Collecting Plankton

This can be one of the most exciting aspects of marine biology. The actual collecting is slow BUT getting to the place where the stuff is to be caught is quite different - ask anyone who has been on a Dale Fort collecting spree! Check out the boat:

Dale Fort RIB

So you have got yourself in position with the boat. The net to catch the little devils is a special one that will be towed behind the boat. It is made of silk that can achieve mesh sizes of around 60 microns. This will allow the zooplankton and a high proportion of the phytoplankton to be caught.

Plankton net

At the tail end of the net is a plastic bottle where the plankton will be collected. It needs to be towed slowly so that pressure does not mount up around the entrance or this will prevent the plankton entering. All this is due to the small mesh size slowing the seiving action down. There is a lead weight attached near the front of the net to take it below the surface. The net can trap air and so float. The time of day is quite crucial and the catch will vary with this.

With a fixed diameter opening and knowing the speed of movement it is possible to work out the volume of water you are sampling. Like any sampling method you need to take many samples.

Once collected it needs to be examined under the microscope and samples do not keep well.