Top > National survey on the natural environment > Survey of Tidal flats, Seaweed Beds and Coral Reefs Distribution/Marine Organisms Biological Environment Survey (4th Survey)
National Survey
Survey of Tidal flats, Seaweed Beds and Coral Reefs Distribution / Marine
Organisms Biological Environment Survey (4th Survey) *2
-- Tidal flats, Seaweed Beds and Coral Reefs Distribution Survey
Survey Sequence and Effective Years
(All years are fiscal years)		 data Result list (Japanese only except )
2nd survey
1978 *1		  
 Report of the National Survey on the Marine Natural Environment (Seashore, Marine Environment, Tidal flats, Seaweed beds and Coral reefs)
4th survey
1989-1992 *2		 Seaweed Beds
Tidal Flats 		 Report of Survey on Marine Organisms Environment Vol.1 (Tidal flats)
Original data of Survey on Marine Organisms Environment (Tidal flats)
Report of Survey on Marine Organisms Environment Vol.2 (Seaweed beds)
Report of Survey on Marine Organisms Environment Vol.3 (Coral Reef)
Original data of Survey on Marine Organisms Environment (Coral Reef)
The distribution map of Coral Reef (1/100,000)
Natural Environment Map (1:200,000) (every all pref.)
5th survey
1998-2002		   Report of the survey on Important Coastal Zone Organisms (1998)
Report of the survey on Important Coastal Zone Organisms (1999)
Report of the survey on Important Coastal Zone Organisms (2000)
Report of the survey on Important Coastal Zone Organisms (2001)
6th survey
2003-		   A result thing (Only Japanese) can be downloaded from here.(Japanese page)
How To Read This Display

When reproducing and distributing this map free of charge, please make acknowledgement as follows,
"This distribution map was generated by the Japan Environment Agency's(*) Marine Biological Environment Survey (4th Survey) Internet Site."
Distribution for a fee requires the agency's(*) permission..
  1. Survey Objectives
 Familiar to many because of clamming and other activities, tidal flats not only support fish and shellfish, they are also important as home to many migratory birds like Sandpipers and Plovers. Many organisms living in shallow coastal waters make their home in seaweed beds. The flora and fauna in seaweed beds are important ecologically. And they function also as important resources for the marine product conservation of the bays and estuaries. Coral reefs are also significant because they support an enormous variety of organisms and have very high productivity. This survey was undertaken to determine the distribution and extent of extinction of these extremely important environments - tidal flats, seaweed beds and coral reefs.
  2. Survey Content and Methods

(1) Tidal Flats
 The location, area, type and environmental condition of tidal flats with an area of 1ha or more presently or as of 1945 were surveyed in the 2nd survey using mainly topographical maps and aerial photos, supplemented as necessary for verification with site surveys.

 The 4th survey investigated recent tidal flat distribution and disappearances since the time of the 2nd.

 The 5th survey was conducted with the following objectives, for the purpose of biologically classifying tidal flats, seaweed beds and coral reefs nationwide:

1) Collect basic data on organism communities in major tidal flats, seaweed beds and coral reefs nationwide, and study the biological classification, etc. of each region; and
2) Establish simple survey items and techniques required for nationwide surveys.

 Approximately 150 tidal flats nationwide were surveyed over a period of three years from fiscal 2002.

 As for the survey method, several survey spots were established in each tidal flat (e.g. upstream, downstream, mouth of a bay and head of a bay) and the biota was determined accordingly. Quadrats (each measuring approx. 5m x 5m) were set, and benthos in the quadrat and their quantity were recorded within a limited time. Benthos in mud and under rocks were recorded by digging the mud and turning over the rocks.


(2) Seaweed Beds
 This survey was done in the same way as the survey of tidal flats. It checked seaweed beds currently or as of 1973 having an area of at least 1ha in coastal waters less than 20 meters deep.

 The 4th survey checked recent distribution and disappearances since the 2nd.

 The 5th survey involved confirming the current location and area of seaweed colonies based on the results of existing surveys and through interviews with local fishermen. Also, composing species of community and their sizes were determined through visual observation, by snorkeling and scuba diving.

