What could go wrong, what we don’t know yet, and who can stop it.
Deep-sea ecosystems recover very slowly, and for most of the seafloor under discussion the baseline data are thin: we do not yet know every species that lives there or how the currents move a plume. That is exactly why the federal process front-loads years of science, review and public comment before any decision — and why this page names the risks plainly alongside the safeguards.
The water column, from the surface to the abyssal plain
Nodules sit around 5,000 m down, but an operation touches every layer above them: ships on the surface, a riser through the water column, and plumes at the seafloor and — if return water is released mid-water — in the layers where tuna, migrating animals and whales spend their time.
- Vessel noise: thrusters and transiting ships disturb behaviour; fish may react out to the ring limit
- Yellowfin tuna typically swim at ~75 m and dive as deep as 1,000 m
- Diel vertical migration: animals rise at night and sink by day, crossing any mid-water plume
- SOFAR channel (~750 – 1,200 m): sound travels furthest here
- Dewatering / mid-water return plume (if used): drifts, dilutes, settles slowly; food-web effects mostly move downward
- Collector plume at the seafloor: the largest plume, drifts downcurrent
- Seamounts carry cobalt-rich crusts; ridges and back-arc basins carry massive sulphides
- Nodules are the main hard ground on the abyssal plain; sea cucumbers, sponges and corals live on and around them
How noise, plumes and disturbance could show up
Effects start with individual animals, add up at the population level, and eventually reach the things people depend on.
Individuals
What a single animal may experience
- Respiratory distress (gills clogged by fine sediment)
- Auditory distress (masking, stress, hearing damage from sustained noise)
- Reduced feeding (prey harder to see or smell in turbid water)
- Reduced visual communication (bioluminescent signals lost in a plume)
- Buoyancy issues (sediment adhering to gelatinous animals)
- Toxicity (metals released from disturbed sediment)
Populations
What happens when many individuals are affected
- Changes in community composition (who lives there shifts)
- Emigration (animals leave the area — including target fish species)
- Mortality
- Decreased fitness and reproduction
Ecosystem services
What people could lose
- Fisheries (catch rates, fish behaviour, fishing grounds)
- Seafood contamination (metal uptake into the food web)
- Carbon transport (the biological pump that moves carbon to depth)
- Biodiversity (species found nowhere else, many still undescribed)
These are potential effects identified in the peer-reviewed literature on mining-related noise, sediment plumes and seafloor disturbance. Not every effect would occur in every operation; which ones do depends on the technology used, where return water is released, the currents, and the animals present. That is precisely what baseline surveys and monitoring are meant to find out before anything is authorised.
The four concerns with commercial extraction
These are the concerns identified for American Samoa in the Steering Committee briefing. Every one of them is being evaluated — none has been settled.
Environmental impacts
Potential disturbance to seafloor habitats, sediment plumes, and effects on deep-sea biodiversity and ecosystem functions that require careful assessment and monitoring.
Fisheries concerns
Possible interactions with commercial, recreational, and subsistence fisheries, including resources vital to local food security and livelihoods in American Samoa.
Unknown long-term effects
Limited baseline scientific data on deep-ocean ecosystems means long-term ecological consequences remain uncertain and demand rigorous, ongoing research.
Cultural considerations
Respect for faʻa Samoa values, traditional ocean knowledge, and community stewardship, ensuring local voices meaningfully shape decisions and outcomes.
The potential benefits are set out with the same honesty on the economics & benefits page.
Why the deep sea is different
Five facts that explain why scientists ask for so much caution — and so much time.
Nodules grow about 1 mm per million years
On human timescales they are non-renewable. Whatever is collected will not grow back in the lifetime of anyone alive today, or their grandchildren's grandchildren.
On the mud, nodules are the main hard ground
Nodule fields are mostly soft sediment, with rock outcrops, boulders and crusts only in places. Sponges, corals, anemones and many smaller animals can only attach to something solid — so many of them depend on the nodules themselves.
Recovery is measured in decades to centuries
Experimental disturbance tracks made in the 1980s are still visible, and the animal communities in them have not fully returned. Slow growth, cold water and scarce food mean the deep sea heals very slowly.
The water column is a highway
Plumes and noise don't stay where they are made. Currents can carry fine sediment for miles, and sound travels furthest in the deep sound channel — so effects can reach animals far from the site.
