Particularly Sensitive Sea Areas: IMO PSSA Guide

A Particularly Sensitive Sea Area (PSSA) is a sea area formally designated by the IMO’s Marine Environment Protection Committee because it meets at least one criterion of ecological, socio-economic, or scientific significance and faces vulnerability to damage from international shipping. The designation is not symbolic: every PSSA must carry at least one IMO-adopted Associated Protective Measure that creates concrete, binding or recommendatory obligations for ships transiting the area.

Definition and regulatory basis

The PSSA concept dates to 1978 in its informal origins, but its modern legal architecture rests on IMO Assembly Resolution A.982(24), adopted on 1 December 2005, which set out the “Revised Guidelines for the Identification and Designation of Particularly Sensitive Sea Areas.” Those guidelines were themselves a consolidation and revision of earlier guidance from 1991 (A.720(17)) and 2001 (A.885(21)). A further amendment, Resolution MEPC.267(68), adopted on 15 May 2015, refined specific provisions without restructuring the core framework.

Resolution A.982(24) defines a PSSA as “an area that needs special protection through action by IMO because of its significance for recognized ecological, socio-economic, or scientific attributes where such attributes may be vulnerable to damage by international shipping activities.” Three elements must all be present: the area must have a recognized attribute, that attribute must be at risk from shipping, and the protective measure must be adoptable under an existing IMO instrument.

The MEPC is the primary committee responsible for evaluating proposals and adopting designation resolutions. The Maritime Safety Committee (MSC) often plays a supporting role when the APMs proposed include routeing measures or ship reporting systems that fall under MSC’s mandate.

Identification criteria

A proposed PSSA must satisfy at least one criterion from three categories. Meeting a single criterion is enough; the guidelines don’t require cumulative scoring across categories. In practice, most successful proposals point to multiple criteria to strengthen the case.

Ecological criteria

The ecological category is the most commonly cited. It includes: uniqueness or rarity (an area is the only or one of very few of its type); critical habitat (essential for a species’ survival, spawning, or nursing); dependency (a biological community tightly linked to the area); representativeness (a good example of a distinct type of ecosystem); diversity (high species richness or habitat variety); productivity (high rates of natural biological production); spawning or breeding grounds; naturalness (a high degree of freedom from human disturbance or degradation); integrity (a functional unit that can sustain itself); fragility (susceptibility to degradation from natural events or human activities); and bio-geographical importance.

The Great Barrier Reef, designated as the first PSSA in 1990 under Resolution MEPC.44(30), satisfied multiple ecological sub-criteria simultaneously: it is a unique ecosystem of exceptional diversity, a critical habitat for over 1,500 fish species and six of the world’s seven marine turtle species, and among the most productive coral reef systems on the planet.

Social, cultural, and economic criteria

This category covers areas of economic dependency (where communities rely heavily on the area’s resources for subsistence or commerce), human dependency (where the well-being of populations is directly linked to the area’s ecological health), and cultural heritage (areas with indigenous, historical, or cultural significance that would be severely diminished by shipping-related damage).

The Strait of Bonifacio PSSA between France and Italy, designated by MEPC.204(62) in July 2011, drew on cultural and economic criteria: the strait has been a contested navigation route between Corsica and Sardinia for centuries, flanked by both a UNESCO-listed biosphere reserve (Maddalena Archipelago) and a regional natural park on the Corsican side.

Scientific and educational criteria

This category covers areas of particular interest for research (baseline monitoring value, opportunities to study undisturbed marine systems), educational value (sites that serve as natural laboratories for university programs or public education), and areas whose protection would support the broader objectives of international environmental agreements.

The Papahānaumokuākea Marine National Monument in the northwestern Hawaiian Islands, designated under MEPC.171(57) on 4 April 2008, illustrates this category well: it is one of the largest marine protected areas in the world, harboring 25% of all US shallow-water coral reef ecosystems, 7,000+ marine species, and ongoing field research programs across ecology, seamount geomorphology, and deep-sea biology.

