DIATOMS: DIATOMS: Stream Monitoring and Stream Monitoring and

Ecological StudiesEcological Studies

Karthick B, M K Mahesh* and T V Ramachandra

Energy and Wetlands Research Group, Centre for Ecological Sciences

*Dept of Botany, Yuvaraja’s College, Mysore

Biomonitoring & ……Biomonitoring & ……Role of Diatom in BiomonitoringRole of Diatom in Biomonitoring

What is living in the stream?What is living in the stream?

What is a biological indicator?

The fundamental principle behind biological indicator theory is that organisms provide information about their habitats. A biological indicator (or bioindicator) is a taxon/taxa selected based on its sensitivity to a particular attribute, and then assessed to make inferences about that attribute.

Why indicator species? Bioindicators make a broad and intangible concept such as biodiversity or ecosystem monitoring manageable by breaking it down into a specific set of quantifiable indicators. Inference through biological indicators replaces direct measurement when such measurements are not possible, too expensive/difficult, or too direct. Some historical events are impossible to observe directly, but can be inferred via bioindicators, such as reconstruction of lake pH using diatom communities in lake sediments from known dates

A bioindicator is an anthropogenically-induced response in biomolecular, biochemical, or physiological parameters that has been causally linked to biological effects at one or more of the organism, population, community, or ecosystem levels of biological organization.

Choose among the many !Choose among the many !

Photos: S Ali, Gururaja K V, Sreekantha & me

BacillariophyceaeBacillariophyceae

Diatoms are unicellularDiatoms are unicellularmicroscopicalmicroscopicalphotosyntheticphotosyntheticeukaryoteeukaryotefreefree--livingliving

What are diatoms ?What are diatoms ?

Abundant BeautyAbundant Beauty

Different components of the cell wallDifferent components of the cell wall

Hallmark of diatoms Hallmark of diatoms : SILICIFIED CELL : SILICIFIED CELL WALLWALLbasic component basic component SiOSiO22 (60%)(60%)completely closed completely closed ‘‘box & coverbox & covercontains 2 large, contains 2 large, heavily sculptured heavily sculptured units: units: VALVESVALVES

upper valve = upper valve = EPIVALVE EPIVALVE (“cover”)(“cover”)lower valve = lower valve = HYPOVALVE HYPOVALVE (“box”)(“box”)

1. Epivalve1. Epivalve2. Epicingulum2. Epicingulum3. Hypocingulum3. Hypocingulum4. Hypovalve4. Hypovalve5. FRUSTULE

EpithecaEpitheca

HypothecaHypotheca

6. Frustule6. Frustule

5. FRUSTULE

Pennate

SEM SEM –– PHOTOGRAPHY OF A PENNATE DIATOM PHOTOGRAPHY OF A PENNATE DIATOM

Why Diatom ???Diatoms constitute a water quality monitoring tool widely accepted

They provide a wide range of ecological information (T°, pH, salinity, trophy, organic load, etc…)

Omnipresence in aquatic systems (even in extreme environments)

Very high diversity (up to 10000 taxons known in fresh and brackish waters)

Other methods (Invertebrates) are difficult to apply (unaccessibility due to depth and lack of some habitats)

Sampling and preparation are quick, easy and standardized

Storage and "traceability" of results (permanent slides)

Taxonomic and ecological data are abundant

Relative low cost for implementation &……

Here, there & EverywhereHere, there & Everywhere

Different forms & their homesDifferent forms & their homes

Fig. 1 and Fig. 2 show a thick layer of diatom cells attached to boulders.

Fig. 3 shows a layer ofdiatom cells growing both on sediment and on pebbles.

Fig. 4 shows diatoms growing thickly aroundsubmerged tree branches.

Fig. 5 shows the film of diatoms to be found on the submerged stems

Fig. 6 shows diatoms inhabiting sediments.

Different forms & their homesDifferent forms & their homes

The diatom The diatom biofilmbiofilm can be found growing can be found growing on many surfaces in running waters ….on many surfaces in running waters ….

rocks

Fine sediments

Rocks plus filamentous algae

Submerged macrophytes

Emergent macrophytes

Man-made surfaces

Source for Collection Source for Collection –– Artificial substratesArtificial substrates

Treatment & Preparation of Permanent Slides of benthic diatom samples from rivers for water quality assessment

100 times

1000 times

It might look very exciting, it is a complex 3-dimensional community of which diatoms are typically the most abundant group of photosynthetic organisms exhibiting a range of ecological strategies.

Stalked taxa, e.g. Synedra

Polysaccharide matrix Plankton

Motile taxa, e.g. Nitzschia

20 µm

Diatoms are very important in the world

Primary production through the photosynthesis processLungs of the earth

through the respiration/oxygen-production in the oceans

Study and understanding of diatoms is therefore very important!!!

DIATOMS ARE FOREVER !!!

THANKS