Purpose

Our survey aims to clarify abundance and weight of marine debris stranded in mangrove and mudflat.

To clarify them, we need to collect samples. A method using quadrats, squared survey areas, includes following merits.

Mangrove contains variety of vegetation and structure. Such differences seem to affect capacity to catch marine debris and we need to control their influence. Besides, we need to implement our survey within reasonable budget and period. Quadrat survey method enable us to implement that. By devising arrangement of survey position combining the quadrat method and random sampling procedure, we can cover relatively wide area within reasonable budget and period while controling their influence.

Figure below shows position of target quadrats. Using PC and smartphone, we can refer to their id numbers and position alltogether. Total number of quadrat is 18, which we set up in 2018 for stationary observation. Each of quadrat is 10m*10m square in size. Based on CEP of GPS, prior surveys, and results of pilot survey, we determined the size in 2016. Larger size might unable us to set up precisely-shaped quadrat. Smaller quadrat might unable us to control errors derived from GPS.

Shape of survey quadrat. Size of that is 10m (10,000mm) in height and 10m (10,000mm) in width. Four white circles demonstrate positions of bamboo sticks to fix the shape. Four black squares demonstrate position of core sampling.

Instrument

• GPS: Holux M-241. The GPS indicate indicates present position and works as logger, recording positions by every 5 minutes. When in use, wrap it with a kitchen wrap to protect it from mud, water, and other obstacles. In addition, to catch signals from GPS satellites, turn on the GPS 5 minutes before use. The GPS is energy-saving and is available to use whole a day with a AA battery. After use, charge the battery for the next use.

• Waterproof camera: Nikon AW-130. The camera enable to add information regarding latitude, longitude, and moving direction to EXIF. Turn on 5 minutes before use. To avoid battery’s attrition, using logger function is not recommended.

• Smartphone: The device is for daily communication and displaying Google maps. Requisite apps should be installed before use. The smartphones are not warterproof. Put them into freezer bags when in use.

• 10m Rope: We use 4 ropes to set up a quadrat. Each position is available to check by table above and GPS. Before use, to hook conveniently, make eye splices for both sides. At 5m position (half length of the rope), bind a yellow tape. After use, drop them as garvage to avoid septic smell by damaged mud / sediment.

• 2m Bamboo stick: To support the ropes, we insert the sticks deeply. After use, to keep the position, only 1 stick should be kept. We buy it in Can Tho city because of lower price. After use, donate it to a driver or local residents.

• Scale: To avoid mud and other stain, use it together with paper sheets or plastic plate. No leaving in the sun to avoid mulfunction. When not in use, keep it in the shade.

• A4 Paper sheet：The sheets works as a basement of picked up items for taking photo. Using \(LaTeX\) commands, we mark scale like a ruler and id number. ID numbers of record sheet, freezing bag, and photo sheet should be the same. For the purpose, refer to each other carefully.

Procedure

1. Prepare requisite items

• Drinking water: 2 or more bottles of bottle warter. Candies supplying salt and minerals should be held together.
• Bamboo stick: 4 sticks per group
• rope: 4 ropes per group
• Bags: 3 degradable plastic bags to pick up stranded items
• GPS: 2 per group. Wrap them with film before departure.
• Camera: 2 per group
• Smartphone: 1 per group
• Toilet paper: For emergency and protecting your human rights

2. Moving to target quadrat: Using Google maps and GPS, find bottom-left point of target quadrat.

3. Set up a quadrat by four bamboo sticks: Start sticking from southwest, southeast, northeast, and northwest in order. Before finishing, NO STEP into the quadrat for better image recognition. The step might interupt the recognition wrongly.

4. Take photos from 4 centers：From yellow-tape marks, take photos to center of quadrat.

5. Pick the stranded items up: Take photos of all items from immediately above before picking up. If difficult, take photos from surroundings.We do not need to take mud and stain off.

6. Move back to meeting point: Bring all back except for a bamboo stick. The left-over stick should be kept.

7. Take photos: Under the items, put a picture mat with ruler and corresponded id. The item should be put inside of angular field.

