New research out of the State of Hawaii Division of Aquatic Resources (DAR) and the Hawaii Institute of Marine Biology (HIMB) have found a management approach that combines manual removal and out planting native urchin to reduce invasive, reef smothering marcoalgae by 85% on a coral reef off O’ahu, Hawaii.
The breakthrough is so important as coral reefs around the world need more help than ever as they are disappearing quicker than we even realize due to warming ocean temperatures, ocean acidification and invasive species which are smothering and eating coral reefs. The impact of climate change on coral reefs has already been devastating so anything scientists can do from here on out is imperative to saving reefs.
Brian J. Neilson, Acting Administrator at DAR, and Chris Wall, doctoral candidate at HIMB in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), tested the new approach to reduce the abundance of invasive macroalgae on the coral reefs of Kāne’ohe Bay, O’ahu.
First divers manually removed invasive macro algae with the assistance of an underwater vacuum system. Then, the researchers deployed hatchery-raised juveniles sea urchins, which are native to Hawaii, were they were out planted to eat the invasive algae to control regrowth.
In the end the team removed over 40,000 pounds of invasive macro algae, deployed 99,000 sea urchins, and treated nearly six acres of reef area over two years. The massive project was able to reduce macro algae growth and researchers observed zero negative effects to reel calcifiers such as corals and crustose coralline algae.
This new study really provides the first non-destructive option to remove invasive algae. “This management approach is the first of its kind at the reef-scale,” said Wall in published research. “Our research shows promise as an effective mean to reduce invasive macroalgae with minimal environmental impact, while also incorporating a native herbivore to regulate a noxious invasive species.”
“Coral reefs are an important part of the economy, culture, sustenance and recreation of Hawai’i,” said Neilson. “Local action is instrumental in supporting the resilience of coral reefs. This study provides an important tool that can assist in the management and conservation of coral reefs.”
“The surprise was just how effective this approach was at reducing invasive macroalgae over the two-year period,” said Wall. “We were able to successfully leverage the rigorous, detailed science of prior studies to assist in scaling the management plan from an aquarium to an entire reef. One of the lessons here is that a well-designed management plan can reap significant benefits and lead to the most effective path forward, both logistically and financially.”
DAR will continue to monitor the reefs around O’ahu and the long-term impact of macro algae removal and urchin herbivory on reefs. As more results of the study become available, they hope that their research will help reefs all around the world with their breakthrough findings.