The Emerging Crisis of Invasive Octocorals in Pearl Harbor

Pearl Harbor, a historic waterway in Hawaii synonymous with naval significance, now faces an ecological battle against invasive octocorals. These soft-bodied marine invertebrates, belonging to the order Alcyonacea, have proliferated across approximately 80 to 100 acres of the harbor floor. Unlike the sturdy, reef-building stony corals (Scleractinia) that form the backbone of Hawaiian reefs, octocorals like Unomia stolonifera—commonly called pulsing xenia coral—and Capnella cf. spicata, known as Kenya tree coral, spread rapidly through fragmentation. When disturbed, they break into pieces that each regenerate into new colonies, smothering native species by overgrowing substrates, shading light-dependent corals, and altering water flow dynamics essential for larval settlement.

This invasion threatens biodiversity in a region already stressed by climate change, overfishing, and pollution. Native Hawaiian reefs support over 7,000 species, contributing billions to the local economy through tourism and fisheries. The unchecked growth of these invasives could cascade into fish population declines and habitat loss, underscoring the need for scientifically grounded intervention.

Discovery and Precise Scientific Identification

The story began in 2020 when U.S. Navy contractor divers spotted an unidentified xeniid octocoral during routine benthic surveys near Bishop Point and Ford Island in Pearl Harbor. Initial observations suggested a novel threat, prompting swift collaboration. By 2022, visual assessments confirmed its presence, but definitive identification required advanced techniques.

Researchers employed morphological examination of sclerites—tiny calcium carbonate structures within the coral tissue—alongside molecular genetic analysis. DNA barcoding matched sequences to Unomia stolonifera from the Indo-Pacific (NCBI accession MT482554.1) and Capnella cf. spicata (JX124371.1). Scanning electron microscopy revealed distinctive microstructures, solidifying the diagnosis. These species, absent from prior Pearl Harbor surveys dating back decades, marked new state records for Hawaii.

Anecdotal evidence hints at earlier presence since 2017, but 2020 marked the first documentation. Their confinement to the harbor entrance as of mid-2023 offers a containment window, critical for management.

University of Hawaii's Leadership in Marine Invasive Research

At the forefront stands the University of Hawaii (UH), a global powerhouse in marine biology through institutions like the School of Ocean and Earth Science and Technology (SOEST), Hawaii Institute of Marine Biology (HIMB), and Waikiki Aquarium. UH Mānoa researchers have long tackled invasive species, building on decades of work with earlier invaders like Carijoa riisei, documented in Pearl Harbor since 1972.

Christy Martin, Program Manager for the Coordinating Group on Alien Pest Species (CGAPS) at UH Mānoa's Pacific Cooperative Studies Unit, exemplifies this expertise. In August 2025, SOEST and Waikiki Aquarium hosted the Unomia Learning Exchange Workshop, drawing experts from Hawaii, Florida, and U.S. territories. Participants dissected rapid response strategies, including tabletop exercises simulating Unomia detections per Aquatic Nuisance Species Task Force protocols. For deeper insights into UH's collaborative approach, explore the workshop coverage.

Waikiki Aquarium maintains live Unomia specimens for study, enabling hands-on research into growth rates and predator vulnerabilities. HIMB contributes ecological modeling, assessing spread risks under varying currents and temperatures characteristic of Pearl Harbor's semi-enclosed waters.

Interdisciplinary Collaborations Fueling Progress

The Hawaii Invasive Octocorals Working Group (HIOWG), formed in 2023, unites UH with Bishop Museum, NOAA's Pacific Islands Fisheries Science Center, USFWS, USGS, and Williams College. Bishop Museum scientists Holly Bolick and Kiana Lee led identification, publishing findings in Bishop Museum Occasional Papers. Their work confirmed aquarium trade origins—Unomia as "pulsing xenia," Capnella as "Kenya tree coral"—likely dumped illegally alongside species like the gold flake angelfish.

Joint efforts include lab trials testing stressors like freshwater immersion, air exposure, and smothering materials. Genetic studies trace invasion pathways, informing biosecurity. UH's CGAPS coordinates with state agencies, emphasizing felony penalties for non-native imports without permits.

Photo by Daniel Lee on Unsplash

Research-Driven Removal Strategies Take Shape

University-backed science guides Navy-led eradication. Initial hand removals by divers cleared 33,850 square feet in January 2024—equivalent to three-quarters of a football field—but regrowth necessitated scaling up. Large-scale operations launched in late 2024 employ adaptive methods from Palmyra Atoll corallimorph successes: tarp smothering with impermeable fabrics, manual excision using fragment-proof bags, and pier pile wrapping.

Divers follow strict protocols to minimize fragmentation, verified by post-removal mortality assays. Hot water treatments are under evaluation, calibrated to kill octocorals without harming natives. Details on these efforts are outlined in official Navy announcements.

• Tarp Smothering: Covers colonies for weeks, inducing anoxia.
• Manual Removal: SCUBA teams excise and bag fragments for disposal.
• Monitoring: Pre- and post-surveys track regrowth via quadrat sampling.

Ecological and Economic Ramifications

Invasive octocorals displace reef-builders, reducing habitat complexity for juvenile fish and invertebrates. In Venezuela, Unomia dominates benthos, slashing native cover by over 90% in affected areas. Pearl Harbor's invasion risks amplifying Hawaii's $16 billion ocean economy losses from reef degradation.

NOAA surveys quantify impacts: reduced native coral recruitment, altered fish assemblages. Without predators in Hawaii, spread accelerates via boat propellers and currents.

Overcoming Eradication Challenges

Fragmentation poses the biggest hurdle; a single colony can spawn dozens. Confined spaces limit machinery, relying on diver-intensive labor. Regrowth rates—doubling in months—demand sustained funding. HIOWG addresses via predictive modeling from UH data, prioritizing hotspots.

Public compliance is key: kayak bans and fishing restrictions curb mechanical spread. "Don’t Let It Loose" campaigns, backed by UH, offer amnesty drop-offs.

Global Lessons Informing Local Action

Unomia's Venezuelan rampage since the 2000s mirrors Pearl Harbor, where early intervention averted wider spread. Cuba and Puerto Rico report similar aquarium releases. UH workshops synthesize these, developing unified protocols. For species details, see the Hawaii Invasive Species Council page.

Photo by Brandon Karaca on Unsplash

Future Trajectories and Research Horizons

Multi-year eradication aims for zero viable colonies by 2030, with annual benchmarks. UH spearheads biocontrol exploration—nudibranch predators like Tritoniopsis elegans tested on relatives—and genomic tools for early detection. Climate resilience studies integrate invasions with bleaching risks.

Prospects brighten with federal funding, like Congressman Ed Case's $1 million for surveys.

Career Pathways in Invasive Species Research

UH's programs attract global talent, offering PhDs in marine biology focused on invasions. Graduates lead HIOWG, blending fieldwork, genetics, and policy. This crisis highlights demand for experts in environmental science.