Creation of microplastics pollution indicators in the marine environment
Hiroshima Prefectural Hiroshima Kokutaiji Senior High School【DiscussionⅡ】1.Introduction
We are conducting research on Microplastics (MPs), which has become an international
issue. So far, we have conducted coastal surveys and fish feeding surveys in Hiroshima
Bay. From the results, we thought that there might be a positive correlation between theMP intake of organisms and the MP density in seawater. From this, we thought that it
would be possible to create an index that can mutually estimate the MP intake and MPdensity in seawater. If such an index can be completed, anyone can easily investigate theMP density in seawater. It is also possible that scientists around the world will use thisindex to speed up MP research worldwide.

2.What are Microplastics
Microplastics are plastics that are 5mm or less due to physical influences such as
ultraviolet rays and ocean waves. There is a possibility of adverse effects such as
dissolution of harmful chemical substances attached to plastic components and surfaces,
and accidental ingestion by living organisms.

3.Purpose‣Anchovy is likely to ingest MPs, so correlation with the amount of MPs in seawater is likely.
‣We thought that it is difficult to recreate the situation of anchovy in the natural world
because anchovy is a migratory fish and its ingestion is influenced by a wide migratory
road and its habitat.

7.Experiment(Ⅰ)
【MethodsⅣ】① Collecting Japanese shore crab(Hemigrapsus
penicillus)(Fig.8)and shore crab(Helice Tridens)(Fig.9)from
Oota river and Motoyasu river.
② Prepare water tanks with different MP densities and putcrabs in and let stand for a certain period of time.
③【Method α】※using electronic balance to weigh MPs

Fig.8 Japanese shore crab

Fig.9 shore crab

【ResultsⅣ】(Ⅰ)To investigate the MP density in Hiroshima Bay and the MP feeding status of fish.
(Ⅱ) To clarify the relationship between the MPs density in seawater and the number ofMPs eaten by crabs and oysters.

4.Investigation(Ⅰ)①

Fig.10 correlation between MP densities and MP intake in the gastrointestinal tract

Fig.11 Consequences of MPs mishandling in Shore crabs【DiscussionⅢ】‣ A positive correlation was found between MP densities and MP intake in the【MethodsⅠ】
gastrointestinal tract of Japanese shore crabs, which is likely to be suitable for MP<Survey date> 2020/9/28 2020/10 / 5-6
Fig.1 Plankton net
index generation.
<Survey point>① Ninoshima island ② Atadajima island 【ResultsⅠ】Table.1 MPs density (numbers/L) Fig.2 Survey point ‣ It has been confirmed that shore crab swallow MPs by mistake . However, a positive
correlation was not found between MP densities and MP intake in the gastrointestinal③ Nasakejima island ④ Hashirajima island Ninoshima Atadajima Nasakejima Hashirajima
islandislandislandislandtract , and therefore, shore crabs are likely not suitable for the creation of a pollution
Drag Plankton net (Diameter 45 cm)
6.20
0.304
1.01
0.589
environment index.
vertically at each of the points (20-35 m)
and measure MPs density in seawater.
Table.7 Amount of MP(Ⅰ)MP survey in seawater on research vessel②④③

https://www.bing.com ps://www.bing.com

5.Investigation(Ⅱ)

8.Experiment(Ⅱ)

50cｍ【MethodsⅡ】<Survey point and survey date>ⒶHeiseigahama beach 2015/6/30ⒷMiyajimamaigann beach 2016/8/4,2017/5/21,2018/5/20ⒸSennennkaigann beach 2019/8/4Fig. 3 Collecting MP①The collected sediment was placed in seawater and thedifference in density was used to separate the sand fromother materials②Classify collected materials by color and shape and component
analysis using FT-IR to identify MPs.

