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How to collect a plankton sample

It is intended to use the plankton / micro-plastic filter from a boat in oceanic water.  However it may be used to test any water, from municipal tap water, to sewage effluent and clear blue oceanic water.  You will find micro-plastics everywhere.  The video to the side shows you how to use the filter for marine plastic.

It is important not to cause contamination of the water sample, so try and avoid wearing clothes such as a fleece that sheds many plastic particles.  Probably not a good idea wearing a fleece in any case,  because you will be breathing in plastic from your clothes.

Make sure you always follow the washing process, we want to try and avoid any contamination which would lead to false readings.


1. Dismantle the filter and remove the two acrylic plates, each plate has 5 x 5mm holes, and 2 x alignment notches on the outside.  Place the filter paper between the plates and align the notches.  Use 2 x pieces of insulating tape, and tape the plates together so they don't slip or move.

Place the filter element sandwich on the bottom section of the filter.  Place the tube section on top, and the screw them together using the threaded union. Make sure the O ring in place or water may leak from the filter

2. Once the filter element is in place, put the end cap onto the pipe.  The filter is now ready for the next sample.

Taking a water sample.

1.   The Goes Filter is fitted with a stainless steel hanging chain and 3m of stainless steel wire. Simply lower the filter over-board to take a water sample. Take a water sample making sure the tube is at least 1/4 full of water and then instantly empty sample and repeat the flushing process 3 times.  This will ensure that the filter is not contaminated by plastic fibres.  On the last fill, make sure the tube is 100% full of water.  

2. Remove the filter from the water and suspended by the chain, allowing the filter to swing with the motion of your vessel. Avoid it from hitting any objects when it swings

3. Water will begin to drip out of the base of the filter, this will continue for 1 to 4 hours, depending upon the number of plankton and solid particle concentration in the water sample. Leave the filter to hang from 4 to 8 hours. 

4. Record the time that the sample was take, in UTC. Please note that it must be the time the sample was taken, not the time that the sample was inspected.  In the adjacent column of the data recording sheet, enter 1 for day and 2 for night. A day sample is taken 6 to 8 hours after sunrise  and a night sample 6 to 8 hours after sunset.

5. If the sample was collected at night, you may leave the sample until; the morning to avoid night vision blindness looking at a PC screen.  Once the water has fully drained from the filter place the filter vertically on a flat surface. Pushing down on the top section, unscrew the ring to release both sections, and carefully remove the plastic plates with the 5 x 5mm holes containing the filter paper and place the entire assembly onto a  90mm Petri plate.  There will be some water on the plastic filter disc, the petri plate is just there to protect the equipment from seawater drips

6. Focus in on the centre hole, and then wind down the microscope on top of the plastic plate, and then adjust the focus to bring the contents of the filter into focus. Make sure the polarising filter is fully on, or there will be reflection from the water that will spoil the image.  Turn the light intensity fully up.  Make sure the 5mm hole fill the whole field of view.

6. On Macs, you may use photobooth, on PC,s there is also a build in photo app that works well with the microscope.  The microscope is 5mp resolution, make sure you also set the computer to the same resolution.

7.Take a picture, and record the number of plankton and plastic on the filter, as well as the size of the plankton. 

8. Move to the second 5mm hole and repeat the process, and then repeat for the remaining holes.  At the end you will have 5 x photos and will have recorded all the plankton and plastic in the sample.  The whole process should take no longer than 15 minutes.  

9. If possible record the data and the images on the spreadsheet

10. Once you have finished, remove the filter paper, and place a new filter paper between the plastic plates, to prepare the filter for the next sample.



The above video demonstrates how you take a plankton/micro-plastic water sample

Life on earth depends upon healthy Oceans, we have 10 years to stop toxic chemical pollution, or life on earth may become impossible

Dr. Howard Dryden, CSO

Goes Foundation

Roslin Innovation Centre
The University of Edinburgh
Easter Bush Campus
Midlothian EH25 9RG