By ShipCalculators.com · Published 8 May 2026

US Caribbean ECA: MARPOL Annex VI emission control area

The US Caribbean ECA is the smallest MARPOL Annex VI emission control area by sea-surface coverage, designated by the United States acting alone under Resolution MEPC.202(62) at MEPC 62 on 15 July 2011. The ECA is a combined Sulphur Emission Control Area (SECA) under Regulation 14 and Nitrogen Emission Control Area (NECA) under Regulation 13, mirroring the structure of the North American ECA but covering a geographically distinct footprint around the US Caribbean territories. The resolution entered into force on 1 January 2014 under the standard MARPOL tacit-acceptance timetable, with the 1.00% m/m sulphur cap applying immediately and the 0.10% m/m cap stepping in on 1 January 2015 in line with the global Annex VI step. The Tier III NOx limit (3.4 g/kWh at n < 130 rpm) applies to engines installed on ships with a keel-laying date on or after 1 January 2016, the same effective date as the North American NECA. The geographic boundary follows a 200 nautical mile seaward line around Puerto Rico and the US Virgin Islands (St Thomas, St John, St Croix), defined by 24 latitude/longitude vertices in the Annex to MEPC.202(62), and excludes all non-US waters of the Wider Caribbean Region. Cuba, the Dominican Republic, the Cayman Islands, Jamaica, Haiti, the Lesser Antilles (British and French Caribbean territories, the Netherlands ABC islands, the independent island states from St Kitts to Trinidad) all lie outside the ECA, leaving most Caribbean cruise itineraries traversing a patchwork of compliant and non-compliant zones. Compliance is via ULSFO ≤ 0.10%, VLSFO/MGO blends, LNG dual-fuel or certified scrubbers. Enforcement is delivered by USCG Sector San Juan and EPA Region 2 under the Act to Prevent Pollution from Ships (APPS, 33 USC 1901 to 1915) and 33 CFR 151 Subpart A. Companion calculators include the Reg 14 sulphur, Reg 13 NOx, Tier III NOx and ECA fuel-cost premium tools at the calculator catalogue. The US Caribbean ECA exists alongside the Baltic SECA + NECA, North Sea SECA + NECA and the geographically distinct North American ECA under the umbrella of the MARPOL Convention.

Contents

Background: Annex VI Reg 14 and Reg 13 framework

MARPOL Annex VI is the air-pollution annex of the MARPOL Convention. The annex was adopted as the 1997 Protocol to MARPOL 73/78, entered into force on 19 May 2005 and was substantially revised by Resolution MEPC.176(58) at MEPC 58 in October 2008. The annex regulates ship-source emissions of sulphur oxides (SOx), nitrogen oxides (NOx), particulate matter (PM), volatile organic compounds (VOC), ozone-depleting substances and, since the 2011 amendments, greenhouse gases through the energy-efficiency framework. Two regulations form the legal basis for the US Caribbean regime.

Regulation 14 caps the sulphur content of any fuel oil used on board. The global limit fell to 0.50% m/m on 1 January 2020 under the IMO 2020 sulphur cap. Inside an Emission Control Area for sulphur the limit is one fifth of that figure, namely 0.10% m/m, in force in the US Caribbean ECA since 1 January 2015. Compliance can be achieved either by burning fuel that meets the cap on a sulphur-content basis, or by operating an equivalent arrangement, typically an exhaust-gas cleaning system (a scrubber), that produces an SO2/CO2 ratio in the stack equivalent to compliant fuel. The US Caribbean numerical cap is identical to the North American, Baltic, North Sea and Mediterranean caps:

c_{S,\text{US Caribbean ECA}} \leq 0.10\% \text{ m/m since 1 Jan 2015}

Regulation 13 caps the NOx emission rate of marine diesel engines of more than 130 kW installed on a ship. The cap is structured in three tiers tied to the engine-installation date (keel-laying or major conversion). Tier I applied from 1 January 2000. Tier II applied globally from 1 January 2011. Tier III applies inside a Nitrogen Emission Control Area (NECA) only and only to engines installed on or after the NECA effective date. The Tier III limit is approximately 80% lower than Tier II:

E_{\text{NOx}} = \begin{cases} 3.4 \text{ g/kWh} & n < 130 \text{ rpm} \\ 9 \cdot n^{-0.2} \text{ g/kWh} & 130 \le n < 2000 \text{ rpm} \\ 2.0 \text{ g/kWh} & n \ge 2000 \text{ rpm} \end{cases}

The geographic and procedural rules for designating either kind of ECA are set out in Appendix III to Annex VI. A coastal state submits a proposal documenting the air-quality case, the population exposed, the shipping density and the proposed boundary; the proposal is adopted as an MEPC resolution amending Regulation 14 (for a SECA) and/or Regulation 13 (for a NECA). The US Caribbean regime, like the North American regime, was designated as a combined SECA and NECA in a single resolution.

US Caribbean ECA: 2011 designation, 2014 entry, 2015 0.10 percent cap

The US Caribbean ECA was proposed by the United States acting alone at MEPC 61 in October 2010, supported by an Air Quality Technical Document prepared by EPA Region 2, USCG District 7 and the Puerto Rico Environmental Quality Board. The technical document quantified premature-mortality and cardiopulmonary-morbidity attribution to ship-source SOx, NOx and PM for the populations of San Juan, Bayamón, Carolina, Ponce, Mayagüez, Charlotte Amalie and Christiansted, with atmospheric-transport modelling using CMAQ and shipping-density inputs from the USCG Nationwide Automatic Identification System (NAIS).

