We are very excited to have experienced visiting and studying the diversity of coral reef habitats in Hawaii during our three week expedition to the islands. Having surveyed a total of 46 sites, along 81km of reef, across five of the main islands of Hawaii, we have experienced first-hand the uniqueness of these systems. Coral reefs in the main islands of Hawaii cover as much as 60-90% in many sites, most of which are endemic species to Hawaii.
The composition and structure of Hawaiian reefs varies at scales from metres to up to 100 kilometres. Coral reefs on Hawai’i Island (locally known as Big Island) were formed by volcanic rocks, creating complex and spectacular reef formations. Porites compressa, an endemic species of coral in Hawai’i, forms large meadows in between these rock formations. In the islands of Mau’i, Moloka’i and Lana’i, reef habitats have a larger diversity of endemic species and more complex reef formations.
Aside from the strong influence of oceanic weather effects on the distribution and assembly of these coral communities, it is clear how Hawaii’s geological history has influenced the modern structure of these reefs. Corals grow slowly, so it would take many decades to directly observe how they develop into mature coral communities, however, on the island of Hawai’i, reef development can be inferred by comparing reefs that colonized lava flow of varying ages.
Despite the high coral cover observed in many reefs around the islands, Hawaiian reefs are currently facing numerous pressures that are compromising the sustainability of these systems. Agricultural, farming activities and land alteration often produce large amounts of unconsolidated sediment and promote soil erosion that ends up on the reef during rain periods. We observed substantial run-off of terrestrial sediment, which often smothers and kills large extensions of corals. Poor watershed management, on the other hand, can promote coral disease and algal blooms that directly affect the integrity of these systems. Lastly, just like other coral reefs around the world, Hawaii’s reefs are also under a great deal of pressure from warming oceans. Nonetheless, ecosystem-based management and centuries of community stewardship offer great possibilities in Hawaii to promote recovery and sustainability.
It was an intense but extremely fruitful survey in Hawaii, from which we have learned a great deal, and continue to learn as we analyse the data collected. However, this expedition would not have been be possible without great collaboration and support from partners, researchers and institutions we interacted with during our trip. We would like to acknowledge the tremendous and continuing support from NOAA Marine Sanctuaries, in particular Mitchell Tartt, Jon Martinez, Shannon Lyday and Malia Chow, for their support in planning, field logistics, and involving us during their highly successful community engagement events. We would also like to thank the Department of Land and Natural Resources, Division of Aquatic Resources, in particular Megan Lamson and Darla White, for their fantastic support and interaction in the field. Finally, we would like to acknowledge the professional support from Maui Divers, Jack Diver’s Locker and Ocean Legends.