Vulnerability to shipping

Identifying ecological or cultural significance alone isn’t enough. The proposing state must show the area is actually vulnerable to harm from international shipping. Vulnerability encompasses several recognized threat pathways.

Groundings and physical damage from ship hulls represent the most direct risk. The 2013 grounding of USS Guardian on the Tubbataha Reefs in the Philippines (PSSA under MEPC.294(71)) remains the most publicized recent incident: the minesweeper ran aground on a coral pinnacle inside an Area To Be Avoided, and the resulting investigation confirmed 1,000 square meters of coral damage.

Discharge threats cover oil, ballast water, grey and black water, garbage, and noxious liquid substance spills. The Wadden Sea between Denmark, Germany, and the Netherlands, designated under MEPC.101(48) in October 2002, faces persistent risk from tanker traffic in the adjacent North Sea; its tidal flats support 12 million migratory birds annually and approximately 10,000 marine species, many of which are immediately impacted by oil contamination.

Noise and physical disturbance from vessels affect cetacean populations, and it’s this threat pathway that motivated the North-Western Mediterranean PSSA under MEPC.380(80) in July 2023. Fin whales and sperm whales using the western Mediterranean for feeding and migration are at elevated risk of lethal collision with fast-moving cargo ships and cruise vessels; ship strike is now documented as one of the leading causes of large cetacean mortality in this basin.

Invasive species introduction via ballast water exchange or biofouling presents a longer-term but increasingly well-documented risk, particularly for island ecosystems and reef systems where native biodiversity evolved in relative isolation.

The designation procedure

The PSSA designation procedure operates in two stages under A.982(24) as amended.

Stage one: submission and approval in principle

A member state (or a group of states) submits a proposal to MEPC. The proposal must include a completed PSSA Proposal Review Form and cover: a full description of the area and its ecological, economic, scientific, or cultural attributes; a description of the threats posed by international shipping; an identification of at least one APM with the legal basis under an existing IMO instrument (such as the Collision Regulations, SOLAS Chapter V, or MARPOL); and a map of the proposed boundaries.

The MEPC Technical Group on PSSAs examines the submission. It checks that the area meets at least one identification criterion, that the vulnerability to shipping is real and documented, and that the proposed APM is legally grounded. If satisfied, the Committee agrees “in principle” to the designation. Peru received in-principle agreement at MEPC 83 in April 2025 for both the Nasca Ridge National Reserve and the Grau Tropical Sea National Reserve, with formal designation pending APM submission to MEPC 84.

Stage two: APM adoption and formal designation

The proposing state must return with fully developed APMs, which are then adopted through the appropriate IMO body. Routeing measures and ship reporting systems go to MSC for adoption. Discharge restrictions go through MARPOL amendment procedures. Once the APMs are formally adopted, MEPC adopts a designation resolution by the same or a subsequent session. Without the APM, no designation occurs; the two elements are inseparable.

The full procedure from first proposal to formal designation typically spans two to four MEPC sessions, meaning 18 to 36 months at typical MEPC meeting cadence. The Western European Waters PSSA, proposed by Belgium, France, Ireland, Portugal, Spain, and the United Kingdom and adopted under MEPC.121(52) in October 2004, took several years of iterative development before it reached the designation stage.

Types of Associated Protective Measures

The APM is the operational heart of a PSSA. A designation without a real APM would be a label, not a protective mechanism. A.982(24) recognizes several categories.

Areas To Be Avoided (ATBAs) are the most common APM type. They designate a geographic zone that ships of a specified class (by size, type, or cargo) are prohibited from entering, or strongly recommended to avoid. The Malpelo Island PSSA (Colombia, MEPC.97(47), 2002) is protected by an ATBA around the island itself; Malpelo is a remote oceanic seamount and UNESCO World Heritage Site whose endemic species evolved over millions of years without human contact.