The resolution was adopted by consensus as Resolution MEPC.202(62) at MEPC 62 on 15 July 2011, with the standard MARPOL article-on-amendments timetable: tacit acceptance by 1 July 2013, entry into force 6 months later on 1 January 2014.

The sulphur cap on entry into force was 1.00% m/m, the same as the contemporary North American, Baltic and EU Directive 2005/33/EC port limits. The cap stepped down to 0.10% m/m on 1 January 2015 under Regulation 14 of the 2008-revised Annex VI, the same date as the parallel step in the Baltic SECA, North Sea SECA and North American ECA. The single-year gap between US Caribbean entry into force (2014) and the 0.10% step (2015) meant operators rarely bunkered specifically for the 1.00% Caribbean cap; most fleets converged directly on 0.10% ULSFO supply contracts in 2014 in anticipation of the 2015 step.

The US Caribbean ECA is the smallest ECA by sea-surface coverage, spanning approximately 95,000 square nautical miles inside the 200 nm offshore line around Puerto Rico and the USVI. Annual port calls subject to ECA compliance run to approximately 4,500, dominated by cruise calls at San Juan and Charlotte Amalie, container calls at San Juan, oil-product calls at Yabucoa and Guayanilla and bulk calls at Ponce.

Tier III NOx for new keels post-2016

The US Caribbean NECA shares its Tier III effective date with the North American NECA. Resolution MEPC.202(62) fixed the Tier III applicability date as 1 January 2016. MEPC 66 in April 2014 adopted Resolution MEPC.251(66) which delayed Tier III in subsequent NECAs (Baltic and North Sea adopted in 2017) but left the North American and US Caribbean Tier III date intact at 2016, making the two US-led regimes the first operational Tier III zones in the world.

The Tier III limit applies only to engines installed on ships with a keel-laying date on or after 1 January 2016 (or, for major conversions, an engine installed on or after that date). Engines installed before that date remain on Tier II (around 14 g/kWh at low rpm) when operating in the US Caribbean ECA. The legal trigger is the keel-laying or block-erection date recorded on the IOPP and EIAPP supplements.

The Tier III limit at low rated speeds:

E_{\text{NOx Tier III}} = 3.4 \text{ g/kWh at } n < 130 \text{ rpm; for new keels post-1 Jan 2016}

The early Tier III date drove SCR or EGR specification on container vessels deployed on US-Caribbean liner trades (Crowley, Tote Maritime, Trailer Bridge, Sea Star Line, Maersk, MSC, CMA CGM), on cruise ships serving San Juan and Charlotte Amalie (Carnival, Royal Caribbean, NCL, MSC, Disney, Holland America, Princess, Celebrity), on product tankers serving Caribbean Petroleum Corporation, Buckeye and Yabucoa terminals, and on bulk carriers serving Ponce and Guayanilla. The Tier III investment is functionally identical to the North American NECA investment and most cruise newbuilds delivered for global deployment after 2016 carry SCR or LNG for Tier III compliance regardless of the ECA they happen to be operating in on a given voyage.

Geographic scope: 200 nm around Puerto Rico and USVI

The geographic boundary of the US Caribbean ECA is defined in the Annex to Resolution MEPC.202(62) by 24 latitude/longitude vertices forming a closed polygon around Puerto Rico, Vieques, Culebra and the US Virgin Islands (St Thomas, St John, St Croix). The boundary is constructed by drawing a line 200 nautical miles seaward from the territorial-sea baseline of each US territory, modified at the points where the 200 nm line would otherwise cross into the territorial waters of the Dominican Republic, the British Virgin Islands or the Lesser Antilles, where the line is drawn along the equidistance line between the US territory and the adjacent state.

The northern vertex sits at approximately 22°00’ N, 65°00’ W in deep Atlantic water north of Puerto Rico. The eastern vertex sits at approximately 17°45’ N, 63°10’ W south-east of St Croix toward the Anguilla and Saba bank. The southern vertex sits at approximately 15°00’ N, 67°00’ W south of Puerto Rico in the Venezuela Basin. The western vertex sits along the Mona Passage equidistance line between Puerto Rico and the Dominican Republic at approximately 18°30’ N, 68°20’ W.

The ECA covers the Mona Passage on the Puerto Rico side (the equidistance line bisects the passage between Puerto Rico and the DR), all of the Vieques Sound, the Sir Francis Drake Channel where it sits inside USVI waters, the Anegada Passage on the USVI side, and the deep Caribbean basin south of the territories out to 200 nm. Total coverage is approximately 95,000 nm² of sea surface, the smallest ECA footprint in the Annex VI regime.

The boundary excludes the Hawaiian Islands, the Aleutian chain west of 165°W, the western Alaskan Bering Sea and the Pacific approaches to the US territories of Guam, Wake Island and the Northern Mariana Islands, all of which lie outside any ECA. The boundary also excludes the Florida Straits, the Yucatan Channel and the Windward Passage, all of which carry significant cruise and container traffic but lie outside any ECA.

Boundary distinction from broader Caribbean

The US Caribbean ECA is a frequent source of confusion in the cruise and bunker-trade press because it is the only ECA-protected portion of the otherwise unprotected Caribbean Sea. The Wider Caribbean Region as defined under the Cartagena Convention covers approximately 4.3 million km² of sea surface from the Florida Straits through the Greater and Lesser Antilles to the South American coast and the Yucatan and Honduran shelves. The US Caribbean ECA covers approximately 326,000 km² of that total, around 7.6% of the Wider Caribbean Region by area.

