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FY 2014 Survey Results of Marine Litter in Coastal Areas

June 3, 2015

We had surveyed the washed-ashore debris in seven coastal spots around Japan and the drifted and ocean floor debris in the Inland Sea from January to March in 2015. In this survey, we have surveyed the amount and kinds of washed-ashore, drifted and ocean floor debris in individual spots. In addition, we have surveyed the microplastics(※)whose impacts on the ocean ecosystem have been apprehended in recent years. We will inform you of the survey results compiled this time.

1. Background

Ministry of the Environment has so far surveyed the amount and the kinds, etc. of washed-ashore debris on the beaches, etc. drifted debris floating on the ocean surface and debris deposited on the ocean floor in the typical coastal areas around Japan.

In the 2014 survey,

① as to the survey of washed-ashore debris, we compiled the survey conducted for the past five years in addition to the conventional survey.

② as to the survey of drifted and ocean floor debris, we compared not the survey which we had so far conducted in six or seven spots over typical coastal areas but focused on the survey of the Inland Sea and compared the differences in the amount and kinds of debris in the neighboring ocean areas.

Still more, we have also surveyed the microplastics whose impacts on the ocean ecosystem have been apprehended in recent years and elucidated a part of the actual conditions in any survey.

2. Outline of Survey Results

(1)Monitoring Survey of Washed-ashore Debris

We have compiled the monitoring results of washed-ashore debris (number, kind and amount, etc.) accomplished in seven coastal spots around Japan(Kamisu-City in Ibaraki prefecture, Hakui-City in Ishikawa prefecture, Awaji-City in Hyogo prefecture, Shimonoseki-City in Yamaguchi prefecture, Tsushima-City in Nagasaki prefecture, Minami-Satsuma-City in Kagoshima prefecture and Ishigaki-City in Okinawa prefecture) for the past five years.

As to the total amount of five years, plastics which have the largest number of all have occupied from 60% to 90%. In addition, there have been a significant number of woods, Tsushima-City, Nagasaki prefecture and Kamisu-City, Ibaraki prefecture and plastics have occupied the majority in other survey spots according to comparisons between artifacts concerning weight.

Next, as to the largest number (the cumulative total) of debris which has washed ashore for the past five years from a local point of view: first, approximately 47,000 pieces in Shimonoseki-City, Yamaguchi prefecture; second, approximately 32,000 pieces in Tsushima-City, Nagasaki prefecture; third, approximately 20,000 pieces in Kamisu-City, Ibaraki prefecture; that is to say, there has been potentially more debris in the Japan Sea side. As to the weight (the cumulative total), first, approximately 6 tons in Tsushima-City, Nagasaki prefecture; second, approximately 5 tons in Kamisu-City, Ibaraki prefecture; third, approximately 4.7 tons in Shimonoseki-City, Yamaguchi prefecture; that is to say, there has been potentially more debris in the Japan Sea side just as the number. By the way, the second rank of Kamisu-City, Ibaraki prefecture results from a large amount of woods, etc. temporarily washed ashore by typhoon, etc..

Moreover, we have surveyed the proportion of debris derived from overseas by means of language indications of plastic bottles. Approximately 80% Chinese indications of all in Ishigaki-City, Okinawa prefecture which has the largest number of plastic bottles washed ashore have been confirmed. Meanwhile, approximately from 30% to 50% Korean indications and approximately from 20% to 30% Chinese indications of all in the Japan Sea side have been confirmed and there have been more Japanese indications in the lower stream of the Tushima Warm Current. Approximately from 70% to 80% Japanese indications of all have been confirmed in Minami-Satsuma-City, Kagoshima prefecture and Kamisu-City, Ibaraki prefecture. Japanese indications have been confirmed in almost all debris of the Inland Sea.

(2)The estimated amount of washed-ashore debris

We have calculated the density of washed-ashore debris in individual areas and estimated the nationwide amount of washed-ashore debris resulting from retrieving and disposing business of washed-ashore debris, which local governments have conducted through the subsidized projects implemented by Ministry of the Environment. As a result, the amount of nationwide washed-ashore debris in 2015 has been estimated as from 310,000 tons to 580,000 tons. By individual prefectures, first, from 62,000 tons to 118,000 tons in Hokkaido prefecture, second, from 43,000 tons to 91,000 tons in Chiba prefecture, third, from 34,000 tons to 56,000 tons in Shimane prefecture, fourth, 26,000 tons to 49,000 tons in Nagasaki prefecture and from 19,000 tons to 35,000 tons in Oita prefecture.

(3)The survey of toxic substances included in washed-ashore microplastics

We have extracted and analyzed Polychlorinated diphenyl ethers(PBDEs)added to them as a flame retardant in the manufacturing process and polychlorinated biphenyl(PCBs)adsorbed on their surfaces concerning the microplastics collected in seven monitoring spots around Japan.

The comparatively higher density of PBDE than other survey spots has been detected from the sample collected in the Shimonoseki-City area of Yamaguchi prefecture while it is lower than the sample collected in the back side of Tokyo Bay. The comparatively higher density of PCB than other survey spots has been detected from samples collected in the Shimonoseki-City area of Yamaguchi prefecture and in the Awaji-City area of Hyogo prefecture while they are much lower than samples collected in Tokyo Bay and Osaka Bay.

(4)Surveys of Ocean Floor Debris

We have surveyed ocean floor debris in cooperation with fishery cooperative associations in eleven prefectures over the coast of the Inland Sea. Approximately 2,400 surveys (the number of hauling nets) have been conducted during the survey period from January to March in 2015.The total weight of collected debris is approximately 4.5 tons and the volume is approximately 30㎥ and the number is approximately 35,000 pieces. The largest number of collected debris as a kind is plastic and subsequently a lot of debris such as metal, cloth, rubber and glass has been found. In addition, these amounts are different in individual bays and open seas.

We have surveyed freshness dates of drink cans to survey how long old debris has deposited on the ocean floor in addition to the above-mentioned surveys. Older cans tend to be a smaller number of cans. The oldest can is dated back to 1983.   

(5)Visual Survey of Drifted Debris

We have conducted visual surveys in the seven areas of the Inland Sea. The largest number of detected debris was plastic film (plastic bags) and the second largest number of it was styrene foam.

(6)The Surveys related to Microplastics Floating on the Ocean Surface

We have collected microplastics by using Neuston net (The mesh size is 0.35 mm. The net usually used to collect plankton and fish spawn and larva floating in the surface portion.) in the same way as the survey method conducted off shore in the seven areas of the Inland Sea last year. The collected microplastics have been classified by size(1mm~5mm)and these numbers have been calculated.

The density (the number in the sea water 1m3 filtrated by Neuston net) of microplastics in the survey areas is 0.037pieces/ m3 and it is smaller than the average result (1.982 pieces/ m3)of off-shore surveys.

(※)Microplastics: The plastic debris which occupies approximately 70% of drifted and washed ashore debris deteriorates due to the ultraviolet rays and temperature difference on the coast and gradually fragments into small pieces due to physical stimulation such as abrasion of coastal sands. These plastics less than 5mm in size are called microplastics and these floating micro pieces approximately less than from several hundred μm to 1mm in size have been confirmed in ocean areas all over the world. Because the microplastics similar to the size of zooplankton can be easily mixed into ecosystem through being wrongly eaten by fish, etc., the potentiality which they may become the carrier catalysts for contaminants adsorbed on the surfaces inside organisms has been pointed out.

For further information, please visit the Ministry of the Environment web site (in Japanese).

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