Traffic Separation Schemes (TSSs) and routeing measures channel ship traffic into defined lanes or away from sensitive zones. The Jomard Entrance PSSA in Papua New Guinea (MEPC.283(70), 2016) is protected by four two-way routes and a precautionary area that direct LNG carriers and other deep-draught vessels through the Louisiade Archipelago without transiting the reef-strewn central passage.

Mandatory ship reporting systems require ships to report their position, course, speed, and cargo to a shore authority on entering a defined zone. The Papahānaumokuākea PSSA uses CORAL SHIPREP, a mandatory reporting system administered by the US Coast Guard. The Canary Islands PSSA (MEPC.134(53), July 2005) uses CANREP. The Galápagos Archipelago PSSA (MEPC.135(53), July 2005) uses GALREP. These systems allow shore authorities to track ship movements in real time, respond quickly to incidents, and build traffic data for future management decisions.

No-anchoring areas are applied where the seabed habitat is too fragile to withstand anchor drops and chain drag. The Saba Bank PSSA in the northeastern Caribbean (Kingdom of the Netherlands, MEPC.226(64), 2012) carries a mandatory no-anchoring area for all vessels over the entire bank, protecting a 2,200-km² platform of deep-water coral and sponge communities at 30 to 60 m depth.

Speed reduction recommendations are the newest APM form. They’re not traditionally mandatory, but the NW Mediterranean PSSA (MEPC.380(80), 2023) formalizes a voluntary speed reduction (VSR) to 10 to 13 knots for commercial ships and yachts of 300 GT and above when cetaceans are detected, plus a requirement to broadcast cetacean positions on VHF to designated coastal authorities. The IMO is watching this model closely; the Mediterranean case is likely to inform future APM design in cetacean-sensitive zones elsewhere.

Special discharge restrictions can be adopted as APMs when the standard MARPOL discharge standards are inadequate for the area’s sensitivity. The Florida Keys PSSA (MEPC.97(47), 2002) includes mandatory no-anchoring areas in the Tortugas Ecological Reserve and the Tortugas Bank, supplementing existing MARPOL Annex V restrictions. The Baltic Sea PSSA (MEPC.136(53), 2005) explicitly references the area’s existing MARPOL Special Area status for Annexes I, II, IV, and V as part of its APM package.

The complete list of designated PSSAs

The table below lists all 19 designated PSSAs as confirmed on the IMO’s official PSSA page and in MEPC.1/Circ.778/Rev.5 (May 2025). The three Australian entries are extensions of a single PSSA rather than three independent designations; the IMO treats the Great Barrier Reef, Torres Strait, and Coral Sea as one evolving designation. Counted by designation resolution, there are 19 separate instruments.

The timeline shows two distinct periods of activity. The first cluster, from 1990 to 2008, produced 12 designations as the PSSA concept proved itself through the Great Barrier Reef experience and states with high-value reef and archipelago habitats followed quickly. The second cluster, from 2011 to 2024, has been sparser, averaging roughly one new designation every two to three years, partly because the “easy” nominations have been made and partly because states have found the two-step process demanding.

Regional snapshots: selected PSSAs in depth

Great Barrier Reef, Torres Strait, and Coral Sea

The Great Barrier Reef is the oldest and best-studied PSSA, making it the reference point against which all subsequent designations are measured. The original 1990 designation covered the reef itself. A 2005 extension (MEPC.133(53)) brought in the Torres Strait, the shallow-water passage between Australia’s Cape York Peninsula and Papua New Guinea where bulk carriers, tankers, and LNG carriers bound for Northeast Asia transit just 12 meters over reef-scattered shoals. Australia imposes compulsory pilotage on this section under domestic law; the PSSA designation backs that requirement with IMO recognition.