Our reefs and fisheries sit downstream
American Samoa's reefs, tuna grounds and subsistence fisheries lie in the same ocean system as the areas under discussion. How and where any work happens — and where return water goes — matters to us directly.
Two plumes, and where the return water goes
A collector stirs up the top layer of sediment: that is the collector plume, at the seafloor. If slurry is pumped to the ship, the water separated from the nodules has to go somewhere: that is the dewatering (return-water) plume. Where it is released changes who is exposed.
Return water released at
Return water is piped back down and released below the surface layer, typically 1,000 – 1,500 m, below where most fishing and daily migration happens.
Reduced exposure for fisheries, but the plume still crosses the pathway of vertically migrating animals and can drift for tens of kilometres before it dilutes.
Rule of thumb: the deeper the return, the less exposure for fisheries and migrating animals. Newer designs try to avoid the return plume entirely — see how on the technology page.
Particle size
Abyssal mud is very fine. The smallest particles stay suspended longest and travel furthest; larger clumps (flocs) settle within tens to hundreds of metres.
Currents
Bottom currents on the abyssal plain are slow but persistent, so even a low plume can spread across a wide area over weeks.
Return depth
Deeper return = less exposure for fisheries and migrating animals. Releasing near the seafloor, or not pumping sediment up at all, is what newer equipment aims for.
Newer collector heads, enclosed lift systems and real-time turbidity monitoring all target these plumes. They are promising but still being tested — read what each one is meant to solve, and what is still unproven.
How the ocean is protected at every step — 8 questions
What the federal rules actually allow, who watches, and who can say stop. Answers are drawn from BOEM's PACM-1 outreach materials and 30 CFR part 581.
Short answer
Under the current lease-stage process, BOEM may authorize only preliminary activities that have no significant adverse impact on the natural resources of the Outer Continental Shelf. Commercial mining is not authorized by the lease or covered by the current EA.
Allowed
✓Acoustic mapping✓Core samples✓Scientific surveysNot allowed
✕Commercial mining✕Large-scale excavationProtection at every step
- Pre-activity review — BOEM reviews each proposal before activities begin.
- Protected species observers — Required when needed to protect marine life.
- Monitoring & reporting — Operators must monitor activities and submit reports.
- Mitigation requirements — BOEM can require measures to avoid, minimize, or reduce any potential impacts.
Short answer
NO.Current evidence shows preliminary activities are not expected to cause irreversible damage. They use proven technologies designed to collect information, not to mine minerals.
Why the footprint is small
- Remote technologies — Remote and autonomous vehicles collect data without large equipment on the seafloor.
- Proven methods — Acoustic mapping and imaging have been used worldwide for decades.
- Small footprint — Samples are small and limited to very small areas across vast lease areas.
Under a robust framework BOEM reviews, consults, mitigates, and monitors
- Review & consultation — Includes experts and federal partners.
- Mitigation — Best management measures required.
- Monitoring — Activities monitored in real time.
- Reporting — Results must be reported to BOEM.
Short answer
Monitoring, reporting, and mitigation are required for all preliminary activities. Monitoring is a lease requirement, not optional.
The process
- 1
Before activity
The lessee provides notice to BOEM before any preliminary activities occur.
- 2
BOEM review
BOEM verifies activities are permissible and consistent with environmental review and lease terms.
- 3
Monitoring during activity
The lessee must monitor all activities in accordance with lease stipulations and applicable regulations.
- 4
Report submitted
The lessee submits a report after completion.
- 5
Additional requirements if needed
Report findings help determine if additional monitoring will be necessary for future work beyond preliminary activities.
Additional protections may include
✓Protected species observers✓Mitigation measures✓Activity restrictions✓Real-time or post-activity monitoring- 1
Short answer
BOEM does not expect preliminary activities to cause long-term or irreversible damage — and evaluates the risks, even small ones, because deep-sea ecosystems recover very slowly.
How BOEM evaluates risk
- High-quality scientific information — From the lease area and similar ocean settings.
- New and additional information — Through strategic research and surveys.
- Expertise — From BOEM scientists and input from partners and other agencies.
- Advanced tools and technology — To study and understand impacts.