Chlorella(mL)【MethodsⅤ】
10.1① Collecting oysters(Crassostrea gigas) from
20.1
Hiroshima Bay.
30.1②【Method α】※ using electronic balance
to weigh MPs.
③ Remove the seawater from the bottle and put it on an absorber

50cm(Ⅱ)Quadrat survey at the coast of Hiroshima Bay

BottleFig. 4 FT-IR analysis

MP(g/L)
0.02
0.04
0.08

Fig.12 Oyster【ResultsⅤ】
Amount of MP

n=12intake(×10⁻⁴g)
4R² = 0.666【ResultsⅡ】

Fig.5 Survey point→
Table.3 PointⒷ 2016/8/4

Table.2 PointⒶ 2015/6/30

Point aPoint bPoint cAll(numbers)

Number of plastics

571

8170

Foamed plastic(numbers)
Hard plastic(numbers)

Table.4

2

Point a1110
1082
28

Point b994
974
20

Point c133
126
7

PointⒷ 2017/5/21
All(numbers)

Foamed plastic(numbers)
Hard plastic(numbers)
Dry weight (mg)Table.5

3

Point a
245
245
010

Point b
340
330
10110

Point c
244
236
870

Point d3065
3040
25470

Point e
1471
1467
4320

Point f
474
466
830

PointⒷ 2018/5/20
Point a941
895
46

Point b
1037
985
52

Point c704
608
96

Point dPoint eAll(numbers)
835
565
Foamed plastic(numbers)
760
524
Hard plastic(numbers)
75
41
Table.6 PointⒸ 2019/8/4【DiscussionⅠ】
Numbers Weight‣ⒶThe amount of hard plastics (blue, black, green) and foam plastics
All20.8

is high. Since there are many rafts in the sea, it is thought that theFoamed plastic
00MP may be caused by the decay of the parts used in the rafts andHard plastic
20.8
the styrofoam used for the floats.
‣ⒷThe number of plastics was greater than in previous years, and most of them were foamed
plastics. It is possible that not only the deterioration of the raft, but also the different weather
conditions may be the cause.
‣ⒸThe survey point is a tidal flat that is under the sea at high tide. The reason for the low MPs
despite the relatively high amount of debris in the surrounding area may be due to the factthat they were washed out into the seawater at high tide.

000.02

0.04

0.06

0.08

0.1

MP density in seawater(g/L)

Fig.13 Changes in MP concentration in seawater and MP intake in oysters

Fig.14 Absorbance of Seawater【DiscussionⅣ】‣Figure13 shows that there is a positive correlation between the MP
densities in seawater and the number of MPs ingested by oysters.

9.Project
Our work is not limited to scientific research; we also
run projects, such as Guru Guru Project, that involve
local people to solve the problems. In this project, weconduct beach cleanups with local people andpresent research results to raise awareness. We havecontinued our exchange with Fukushima Prefectural
Futaba Mirai Gakuen High School and participation inthe "High School Students' Forum on theEnvironment of the Seto Inland Sea" organized by
Hyogo Prefectural Amagasaki Oda High School, as wellas interaction with high school students from otherprefectures to address environmental issues.

10.Future Research

6.Investigation(Ⅲ)(Ⅲ)Correlation survey of MP intake, habitat depth of fish in Hiroshima Bay.

【ResultsⅢ】【MethodsⅢ】1

We would like to continue to conduct surveys and research to create an index that is easy to use
around the world and which can contribute to the resolution of the MP problem, which is a globalproblem. We would also like to contribute to the fundamental solution of the problem through Guru
Guru Project and other activities in cooperation with local communities and governments.

11. Reference

Fig.7 Correlation survey of MPs intake, habitat depth of fish

Fig.6【Methods α】

And the upper level fish took in more
MPs than the lower level fish.

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[2] 高田秀重・山下麗（2014）「海洋プラスチック汚染の概況と今後の課題」『海洋生物』215，555-564．
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公益財団法人 日本水環境学会．
[4] 高田秀重「東京農工大学農学部環境資源科学科マイクロプラスチック汚染：地球規模での汚染.継時的トレンド.解決への方向性」.www.env.go.jp/press/y030-21-2/mat02.pdf（2018年8月31日アクセス）[5] 牛島大志他(2018)「日本内湾及び琵琶湖における摂食方法別にみた魚類消化管中のマイクロプラスチックの存在実態」..水環境学会誌
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http://mt-utoa.webmasters.co.jp/learnocean/news/0003.html.（2018/9/3アクセス）[7]「エビ・カニ－番匠おさかな館の図鑑」.
http://michinoeki-yayoi.com/osakanakan/zukan/shrimpcrub/kani%20takanokehusaisogani01.htm.（2019/5/20アクセス）[8]「市場魚貝類図鑑」.https://www.zukan-bouz.com/syu.（2019/5/20アクセス）