1:45 PM - 3:15 PM
[O11-P22] Microplastics survey between Heda and Miho
Keywords:microplastics, Surugabay, Izu Peninsula
Summary
The problem of microplastics(hereafter referred to as MP) in oceans and rivers is serious these days. Our school has conducted MP surveys for four years and has studied MP in the Izu Peninsula. Because MP surveys in the ocean are expensive,our research up to now has been MP surveys in rivers, but this year we were able to conduct MP surveys in the ocean with a low budget. This was because Mr. Matsunaga of the Toda Yacht Race Executive Committee, who saw our presentation of the MP survey the year before last, asked us to cooperate in the survey by having our school analyze the samples collected in the race. The Toda Yacht Race Executive Committee's desire to contribute not only to yacht racing but also to environmental research matched our desire, and we carried out a low-budget marine plastic survey.
First, in order to elucidate the causal relationship between the amount of MP sedimentation on the beach and the aspect of the ocean currents that flow along its coast, we paid attention to the spit located in Miho and Toda, and investigated the relationship with the longshore currents. Sand samples were taken from these two sites and the amount of MP was counted. Next, with the cooperation of the Toda Yacht Race Executive Committee, MPs were collected and counted in the Suruga Bay waters between Miho and Toda. We also compared them with open data from various organizations.
We then provided the samples we collected to the Utsukusii Izu Creation Center and used them as teaching materials for environmental education at the Numazu Special Needs School for the Deaf.
Materials and Methods
Collect 3 samples of sand near where drifting debris washed ashore at the locations indicated by the red circles in the photos of Miho and Toda in a volume of 30 cm square and 1 cm deep at each location 2 Sieve the collected sand through a 4 mm sieve to remove large organic matter 3 Take 100 g and sieve it through a 300 μm sieve 4 Treat the organic matter derived from the drifting debris with hydrogen peroxide and sodium hydroxide to remove organic matter 5 After filtration, specific gravity separation of MP with 70% potassium hydroxide 6 After filtration again, stain MP with Nile Red Specific gravity separation of MP with 70% potassium iodide 6 After filtration again, MP was stained with Nile Red 7 Blue light was applied and the number of fluorescent MP was counted under a microscope.
Results
See Table 1 for results.
Discussion
The amount of MP deposition in Miho and Toda is considered to be influenced by the ocean currents. Figure 2 shows that the current turns leftward in Suruga Bay. Since this current circulates within the bay, the amount of MP deposition at sites 3 and 4 is high, while it is low at the other two sites where the current is slower. On the other hand, on the east coast, a branch current of the Kuroshio enters the bay along the Izu Peninsula and turns counterclockwise to the left. It is thought that the current flows into the spit of Toda as shown in Figure 3, carrying drifting debris from the river and depositing MP.
An MP survey conducted by Shimoda High School on the Shirahama coast in 2020 identified 54 MPs. It is presumed that the ocean currents on the east coast are faster and carry more MPs. In contrast, the ocean currents in Miho are calm and the amount of MP deposition is low. From this, we hypothesized that the amount of MP deposition is influenced by the speed of the ocean currents. However, the current in Toda is calmer than that on the east coast, but the amount of MP deposition is higher. This may be due to the presence of the river shown by the orange dotted line in Fig. 3 in Toda, from which MP may have flowed in. However, this study did not examine the number of river-derived MPs, and this point cannot be considered.
In the ocean, the MP counts were 2 and 4. In the previous study in 2021, 3 and 2 MPs were collected at the Shizuura Diving Center and Awashima Island. We considered that MPs inflow from rivers and exit from inner bays to the open ocean, and therefore the amount of MPs in the open ocean was the lowest. However, in the present data, the amount of MP off Suruga Bay and in the coastal area is almost the same, and further verification of the sampling and detection methods is needed.
For the first time, we were able to collect MP off Suruga Bay in a high school experiment at almost no cost. This was made possible through collaboration with the Toda Yacht Race Executive Committee and led to the establishment of new research methods in cooperation with outside organizations. Further development of MP research in the Izu Peninsula is expected.
