Hawaii’s Twilight Zone: Highest Rate Of Unique Marine Species Discovered

The twilight zone of Hawaii, an extensive area of the ocean which is rich with deep coral reefs is flourishing with vast algae meadows that are home to the highest rates of species unique only to the area, and not seen in any other seas or oceans on our planet. The discovery was recently announced by researchers, after the end of a 20 year long study.

One of the most detailed and comprehensive of its kind, the study covered two decades of combing the entire 2,590km Hawaiian archipelago with a combination of advanced diving techniques, data recorders, drop cameras, remote operated vehicles and submersibles. The research results identified more than 70 species of macroalgae present in extensive meadows that host endemic types of fish and invertebrates.

"We found that the diversity of macroalgal species actually peaked at around 90m," said Heather Spalding, co-author of the study. "These extensive algae meadows represent a major component of the deep-reef communities, and play a fundamentally important role in the overall ecology."

Furthermore, the team of researchers discovered that the rate of endemism, i.e. species unique to a particular area, increased noticeably on the deep reefs in Hawaii's twilight zone. The findings suggested that while only 17% of the fish surveyed at depths of 30 meters and less were unique to Hawaii, more than half of the marine life found at depths of 70 meters and more were endemic species. The rate of endemic species was found to be 100% in the Northwestern Hawaiian Islands.

According to the researchers, the study results have important implications for managing conservation. The findings suggest deep coral reefs serve as a shelter for species that belong to shallow coral reefs. Today, many coral reefs face numerous threats; therefore discovering extensive reefs in Hawaii's twilight zone, near Maui provides an opportunity to make sure that those are not endangered with activities like deep sewer outfalls or cable laying.