Biological productivity of water bodies

BIOLOGICAL PRODUCTIVITY
OF WATER BODIES

Jitendra Kumar
Depat. Fisheries Resource Management)
College of Fisheries, Mangalore
jitenderanduat@gmail.com

Introduction
• Biological productivity as an index of water
quality and production potential of cultured
organism needs prime consideration for site
selection.
• Productivity
quantitative

in

terms

of

qualitative

and

• Before we enter into a discussion on productivity,
it would be helpful to look at the concepts of the
ecosystem, habitat and ecological niche, and food
cycle in water bodies, including food chain and
trophic structure.

What is an ecosystem?
• An ecosystem is formed by the interactions between
all living and non-living things
• Ecosystem is the basic functional unit of ecology in
which include both living and non-living things
• Eco= Environment
• System = Regularly interacting and interdependent
components forming a unified whole
• Ecosystem = an ecological system;
= a community and its physical environment treated
together as a functional system

Components of an Ecosystem
ABIOTIC
COMPONENTS
Sunlight
Temperature
Precipitation
Water or moisture
Soil or water chemistry
etc.

BIOTIC
COMPONENTS
Primary producers
Herbivores
Carnivores
Omnivores
Detritivores
etc.


Habitat and ecological niche
Habitat and niche
• “the place Habitat = Address or home of an organism
Niche = Occupation of an organism in its
where it lives”,
community

• whereas the
ecological
niche
• Term coined
by Elton in
1927.


Food cycle in water bodies
The transfer of
food energy
from the plants
through a series
of organisms is
referred to as
the “food
chain”.

• The term “productivity” is always used in this
context to mean „rate of production‟ or „rate of
energy flow‟.
• Gross production (PG)

• Net production (PN)
• Secondary productivities (P2 - P5)

Concept of productivity
• The biological productivity of aquatic systems,
as of land, has been at several levels.
• Primary productivity
• Gross
• Net primary productivity

• Secondary
– various trophic levels

• Basic or primary productivity
– rate at which energy is stored by photosynthetic
activity of producer organisms
– (chlorophyll bearing organisms, mainly plants and
phytoplankton)
– In the form of organic substances which can be
used as food substances.


• Gross primary productivity
–The total rate of photosynthesis
including organic matter used up in
respiration during the measurement
period
–(also known as total photosynthesis or
total assimilation).

• Net primary productivity
–The rate of storage of energy as food
matter i.e. excluding the energy
dissipated as respiration by plants
–(also referred to as “apparent”
photosynthesis or net assimilation).


• Secondary productivity
–The rates of energy storage at trophic
levels of consumers and decomposers
are referred to as “secondary
productivities”;


Measurement of productivity
Harvest method

• This is the simplest and measuring the
productivity of a water body such as fish
pond by harvest at the end of the season.

• The productivity given is secondary
productivity
and
indicates
net
productivity and also quite often fish
production given is in net weight giving
productivity value.

Oxygen measurement method
• Primary productivity can be measured from the
amount of oxygen consumed by a volume of
water in a fixed period of time
• White and dark bottles

• (bottle painted dark so light would not enter)
• Do (dissolved oxygen) measurement
• BOD

Diel method
• Estimates of primary productivity can also be made
from diel changes in oxygen, considering the day as the
light bottle and night as the dark bottle.
• The increase in DO in the day time is net primary
production and the decrease in the night is half the diel
respiration.
• This can be added on to the day-time gain to obtain
daily gross photosynthesis.

• This volume should normally be corrected for the loss
or gain in oxygen due to concentration gradient over
the day.

C14 method
• The most accurate method for determining productivity
is the method of using radioactive carbon (C14) added
as carbonate.
• Labelled carbonate is added into a bottle containing
water with the phytoplankton and other organisms and
after a short period of time the plankton is separated
• dried and planchetted and the radioactive carbon fixed
can be measured from the radioactive counts made.
• The productivity measured thus is net primary
productivity as the carbon fixed in the tissues only are
measured here.

References
• http://www.scribd.com/doc/14179924/13-Structureand-Function-of-Ecosystem
• www.fao.org/docrep/field/003/AC176E/AC176E05.htm
• www.britannica.com/EBchecked/topic/66012/biologica
l-productivity
• http://www.globalchange.umich.edu/globalchange1/c
urrent/lectures/kling/ecosystem/ecosystem.html
• www.wikipedia.org/wiki/Ecosystem


THANK YOU

Biological productivity of water bodies

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