A further 2015 extension (MEPC.268(68)) added the south-west Coral Sea, including routeing measures such as a two-way route through the Prince of Wales Channel and an ATBA northeast of the reef between Palm Passage and Hydrographers Passage. The full PSSA now covers approximately 345,000 km² across three instruments.

Baltic Sea area

The Baltic PSSA (MEPC.136(53)) is unique for two reasons. First, it is the only PSSA designated by eight states acting together. Second, its APM package doesn’t add new measures but rather formally incorporates the Baltic Sea’s existing protection regime: MARPOL Annex I, II, IV, and V Special Area status, an Emission Control Area under MARPOL Annex VI for both SOx and NOx, deep-water routes, and mandatory pilot reporting under the Baltic HELCOM system. The PSSA designation functions here as an umbrella recognition that these measures collectively serve a PSSA-quality protection purpose.

The Wadden Sea on the southern North Sea coast and the Baltic Sea PSSA together frame the approach routes and departure lanes of Northern European ports. Traffic through the Kattegat and Øresund between the North Sea and Baltic must navigate past or near both protected areas; this geographic proximity creates real coordination demands for vessel traffic services.

Galápagos Archipelago

Ecuador proposed the Galápagos PSSA (MEPC.135(53)) against a background of two major incidents: the 2001 grounding of the tanker Jessica in San Cristóbal and the resulting heavy-fuel oil spill that killed marine iguanas, sea lions, and penguins. The APMs include GALREP (a mandatory ship reporting system), recommended port approach tracks that are treated as mandatory conditions of port entry, and an ATBA around the island group. The Galápagos is one of the few areas where the PSSA sits on top of a nationally enforced marine reserve; Ecuador’s domestic law pre-dates the IMO designation and goes further in some respects.

Papahānaumokuākea Marine National Monument

MEPC.171(57) designated Papahānaumokuākea in April 2008, two years after it received US Presidential proclamation as a Marine National Monument. The PSSA covers approximately 362,000 km² of the northwestern Hawaiian Islands and associated seamounts. Its APMs include CORAL SHIPREP, under which vessels 300 GT and above must report to the US Coast Guard Joint Rescue Coordination Center in Honolulu before entering the area, and six ATBAs covering the most ecologically sensitive atolls and reefs. The Papahānaumokuākea PSSA article on this site covers the full APM geography and the incident history that motivated the nomination.

Tubbataha Reefs Natural Park

The Philippines designated the Tubbataha Reefs under MEPC.294(71) at MEPC 71 in July 2017. The APM is a single ATBA around the reef system in the Sulu Sea. The Tubbataha Reefs PSSA article details the 2013 USS Guardian grounding, which occurred before formal PSSA designation but within an existing ATBA established under national law, and the subsequent litigation and penalty proceedings that drew international attention to the reef’s vulnerability. The PSSA designation adds IMO-level recognition to protections that Philippine domestic law had established earlier.

North-Western Mediterranean Sea

The 2023 NW Mediterranean PSSA (MEPC.380(80)) is the most recent example of a PSSA built primarily around cetacean protection, a relatively new direction for the designation system. France, Italy, Monaco, and Spain jointly proposed the area, which encompasses the Pelagos Sanctuary, Spain’s cetacean migration corridor, and two areas recognized by the Convention on Biological Diversity as ecologically significant.

The APMs are explicitly described as “recommendatory in nature” and apply to commercial ships and pleasure yachts of 300 GT and above. When large or medium cetaceans are detected within the PSSA, mariners should reduce speed to 10 to 13 knots and maintain a safe separation distance. Mariners must also broadcast cetacean positions on VHF to coastal authorities, and any ship strike must be reported to those authorities for forwarding to the International Whaling Commission’s global cetacean ship-strikes database.

This is the first PSSA whose primary APM relies on real-time detection and responsive behavior by the master rather than fixed geographic exclusion zones. Whether the recommendatory framing limits its protective effectiveness is a live debate at MEPC.

