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Management of Enclosed Coastal Seas
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The World's Enclosed Coastal Seas

The Environmental Management of Enclosed Coastal Seas Protecting Our Coastal Seas for Future Generations

The World’s Major Enclosed Coastal Seas

In many parts of the world there are bodies of sea water that are almost entirely enclosed by land. These bodies of water are called enclosed coastal seas. Examples include the Mediterranean Sea, the Baltic Sea, Chesapeake Bay, the Gulf of Thailand, the Bo Hai in northern China and, in Japan, the Seto Inland Sea, Tokyo Bay and Ise Bay. Since ancient times, enclosed coastal seas have been known for their great scenic beauty. Their outstanding natural attributes have spurred the development of transportation networks and many types of industry in the ocean and coastal regions, and they have been the setting for cultural and recreational activities throughout the ages. But man’s activities have exceeded the natural ability of the seas to cleanse themselves, giving rise to problems of pollution in the world’s enclosed coastal seas such as eutrophication, “red tides” and “blue tides”. We must work to preserve these priceless natural treasures if we are to pass them onto future generations.

Major Enclosed Coastal Seas of the World

  1. Chesapeake Bay(11,603km2,6.4m)
  2. San Francisco Bay(1,040km2,6m)
  3. Gulf of Mexico(1,592,800km2,1,486m)
  4. Mediterranean Sea(2,536,000km2,>5,150m)
  5. North Sea(575,200km2,94m)
  6. Baltic Sea(422,200km2,55m)
  7. Persian Sea(233,000km2,35m)
  8. Gulf of Thailand(320,000km2,45m)
  9. Bohai Sea(77,284km2,26m)
  10. Seto Inland Sea(23,203km2,38m)
  11. Black Sea(508,000km2,1,240m)
  12. Puget Sound(2,600km2,>300m)
  13. Hudson Bay(1,232,300km2,128m)
  14. Gulf of California(153,000km2,1,200m)
  15. Caribbean Sea(2,718,200km2,2,647m)
  16. Red Sea(438,000km2,491m)
  17. Bay of Bengal(2,173,000km2,2,600m)
  18. South China Sea(2,319,000km2,1,652m)
  19. Yellow Sea(466,200km2,40m)
  20. East China Sea(735,800km2,175m)
  21. Sea of Japan(978,000km2,1,752m)

※area, average depth, > maximum depth

Environmental Guidebook on the Enclosed Coastal Seas of the World(9MB/PDF)

