How are you sampling algae in the paddy field? If you are using quadrat sampling (i.e. sample a given area/volume) you could assess abundance of species of algae within a quadrat by percent cover sampling using the a point-intercept method. If you want to assess by biomass, sample all algae within a given area (quadrat) dry all algae and weigh it to get abundance as dry weight of algae.

Thanks for your reply. We are just collecting the algae from a paddy field and identifying, and want to know their abundance on the basis of their number. Some are unicellular and others filamentous or colonial too. So abundance for specific member to be precise..

Dear Amrik Singh Ahluwalia Ji

I am Agreed with Simon Reeves you may follow as he said, There is two way to represent algal cell population in a given sample i) number of algal cell per unit volume/area ii) dry cell weight of algae per unit volume/area. 

In your case you taking sample from natural habitat so first one is better suited because you count only algal cell by visualization in rafter chamber it gives you precise results  but it is a hectic task then you may proceed toward the second one but in this case during harvesting algae from your you may collect other Phyto and zooplankton with algal cell then in this case it will gives you Total suspended solids per unit volume /area. Some researchers using ash free dry weight for the estimation of an algal conc. in a given sample.

above are the direct method but chlorophyll-A estimation is an indirect method for algal cell population study.

Now its up to you.....

thanks for your answer. Chlorophyll gives you total algae not the specific algal abundance please.

Hello dear Amrik

You can use differents methods, to make estimations of the microalgae cell population on samples, the methods described before are good for this purpose:

Ypu can use the dry weight techniques where you realize a relation of the weight on filters with the biomass generated, another direct technique is the cell counting, you need a microscope and a neubauer chamber, with these you can obtain the numbers of cells/mililiters using a relation  with a known volume and the microscope (i think is one of the most accurate methods), another techniques you can use is: the spectophotometry, here you can relate the absorbance of the samples with the biomass generated, is an indirect method but could be really accurate if you make it correctly, i send you a paper where developed these both techniques for measuring growth of 4 microalgaes and make a correlation between them.

I hope this information could help you

Good luck  

Thanks a lot for your thought provoking reply.

Respected Sir,

I think you are asking about abundance of algae in natural sample which contains mixture of different algae. As per my best knowledge, the cell counting method explained by Mr. David Ulises Santos Ballardo is more accurate for knowing abundance of different algae. Sedgwick-Rafter counting cell can be used for the above purpose.

The procedure is given in Wetzel and Likens (2000).

Wetzel, R.G. and Likens, G.E. 2000. Limnological Analysis, 3rd ed., Springer, New York, 429 pp

Thanks.

thank you.

I also recommend using a counting protocol that uses a Sedgwick-Rafter slide (if solely after species within the water i.e. plankters and tychoplankters). It is commonly used in Australia to enumerate algae abundances by cells/mL. Biovolume can then be calculated from the cell counts. See  A Phytoplankton Methods Manual for Australian Freshwaters by Hotzel & Croome.

As I have discussed cell counting is species specific then you may go with it and for total algal/phytoplankton population you may use chlorophyll estimation please it is up to you wat u want to estimate.

Thank you Dr Pandey.

Algal cell density is counted by using improved Neubaur chamber   (Haemocytometer). The samples are taken from the field and fix with formalin in order to immobilize the cells. After stirring by 0.1 ml pipette, the algal cells are pipetted into the haemocytometer and a coverslip is place over it. The haemocytometer is place under a light compound microscope (5 × 10x) and the cells present in 5 squares (4 corners and center) out of 25 squares of the counting grid of haemocytometer are count and then the total count is calculated using the formula.

Total cell count =Number of cell counted/Number of square counted × Total No. of squares in particular type × 10000

May be the following link useful:

https://link.springer.com/article/10.1007/BF00257642

The abundance of heterocystous blue-green algae in rice soils.....

Thanks for your suggested additions and methods.

please look at Utermohl, 1958; Lund et al., 1958; Rott, 1981; EN 15204; EN 16698

Similarly to Ponnusawmy Gopal, you can use different counting chambers to enumerate algal cells in your water sample, e.g. Nageotte or Sedgewick Rafter counting chambers.

Thanks Dr Nicolas.

Algal cell density is counted by using improved Neubaur chamber   (Haemocytometer). The samples are taken from the field and fix with formalin in order to immobilize the cells. After stirring by 0.1 ml pipette, the algal cells are pipetted into the haemocytometer and a coverslip is place over it. The haemocytometer is place under a light compound microscope (5 × 10x) and the cells present in 5 squares (4 corners and center) out of 25 squares of the counting grid of haemocytometer are count and then the total count is calculated using the formula.

Total cell count =Number of cell counted/Number of square counted × Total No. of squares in particular type × 10000

Thanks for your answer, however, when a sample is unicellular, it works well but how about filamentous or colonial forms of algae.