The remaining 92.4% of the Wider Caribbean Region is not a SECA or NECA. Inside that area only the global cap applies: 0.50% m/m sulphur under the IMO 2020 sulphur cap (in force since 1 January 2020), with no NOx Tier III obligation regardless of keel-laying date. A cruise ship leaving Miami for Cozumel, Grand Cayman, Ocho Rios and Labadee operates entirely on 0.50% VLSFO and Tier II NOx; the same vessel rerouting through San Juan and Charlotte Amalie must switch to 0.10% ULSFO and, if on a post-2016 keel, must operate Tier III SCR or EGR while inside the US Caribbean ECA polygon.

The ECA boundary is a hard line. There is no transition buffer, no de-minimis exemption for short transits and no waiver for itineraries that cross the boundary at speed. A ship entering the ECA must complete its fuel-changeover or scrubber-startup procedure before crossing the polygon and must record the changeover in the MARPOL Oil Record Book Part I (for fuel switching) or the EIAPP supplement (for Tier III activation). The standard industry practice is to switch fuel approximately 25 to 30 nm outside the polygon to accommodate the changeover time without risk of an in-ECA non-compliance.

Political dynamics: Cuba, DR, Lesser Antilles outside

The political boundary of the ECA reflects a single-state designation. Only the United States, acting through EPA and the Department of State, submitted the MEPC.202(62) proposal. Cuba is a Party to MARPOL Annex VI but did not co-sponsor the designation and operates the entirety of its territorial sea and EEZ outside any ECA, including the heavily-trafficked north coast (Havana, Mariel, Matanzas, Cárdenas), the south coast (Cienfuegos, Santiago de Cuba, Manzanillo) and the Sabana-Camagüey archipelago. The political relationship between the United States and Cuba precluded a joint Caribbean designation in the 2010 to 2011 timeframe and there has been no Cuban accession to the ECA since.

The Dominican Republic is a Party to MARPOL Annex VI but did not co-sponsor and operates its waters outside any ECA, including the major ports of Santo Domingo, Caucedo, Puerto Plata, Samaná, La Romana and Punta Cana. The DR cruise industry, including the Carnival Amber Cove and the Costa Maya alternative at Catalina Island, has lobbied periodically for a Hispaniola-wide ECA but no MEPC proposal has emerged.

The Cayman Islands (a UK overseas territory, MARPOL coverage via the United Kingdom), Jamaica, Haiti, the Bahamas, the Turks and Caicos, the British Virgin Islands (immediately adjacent to the USVI), the French Caribbean territories (Guadeloupe, Martinique, St Barthélemy, St Martin, Saba, Sint Eustatius, Sint Maarten as a Netherlands territory, Aruba, Curaçao, Bonaire), the independent states of the Lesser Antilles (St Kitts and Nevis, Antigua and Barbuda, Dominica, St Lucia, St Vincent and the Grenadines, Barbados, Grenada, Trinidad and Tobago) all lie outside the ECA. Several of these territories are MARPOL Annex VI Parties through the metropolitan administering state (UK, France, Netherlands) but none has co-sponsored an ECA designation for its own waters.

The political pattern is consistent with the broader Annex VI experience: ECAs are difficult to designate because they require sustained domestic political backing for a costly compliance regime that imposes most of its burden on transiting foreign-flag vessels. The cruise sector, which operates predominantly under Bahamas, Panama, Marshall Islands and Malta flags, has limited interest in promoting Caribbean-wide ECAs that would raise its own bunker bill.

USCG / EPA enforcement under CFR 33 + APPS

US enforcement of the US Caribbean ECA is delivered through three statutory and regulatory channels. The first is the Act to Prevent Pollution from Ships (APPS, 33 USC 1901 to 1915), the US implementing legislation for MARPOL. APPS criminalises the use of non-compliant fuel and the falsification of MARPOL records, with penalties up to USD 70,000 per day per violation and criminal prosecution by the Department of Justice for wilful or negligent violations.

The second channel is 33 CFR 151 Subpart A (Implementation of MARPOL 73/78) and 40 CFR 1043 (Control of NOx, SOx and PM Emissions from Marine Engines and Vessels in the Caribbean Sea Near Puerto Rico and the United States Virgin Islands). The EPA Final Rule 76 FR 42035 (15 July 2011) codified the US Caribbean ECA in domestic regulation simultaneously with the MEPC adoption of MEPC.202(62), with a delegated-enforcement memorandum-of-understanding between EPA and the USCG.

The third channel is USCG Sector San Juan, the operational enforcement unit. Sector San Juan boards approximately 350 to 450 foreign-flag vessels per year for MARPOL Annex VI Reg 11 inspection, with a sub-set of approximately 60 to 80 inspections triggering fuel-sample collection, BDN review, oil-record-book review and engine-log examination. Samples are sealed under chain-of-custody and shipped to the EPA Region 2 fuel-sample analysis laboratory for ASTM D2622 sulphur quantification. Confirmed non-compliance triggers either a port-state-control deficiency record (for foreign-flag vessels with a non-US owner) or a Notice of Violation under APPS (for any vessel calling at a US port).

The most-prosecuted category is fuel-changeover record falsification, where engineers backdate the Oil Record Book Part I to claim a switchover that did not occur. Fuel-sample analysis of in-use bunker tanks then contradicts the record book, and the criminal-record-falsification charge under APPS carries higher penalties than the underlying sulphur-cap violation. The pattern echoes the 2010 to 2020 enforcement record in the North American ECA, where DOJ prosecutions of MSC, Princess, Carnival Corporation, Anglo-Eastern and other operators delivered nine-figure cumulative settlements.

