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Unit 2 - Microbes as Component of
Aquatic Environments
Aquatic Environments (Aquatic Microbiology)

Aquatic microbiology: the study of microbes and microbial communities in relation to
water environments
70% of earth's surface is covered with water
Aquatic environments include:
-

Oceans

-

Estuaries

-

Rivers

-

Lakes

-

Springs

-

Harbors

-

Aquifers

Protection and preservation of water environment is essential for the continuation of life

Aquatic Microbes
Viruses, bacteria, fungi, algae, protozoa
Microbes act as:

-

Primary producers

-

Primary consumers

How do microbes grow in aquatic environments?
1
...
Sediments (found in sedimentation)
3
...
They may be found in biofilm communities

Planktonic Habitat
Planktonic habitat: the microbial communities which are suspended in water column
- also called floating forms
Nektons: when the microbes swim freely
Neustons: these microbes rest on the water's surface
Periphytons: these microbes grow on plants
Phytoplanktons: These are photoautotrophic microbes
- ex
...
Submerged surfaces / moist environment

b
...
Nutrient cycling
b
...
Attachment of bacteria with solid surface
2
...
Permanent attachment of bacteria takes place in two steps:
i
...
Irreversible attachment (phase 2)
Phase 1 and Phase 2
Phase 1 (Reversible): It is controlled by various attractive or repulsive physio-chemical
forces leading to passive reversible attachment to the surface
Phase 2 (Irreversible): An irreversible attachment is a biological, time dependent
process related to proliferation of bacteria & forming a chemical bridge to the solid
surface
Biofilm is a good strategy for bacterial survival under nutrient-poor environment on rock
surfaces
Bacteria in the biofilms act as a biological filter to remove dissolved organic material

These biological filter systems have been exploited from municipal and industrial wastes
However, there are some problems in pipe lines fitted in industries for heating and
cooling system: resistant to antibiotics & disinfectants

Types of Aquatic Environments
1
...
Estuarine Environments: Brackish Water (high salt conditions)
3
...
Ground Water (underground water)

Freshwater Environments
Examples: springs, rivers, streams, lakes - not directly influenced by marine water
Limnology: science which focuses on the study of all aspects (physical, chemical,
geological, and biological) of freshwater habitats
Freshwater habitats are smaller than marine and terrestrial habitats on the earth surface
Lentic: standing water
- Ponds, lakes, swamps, bogs (wet spongy ground)
Lotic: Running water
- Springs, streams, rivers
Types of Springs
1
...
Hot springs: originate from volcanic areas or great depths
ex
...
plant exudates, dead plants and animals, seepage and wind
Rivers and streams: photosynthetic microbes are dominant in these water bodies
Lakes
- Have large surface area and very deep
-

Have inflow and outlet

-

Types of lakes
a
...
Bitter lakes (Rich in Na2B4O7)
c
...
river mouths, coastal bays, tidal marshes
Microbes: bacteria and algae are common

Marine Environments
Highly diverse environment
Oceanography: study of all aspects including physical, chemical, geological, and
biological of oceans
Main features of marine environments:
-

Major water body, covering 70% of earth's surface

-

Sea is deep, continuous, not separated as are land and fresh water

-

Temperature, salinity and depths are chief barriers to free movement of marine
organisms

-

Dominated by waves of many kinds

Environment is salty, the salts are chlorides, sulfates, bicarbonates, carbonates,
bromides, sodium, magnesium, calcium, and potassium of which sodium chloride is in
maximum amount

Dissolved nutrients are in low concentrations

Various Zones of Marine Environments
Neritic zone: shallow water near shore
Intertidal zone: zone between high and low tides
Oceanic zone: region of continental slope and rise
Bathyal zone: deep area of ocean

Microbial Status of Marine Environments
Usually in deep waters, microbial concentrations are highest in neuston dropping
markedly below this region
Immediately below neuston, the numbers on the average are 10^7 microbes/mL
More or less bacteria are uniform at all depths except when water is calm
Algal bloom: phenomena which occur in water bodies which are warm, sunny, and
calm conditions
...
Shallow aquifers: these are closely connected to the earth's surface
...
Intermediate aquifers: within the range of 300m of the soil surface
...
Deep aquifers: beyond the range of 300m
-

Anaerobic, very slow flow rate

-

Not directly charged with surface rainfall

Microbial status of Groundwater
Bacteria remain more or less same, 107 cell/g of sediment
Viruses, protozoa, fungi
Shallow aquifers: aerobic heterotrophic bacteria
Deep aquifers: includes

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