The problem of microplastics(hereafter referred to as MP) in oceans and rivers is serious these days. Our school has conducted MP surveys for four years and has studied MP in the Izu Peninsula. Because MP surveys in the ocean are expensive,our research up to now has been MP surveys in rivers, but this year we were able to conduct MP surveys in the ocean with a low budget. This was because Mr. Matsunaga of the Toda Yacht Race Executive Committee, who saw our presentation of the MP survey the year before last, asked us to cooperate in the survey by having our school analyze the samples collected in the race. The Toda Yacht Race Executive Committee's desire to contribute not only to yacht racing but also to environmental research matched our desire, and we carried out a low-budget marine plastic survey.
First, in order to elucidate the causal relationship between the amount of MP sedimentation on the beach and the aspect of the ocean currents that flow along its coast, we paid attention to the spit located in Miho and Toda, and investigated the relationship with the longshore currents. Sand samples were taken from these two sites and the amount of MP was counted. Next, with the cooperation of the Toda Yacht Race Executive Committee, MPs were collected and counted in the Suruga Bay waters between Miho and Toda. We also compared them with open data from various organizations.
We then provided the samples we collected to the Utsukusii Izu Creation Center and used them as teaching materials for environmental education at the Numazu Special Needs School for the Deaf.
Materials and Methods
Collect 3 samples of sand near where drifting debris washed ashore at the locations indicated by the red circles in the photos of Miho and Toda in a volume of 30 cm square and 1 cm deep at each location 2 Sieve the collected sand through a 4 mm sieve to remove large organic matter 3 Take 100 g and sieve it through a 300 μm sieve 4 Treat the organic matter derived from the drifting debris with hydrogen peroxide and sodium hydroxide to remove organic matter 5 After filtration, specific gravity separation of MP with 70% potassium hydroxide 6 After filtration again, stain MP with Nile Red Specific gravity separation of MP with 70% potassium iodide 6 After filtration again, MP was stained with Nile Red 7 Blue light was applied and the number of fluorescent MP was counted under a microscope.
Results
See Table 1 for results.
Discussion
The amount of MP deposition in Miho and Toda is considered to be influenced by the ocean currents. Figure 2 shows that the current turns leftward in Suruga Bay. Since this current circulates within the bay, the amount of MP deposition at sites 3 and 4 is high, while it is low at the other two sites where the current is slower. On the other hand, on the east coast, a branch current of the Kuroshio enters the bay along the Izu Peninsula and turns counterclockwise to the left. It is thought that the current flows into the spit of Toda as shown in Figure 3, carrying drifting debris from the river and depositing MP.
An MP survey conducted by Shimoda High School on the Shirahama coast in 2020 identified 54 MPs. It is presumed that the ocean currents on the east coast are faster and carry more MPs. In contrast, the ocean currents in Miho are calm and the amount of MP deposition is low. From this, we hypothesized that the amount of MP deposition is influenced by the speed of the ocean currents. However, the current in Toda is calmer than that on the east coast, but the amount of MP deposition is higher. This may be due to the presence of the river shown by the orange dotted line in Fig. 3 in Toda, from which MP may have flowed in. However, this study did not examine the number of river-derived MPs, and this point cannot be considered.
In the ocean, the MP counts were 2 and 4. In the previous study in 2021, 3 and 2 MPs were collected at the Shizuura Diving Center and Awashima Island. We considered that MPs inflow from rivers and exit from inner bays to the open ocean, and therefore the amount of MPs in the open ocean was the lowest. However, in the present data, the amount of MP off Suruga Bay and in the coastal area is almost the same, and further verification of the sampling and detection methods is needed.
For the first time, we were able to collect MP off Suruga Bay in a high school experiment at almost no cost. This was made possible through collaboration with the Toda Yacht Race Executive Committee and led to the establishment of new research methods in cooperation with outside organizations. Further development of MP research in the Izu Peninsula is expected.