Impact on Caribbean cruise traffic

The US Caribbean ECA has a disproportionate impact on cruise traffic because the cruise sector is the dominant operator at the two main protected ports. San Juan receives approximately 1.7 million cruise passengers per year on approximately 600 cruise calls, the second-largest cruise port in the Caribbean by passenger throughput after PortMiami. Charlotte Amalie (St Thomas, USVI) receives approximately 1.9 million cruise passengers per year on approximately 550 cruise calls, with Crown Bay taking the larger vessels and Havensight taking the older mid-size tonnage. Frederiksted (St Croix, USVI) takes a smaller share at approximately 250,000 passengers per year.

A typical Eastern Caribbean cruise itinerary from a Florida home port (Miami, Port Everglades, Port Canaveral, Tampa) routes:

Day 1: depart Florida, transit south-east at 0.50% VLSFO and Tier II NOx
Day 2: at sea, still outside any ECA
Day 3: arrive San Juan, switching to 0.10% ULSFO 25 to 30 nm before crossing the ECA boundary; Tier III activation if on post-2016 keel
Day 4: depart San Juan for St Thomas, remaining inside the ECA throughout (Vieques Passage, Sir Francis Drake Channel)
Day 5: arrive St Thomas, ULSFO and Tier III continue
Day 6: depart St Thomas for a non-US Caribbean port (e.g. Philipsburg, Sint Maarten, or Basseterre, St Kitts), crossing the ECA boundary outbound and switching back to VLSFO and Tier II
Day 7: at sea
Day 8: return Florida

The fuel-cost premium for the two-day ECA segment is approximately USD 25,000 to USD 45,000 per call for a 5,000-passenger megaship at 2024 ULSFO-VLSFO spreads of USD 80 to USD 140 per tonne. For a 600-call San Juan year and a 550-call Charlotte Amalie year, the cumulative ECA bunker premium against an unregulated baseline runs to approximately USD 30 to USD 60 million across the two ports, distributed across approximately 30 cruise operators.

The four largest operators at the protected ports are:

Carnival Corporation (Carnival Cruise Line, Princess, Holland America, Costa, AIDA brands) with approximately 35% of the protected-port share by passenger
Royal Caribbean Group (Royal Caribbean International, Celebrity Cruises, Silversea) with approximately 30%
Norwegian Cruise Line Holdings (Norwegian Cruise Line, Oceania, Regent Seven Seas) with approximately 18%
MSC Cruises with approximately 8%

The remaining ~9% is divided among Disney, Virgin Voyages, Viking, Seabourn, Crystal, Windstar, Cunard, P&O, SeaDream and the smaller expedition operators.

Bunker fuel implications: ULSFO inside, VLSFO outside

The US Caribbean ECA imposes a dual-fuel logistics regime on operators that call at San Juan and the USVI. Inside the ECA the requirement is ULSFO ≤ 0.10% m/m sulphur or an equivalent compliance arrangement (scrubber stack SO2/CO2 ratio ≤ 4.3, or LNG dual-fuel). Outside the ECA but in the broader Caribbean the requirement is the global 0.50% m/m VLSFO under IMO 2020.

The price differential between ULSFO and VLSFO at Caribbean bunker hubs (Las Palmas as a reference, San Juan, Aruba, Trinidad) has averaged USD 80 to USD 140 per tonne over 2020 to 2025, with episodic spikes above USD 200 per tonne during refinery-outage events (Hurricane Maria aftermath, Hurricane Fiona disruption to the Yabucoa terminal, periodic Trinidad Petrotrin shutdowns) and during the early-2022 distillate squeeze tied to the Russia-Ukraine event.

San Juan is itself a small bunker port, supplied through Caribbean Petroleum Corporation (CAPECO, returned to operation post-2009-explosion under new ownership) and through coastal-trade barge deliveries from Yabucoa and Guayanilla. ULSFO availability at San Juan is reliable for cruise tonnage but stocks are smaller than at the main Caribbean bunker hubs of Aruba (Valero / Citgo legacy), Curaçao (Refineria di Kòrsou), Trinidad (Pointe-à-Pierre), Cartagena (Colombia) (Reficar) and Las Palmas (off the Caribbean but commonly used as a transatlantic bunker stop). Operators on tight Eastern Caribbean rotations frequently bunker at a non-US Caribbean hub for cost reasons and budget the spot ULSFO at San Juan only as a top-up.

LNG bunkering in the Caribbean is concentrated at Jacksonville (US) and Tampa (US) for the Crowley con-ro and Tote Maritime trades, with limited Caribbean-side LNG infrastructure at Aruba, Curaçao and the Bahamas. Cruise LNG bunkering for Caribbean itineraries typically loads at Port Canaveral or Port Everglades before the Caribbean leg, with bunker barge service from Polaris (Shell) and Q-LNG.

Caribbean shore-power: San Juan, Charlotte Amalie, Frederiksted

Shore power (cold ironing, alternate marine power, AMP) deployment in the US Caribbean lags the North American ECA but has accelerated since 2020 under EPA Diesel Emissions Reduction Act (DERA) and Maritime Administration Port Infrastructure Development Program (PIDP) grants.

