This document summarizes uniclullular protists and plankton found in the Indian Ocean. It defines protists as mostly unicellular eukaryotes that can be autotrophic algae or heterotrophic protozoa. Plankton are diverse microscopic organisms that live in water bodies and include phytoplankton, zooplankton, bacterioplankton, and mycoplankton. The document discusses the primary productivity of phytoplankton in different regions of the Indian Ocean, noting differences in species composition and abundance between the Arabian Sea and Bay of Bengal, as well as seasonal variations. It also provides an overview of the types and distributions of zooplankton found

1. Unicellular Protists and Plankton
of the Indian Ocean
Akansha Ganguly
MB0415
Department of Biotechnology, Goa University
21st March 2016

2. What are protists?
• Eukaryotes
• Mostly unicellular
• Two broad sub-groups – 1. Algae (autotrophic)
2. Protozoa (heterotrophic)
• Reproduce asexually (binary fission) and sexually (gametes)
• Found in water bodies
• Commonly pathogenic or part of plankton

3. What are plankton?
• Diverse group of microscopic organisms-live in large water
bodies-cannot swim against a current
• Include-
1. Phytoplankton (autotrophic, prokaryotic/eukaryotic algae, e.g.
diatoms, cyanobacteria, dinoflagellates)
2. Zooplankton (protozoans)
3. Bacterioplankton (bacteria/archaea)
4. Mycoplankton (fungi/fungus-like)
• Important food source

4. Primary productivity
• Autotrophs: phytoplankton, macroalgae, marine bacteria
• “Standing crop”: measure of total phytoplankton biomass in terms of
chlorophyll content/numbers/cell volume in unit volume
• Phytoplankton cell size: 1µm (flagellate) – 2mm (large diatoms)
• Net plankton (retained by 63 µm net) and nanoplankton
• Availability depends on degree of nutrient recycling from deep waters
to surface (upwelling, turbulence)

5. • Winter – wind induced turbulence, phytoplankton growth reduces
• Spring – increase in irradiance, length of day, winds become
moderate, outburst of phytoplankton blooms
• Indian Ocean: unique reversion of surface circulation in northern part
every half year (north-east and south-west monsoon circulation)
• SW monsoon upwelling in Arabian Sea: west coast blooms of diatoms
such as Fragillaria, Coscinodiscus, Chaetoceros, Thalassiothrix,
Pleurosigma, Rhizosolenia and Skeletonema
• Phytoplankton biomass and productivity higher in coastal waters than
deep seas due to shallow benthos (better upwelling)
• Trichodesmium erythraeum blooms on offshore waters from February
to May
• “Mass forms” – bulk of flora on west coast- 29 species of
Bacillariophyceae, 7 species of Dinophyceae and 1 of Cyanophyceae

6. Phytoplankton in the Arabian
Sea
Source: Understanding the
Indian Ocean – Rao and
Griffiths

7. • Northern Bay of Bengal highly productive during NE monsoons
• Abundance of phytoplankton due to high-nutrient discharge from
rivers on east coast
135 phytoplankton subspecies belonging to 2 species of cyanobacteria,
78 species of diatoms, 53 species of dinoflagellates and 1 species of
silicoflagellate
Oscillatoria erythraea , Proboscia alata - dominant species in all areas
Pseudonitzschia pseudodelicatissima high density blooms in the
Northern Bay (Chaetoceros messanensis as associated species)

8. Source: Boonyapiwat
et al, 2007.

9. Zooplankton
• General term for drifting animal populations in the water column,
present in all regions of the ocean
• Tropical zooplankton generally smaller than temperate zooplankton
(short generation time, high metabolic requirements)
• Mostly invertebrates (microscopic ciliates to metres long medusa)
• Distribution and abundance closely connected to phytoplankton
(limiting factor)
• Herbivores, carnivores, detritivores, omnivores

10. Source: The Indian
Ocean: A
Perspective, Volume
2 – Rabin Sen Gupta

11. • Biomass distribution differs at upwelling, coastal waters and offshore
waters and at various depths
• Abundance more in coastal belt as compared to offshore seas
• Pleuston: living at sea surface with part of body projecting in air
(Porpita, Physalia, Velella, Ianthina)
• Neuston: assemblage of zooplankton, closely associated with
immediate surface film of the ocean
• Neuston organisms: small-medium size, all taxa, serve as feeding layer
for fish larvae
• Reduction of predation pressure but limited food availability
• Vertical migration: zooplankton move up-down the water column
regularly, caused due to changes in light intensity, food availability, life
cycle stage development etc.

12. • Copepods dominate zooplankton populations throughout the ocean
• Arabian Sea:
SW monsoon- highest numbers in eutrophic upwelling waters, lowest
in offshore waters
Aloricate ciliates (44 species such as Strombidium spp and Strobilidium
spp), tintinnids (Amphorella, Dictyocysta, Rhabdonella etc.), metazoan
nauplii etc.

13. Source: Veronica et al.,2007

14. • Zooplankton are good bio-geo indicators of a water body…
e.g. Sagitta sp. (chaetognath) indicates salinity incursion in Indian
estuaries
planktonic foraminifera are good ecological indicators (Globigerina spp
occupy distinct latitudes)
copepods dominate areas of rich phytoplankton production, etc.

15. References
• The Indian Ocean: A Perspective, Volume 2 - Rabin Sen Gupta (2001)
• Understanding the Indian Ocean: Perspectives on Oceanography – T.S.S. Rao and Ray C. Griffiths
(1998)
• Mesozooplankton community in the Bay of Bengal (India): spatial variability during the summer
monsoon. V Fernandes and N Ramaiah. Aquat. Ecol., vol.43(4); 2009; 951-963
• Composition, Abundance and Distribution of Zooplankton in the Bay of Bengal. I Jitlang, S
Pattarajinda, R Mishra, L Wongrat. The Ecosystem-Based Fishery Management in the Bay of
Bengal; 65-92
• The structure of zooplankton communities, in the 2 to 2000 µm size range, in the Arabian Sea
during and after the SW monsoon, 1994. CE Stelfox, PH Burkill, ES Edwards, RP Harris, MA Sleigh.
Deep-Sea Research, vol.46(II); 1999; 815-842
• Species Composition, Abundance and Distribution of Phytoplankton in the Bay of Bengal. S
Booonyapiwat, MN Sada, JK Mandal and MK Sinha. The Ecosystem-Based Fishery Management in
the Bay of Bengal; 53-64
• Phytoplankton composition and biomass across the southern Indian Ocean. L Schluter, P
Henriksen, TG Nielsen, HH Jakobsen. Deep-Sea Research, vol.58 (I); 2011; 546–556