230
the calculated potential value and ranges from 5
to 10 kg/m
2 /day.
15.3.3.2 Mires
Concomitant to above, the ombrotrophic mires
are rarely affected by drought, but their mineral
nutrition is dependent on wind-blown dust, solutes in precipitation. Nitrogen fi xation is probably limited to BGA. Greater productivity is
generally found amongst the sub-aquatic bog
masses. Rheotropic mires include the highly
productive fens. But even if the groundwater is
acid and oligotrophic, it provides some nutrient
input which increases productivity and species
diversity.
15.4 Wetland Fauna
15.4.1 Invertebrates
Small invertebrates inhabit the water fi lm
between soil particles. Hence, there is an overlap of species composition between open water
and soil. These animals include many protozoans, rotifers and nematodes. They occur in both
organically rich water and in wet soil litter.
Similar overlaps are found amongst the larger
invertebrates also.
Most of the soil fauna are susceptible to loss
of air-fi lled pore space, anoxia of soil and water
and chemical toxicity of the reducing environment in the waterlogged soil. The ecology of the
soil invertebrates is quite strongly dependent on
the differences between wet and well-drained
soils. Small differences of level are refl ected in
large variations in soil wetness, animal species
and soil organic matter. Thus, these may permit
cohabitation of hygrophilous and xerophilous
organisms.
The invertebrate inhabitant of the wetlands
ranges from obligate to facultative forms because
of the following reasons:
(a) Whole or part of their life cycle is aquatic.
(b) The organism requires high humidity or free
water.
(c) A specifi c wetland food plant or animal is
required.
(d) A specifi c habitat physiognomy is required:
This may or may not overlap with dry-land
ecosystems.
(e) The wetland provides a refuse from predation or competition.
Several unrelated organisms have become
adapted to low partial pressure of oxygen. Such
organisms like the tubifi cid and lumbricid oligochaete worms, some pulmonate molluscs
( Planorbis spp.) and insect midge larva of the
genus Chironomus have separately evolved
this mechanism.
Tubifex worms inhabit mud tubes in sapropel
sediments. They contain several per cent of FeS.
The tails extend into the more oxygenated water
above as a pseudo-gill. The amount of tail protruded is negatively correlated with the oxygen
content of the water. These are the worms sold by
the aquarists in knotted masses as fi sh food.
Relatively little is known of animal responses
to the other reduced chemicals which accumulate
in waterlogged soil. Further, many wetland gastropods are of aquatic origin, e.g. the marsh snail
( Lymnaea glabra ) and the dwarf marsh snail
( L. truncatula ). Both wander freely from the
freshwater into adjacent marsh grassland. The
latter snail is the intermediate host of the sheep
liver fl uke ( Fasciola hepatica ) .
Wetlands support a variety of blood-sucking
insects whose larvae inhabit water, wet moss and
litter. The most common are the mosquitoes
(Culicidae) which lay eggs on water. Some Aedes
spp. lay eggs on wet soil or in rain-fi lled cavities.
Other carnivorous insects occur at the land–water
interface, e.g. shallow water of reed swamps, in
which the nymphs of dragon fl ies (Odonata) are
found. Some of them are able to consume creatures bigger than themselves, even could be a
small fi sh. Further, the canopy of wetland vegetation provides conditions which are not much different from those of any other plant cover. Thus,
the hunting spider ( Lycosa nigriceps ) is equally
at home in deep mixed fen, in gorse-heather
heath or in sand dune marram grass.
More information in this regard may be
obtained from Ellis ( 1965 ), Kuhnelt ( 1961 ),
Jackson and Raw ( 1966 ), Andrews (1973),
Wallwork ( 1976 ), etc.
15 Wetland Flora, Plankton, Productivity, Fauna and Fishes
the calculated potential value and ranges from 5
to 10 kg/m
2 /day.
15.3.3.2 Mires
Concomitant to above, the ombrotrophic mires
are rarely affected by drought, but their mineral
nutrition is dependent on wind-blown dust, solutes in precipitation. Nitrogen fi xation is probably limited to BGA. Greater productivity is
generally found amongst the sub-aquatic bog
masses. Rheotropic mires include the highly
productive fens. But even if the groundwater is
acid and oligotrophic, it provides some nutrient
input which increases productivity and species
diversity.
15.4 Wetland Fauna
15.4.1 Invertebrates
Small invertebrates inhabit the water fi lm
between soil particles. Hence, there is an overlap of species composition between open water
and soil. These animals include many protozoans, rotifers and nematodes. They occur in both
organically rich water and in wet soil litter.
Similar overlaps are found amongst the larger
invertebrates also.
Most of the soil fauna are susceptible to loss
of air-fi lled pore space, anoxia of soil and water
and chemical toxicity of the reducing environment in the waterlogged soil. The ecology of the
soil invertebrates is quite strongly dependent on
the differences between wet and well-drained
soils. Small differences of level are refl ected in
large variations in soil wetness, animal species
and soil organic matter. Thus, these may permit
cohabitation of hygrophilous and xerophilous
organisms.
The invertebrate inhabitant of the wetlands
ranges from obligate to facultative forms because
of the following reasons:
(a) Whole or part of their life cycle is aquatic.
(b) The organism requires high humidity or free
water.
(c) A specifi c wetland food plant or animal is
required.
(d) A specifi c habitat physiognomy is required:
This may or may not overlap with dry-land
ecosystems.
(e) The wetland provides a refuse from predation or competition.
Several unrelated organisms have become
adapted to low partial pressure of oxygen. Such
organisms like the tubifi cid and lumbricid oligochaete worms, some pulmonate molluscs
( Planorbis spp.) and insect midge larva of the
genus Chironomus have separately evolved
this mechanism.
Tubifex worms inhabit mud tubes in sapropel
sediments. They contain several per cent of FeS.
The tails extend into the more oxygenated water
above as a pseudo-gill. The amount of tail protruded is negatively correlated with the oxygen
content of the water. These are the worms sold by
the aquarists in knotted masses as fi sh food.
Relatively little is known of animal responses
to the other reduced chemicals which accumulate
in waterlogged soil. Further, many wetland gastropods are of aquatic origin, e.g. the marsh snail
( Lymnaea glabra ) and the dwarf marsh snail
( L. truncatula ). Both wander freely from the
freshwater into adjacent marsh grassland. The
latter snail is the intermediate host of the sheep
liver fl uke ( Fasciola hepatica ) .
Wetlands support a variety of blood-sucking
insects whose larvae inhabit water, wet moss and
litter. The most common are the mosquitoes
(Culicidae) which lay eggs on water. Some Aedes
spp. lay eggs on wet soil or in rain-fi lled cavities.
Other carnivorous insects occur at the land–water
interface, e.g. shallow water of reed swamps, in
which the nymphs of dragon fl ies (Odonata) are
found. Some of them are able to consume creatures bigger than themselves, even could be a
small fi sh. Further, the canopy of wetland vegetation provides conditions which are not much different from those of any other plant cover. Thus,
the hunting spider ( Lycosa nigriceps ) is equally
at home in deep mixed fen, in gorse-heather
heath or in sand dune marram grass.
More information in this regard may be
obtained from Ellis ( 1965 ), Kuhnelt ( 1961 ),
Jackson and Raw ( 1966 ), Andrews (1973),
Wallwork ( 1976 ), etc.
15 Wetland Flora, Plankton, Productivity, Fauna and Fishes