San Juan (Pan American Pier and Pier 4) has a partial shore-power deployment delivered in phases from 2022, capable of serving a single megaship at 11 kV, 60 Hz at up to 16 MW. Carnival, Royal Caribbean and NCL have retrofitted a subset of their Caribbean-deployed tonnage with shore-power inlet modules (Quantum-class, Edge-class, Excel-class, Encore-class). The connection-time penalty (typically 30 to 45 minutes) is acceptable for the 8 to 12 hour San Juan dwell.

Charlotte Amalie (Crown Bay and Havensight) has a 2024 PIDP-funded shore-power project under construction, scheduled for partial commissioning in 2026. The USVI grid is supplied by Virgin Islands Water and Power Authority (VIWAPA), with diesel and LNG generation; the marginal kWh emission factor at the USVI quayside is higher than at San Juan, partially offsetting the ECA-protected at-berth emission savings.

Frederiksted (St Croix) has no shore-power deployment as of 2025 and is unlikely to attract one given the smaller call volume.

The Caribbean shore-power case is weaker than the Pacific Northwest or California cases because the local grid is itself fossil-heavy. The lifecycle emissions calculus (compare quayside ship MGO to grid kWh including transmission losses) gives a smaller margin than the equivalent calculation at Long Beach, Vancouver or Seattle, but the local-air-quality case (PM2.5, NO2, SO2 reductions in dense port-city populations) holds regardless of the upstream grid.

Relationship to N-AM ECA (geographically distinct)

The US Caribbean ECA and the North American ECA are two geographically distinct ECAs with identical legal force. Both were proposed by the United States. Both adopt the same 0.10% m/m sulphur cap from 1 January 2015 and the same Tier III NOx cap for keels laid on or after 1 January 2016. Neither covers the other’s footprint and there is no common boundary or transit corridor between them.

The North American ECA covers the US Atlantic, Gulf of Mexico and Pacific seaboards out to 200 nm, plus the Canadian seaboards out to 200 nm, plus Saint Pierre and Miquelon. The US Caribbean ECA covers Puerto Rico and the USVI out to 200 nm. The Florida Straits, the Yucatan Channel, the Windward Passage and the deep Caribbean basin between the two ECAs are not covered by either, leaving cruise and container itineraries that stay west of approximately 67°W in unregulated water for the bulk of their voyage.

The dual-ECA logic was deliberate. EPA and USCG argued in the MEPC.202(62) proposal that the Caribbean territories had a separate air-quality case (different population centres, different shipping density, different topography for atmospheric transport) and a separate enforcement footprint (USCG Sector San Juan operationally distinct from the mainland sectors), justifying a standalone designation rather than an extension of MEPC.190(60).

The single-ship operational consequence is that a ship circumnavigating the US Atlantic and Gulf coasts via the Florida Straits and arriving at San Juan crosses three boundary segments: out of the North American ECA off Cape Florida, through unregulated Caribbean water for approximately 1,000 nm, into the US Caribbean ECA approximately 200 nm north of Puerto Rico. Operators that handle this routing daily (Crowley, Tote, Trailer Bridge, Sea Star Line) maintain dual-tank bunker arrangements with documented changeover procedures for both transitions.

Relationship to Mediterranean SECA (effective 2025)

The Mediterranean Sea SECA was designated by Resolution MEPC.361(79) at MEPC 79 in December 2022 and entered into force on 1 May 2025 with a 0.10% m/m sulphur cap, no NECA component. The Mediterranean SECA is the most recent ECA addition before the 2027 Canadian Arctic and Norwegian Sea designations and brings the global ECA inventory to seven distinct geographies: North American, US Caribbean, Baltic SECA + NECA, North Sea SECA + NECA (English Channel included), Mediterranean SECA, plus the planned Canadian Arctic and Norwegian Sea zones.

The pattern emerging across the seven ECAs is one of regional clustering rather than global coverage. Each ECA is the product of a sustained domestic political coalition (the European Commission and EU member-state environment ministries for the European zones; EPA and USCG for the two US zones; Norway’s Klima- og miljødepartement for the Norwegian Sea; Environment and Climate Change Canada for the Canadian Arctic). There is no global SECA proposal in front of MEPC and the IMO Secretariat has consistently characterised the global 0.50% cap and the regional 0.10% caps as a settled architecture for the 2020 to 2030 decade.

The US Caribbean ECA sits at the smallest end of the regional spectrum. Mediterranean SECA covers approximately 2.5 million km², North American approximately 13 million km², Baltic approximately 415,000 km², North Sea approximately 750,000 km², US Caribbean approximately 326,000 km². The smaller footprint reduces compliance burden in absolute terms but increases the proportion of cruise-itinerary bunker switching events per protected square kilometre, because the polygon is short across in any direction.

Commercial impacts: cruise sector

The Caribbean cruise sector handles approximately 25 million passengers per year in 2024, the largest regional cruise market in the world by passenger throughput, surpassing the Mediterranean (approximately 10 million), the Northern Europe / Baltic (approximately 6 million), the Alaska summer (approximately 1.6 million) and the Asia / Pacific (approximately 6 million combined) markets.

The four largest cruise operators globally, in order of fleet capacity in lower-berth terms:

Carnival Corporation (Carnival, Princess, Holland America, Costa, AIDA, Cunard, Seabourn, P&O Australia, P&O UK) at approximately 250,000 lower berths
Royal Caribbean Group (Royal Caribbean International, Celebrity, Silversea) at approximately 180,000 lower berths
Norwegian Cruise Line Holdings (NCL, Oceania, Regent Seven Seas) at approximately 70,000 lower berths
MSC Cruises (MSC, Explora Journeys) at approximately 100,000 lower berths

All four are heavy users of the US Caribbean ECA at San Juan and Charlotte Amalie. The cumulative ECA bunker premium for the four operators at the two main protected ports runs to approximately USD 25 to USD 50 million per year, distributed across approximately 1,150 calls. Per-passenger the premium is approximately USD 2 to USD 4 per port call for a 5,000-passenger megaship, comfortably absorbed in the cruise fare structure.

