Planktonic organisms in Inland Water Planktonic organisms The

Planktonic organisms in Inland Water

Planktonic organisms • The term plankton was first proposed by an Oceanographer, Victor Hensen in 1887 to designate that the heterogeneous assemblage of minute organism and finely divided, non-living materials which are known to occur in the waters and to float at the will of the waves and other water movements.

Classifications • Plankton of the various freshwaters differs widely in quality. The following outline is an abbreviated indication of the organism which may occur in the plankton of fresh water. • 1. Plants : • a) Algae are represented in the plankton of inland waters • b) Fungi, which occur as bacteria abundantly in the plankton, in fact it is likely that no water in nature is free from them.

• 2. Animals : • a) Protozoa – These are the representative of the plankton by many genera and species • b) Coelenterate - Mainly hydra is facultative plankter occurring at times free in open water • c) Rotatoria is the most important groups of zooplankton • d) Gastrotricha - occur in limited numbers • e) Bryozoa whose larvae are free swimming • f) Arthropoda – Mainly i) Crustacea and ii) Insects

• 3. Occasional plankters : • a) Flowering plants for eg. Wolffia (Lemnaceae) occur at various depth and are recorded as plankton organisms especially in rivers. • b) Platyhelminthes eg, Turbellaria are of less importance in freshwaters. • c) Coelentrata eg, Medusa (Craspedacusta) • d) Insecta eg, May-fly nymphs • e) Arachnida eg, Water mites • f) Vertebrata eg, Juvenile stages of fishes

Classification and Terminology of Plankton Some of the important groups of plankton are : 1. Classification based on Quality A. Phytoplankton – plant plankton a. Phytoplankton proper – chlorophyll bearing plankton • b. Saproplankton – bacteria and fungi • B. Zooplankton – animal plankton • •

• 2. On the basis of Size: • A. Meroplankton – the large units of plankton, visible to the unaided eye • B. Net plankton (Mesoplankton) – plankton secured by the plankton net equipped with No. 25 silk bolting cloth (mesh 0. 03 to 0. 04 mm) • C. Nanoplankton (Microplankton) – very minute plankton not secured by the plankton net with No 25 bolting cloth • a) Ultra plankton : <5 µm (<0. 005 mm) • b) Nano plankton : 5 -60 µm (0. 005 – 0. 06 mm) (Dwarf / runts) • c) Microplankton : 60 -500 µm (0. 06 -0. 5 mm) (Net plankton) • d) Meso plankton : 500 -1000 µm (0. 5 -1. 0 mm) • e) Macroplankton : 1. 0 mm – 1. 0 cm • f) Megaloplankton : > 1. 0 cm

• 3. On the basis of local environmental distribution: • A. Limnoplankton : lake plankton • B. Rheoplankton (Potamoplankton) : running water plankton • C. Heleoplankton : pond plankton • D. Haliplankton : salt water plankton • E. Hypalmyroplankton : brackish water plankton

• 4. Based on Origin • A. Autogenic plankton : plankton produced locally • B. Allogenic plankton : plankton introduced from other localities • 5. On the basis of content • A. Euplankton / True plankton • B. Pseudoplankton (Flase plankton) : debris mingled in plankton

• 6. Based on the life history / plank tonic life (Length of time): • A. Holoplankton / Permanent plankton : organisms free floating throughout their life • B. Meroplankton / Temperory plankton : organisms free floating only at certain times or stages of life cycle • 7. Based on habitat in water body • A. Hypoplankton : Benthic • B. Epiplankton : Surface • C. Bathyplankton : Aphotic zone • D. Mesoplankton : Disphotic/lighted zone