Nusa Penida and Gili Matra Islands

Indonesia’s designation of the Nusa Penida Islands and the Gili Matra Islands in the Lombok Strait (MEPC.396(82), October 2024) is the most recent formal designation. The area sits within the Coral Triangle, recognized globally as the most marine-biodiverse region on Earth, with approximately 1,419 hectares of coral reef and 296 documented coral species. The Lombok Strait is a principal traffic corridor for ships transiting between the Indian Ocean and the Java Sea, and traffic density has risen steadily as LNG exports from eastern Indonesia increased through the 2010s and 2020s.

The APM is the existing Traffic Separation Scheme adopted in 2019 (COLREG.2/Circ.74, in force from 1 July 2019), which the PSSA designation now formally recognizes as the primary protective measure. Vessels transiting through the area are directed through defined TSS lanes away from the Nusa Penida MPA and the Gili Matra marine reserve.

PSSA versus MARPOL Special Area

A MARPOL Special Area is a discharge-control measure; a PSSA is a multi-instrument protection regime. The distinction matters because masters, deck officers, and port state control inspectors deal with them through different regulatory pathways.

MARPOL Special Areas are established under Annexes I (oil), II (noxious liquid substances), IV (sewage), and V (garbage). Once an area is designated under a given Annex, ships transiting it must meet stricter discharge standards than the global default. In a MARPOL Annex V Special Area, for example, garbage overboard is completely prohibited, whereas the standard allows food waste under certain conditions beyond 12 nautical miles. The Baltic Sea is a MARPOL Special Area under all four Annexes.

A PSSA doesn’t, by itself, change any discharge standard. Its effect comes through its APMs, which may or may not include discharge restrictions. The APMs might instead be routing measures, ship reporting requirements, or ATBAs, none of which address discharge at all. The Florida Keys PSSA’s primary APMs are no-anchoring areas, not discharge prohibitions.

The two designations can and often do overlap. The Baltic Sea is both a MARPOL Special Area (for Annexes I, II, IV, and V) and a PSSA. The overlap means ships transiting the Baltic face both the MARPOL discharge regime and the PSSA-linked obligations such as mandatory ship reporting. The MARPOL Annex I and MARPOL convention articles on this site describe the Special Area discharge standards in detail.

The practical difference for a ship operator:

• MARPOL Special Area: check which Annex(es) apply, verify reception facility availability, operate the oil water separator and incinerator within the stricter limits, keep records in the relevant record book.
• PSSA APM compliance: check the specific APMs in the relevant MEPC resolution (not always clearly labeled in chart folios), report to the mandatory ship reporting authority if one exists, observe any ATBAs, and follow any speed or routing advisories.

Neither regime depends on the other for validity. An area can be a MARPOL Special Area without PSSA status (most MARPOL Special Areas are not PSSAs), and a PSSA can exist without MARPOL Special Area status.

PSSA versus marine protected areas under the BBNJ Agreement

The 2023 UN Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Agreement, or “High Seas Treaty”) creates a new global mechanism for establishing marine protected areas on the high seas. This is the first international legal instrument that can designate MPAs in waters outside any national exclusive economic zone.

PSSAs and BBNJ MPAs are structurally different. A PSSA is a sectoral, shipping-specific measure; it controls what international shipping can do in an area, but it doesn’t restrict fishing, deep-sea mining proposals, or cable-laying. A BBNJ MPA can be cross-sectoral, restricting multiple industries. The BBNJ Agreement also explicitly acknowledges the IMO’s role: shipping-specific measures within a BBNJ MPA would still need to go through IMO and would likely take the form of PSSA APMs or equivalent instruments.

No state has yet proposed a high-seas PSSA, though A.982(24) permits it in principle. The BBNJ Agreement’s entry into force (pending sufficient ratifications as of mid-2026) may prompt the first high-seas PSSA proposal by providing a political framework within which the IMO contribution would be clearly scoped. The Frontiers in Marine Science 2025 paper by Gjerde et al. argues that PSSAs could become the IMO’s primary delivery mechanism for shipping controls within BBNJ-designated areas on the high seas.