The capex consequence has been larger than the opex. Tier III specification on post-2016 newbuilds adds approximately USD 8 to USD 15 million per ship for SCR with urea dosing, or approximately USD 60 to USD 120 million for full LNG dual-fuel propulsion. The major LNG cruise newbuild cluster (AIDAnova 2018, Costa Smeralda 2019, Mardi Gras 2021, Iona 2020, Carnival Celebration 2022, Carnival Jubilee 2023) traces directly to the combined US-Caribbean-and-North-American-ECA Tier III obligation rather than to either zone individually, but Caribbean deployment is a primary use case for all six.

The cruise sector has been the largest single political beneficiary of the US Caribbean ECA in air-quality terms. San Juan harbour has experienced measurable PM2.5 and NO2 reductions on cruise-call days since 2015, with EPA AirNow monitor data showing approximately 30 to 40% reductions in port-quayside PM2.5 attributed to the fuel-switch and the gradual Tier III penetration of the cruise fleet. Charlotte Amalie monitor data shows similar reductions, smaller in absolute concentration because the baseline is lower.

Cartagena Convention Annex IV/V special area (not yet in force)

The Wider Caribbean Region is also the subject of a parallel marine-pollution regime under the Cartagena Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (1983, in force 1986), administered by the UNEP Caribbean Environment Programme (CEP) in Kingston. The Cartagena Convention has three protocols:

Oil Spills Protocol (1983, in force 1986)
Specially Protected Areas and Wildlife Protocol (SPAW, 1990, in force 2000)
Land-Based Sources of Marine Pollution Protocol (LBS, 1999, in force 2010)

The Cartagena Convention is the regional-seas legal architecture for the Caribbean and is the sponsor for the long-pending MARPOL Annex IV (sewage) and Annex V (garbage) Special Area designation for the Wider Caribbean. The Special Area has been on the MEPC agenda since 1991 and has been reviewed multiple times (MEPC 36, 41, 43, 51, 56, 60, 65) but the in-force date has never been declared because the IMO MEPC requires demonstrated reception-facility availability at the principal Caribbean ports before the Special Area can take effect, and the reception-facility surveys returned by CEP have consistently shown gaps at the Lesser Antilles and Central American ports.

The status as of 2025 is that the Annex IV/V Special Area for the Wider Caribbean has been adopted in principle by MEPC but has not yet entered into force. The MARPOL Annex VI US Caribbean ECA is a separate regulatory instrument (air pollution rather than sewage or garbage) and operates independently of the Cartagena Convention. The two regimes share an underlying geographic concept (the Caribbean as a marine environment of high cumulative pollution risk) but are legally distinct: the ECA is a unilateral US designation under MARPOL Annex VI Reg 14 and Reg 13; the Cartagena Convention is a multilateral regional-seas treaty.

ESI ratings and incentives at San Juan

The Environmental Ship Index (ESI) is a voluntary port-incentive scheme operated by the International Association of Ports and Harbors (IAPH) and the World Ports Climate Initiative since 2011. The ESI score combines NOx emission rate, SOx emission rate (proxied by fuel sulphur content) and CO2 efficiency, scoring each ship on a 0 to 100 scale. Ports offering ESI incentives provide port-fee discounts (typically 5 to 20% on vessel-based dues) for vessels above a threshold ESI score, usually 30 or 50.

San Juan participated in the ESI from 2018 to 2023 with a 5% port-fee discount for vessels at ESI ≥ 30 and a 10% discount for vessels at ESI ≥ 50. Cruise operators routinely achieve ESI scores in the 35 to 65 range for Tier III newbuilds and LNG dual-fuel newbuilds. The San Juan incentive was discontinued in 2024 in favour of a flat per-passenger sustainability surcharge tied to PR Ports Authority infrastructure investments at the Pan American Pier.

Charlotte Amalie has not joined the ESI as of 2025; the West Indian Company Limited (WICO) and the Virgin Islands Port Authority operate a more limited tariff structure focused on call volume rather than environmental performance.

The ESI at San Juan was a small absolute incentive (5 to 10% on a typical USD 25,000 to USD 45,000 cruise port fee, so USD 1,250 to USD 4,500 per call) but a meaningful signalling instrument for newbuild specification decisions. The discontinuation of the San Juan ESI in 2024 is consistent with a broader pattern at smaller cruise ports of moving from environmental-index discounts toward flat-rate sustainability charges that fund local infrastructure investment.

Controversy: small footprint vs broader Caribbean traffic

The most persistent critique of the US Caribbean ECA is that its geographic footprint is too small to capture the dominant Caribbean traffic flows. The 326,000 km² polygon around Puerto Rico and the USVI sits inside a 4.3 million km² Wider Caribbean Region carrying approximately 25 million cruise passengers and approximately 9 million TEU of container traffic annually. Most of that traffic transits west of approximately 67°W (the western edge of the ECA polygon), through the Florida Straits, the Yucatan Channel, the Windward Passage and the central Caribbean basin. The ECA captures the eastern Caribbean cruise tail but misses the dominant western Caribbean cruise loop (Cozumel, Costa Maya, Roatán, Belize City, Grand Cayman, Jamaica) entirely.

