We work on Freshwater phytoplanktons but have less knowledge about marine one. Yes specially river phytoplanktons are pretty small. we felt difficulties in collection using bolting silk plankton net of 60 micron mesh size and we also observe shape deformities. Hence, we planned to go for whole water sample collection from different depth. That is more accurate and also we get diversity along with various size range.

Hi Abebe,

I have only worked with marine plankton sampling, where it is standard to use at least a couple of different mesh sizes, so that your sample is representative of the whole community present. Unless you are attempting to sample a particular size fraction of the plankton community - in which case you would use the size of your target species as a guide for the mesh size of your net.

As Soma suggests, taking water samples is also a good option, however it depends what analyses you are planning on carrying out. It can be difficult to get large numbers of plankton from water samples. You will sample a larger body of water if you use a net, so you will be likely to capture more individual plankton (i.e. get a larger sample size), which may be important if you are attempting to undertake any kind of statistical analyses on the data.

Hope this helps. Alice

Dear Alice, yes your point is well appreciated. I collect sample in river, where I take whole water sample using sampler at specific depth in triplicates. this is mostly for biomass study and also record diversity as well.

Thanks and Regards

I have collected and enumerated countless phytoplankton samples in both marine and freshwater systems. Comparing the size of marine and freshwater species, the range is larger in marine phytoplankton. In both marine and freshwater systems you usually find small species (≤ 5 µm), but large species tend to bigger in marine than in freshwater systems. In freshwater studies net (phyto-) plankton traditionally refers to a mesh size of 64 µm. Net samples, however, will provide qualitative data only. This is for two reasons. 1) Many smaller cells will be washed through the net and 2) It is not possible to quantitatively sample a water column with a small mesh seize net because of the turbulence created by pulling the net up. If you want to study phytoplankton biomass and diversity, I highly recommend taking water samples from different depth and using settling (Utermoehl) chambers. You can always create a combined sample by mixing same quantities of water from the different depths, if you want to reduce the work load.

I use 25 to 40 Micron mesh size 2 feet long net having a dia of 1feet

I highly agree with Sabine. Indeed collecting water sample at different depth using water sampler will provide much accurate mode of enumeration for phytoplankton of freshwater origin. The sedimentation procedure of 24-72 h in a dark chamber (described in Belinger and Sigee, 2010) can be followed.