Enforcement and jurisdiction

A PSSA APM’s enforceability depends on the type of measure and the jurisdiction category.

ATBAs are formally “recommendations” under the International Regulations for Preventing Collisions at Sea (COLREGS) and the SOLAS Chapter V framework. A master who transits an ATBA doesn’t automatically face criminal prosecution under IMO instruments, but does so under the domestic law of any coastal or port state that has implemented the ATBA in national legislation. Australia has done this for the Great Barrier Reef; the Philippines has done this for the Tubbataha ATBA. Port state control officers at the next port of call can inspect vessel records to check whether ATBAs were respected.

Mandatory ship reporting systems carry clearer enforcement hooks. Failure to report on entering a mandatory reporting zone can constitute a violation of SOLAS Chapter V (safe navigation), which is directly enforceable by flag states, port states, and coastal states under UNCLOS Articles 217, 218, and 220.

No-anchoring areas in a PSSA create obligations that port states and coastal states can enforce against visiting ships. The Saba Bank no-anchoring area is monitored by the Netherlands Caribbean Coast Guard; violations result in administrative fines under Netherlands Antilles domestic law.

Speed recommendations (as in the NW Mediterranean PSSA) are the weakest tool: because the APM is explicitly recommendatory, flag state enforcement depends on voluntary compliance, and port state control officers cannot easily detect non-compliance after the fact unless AIS records are analyzed.

Flag state obligations run in parallel: states that are SOLAS and MARPOL parties must ensure their flag vessels comply with all adopted routeing measures and reporting systems. Effective flag state enforcement requires that the APMs be clearly communicated to masters through the relevant edition of IMO Publication IA545E (the PSSA compendium) and through Notice to Mariners.

Relationship to other IMO area-based measures

PSSAs and MARPOL Special Areas are the two best-known IMO area-based protection regimes, but they sit alongside others.

Emission Control Areas (ECAs) under MARPOL Annex VI impose stricter limits on sulphur oxide, nitrogen oxide, and particulate matter emissions. The Baltic Sea is simultaneously a MARPOL Special Area (for oil, garbage, sewage, and noxious liquids), a PSSA, and an ECA, making it the most regulated shipping corridor in the world. The emission control areas article covers the ECA framework and its interaction with MARPOL Annex VI.

Special Areas under MARPOL Annex VI are different again: they cover particular regions where stricter data-collection or carbon-intensity requirements apply. These are newer instruments that sit outside the classical Special Area / PSSA framework.

The Regional Seas Programme administered by UNEP coordinates regional environmental action through 18 regional agreements. The Wadden Sea is protected under the Agreement on the Conservation of Wadden Sea Seals and the Trilateral Wadden Sea Plan; the PSSA designation adds IMO-level shipping controls on top of that regional framework. The UNEP Regional Seas Programme article and the Wider Caribbean Region article discuss how regional marine governance structures interact with IMO instruments in their respective ocean basins.

The Ramsar Convention on Wetlands designates internationally important wetland habitats. Several PSSA areas include Ramsar-listed wetlands: the Wadden Sea is a UNESCO World Heritage Site and a Ramsar site. The Ramsar designation protects the intertidal zone; the PSSA protects it from shipping threats specifically. The Ramsar Convention article explains the wetland-specific designation system.

The designation pipeline: PSSAs agreed in principle at MEPC 83

At its 83rd session in April 2025, MEPC agreed in principle to the designation of two Peruvian areas: the Reserva Nacional Dorsal de Nasca (Nasca Ridge National Reserve) and the Reserva Nacional Mar Tropical de Grau (Grau Tropical Sea National Reserve). Both proposals were submitted by Peru, which already has a PSSA (the Paracas National Reserve, MEPC.106(49), 2003). Peru was invited to further develop its proposed APMs and submit them to MEPC 84 for consideration.

