A Particularly Sensitive Sea Area (PSSA) is an area that needs special protection through action by IMO because of its significance for recognised ecological or socio-economic or scientific reasons and which may be vulnerable to damage by international shipping activities. The concept was developed to provide an additional measure of protection for special marine areas, distinct from merely routing/control, and is applied under the IMO guidelines for the identification and designation of PSSAs (in association with MARPOL special areas and routing measures).

Criteria used to designate a PSSA (three types of criteria - at least one must be met):

• Ecological criteria: uniqueness or rarity of ecosystem, critical habitat (spawning/breeding/feeding grounds), biological diversity (richness in species, endemism), vulnerability (to degradation by natural/human factors), representative character, or a fragile ecosystem.
• Social, cultural and economic criteria: the area is of significant economic benefit to the region (tourism, fishing, or marine resources), or of cultural/scientific importance (historic wrecks, research sites).
• Scientific and educational criteria: the area is a research/education site, or representative of important ecosystems.

Additionally, the area must be vulnerable to damage by international shipping, and available associated protective measures (APM) such as routing (traffic separation, TSS), areas to be avoided, mandatory reporting, or discharge restrictions must be identified as appropriate and adopted by IMO.

Process:

• The interested coastal State(s) submit a proposal to the Marine Environment Protection Committee (MEPC) of IMO, detailing the area, why it meets criteria, the shipping risk, and the proposed Associated Protective Measures.
• MEPC reviews the proposal; if satisfied it designates the PSSA by a resolution/decision, and the associated protective measures are adopted through the appropriate IMO instruments (e.g. COLREGS routing measures adopted by the appropriate committee; MARPOL discharge restrictions adopted as special area status).
• Once designated, the PSSA gives the coastal State authority to take the protective measures and to enforce restrictions on international shipping within it.

Another example: the Great Barrier Reef, Galapagos, Mediterranean cetacean region, the Wadden Sea, the Baltic? Examples of PSSAs include the Great Barrier Reef (first), Galapagos Archipelago, western European waters, the Wadden Sea, the Straits of Florida (temporary), and possibly areas in Indian waters.

Associated Protective Measures and shipping restrictions in a PSSA may include:

• Routing measures under SOLAS/COLREGS: traffic separation schemes, areas to be avoided, recommended routes, precautionary areas, deep water routes - keeping ships away from sensitive shoals, reefs and habitats.
• Mandatory ship reporting (VTS) and ship movement monitoring, so coastal States can warn or route traffic.
• AIS/S-AIS monitoring of vessels.
• Discharge restrictions: many PSSAs also carry MARPOL special-area status so that discharge of oil, garbage, noxious liquids, sewage and/or air emissions are prohibited or restricted within them; the coastal State can impose more stringent requirements (e.g. various stricter measures within the PSSA agreed by IMO).
• Areas to be avoided and navigational warnings: requiring ships to follow specific routes and speeds.
• Requirement on ships to use an appropriate depth/speed; the emergency towing arrangements in case of casualty in PSSA.
• Reporting of casualties/incidents; provisions for SAR and pollution response cooperation between the coastal State and ships.
• Enforcement: PSC inspection to ensure vessels comply with the routing/transit/discharge rules, and the appropriate discipline under the coastal State's legislation.

The combined effect is a reduction in the risk of groundings, collisions, oil spills, invasive species introduction, and other pollution in the specially sensitive area, safeguarding biodiversity, fisheries, tourism and the marine environment while keeping international shipping safer and predictable.