Enclosed Coastal Seas in the World.pdf

No Sea area Dimensions Main Environmental
Protection Measures
Related Organizations and NGOs Current Status and New Directions
1 Chesapeake Bay Surface Area 11,603km2
Volume 68.1km3
Average Depth 6.4m
  • 29 % were met the water quality standards (DO, transparency, Chl-a, underwater grasses)
  • Overabundance of N & P from air, land and water
  • Sedimentation into sea floor
  • Toxic chemicals (pesticides, pharmaceuticals, PCBs)
  • EO 13508 for Chesapeake Bay Protection and Restoration
  • Total Maximum Daily Load (TMDL)
  • Chesapeake Bay Program
  • Chesapeake Bay Foundation
  • Maryland Department of National Resources
  • Virginia Department of Environmental Quality
  • NOAA Chesapeake Bay Office
  • USGS Chesapeake Bay Features
2 San Francisco Bay Surface Area 1,040km2
Volume 7km3
Average Depth 6m
  • Water quality of Bay has improved
  • Bottom sediment (70% were toxic to aquatic organisms)
  • PCBs, methyl mercury and dioxin are highly detected in fish
  • Decrease and regeneration of Habitats
  • Decline of biological resources
  • San Francisco Estuary Project(SFEP)
  • San Francisco Estuary Institute
3 Gulf of Mexico Surface Area 1,592,800km2
Volume 2,366,901km3
Average Depth 1,486m
  • Loss of coastal wetland
  • Fish contaminants
  • Sediment quality
  • Oil spills
  • Federal Fishery Management Council (stop overfishing, reduce bycatch, protect deep water coral reefs)
  • US EPA Gulf of Mexico Program
  • Centro de Ecologia, Pesquerias y Oceanografia del Golfo Mexico (EPOMEX)
  • Centro de Investigaciones Marinas (CIM)
4 Mediterranean Sea Surface Area 2,536,000km2
Volume 3,750,000km3
Average Depth -
  • Eutrophication, heavy metals pollution, organic pollution, microbial pollution (coastal areas)
  • POPs
  • Marine litter
  • Marine noise
  • Barcelona Convention (21 countries surrounding Mediterranean Sea)
  • Mediteranean Strategy or Sustainable Development (MSSD)
  • UNEP Mediterranean Action Plan
5 North Sea Surface Area 575,200km2
Volume 54,069km3
Average Depth 94m
  • Eutrophication
  • Contamination by trace organic compounds
  • Marine litter
  • Impacts of climate change
  • Damage to shallow sediment habitats
  • Convention for the Protection of the Marine Environment of the North-EastAtlantic (OSPAR Convention)
  • Bonn Agreement
  • The North Sea Commission
  • European Environment Agency (EEA)
  • International Council for the Exploration of the Sea (ICES)
  • Risk assessment for marine pollution in the Greater North Sea and its wider approaches
6 Baltic Sea Surface Area 422,200km2
Volume 23,221km3
Average Depth 55m
  • Eutrophication
  • Pollution by hazardous substances
  • Oil pollution
  • Threat to biodiversity
  • Convention on the Protection of the Marine Environment of the Baltic Sea Area (Helsinki Convention)
  • Helsinki Commission (HELCOM)
  • International Council for the Exploration of the Sea (ICES)
  • Coalition Clean Baltic (CCB)
  • Baltic Sea Research Institute Warnemunde
7 Persian Gulf Surface Area 233,000km2
Volume 8,155km3
Average Depth 35m
  • Oil pollution
  • Land-based pollution
  • Destruction of habitats
  • Kuwait Convention and Action Plan
  • Regional Organization for the Protection of the Marine Environment (ROPME)
  • Regional Organization for the Protection of the Marine Environment (ROPME9)
  • the Marine Emergency Mutual Aid Centre (MEMAC)
  • UN Division for Ocean Affairs
  • Commission on Sustainable Development (CSD)
  • Economic and Social Commission for Western Asia (ESCWA)
  • Global Programme of Action (GPA)
  • Regional Office for West Asia (ROWA)
  • United Nations Industrial Development Organization (UNIDO)
  • United Nations Development Programme (UNDP)
  • International Maritime Organization (IMO)
  • etc.
8 Gulf of Thailand Surface Area 320,000km2
Volume 14,400km3
Average Depth 45m
  • Water quality of Main river
    Chao Praya; deteriorated
    Tha Chin; deteriorated
    Mae Klong; fair
    Bangpakong; fair
  • Pollution in the Gulf (mercury)
  • Sediment quality (heavy metals)
  • Degradation and decline of habitats
  • Reduction of coral reefs
  • Project "Reversing Environmental Degradation Trends in the South China Sea and Gulf of Thailand"
  • Partnership in Environmental Management for the seas of East Asia (PEMSEA)
  • CORE sea
  • Mangroves for the Future
  • Bird Conservation Society of Thailand (BCST)
9 Bohai Sea Surface Area 77,284km2
Volume 2,009km3
Average Depth 26m
  • Nearshore areas (pollution of organic matters, active phosphate, petroleum hydrocarbon, inorganic nitrogen and heavy metals)
  • Red tides
  • Oil spills
  • Coastal erosion
  • Blue Sea Action Plan for the Bohai Sea
10 Seto Inland Sea Surface Area 23,203km2
Volume 881.5km3
Average Depth 38m
  • Water quality (COD, TP and TN pollution from land has been greatly reduced)
  • Red tides (200-300 in 1975, 100 in recent year)
  • Reduction of neritic region
  • Water Pollution Control Law (Control of Total Maximum Daily Load, Environmental Standards of Nitrogen and Phosphorus)
  • Seto Inland Sea Environmental Protection Temporary Measure Law
  • Seto Inland Sea Environmental Conservation Governor, Mayor Meeting
  • Health Organizations Federation
  • the Association for the Environmental Conservation of Seto inland Sea
11 Black Sea Surface Area 508,000km2
Volume 629,920km3
Average Depth 1,240m
  • Invasive species
  • Land reclamation
  • Change wettland to agricultural polder
  • Environmental Protection Measure by the Black Sea Economic Cooperation (BSEC)