8. Scale their weight: scale their weight together with mud and other stains.

9. Put the item into freezing bag: Before scaling dry weight, we need to wash and dry the samples. However, because of tidal schedule, we cannot use sea water for cleaning. IDs of recording form and ones of bags should be corresponded correctly.

   \[ \underbrace{1234}_{\substack{Quadrat\\No.}}\_\underbrace{001}_{\substack{ID}} \]

10. Clean the sample up by sea water: Using the warter, wash dirty samples only. If inside of freezer bag would be muddy, wash it as well. When you wash them, use a bucket. NO CLEANING OUTSIDE OF that.

11. Put the samples into the freezer bags: If possible, before inserting, wipe water out from them.The scale paper should be left as it was.

Purpose

The purpose of core sampling is to detect degraded marine debris in mud / sediment and clarify their distribution of weight. Core sampling method refers to a method to detect samples such as animals, objects, and materials in mud / sediment / soil.

Based on our prior survey in 2017, September 2018, and December 2018, we found that debris stranded by branch and mud seem to be seen and become fragmented as time goes by. This implies that the marine debris might be buried and discharged after being retained, degraded, and fragmented. If the debris would be buried, using core sampling method, we would be able to detect them from mud.

Implementing the sampling, we can clarify hidden abundance of marine debris in mangroves and mudflats. In addition, we may be able to clarify a degrading process of debris in such field.

Instrument

• Acrylic core tube: Internal diameter is 30mm. In both sides of that, two rubber plugs are inserted for ceiling.
• Freezer bags: M-sized freezer bag is for preserving sampled materials. We use 8 bags per quadrat and 144 bags in total (8 \(\times\) 18 = 144).
• Label: A sticker with quadrat id and items’ id.
• Filter: This removes mud, silt, and other small materials such as microplastics ($$5.0mm), we employ 2-mm mesh.
• Bucket and buts: It is for cleaning samples with sea water.
• Precise scales: They scale weight of samples. No leaving in the sun.
• Tweezer:Qweeze tips and sharpen them well to pick tiny items up.

Core sampler

Procedure

Works by survey group

1. Move to a target quadrat: The core sampler should be carried by bag. No HOLDING THE SAMPLER BY HAND to avoid loss the sampler.

2. Identify survey points

3. Insert the core sampler: Referring to the instruction below, at the demonstrated points, insert the tubes until upper sides of tubes will reach surface of mud / sediment.

Insert a core sampler

4. Insert a rubber plug to upper side.

Insert a rubber plug into upper side.

5. Pull out the sampler while swinging.

Pull out the core sampler while swinging.

6. Insert another rubber plug into another side. NO PULLING IT UP VERTICALLY. Otherwise, the sample would be fall out of sampler.

Insert another rubber plug into lower side.

4. Moving back carefully.

5. Pass the samplers to scaling group and receive the next samplers.

Recording sheet and relevant references

• Sheet 1　Sheets for recording weights
• Mount papers for picked-up samples’ images: 220|227|410|729|822|1053|1132|1138|1280|1323|1357|1554|1808|2072|2085|2090|2253|2280|

Survey group and record group

We establish some groups in accordance with work contents; survey group and record group

A survey group consists of 3 or 4 members per group. Total number of the group is 3. Work contents are in the following.

1. Making quadrats and collecting samples (2 or 4 persons per group): Persons in charge make survey quadrats and collect samples.
2. Collecting samples with core sampler (1 person per group): Person in charge collects muds / sediments using core samplers.

A record group consists of 3 or 4 persons. Their work contents are in the following.

1. Takeing photos (1 person)
2. Scaling weights (1 person)
3. Recording (1 person)
4. Processing core-sampled mud /sediment (1 person)

Notice

• Safety first: The mangroves are full of danger such as bees, dirty warter, heavy mud, fast tidal movement, and others. To avoid insects, repellent may help you some. To escape from insects’ (especially bee’s) bite, WALK WHILE LOOKING AROUND CAREFULLY. Washing yourselves carefully will enhance your health. MOVE BACK TO OUR MEETING POINT IN TIME.

• Water supply: The survey field is extremely hot. Moving around while supplying water and minerals helps you a lot. Fruits and snacks are also fun of you.

• No step on breething roots: Without the roots, mangroves would be stifled due to our ecosystem conservation activity.

• Use instruments carefully: Any instruments such as GPS, camera, and smart phone are mass of precision parts.

• Maintain the instruments every day: Clean up!! Charge their batteries!!

• Show sincere respects to residents: Thanks to their kindness, we can implement our survey.