What BOEM considers — all three weighed before authorizing any preliminary activities
- Likelihood — How likely is the impact to occur?
- Consequence — How serious could the impact be?
- Vulnerability — How sensitive are these deep-sea ecosystems?
Even after preliminary activities, lessees must submit testing or mining plans. BOEM reviews these plans, evaluates potential impacts, and requires additional studies. Data collected during preliminary activities help inform this process.
Short answer
BOEM can stop or modify the activity.
BOEM's authority includes
- Suspend activities — Stop the activity temporarily.
- Add new restrictions — Additional conditions or safeguards.
- Modify lease terms — Change the plan or lease requirements.
- Cancel the lease — End the activity or lease when warranted.
If science identifies unacceptable environmental risks, BOEM has the authority to stop, suspend, modify, or cancel activities to protect the ocean.
Short answer
Preliminary activities collect baseline data about the deep-sea environment.
What is collected
- Biodiversity — Species and habitats.
- Ocean conditions — Water properties and currents.
- Seafloor — Geology and seabed features.
- Sediments — Chemical and physical composition.
- Cultural resources — Historical and archaeological sites.
How it's reviewed
- Independent review — BOEM and experts evaluate the data.
- Peer input — Federal partners and scientists contribute.
- Public access — Information is generally made public unless confidential.
Better information = better decisions.
Short answer
BOEM approves activities only if the potential environmental impacts are acceptable and all requirements are met. No single factor decides the outcome.
BOEM considers all relevant factors together
- Science — What do the data and research show?
- Environment — What could be the impacts on ocean life and habitats?
- Public input — What do communities, partners, and experts say?
- Laws & policies — Are all legal and policy requirements satisfied?
The review process
- 1
Plans submitted
The lessee submits its proposed plan.
- 2
Technical review
Accuracy, safety, compliance.
- 3
Environmental review
EA or EIS and other studies.
- 4
Public & partner input
Public and federal, territorial, and state partners.
- 5
Decision
BOEM weighs every factor.
- 6
Possible approval
Only if all criteria are met — often with conditions and monitoring.
No approval is guaranteed.
Short answer
Approval only happens if all requirements are met.
Possible outcomes
- Approve — Activities may move forward with conditions and monitoring in place.
- Approve with conditions — Extra safeguards, limits, or monitoring required.
- Modify the plan — Changes required to better protect the environment.
- Do not approve — Activities are stopped or denied if risks are unacceptable.
The final decision process
- 1
All reviews complete
Technical and environmental reviews finished.
- 2
Public & partner input
Comments considered.
- 3
Weigh all factors
Benefits, risks, and the best available science.
- 4
Decision made
Documented and made public.
- 5
Monitor & enforce
If approved, BOEM monitors activities and enforces all conditions.
Remember: no approval is guaranteed.
The big picture
A careful, step-by-step process
- 01
Lease sale
Area offered for potential exploration
- 02
Preliminary activities
Limited surveys and data collection
- 03
Ongoing monitoring
Oversight, reporting, compliance
- 04
Environmental reviews
EA, EIS, and public comment
- 05
Federal decision
All factors weighed
- 06
Protecting our ocean & future
Science, transparency, accountability
BOEM’s goal is simple: enable science, not harm. Strong oversight. Real accountability. A protected ocean.
Where this comes from
- BOEM — Proposed Leasing Notice, PACM-1 (Pacific Critical Minerals lease sale)The notice describing what a lease would and would not allow offshore American Samoa.
- 30 CFR part 581, including § 581.47(d)Federal regulations for OCS mineral leasing other than oil, gas and sulphur; § 581.47(d) limits preliminary activities to those not expected to cause significant adverse impacts.
- National Environmental Policy Act (NEPA)The law requiring environmental assessments (EA) and environmental impact statements (EIS) with public comment.
- Te Ipukarea Society (June 2025) — seabed pressures in the Cook IslandsSource of the water-column pressures figure adapted above.
- Muñoz-Royo et al. (2021), Communications Earth & Environment — DOI 10.1038/s43247-021-00213-8Peer-reviewed modelling of how mid-water (dewatering) plumes disperse and dilute in the water column.
- Marine Scotland (marine.gov.scot) — underwater-noise guidanceGuidance on vessel and construction noise and its effects on fish and marine mammals.