Documenting the Biodiversity of Papahānaumokuākea’s Mesophotic Coral Ecosystems

by Megan Howes

December 2016

Our ocean is vastly unexplored. We share our blue planet with an abundance of life forms, most of which we have yet to encounter. A new Marine Sanctuaries Conservation Series report underscores just how much there remains to be discovered.

The report catalogues over 200 species of algae, corals, sponges, anemones, urchins and sea stars found within the Northwestern Hawaiian Islands. This publication is a first step towards understanding what resources are found within the region, and will aid in research and management efforts of Papahānaumokuākea Marine National Monument.

Papahānaumokuākea Marine National Monument is a global treasure of scientific and natural value. The newly expanded monument surrounds a little-known, rarely-visited, and ecologically-important area. From 2012 to 2015, annual research expeditions embarked on a mission to characterize the biodiversity found on deeper coral reefs of the monument, surveying reefs at depths between 150 and 330 feet with a team of technical scuba divers. Previous surveys in the region focused largely on reefs shallower than 100 feet or on much deeper reefs below 600 feet -- so until recently, little was known about the biodiversity between those two depths. This new research greatly contributes to our understanding of the monument's biodiversity and that of reefs worldwide.

This intermediate depth range contains mesophotic coral ecosystems, which are warm-water, light-dependent coral reef communities found between 100 and 450 feet. Due to their isolation -- thousands of miles from any continent -- the mesophotic coral ecosystems in Papahānaumokuākea are among the few remaining pristine reefs that have not yet been significantly impacted by human activity. For this reason, mesophotic coral ecosystems have become a priority for research and conservation around the world. Coral reefs are vital to maintaining the biological diversity of our global oceans, but until recently the largest depth range of coral reefs (100-450 feet) was largely unexplored. As a result, we lacked scientific knowledge necessary for sound resource management and conservation

Most of the species included in this study were documented for the first time in the Hawaiian Islands, and a substantial number of these species are new to science, having not been found anywhere else before. Dr. Randy Kosaki, deputy superintendent for research and field operations at Papahānaumokuākea Marine National Monument explains, "there is some time-sensitivity regarding the need for adequate characterization of these deep reef habitats. In the face of climate change, we are at risk of losing species before we even know they exist."

The following is an example of the documentation provided for each species, as it appears in the report:

In addition to the timely and dedicated effort to thoroughly characterize the Hawaiian mesophotic coral ecosystems, the report also emphasizes the importance of protecting the unique resources of the monument. The report's lead author, Dr. Daniel Wagner, stated: “a large portion of the species we documented on these deeper coral reefs are either new to science, or were not previously known to exist in Hawaiʻi. This indicates that these ecosystems represent important reservoirs of biodiversity, and underscores the need for protection of this area.” Anthropogenic stress on shallow water reef systems has led to global degradation and loss of regional biodiversity. Since mesophotic coral ecosystems are more sheltered from disturbance, they are gaining attention for their capacity to act effectively as a “refuge” of sorts for the many species that exist across various depths.

With this new biodiversity baseline, researchers from NOAA and other organizations will be better equipped to track changes and understand ecological dynamics of climate change throughout the monument’s coral ecosystems.