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D4134-82 – Standard Test Method Technical Guide
🌊 Scope and Summary
This standard practice describes procedures for collecting semiquantitative samples of phytoplankton using a Clarke‑Bumpus plankton sampler. The sampler is towed from a moving boat at a specified depth, employing a net to concentrate organisms and a calibrated flowmeter to measure the water volume filtered. The towing speed is maintained at 3 to 5 knots, and the phytoplankton are preserved as per study objectives.
The sampler offers several advantages, including discrete depth sampling, lightweight construction, and a high filtration efficiency factor of 0.88. It is versatile and can be used in most waters except the shallowest. However, disadvantages include the need for frequent flowmeter maintenance and limitations in small areas or shallow waters.
🛠 Apparatus Specifications
The Clarke‑Bumpus sampler consists of a metal frame with a plankton net attached at the mouth and cod end. It is available in three sizes: 120 mm, 200 mm, and 300 mm, with the 200 mm diameter net being the most widely used. The flowmeter records the volume of water entering the net, and overspill due to excess speed is minimal.
| 🟦 Parameter | 📏 Value | 📐 Notes |
|---|---|---|
| Sampler Sizes | 120 mm, 200 mm, 300 mm | 200 mm most common |
| Towing Speed | 3 – 5 knots | Slow to medium |
| Filtration Efficiency | 0.88 | High efficiency factor |
| Flowmeter | Calibrated | Measures water volume |
| Overspill Effect | Minimal | Excess speed has little impact |
⚙️ Key Operational Tips
Proper maintenance and handling are crucial. The flowmeter must be calibrated and serviced frequently, including lubrication. The sampler is fragile, particularly the closing device and flowmeter, so careful deployment and recovery are necessary. After each collection, wash the net thoroughly and inspect for pin‑size holes or tears. The wet net should be hung full length in air and in subdued light to dry. Ensure the cable strength is adequate to prevent loss. Avoid using the sampler in beds of macrophytes, shallow waters, or near the bottom.
💡 Regularly calibrate and lubricate the flowmeter to ensure accurate measurements.
⚠️ Handle the sampler with care and avoid shallow or obstructed areas to prevent damage.
❓ Frequently Asked Questions
🔍 What towing speed is required for the sampler?
The recommended towing speed is 3 to 5 knots.
💡 How is the flowmeter maintained?
It requires frequent calibration and lubrication for accurate operation.
📌 What are the sampler’s key advantages?
It includes discrete depth sampling, lightweight design, and a filtration efficiency of 0.88.
⚡ What are important usage precautions?
Avoid shallow waters and obstacles, handle carefully, and wash the net after each use.