  • Natura 2000 programme
  • Black Sea NGO Network
  • Agreement for the Conservation of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS)
  • Mediterranean Coastal Foundation (MEDCOAST)
12 Puget Sound Surface Area 2,600km2
Volume 169km3
Average Depth -
  • Low dissolved oxygen
  • High fecal coliform bacteria contamination
  • Eutrophication
  • Chemical contamination (PCBs, DDT)
  • Sediment (arsenic, copper, mercury, lead and zinc)
  • Shoreline modification
  • Puget Sound Water Quality Management Plan
  • Puget Sound/Georgia Basin International Task Force
  • Puget Sound Partnership
  • The Association of National Estuary Programs (ANEP)
  • People for Puget Sound
13 Hudson Bay Surface Area 1,232,300km2
Volume 157,734km3
Average Depth 128m
  • Ecosystem pollution (organochlorine; DDT, PCBs radionuclides; Cs-137)
  • Climate change
  • Canadian Ocean Act
  • Nunavut Wildlife Management Board (NWMB)
  • the Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
  • Canadian Arctic Resource Committee
14 Gulf of California Surface Area 153,000km2
Volume 183,600km3
Average Depth 1,200m
  • Fish reproduction (high salinity)
  • Pesticide input from agricultural area
  • Species in danger of economic extinction
  • Greater local control over marine resources
  • more law enforcement in the government
  • USA provides finantial assistance for the environmental protection of the Gulf
  • To develop public educational materials
  • Sea of Cortez International Preservation Foundation
15 Caribbean Sea Surface Area 2,718,200km2
Volume 7,195,075km3
Average Depth 2,647m
  • Water pollution (sewage, eutrophication)
  • Degradation of seagrass and coral reefs
  • POPs
  • Solid waste
  • Offshore oil and gas exploitation are sources of pollution
  • Habitat destruction due to coastal development
  • Cartagena Convention (Cooperation in Combating Oil Spill, Special Protected Areas and Wildlife (SPAW), Pollution from Land-based Sourcesand Activities (LBS))
  • Caribbian Action Plan
  • Caribbean Environment Programme (CEP)
  • Assessment and Management of Environmet Pollution (AMEP)
  • Caribbean Environment Programme (CEP)
  • Caribbean Regional Fund for Wastewater Management
  • Caribbean Natural Resource Institute (CANARI)
  • UNEP Global Programme of Action for the Protection of the Marine Environment from Land-based Activities
16 Red Sea Surface Area 438,000km2
Volume 215,058km3
Average Depth 491m
  • Pollution comes from land-based activities
  • Oil exploitation
  • Destraction of habitat
  • Over exploitation of marine resources
  • Jeddah Convention (Regional Convention for the Conservation of the Environment of the Red Sea and Gulf of Aden Environment)
  • A Strategic Action Plan (SAP)
  • Regional Organization for the Conservation of the Environment of the Red Sea and Gulf of Aden (PERSGA)
  • Friends of the Earth Middle East (FoEME)
17 Bay of Bengal Surface Area 2,173,000km2
Volume 5,649,800km3
Average Depth 2,600m
  • Pollution in the Bay is localized (eutrophication, POPs)
  • 1,800 ton/year of pesticides enter the Bay
  • Oil pollution (offshore oil and gas exploration)
  • Seabed mining
  • Bay of Bengal Program (BOBP)
    • Bangladesh, India, Myanmar, Sri Lanka, Thailand Economic Cooperation (BIMST-EC)
    • South Asia Association for Regional Co-operation (SAARC)
    • United Nations Economic and Social Commission for Asia and Pacific (ESCAP)
    • South Asia Co-operative Environment Programme (SACEP)
    • Indian Ocean Marine Affairs Co-opration (IOMA)
    • Indian Ocean Tuna Commission (IOTC)
    • Indian Ocean Rim Association (IORA)
    • Asia@Pacific Fishery Commission (APFIC)
    • Network of Aquaculture Centres in Asia -Pacific (NACA)
    18 South China Sea Surface Area 2,319,000km2
    Volume 3,830,988km3
    Average Depth 1,652m
    • Water pollution (sewage, BOD, eutrophication)
    • Trans Boundary Issues associated with Regional Food Security
    • Threats to coral reefs
    19 Yellow Sea Surface Area 466,200km2
    Volume 18,648km3
    Average Depth 40m
    • Water Quality (general good)
    • Sediment Quality (High organic concentration)
    • Over exploitation of fishery resources
    • Harmuful Algal Blooms (HAB)
    • Strict controls on fishing efforts
    • Transboundary cooperation (NOWPAP, TRADP, APEC, GEF/UNDP/IMO)
    • Northwest Pacific Action Plan (NOWPAP)
    • UNDP/GEF Yellow Sea LME Project
    • Korean Institute of Ocean Science & Technology (KIOST)
    • World Wildlife Fund (WWF) China
    20 East China Sea Surface Area 735,800km2
    Volume 128,765km3
    Average Depth 175m
    • Urbanization and industrialization accerated environmental pollution and water quality deterioration
    • Sediment quality (not serious polluted)
    • Environmental Protection Law of the People's Republic of China
    21 Sea of Japan Surface Area 978,000km2
    Volume 1,713,456km3
    Average Depth 1,752m
    • Red Tides
    • Influence of global warming
    • Marine litter
    • Radioactive pollution
    • Oil spill
    • Ongoing environmental protection measure
    • Northwest Pacific Action Plan (NOWPAP)
    • Coastal Marine litter Survey
    • Northwest Pacific Regional Environmental Cooperation (NPEC)
    • the Economic Research Institute for Northeast Asia (ERINA)
    • Japan Seaology Promotion Organization
    • Ocean Energy of Japan Sea Governments
    • The Association of North East Asia Regional Governments (NEAR)
    • Association for Northeast Asia Regional Studies