The Nasca Ridge is a 1,100-km aseismic oceanic ridge in the southeastern Pacific whose seamount chain supports deep-sea coral and sponge communities, endemic demersal fish, and aggregations of toothed whales. The Mar Tropical de Grau encompasses warm-water reef environments in northern Peru, influenced by the equatorial countercurrent and shared with Ecuador’s Galápagos margin. If both are formally designated at MEPC 84, Peru will hold three PSSAs, more than any other state except Australia.

Practical implications for ships

A ship transiting a PSSA area has specific obligations that vary by APM type. The starting point is the latest edition of IMO circular MEPC.1/Circ.778 (Rev.5, May 2025), which lists all special areas and PSSAs in force. Ships should also consult the relevant MEPC designation resolution (freely available on the IMO website) for the exact APM boundaries and requirements.

For the Great Barrier Reef and Torres Strait, any ship over 70 meters in length or carrying oil in bulk, chemicals, or liquefied gas must take an IMO-recognized pilot if it transits the inner route. This is a domestic Australian requirement backed by PSSA recognition.

For the Galápagos, ships must report via GALREP before entering the area and follow the recommended approach tracks. Failure to do so can result in denial of port entry at Puerto Ayora or Academy Bay.

For the Papahānaumokuākea, CORAL SHIPREP is mandatory for ships of 300 GT and above. Non-reporting is treated as a SOLAS violation and is enforceable by the US Coast Guard both at sea and in port.

For the NW Mediterranean, the obligation is lighter but more behaviorally demanding: masters must maintain cetacean watch and react to sightings by reducing speed and notifying coastal authorities.

Limitations

The PSSA system has genuine strengths, but several structural weaknesses deserve attention.

APM enforceability varies widely. Recommendatory APMs (speed guidelines, cetacean watch requirements) depend on voluntary compliance by masters and flag states. No independent real-time monitoring exists for most PSSAs. The IMO has no enforcement arm; it relies entirely on flag and port state implementation.

Coverage gaps. Nineteen PSSAs cover a very small fraction of the world’s ecologically sensitive coastal and oceanic environments. Nomination requires state initiative, sustained diplomatic effort at IMO, and the development of technically credible APM proposals. States without well-funded maritime administrations find the process difficult, which means under-represented regions (much of West Africa, South and Southeast Asian small island states, Pacific island nations) face a structural barrier to achieving designations even for genuinely threatened areas.

The high-seas gap. As noted above, no PSSA has been designated on the high seas, even though A.982(24) explicitly permits it. The majority of the world’s seamount ecosystems, mid-ocean ridge communities, and pelagic cetacean habitats are in ABNJ and receive no PSSA protection.

Overlap and coordination complexity. In areas like the Baltic Sea where multiple protection regimes operate simultaneously (PSSA, MARPOL Special Areas, ECA, HELCOM mandatory pilot reporting, domestic pilotage requirements), the compliance burden on ship operators is substantial, and the interaction between regimes isn’t always clearly mapped in available guidance.

Outdated APMs. Some early PSSA APMs have not been updated to reflect changes in traffic patterns, new vessel types, or updated scientific understanding of the area. The original Great Barrier Reef APMs predate LNG carrier traffic through the Torres Strait and the expansion of cruise ship movements in the Coral Sea.

Monitoring and data feedback. The IMO has no systematic mechanism for reviewing whether PSSA APMs are actually reducing the threats they were designed to address. MEPC receives periodic voluntary reports from proposing states, but no mandatory incident-reporting or biodiversity-monitoring framework is linked to the PSSA designation.

These limitations don’t invalidate the system. They describe the boundaries of what the current framework can achieve and the directions in which it needs to develop, particularly as the BBNJ Agreement creates a new institutional context for area-based ocean governance.