 In the 6th survey, approximately 130 seaweed beds across the country were surveyed over a five-year period from fiscal 2002. The survey was conducted by snorkeling or scuba-diving into the site, and by recording the species found. At priority survey spots, seaweeds inside quadrats placed within the survey zone were harvested and weighed, to measure the biomass. Also, specimens were produced and the species were identified with respect to animals living on the leaves.


(3) Coral Reefs
 The 2nd survey examined scleractinian coral communities presently in existence or in existence in 1973 (southward from the Tokara Islands, with an area of at least 1ha) using the same methods as the tidal flats survey.

 The 4th survey made a distinction between reef region (southward from Kodakara Island in the Tokara islands) and non-reef region (northward from Akuseki-jima Island in the Tokara islands) and examined hermatypic coral community distribution and disappearance since the 2nd survey, using document collections plus the manta towing method and site surveys from station installations.

 The 5th survey involved setting survey lines, swimming along the lines for 10 minutes, and recording the dominant coral species, live coral coverage, damage by Acanthaster planci, coral bleaching status and other information on coral reefs.
  3. Survey Results
(1) Tidal Flats
 The 4th survey confirmed 51,443ha of currently existing tidal flats and also that 3,857ha of tidal flats had disappeared since the previous survey in 1978.

 Four examples of tidal flats with area of greater than 1,000ha were reported from the Ariake Sea. Including these, the Ariake Sea had some 40% of all the tidel flats in Japan.

 However, disappearance of tidal flats was also greatest in the Ariake Sea, reaching 1,357ha.

 In the 5th survey, basic data on species were collected from 9 tidal flats nationwide, and their biological classification was attempted. Further, problems in the survey method were studied and plans for a new method were developed.

 The 6th survey is currently underway.


(2) Seaweed Beds
 The 4th survey confirmed 201,212ha of seaweed beds. Since the last survey (1978) 6,403ha had disappeared.

 The seaweed bed with the greatest continuous area was 7,891ha in size, stretching from Sagara to Omaezaki in Shizuoka Prefecture. The area with the greatest number of non-continuous seaweed beds was found to be the sea around the Noto Peninsula. The total seaweed area here was 14,761ha, 7.3% of the total for Japan.

 The survey found that a large area of seaweed has disappeared in the Amakusa open sea and in the Akita Sea. Rapid disappearance was also seen in Osaka and Okayama Prefectures.

 In the 5th survey, basic data on species were collected from 10 coral leafs nationwide, and their biological classification was attempted. Further, problems in the survey method were studied and plans for a new method were developed.

 The 6th survey is currently underway.


(3) Coral Reefs
 The 4th survey found 1,409.3ha of coral reefs in non-reef region (Akuseki-jima Island in the Tokara Islands north, excluding the Ogasawara Islands) and 96,023.3ha in reef region (south of Kodakara Island in the Tokara group). The Ogasawara Islands had 456ha.

 In the non-reef region, coral disappearance due to dredging and filling work and other changes was 3ha in Kagoshima Prefecture due to fill land, and 0.03ha in Kochi prefecture due to construction work. Crown-of-thorns starfish (Acanthaster planci) depredations killed 3.06ha of coral in 7 places in Kochi Prefecture. In the reef region, 1,506.7ha of reefs disappeared since the 2nd survey, mainly due to fill work. The seas around Okinawa island saw the greatest loss with 1,224.0ha. This is a loss of 4.4% of that area's coral reefs. In the seas of the Ogasawara Islands, human activities cost 5ha of coral.

 In the 5th survey, basic data on species were collected from 10 coral reefs nationwide, and their biological classification was attempted. Further, problems in the survey method were studied and plans for a new method were developed.
Tidal flats, Seaweed Beds and Coral Reef Areas

Present Area*1 Disappearance*2 Present Area +
Disappearance		 % of
Disappearance
Tidal flats 51,443ha 3,857ha 55,300ha 7.0%
Seaweed bed 201,212ha 6,403ha 207,615ha 3.1%
Coral Reef Seas 96,479ha 1,512ha 97,991ha 1.5%
Non-reef seas 1,409ha 15ha 1,424ha 1.1%
*1: Results of the 4th survey
*2: Area lost since the 2nd survey
back
All Rights Reserved, Copyright Ministry of the Environment.

*) The organization was changed to the Ministry of Environment in 2000.