Ecology of Bacillariophyceae in Freshwater and Marine water environments

1. Dr. A. Sankaranarayanan
C.G. Bhakta Institute of Biotechnology
Uka Tarsadia University, Surat District.
Gujarat state. INDIA.
e-mail: drsankarkamal@gmail.com
ECOLOGY OF BACILLARIOPYCEAE

2. • Diatoms comprise the main component of the
open-water marine flora and freshwater flora.
• Attached diatoms can be characterized by the
brown scums found on various kinds of
substrate; fluffy growth caused by abundant
epiphytic diatoms.
• Pennate algae are equal in freshwater and
marine habitats; centric and gonoid algae are
present in marine;
• pennate algae that has bilateral symmetry. ; Centric algae are radially
• symmetrical ;

3. General habitat features
Marine environment, colder more diatom
population; open oceans have larger number of
species with a low organisms;
Near to the shore, the total number of diatoms are
very high but species diversity is low.
Un enriched water and enriched water (coastal
water receiving enrichment from the land).
Regarding Bacillariophyceae, two aquatic habitats:
i. Marine environment
ii. Freshwater environment

4. Marine Environment
i* In general, marine enviornment, algae have some
adaptations to make them buoyant.
• Density of sea water varies from 1.021 to 1.028,
algae have lighter cellular components than sea
water, to achieve buoyancy.
• But cytoplasm little heavier than sea water,
vacoule as a source of positive buoyancy.
• Vacoular sap being isotonic.
• Vacoule of the algae have lighter ions than the
surrounding sea water; concentration of Na+
relative to K+

5. • Algae vary in density during day time. They
can move up and down in surface of water
absorb more nutrients. Eg. Ditylum
brightwelli.
• In dark hours (night) sedimentation rates are
more.

6. Marine environment
• Surface area relative to the volume of the cell,
placing a role in drag of cell to water.
• Discs, ribbon elongate forms; aggregation of cells
into chains increase the dragging rate.
• Increase the size of algal cells results increase in
the ascension rate.
• Planktonic diatoms can vary in density during the
day, moving up and down in the water column,
enabling better absorption of nutrients.
• Ascension rate – how deep it go inside

7. Centric Diatoms (Centrales)
• Radial symmetry
• Primitive
• Raphe Absent
• Almost immoblie
• Large vacuole with
many discoid
cloroplasts

8. Pennate Diatoms (Pennales)
• Bilateral symmetry
• Boat-shaped
• Raphe/pseudoraphe
is present
• Few elongated
chloroplasts
• advanced

9. The Raphe

10. Freshwater Environment
• Large in spring and less in autumn. Reason is temperature;
• Presence of silica
• Silica level reaches 0.5 mg / litre algae growth ceases.
• Enrichment in freshwater by inputs from industry and
agricultural run off. (Richardson et al. 1996).
• Diatoms in streams having two factors.
• i. Increasing in currents retard the attachment of diatoms
to the substrate.
• Ii. Increase in water current increase the growth of
organisms (long term) but initially fast flowing remove the
algae from the substratum.

11. Attached diatoms in standing water have a good growth.
Silica 0.5 mg/l or less good growth; but too less decrease
the population.
Epiphytic good growth but benthic less growth in winter
– due to production of some organic products.
In freshwater habitats, diatoms often comprise the
dominant algal flora in thermal waters between 30 and
40 °C. Fairchild and Sheriden (1974) showed that
Achnanthes exigua isolated from a hot spring showed
optimum photosynthesis at 42 °C, with maximum and
minimum temperatures for growth at 44 and 10 °C,
respectively – characteristics of a thermophilic
organism.

12. Other ecological features
• wide range of pH levels, temperatures and
organic pollution.
• This variety of living conditions can help tell
pollution or other ecological levels of the water.
• They also vary in their lifestyle, living singly or in
a colony. They do not always float freely in the
water, they will attach themselves to a rock or
another animal in the water.
• Diatoms may just seem like they are just part of
the plankton that feed that fish and animals.

13. Further Readings
• Phycology by Robert Edward Lee ; 2008
Cambridge University Press.
• Richardson, J. L., Mody, N. S., and Stacey, M. E.
(1996). Diatoms and water quality in Lancaster
County (PA) streams: a 45-year perspective.
Pennsylvania Acad. Sci. 70:30–9.