Submersible used during the expedition.

Discoveries in the Twilight Zone

Dutch Caribbean Nature Alliance (DCNA)
10-AUG-2024 - A recent scientific study has shed light on the remarkable and little-known ecosystems thriving in the mesophotic reefs of the Dutch Caribbean. Researchers explored these 'Twilight Zone' reefs, located at depths of 30 to 150 meters. They used advanced submersible technology to uncover the diversity and complexity of sponge-associated microbial communities.

Mesophotic reefs, receiving less sunlight than their shallow counterparts, are home to unique species adapted to these lower light levels. Conducted off the coasts of Curaçao and Klein Curaçao, 26 sponge specimens representing 11 different species were collected from depths ranging from 90 to 188 meters (with the exception of one species collected at 13 meters). These specimens were analyzed using transmission electron microscopy (TEM) and high-throughput sequencing to uncover their microbial populations. 

Mesophotic reefs are home to unique species adapted to lower light levels

Microbial Marvels

This research identified significant differences in the microbial communities associated with high microbial abundance (HMA) and low microbial abundance (LMA) sponges. HMA sponges were found to be more diverse and richer in microbial species compared to their LMA counterparts. Machine learning techniques further identified key bacterial classes predictive of HMA or LMA status, highlighting the ecological complexity of these mesophotic sponge communities.

Mesophotic reefs serve as a buffer zone, providing a source of coral larvae and other organisms that can repopulate damaged shallow reefs

Given their unique biodiversity and ecological functions, these reefs are vital for the health of the entire marine ecosystem

Ecological Significance

These findings are crucial for understanding the role of mesophotic reefs in marine ecosystems. Mesophotic reefs act as refuges for species threatened in shallower waters, contributing to the resilience and recovery of coral reef ecosystems. They also serve as a buffer zone, providing a source of coral larvae and other marine organisms that can repopulate damaged shallow reefs.

Submersible used during the expedition

Expedition team

Conservation Implications

The study underscores the importance of protecting mesophotic reefs as part of broader conservation efforts in the Dutch Caribbean. Given their unique biodiversity and ecological functions, these reefs are vital for the health of the entire marine ecosystem. Conservation strategies must prioritize these deeper reef systems to ensure the sustainability of marine life in the region.

Collaboration

The study was a collaborative effort between University of Aveiro, University of Amsterdam, Naturalis Biodiversity Center and Leiden University.  The study was part of a broader research program supported by the Netherlands Organization for Scientific Research (NWO) and the Portuguese Foundation for Science and Technology (FCT).

Text: Dutch Caribbean Nature Alliance
Images: Daniel FR Cleary and Substation Curacao; Nicole de Voogd

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