Estimates of the proportion of total Caribbean ship-source SOx, NOx and PM emissions captured by the US Caribbean ECA range from approximately 8% to 18%, depending on the modelling assumptions for shipping density and emission factors. The remainder is unregulated beyond the global 0.50% sulphur cap, with no NOx Tier III obligation at all.

The political constraint behind the small footprint is the absence of a multilateral Caribbean ECA proposal. Cuba, the Dominican Republic, Jamaica, the Cayman Islands and the Lesser Antilles have shown limited appetite for the domestic political and bunker-cost consequences of an ECA designation, and no co-sponsoring coalition has emerged at MEPC. The cruise industry, which would bear most of the bunker premium, is not actively lobbying for a wider ECA. The flag-state interests dominant in the cruise sector (Bahamas, Panama, Marshall Islands, Malta) are not coastal-state Caribbean parties and have no domestic constituency to drive a wider proposal.

A second critique is that the Tier III NOx requirement is duplicative with the North American NECA for ships that operate across both zones. A cruise vessel built post-2016 for combined Florida-and-Caribbean deployment carries SCR or LNG regardless of which ECA it is in, so the marginal compliance value of the US Caribbean Tier III is low for the cruise sector. The marginal value is higher for the dedicated Caribbean container and tanker fleets (Crowley, Tote, Trailer Bridge, Sea Star Line, the Yabucoa product-tanker rotation) that would not otherwise have specified Tier III, but these are a smaller share of the total port-call volume.

A third critique is that the 2014 entry / 2015 step-down sequence delivered minimal incremental emission reduction at the 1.00% intermediate level. Operators converged directly on 0.10% ULSFO for the 1 January 2015 step in any case, and the 2014 1.00% interim cap collected almost no compliance investment. The sequence is now widely viewed as a procedural artefact of MARPOL tacit-acceptance timing rather than a meaningful regulatory waypoint.

A fourth critique, from environmental NGOs (CleanShipping Coalition, Pacific Environment, Transport & Environment), is that the Wider Caribbean Region MARPOL Annex IV/V Special Area has been pending MEPC declaration for more than three decades and that the absence of an in-force sewage and garbage Special Area undermines the credibility of the Annex VI ECA as a comprehensive marine-environment instrument. The two regimes are legally separate, but the political optics suggest that the United States is willing to designate where it can act unilaterally and reluctant to lead a multilateral process where it must coordinate with twenty-plus regional states.

The defence of the small footprint, articulated by EPA in its 2011 Final Rule preamble and reiterated in subsequent enforcement reports, is that a small protected zone with credible enforcement is more valuable than a large protected zone with weak enforcement. The US Caribbean ECA covers the territory where USCG and EPA have unambiguous jurisdiction, where the population at risk lives in US territories with US air-quality standards, and where the enforcement infrastructure (Sector San Juan, EPA Region 2 fuel-sample lab, DOJ prosecutorial track record) is operational. Extending the regime to cover unregulated waters where US enforcement has no legal footing would, on this view, dilute rather than strengthen the Annex VI architecture.

Formula, assumptions, and limits

Formula

The two binding numerical limits for the US Caribbean ECA are the Regulation 14 sulphur cap and the Regulation 13 Tier III NOx cap.

Sulphur cap (since 1 January 2015):

c_{S,\text{US Caribbean ECA}} \leq 0.10\% \text{ m/m}

Tier III NOx cap (for engines on keels laid on or after 1 January 2016):

E_{\text{NOx Tier III}} = \begin{cases} 3.4 \text{ g/kWh} & n < 130 \text{ rpm} \\ 9 \cdot n^{-0.2} \text{ g/kWh} & 130 \le n < 2000 \text{ rpm} \\ 2.0 \text{ g/kWh} & n \ge 2000 \text{ rpm} \end{cases}

The ECA fuel-cost premium per voyage is:

\Delta C = m_{\text{ECA fuel}} \cdot (P_{\text{ULSFO}} - P_{\text{VLSFO}})

where $m_{\text{ECA fuel}}$ is the mass of fuel consumed inside the ECA polygon and $(P_{\text{ULSFO}} - P_{\text{VLSFO}})$ is the spot-market spread between 0.10% m/m ULSFO and 0.50% m/m VLSFO at the bunker port of supply.

Derivation

The 0.10% m/m sulphur cap derives from MARPOL Annex VI Regulation 14.4, which sets the sulphur content limit inside any Emission Control Area for SOx as one fifth of the global cap on 1 January 2020, namely 0.10% m/m. The global cap stepped from 3.50% (in force 2012 to 2019) to 0.50% on 1 January 2020 under Regulation 14.1.3. The ECA cap, originally 1.50% under the 1997 Protocol text, stepped to 1.00% on 1 July 2010 under MEPC.176(58) and to 0.10% on 1 January 2015 under the same revision.

The Tier III NOx limit derives from Regulation 13.5.1.1 with the curve given in Regulation 13.3 and 13.5. The functional form $9 \cdot n^{-0.2}$ for medium-speed engines is the result of a 2008 IMO/ISO joint proposal targeting an 80% reduction relative to Tier II (the Tier II curve is approximately $44 \cdot n^{-0.23}$ between 130 and 2000 rpm).

