tourism and Recreation: Beyond their scientific value, the sinkholes on Saba Bank may be a draw for divers and tourists. It remains to be seen whether with correct management, they may offer an unparalleled opportunity for underwater exploration and adventure tourism, bringing economic benefits to the region while also raising awareness about the importance of marine conservation.

The 2023 20th anniversary of the Sea & Learn program not only includes public outings to these blue holes, but they incorporate 3 scientists on board the vessel. Drawing on the expertise of Drs. Erica Moulton and Nathan Robinson in the world of ROVs combined with Will Barnes' knowledge from his work with Erik Meester's, the team of 3 will reexamine a select few of the deep-sea sinkholes that were identified in the 2019 expedition. And now you can be part of it! The Sea & Learn field projects provide the opportunity to be a citizen scientist by joining these hands-on activities. This particular project aims to carry out further surveys of the associated flora and fauna found in the sinkholes by deploying a Deep Trekker ROV, capable of diving to depths of nearly 100 meters (330 ft).

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