Unifesp Breakthrough: Air Gun Controls Invasive Sun Coral Without Regeneration

The Invasive Threat of Sun Coral to Brazil's Reefs

Brazil's coastal waters, home to vibrant coral ecosystems, face a growing menace from the sun coral, scientifically known as Tubastraea species. Originally from the Indo-Pacific, these azooxanthellate corals—lacking symbiotic algae—arrived in Brazilian waters in the 1980s, likely hitchhiking on oil platform structures and ship hulls. Today, they blanket reefs from Rio de Janeiro to Bahia, outcompeting native species like the endangered brain coral Mussismilia harttii for space and resources. Their rapid spread disrupts food webs, reduces biodiversity, and alters reef structures, making them less resilient to climate stressors such as warming oceans and acidification.

In areas like the Alcatrazes Archipelago off São Paulo—a protected marine area—the sun coral covers up to 80 percent of hard substrates in some spots. Native corals, which rely on sunlight-filtering zooxanthellae, struggle against these shade-tolerant invaders that spawn massive larval clouds annually, dispersing millions of planulae over vast distances. Without effective control, experts warn of irreversible shifts in Brazil's Southwestern Atlantic reefs, which support fisheries yielding over 100,000 tons annually and tourism worth billions.

Limitations of Conventional Removal Techniques

Traditional management relies on manual extraction using hammers, chisels, or pneumatic tools. Divers painstakingly chip away colonies, but this often shatters the coral into fragments as small as 1 millimeter. Sun corals' remarkable regenerative power allows these pieces to settle and grow into new colonies, exacerbating the invasion. Collection and disposal of debris demand boats, bags, and incineration facilities, straining logistics in remote sites.

Field campaigns at Alcatrazes have removed thousands of kilograms, yet regrowth rates exceed 50 percent within months. Chemical biocides risk harming non-target marine life, while scraping leaves skeletons that fragments can recolonize. These methods, while necessary, are labor-intensive, costly—up to R$50,000 per expedition—and ineffective long-term, prompting Brazilian researchers to seek innovative alternatives.

Unifesp's Marine Ecology Lab Leads the Charge

At the forefront stands the Laboratory of Ecology and Marine Conservation at Universidade Federal de São Paulo (Unifesp), a leading federal institution renowned for health sciences and now environmental innovation. Researchers Guilherme Henrique Piazzaroli and Guilherme Pereira-Filho, drawing from years monitoring Brazilian reefs, devised a non-extractive solution inspired by lab tissue separation techniques.

Unifesp's campus in Santos, near key reef sites, facilitates hands-on testing. The team's multidisciplinary approach combines ecology, engineering, and policy, aligning with Brazil's National Plan for Prevention, Control, and Monitoring of Sun Coral (Plano Nacional do Coral-sol). Their work exemplifies how public universities bridge academia and conservation, training divers and influencing Ibama guidelines.

How the Compressed-Air Blasting Method Works

The technique employs a simple adaptation: a high-pressure air pistol connected to a scuba diver's regulator and auxiliary tank. Operating at depths up to 20 meters, the diver aims short bursts (2-5 seconds) at colonies, blasting away the soft polyp tissue while the calcareous skeleton remains anchored to the rock.

1. Preparation: Attach pistol nozzle (adapted from industrial models) to second-stage regulator; calibrate pressure to 200-300 psi.
2. Targeting: Focus on polyp mouths and branches; avoid substrate damage.
3. Blasting: Pulse air jets pulverize tissue into micro-fragments (<0.5 mm), dispersing them harmlessly.
4. Post-treatment: Skeleton weathers naturally, colonized by algae and invertebrates.

This process takes seconds per colony, versus minutes for hammering, and requires no waste handling.

Rigorous Testing in Lab and Field

Unifesp validated the method through controlled experiments. In labs, blasted fragments were monitored for 180 days; zero regeneration occurred, unlike hammer fragments that grew 20-30 percent. Field trials at Alcatrazes targeted 48 colonies (10-20 cm diameter), compared to 14 controls.

Photographic analysis via Coral Point Count showed treated areas reduced by 92 percent post-blast, with polyps dropping from averages of 150 to under 5 per cm². After six months, controls expanded 15 percent, while treated sites stabilized, allowing native algae to reclaim space. No adverse effects on surrounding biota were observed, confirming selectivity.

Photo by Karl Solano on Unsplash

Superior Effectiveness and Safety Profile

Key metrics highlight superiority: tissue removal efficiency hit 95 percent versus 70 percent for mechanical methods; regeneration risk near zero (0% vs. 40-60%). Cost per colony: R$2-5 in air, versus R$20+ for tools and disposal.

• Efficiency: 10x faster application.
• Safety: No chemicals, minimal diver fatigue, low noise.
• Sustainability: Preserves substrate for natives.

Independent experts like Joel Creed (UERJ) praise its design, addressing fragmentation pitfalls head-on. For Brazil's 3,000+ km infested coast, it promises scalable impact.

Broad Applications for Marine Infrastructure

Beyond reefs, the tool targets vectors: ship hulls, oil rigs (Petrobras hotspots), piers. Prototypes for boat-mounted versions are in development, potentially curbing larval spread. In marinas like Ilhabela, pilots could prevent inter-port jumps.

Integration with drones for mapping and robotic blasters envisions autonomous control, aligning with Brazil's blue economy goals. Partnerships with Ibama and NGOs like Projeto Coral-Sol position Unifesp as a hub for tech transfer.

Ecological and Economic Implications

Restoring reefs bolsters fisheries (sun coral reduces fish by 30-50%) and tourism (R$10B/year). Native coral recovery timelines: 2-5 years post-control. Economically, R$1M invested yields R$10M in preserved services.

Stakeholders—fishers, divers, Petrobras—welcome it. Pereira-Filho notes: "Simple ideas yield big benefits, repaying society's science investment." Multi-perspective: Environmentalists hail non-lethal skeleton preservation; industry eyes rig cleanups.

Unifesp's Growing Role in Marine Research

Unifesp, with 40,000+ students across nine campuses, excels in applied ecology. Santos campus leads reef monitoring; collaborations with USP, UERJ amplify impact. Funding from FAPESP, CNPq supports such innovations, training 100+ divers yearly.

This breakthrough underscores universities' pivot to actionable science amid climate crises, positioning Brazil globally in invasion biology.

Challenges Ahead and Future Outlook

Scaling requires diver training, equipment standardization, monitoring protocols. Larval timing avoidance (peak spawning Feb-May) maximizes efficacy. Policy integration into national plans is key.

Optimism prevails: Pilots expand to Abrolhos, Fernando de Noronha. Long-term: Genetic tools, biocontrol hybrids. Unifesp eyes international export to Caribbean invasions.

Photo by Karl Solano on Unsplash

Stakeholder Perspectives and Actionable Steps

Fishers report 20% catch drops; conservationists urge urgency. Steps: Train locals via university programs; fund via green bonds; monitor via citizen science apps.

Brazil's reefs—second largest globally—demand such ingenuity. Unifesp exemplifies higher ed's societal return.