Marine Biology

Based on size

Based on size, these organisms are classified as follows into seven groups:.

1.     Megaplankton  -  are  organisms above 20 cm in size

2.     Macroplankton  - are organisms in size range of  2-20 cm

3.     Mesoplankton  -  fall between 0.2&20 mm in size range

4.     Microplankton  - are organisms in size range of 20to200  µm

5.     Nanoplankton - are very small organisms ranging from 2-20 µm in size.

6.     Picoplankton  - are minute organisms of 0.02-2.0 µm in size

7.     Femtoplankton - are still smaller organisms of 0.02-0.20 µm in size.

          

Of the seven size groups, megaplankton, macroplankton microplanktonand mesoplankton  are normally captured by using standard plankton nets. Hence, they are called net plankton. The nanoplankton, picoplankton and femtoplankton cannot be collected by using plankton nets and these organisms can be obtained only by centrifuging samples of seawater, filtering water samples on fine filters such as Millipore filters, or allowing them to settle down from water samples.