Transcript 3.Pond ecosystem and productivity

A freshwater ecosystem
1
2
Pondfish Ecosystem
An ecosystem is a dynamic complex of
plant, animal,and microorganism
communities and the nonliving
environment, interacting as a functional
uit.
The non-living substances of pond
ecosystem include the inorganic and organic
compounds. These compounds remain in
solution in pond water, in reserve in
bottom deposits as well in the living
organisms - both plants and animals.
3
• The living organisms (biotic community) in a pond
ecosystem, consisting of all sorts of plants
and animals, are broadly categorized into two
main groups:
• The autotrophic community viz. the
producers include all the green plants which
produce complex organic substances or cell
materials from inorganic soluble nutrients in
presence of sun light (photosynthesis).
• The producers are of two types :
phytoplankton and macrophytes.
4
• The minute floating algae or phytoplankton
distributed in the pond water column mainly
throughout the light-limited limnetic zone. Abundance
of phytoplankton population in water gives greenish
colour. Production of phytoplankton is thus
dependent on sun light and available soluble
nutrients in water. Tropical fish ponds are
generally found rich in natural food organisms as the
sun light duration is longer.
• The macrovegetation, though fall under producer
group, in reality, their contribution is negligible in
primary productivity of well managed fish pond. They
are, however, found inhibitor in fish production
system if not utilized properly as fish feed. 5
• The heterotrophic community in a fish pond ecosystem
comprising of two major groups of organisms namely:
• The consumers - the organisms depending on other
organisms living or dead for food such as zooplankton,
insect larvae, fish etc. The consumers group (benthic
invertebrates and bottom feeding fish) subsisting on
organic detritus are called detritivores.
• The decomposers - the group of heterotrophic
organisms such as bacteria and fungi break down the
dead plants and animals and release partially
decomposed materials and inorganic nutrients into
pond water for utilization by the producers viz.
phytoplankton and macrophytes. The decomposers are
most abundant at the pond bottom where the dead
plants and animal bodies are most abundant.
6
• The food chains or energy pathways in a pond
ecosystem are of two types: the autotrophic
food chain and the heterotrophic food chain.
• Autotrophic food chain - It is the solar energy
dependent food chain which begins with the
plants, basically phytoplankton, at the pond
surface and then sequentially pass through
primary consumers (zooplankton and
planktivours fishes) to secondary and tertiary
consumers (carnivorous insects and fishes).
7
The pathways in autotrophic food
chain are:
• Phytoplankton  fish
Phytoplankton  zooplankton  fish
Phytoplankton  zooplankton  aquatic
insects  fish
 predator fish
8
9
10
11
12
• Heterotrophic food chain - This energy
pathway starts from the decomposition of dead
organic matters by the decomposing bacteria
and fungi at the pond bottom and then pass
through zooplankton - aquatic insects to fishes
(secondary and tertiary consumers) as shown
below :
• Bacteria  fish
Bacteria  protozoa  fish
Bacteria Protozoa  zooplankton  Aquatic
insect larvae  fish
13
Bacteria
14
15
16
Aquatic Insects
17
Floating Plants
18
Submerged Plants
19
Emergent Plants
20
• The productivity of a fish pond
depends on the availability of
dissolved nutrients in pond water
which can be utilized for production
of organic materials by the
producers (mainly phytoplankton)
using solar energy.
21
• The sources of pond nutrients may be of
organic and/or inorganic origin. Organic
manure mainly supports the heterotrophic
food chain while the inorganic fertilizers
supports the autotrophic food chain. Both the
pathways are closely inter-linked to each
other. However, in most fish ponds, production
largely depends on the solar energy dependent
autotrophic food chain, but the ponds
receiving high quantity of organic manures on
regular basis have significant heterotrophic
use of wastes by bacteria and protozoa.
22
•Fish production not only depends on
the rich food chains but also largely
on the stocking density of fish as well
as the species combination having
different feeding and spatial niches so that total fish food organisms of a
pond originated from both the food
chains are properly utilized by the fish.
23
The End
Man Jadda Wa Jadda
24