Assumptions

The compliance regime relies on five operational assumptions:

Fuel sulphur content is testable to ASTM D2622 accuracy at EPA Region 2 and equivalent labs, with sample integrity preserved through the chain of custody from ship to lab
Engine NOx emission rate at certification matches in-service rate when the engine is operated within the certified range and has not been subject to undisclosed modification
Fuel changeover at the ECA boundary completes before any in-ECA fuel use, with the sequence and timestamps recorded in the Oil Record Book Part I
Tier III SCR or EGR systems are available and active when the ship is inside the ECA, with urea-dosing rate sufficient to meet the 3.4 g/kWh limit
The 200 nm boundary is identifiable to the navigator through ECDIS chart updates, AIS-based ECA-zone alerts and bridge-team awareness training

Failure of any assumption shifts the regime from MARPOL compliance to APPS criminal-record-falsification exposure, which is the more onerous regulatory state.

Worked example

A 5,000-passenger cruise ship transits from Port Everglades to San Juan to Charlotte Amalie to Philipsburg (Sint Maarten) and back to Port Everglades over an 8-day cycle. Assume:

Total voyage fuel burn: 1,400 tonnes
Fraction inside the US Caribbean ECA (San Juan + Charlotte Amalie inbound, ECA segment): 380 tonnes
Fraction outside any ECA: 1,020 tonnes
ULSFO spot at San Juan: USD 720 per tonne
VLSFO spot at Aruba: USD 600 per tonne
Spread: USD 120 per tonne

ECA fuel-cost premium for the voyage:

\Delta C = 380 \text{ t} \cdot 120 \text{ USD/t} = 45{,}600 \text{ USD}

For a 50-voyage annual rotation: USD 2.28 million per ship per year. For a 600-call San Juan year across approximately 30 cruise operators and approximately 50 deployed ships, the cumulative ECA bunker premium runs to approximately USD 30 to USD 45 million per year at the San Juan side alone.

Edge cases and limits

Several edge cases in the US Caribbean ECA enforcement record warrant attention:

Mona Passage equidistance line: a ship transiting the Mona Passage between Puerto Rico and the Dominican Republic is inside the ECA when on the PR side of the equidistance line and outside on the DR side; cruise itineraries that overnight at Punta Cana with a daytime call at Old San Juan cross the line twice per day
Sir Francis Drake Channel and Tortola: the channel sits between St John (US) and Tortola (UK BVI); a ship anchored in the channel is inside or outside the ECA depending on which shore the anchorage is closest to, and cruise tenders operating between the two shores cross the boundary repeatedly
Yabucoa product tanker rotation: ships running a fast rotation between Yabucoa and Galveston cross both the US Caribbean ECA boundary (off Puerto Rico) and the North American ECA boundary (off Texas) on each leg, with two changeovers per voyage
Hurricane diversion: ships diverting to a non-US Caribbean port during hurricane season may legitimately exit the ECA mid-voyage; the OS / chief engineer must record the diversion and the changeover in the Oil Record Book to defend the in-ECA record
Scrubber wash-water discharge: open-loop scrubbers compliant with Reg 14 equivalent-arrangement on the SO2/CO2 ratio must still meet the local discharge rules; Puerto Rico has not banned open-loop scrubber discharge but several operators voluntarily switch to closed-loop while inside the ECA polygon to manage local-authority risk

The principal enforcement limit is detection of fuel-changeover record falsification, which depends on USCG boarding rate (a function of Sector San Juan resourcing) and EPA fuel-sample lab capacity (constrained by Region 2 budget appropriations).

Regulatory basis

The legal basis for the US Caribbean ECA is the chain:

MARPOL Annex VI (1997 Protocol, in force 19 May 2005, revised by MEPC.176(58) in October 2008)
Regulation 14 (sulphur cap) and Regulation 13 (NOx cap), with the ECA designation procedure in Appendix III
Resolution MEPC.202(62) (15 July 2011), entry into force 1 January 2014, sulphur cap 0.10% from 1 January 2015, Tier III NOx for keels post 1 January 2016
EPA Final Rule 76 FR 42035 (15 July 2011), the US domestic implementation
Act to Prevent Pollution from Ships (APPS, 33 USC 1901 to 1915)
33 CFR 151 Subpart A and 40 CFR 1043, the operational US enforcement regulations
USCG Sector San Juan and EPA Region 2 enforcement memorandum-of-understanding

The enforcement chain is complete in US territorial waters and US EEZ around Puerto Rico and the USVI. Outside US waters the chain has no domestic enforcement reach, and compliance depends on flag-state Port State Control reporting and the standard MARPOL Annex VI Reg 11 inspection regime at the next port of call.

Common errors

Five recurring compliance errors observed in USCG Sector San Juan boarding records and EPA Region 2 fuel-sample analysis since 2015:

Late changeover: starting the fuel-switch procedure after crossing the ECA boundary, with in-ECA fuel use recorded on the high-sulphur tank
Backdated Oil Record Book Part I: writing the changeover entry after the boarding to match the boarding-team query, contradicted by the in-use bunker tank fuel-sample analysis
Tier III deactivation: turning off SCR urea dosing or bypassing the catalyst inside the ECA to save consumables, detectable by stack NOx measurement during a USCG-led emission survey
BDN sulphur misdeclaration: relying on a Bunker Delivery Note that overstates compliance, without sampling the as-delivered fuel; APPS treats the master and chief engineer as responsible for the in-tank composition regardless of the BDN
Boundary-crossing inattention: navigators failing to update the ECDIS ECA layer or relying on stale charts that show the wrong polygon, leading to inadvertent in-ECA fuel use

The pattern across the five errors is that operational discipline at the bridge and engine-room interface (the changeover sequence, the record-book entry, the Tier III activation log) determines compliance outcomes more than fuel-procurement or capex decisions.