178
9.3
Tripton
It may be of autochthonous or allochthonous
origins, termed ‘eutripton’ and ‘pseudotripton’,
respectively.
9.4
Fringing Communities
In marginal and other shallow regions of aquatic
habitats, a second input of photosynthetically
fi xed materials is provided by the fringing fl ora.
This fl oral set-up may assume different forms as
given below:
(a) These could be dense strands of vegetation of
basically terrestrial ancestry rooted and
sometimes submerged.
(b) Somewhat equivalent strands of essentially
aquatic macro-algae, which could be temporarily exposed to the air or could be permanently submerged in shallow water.
(c) Simple or colonial micro-algae forming mats
on the bottom sediments or rocks.
The importance of these larger plants to the
aquatic systems, which they fringe, lies in the
smaller epiphytic algae for which they provide an
attachment site. The litter and the detritus, on
their decomposition, are supplied to the water
and to the sediments. However, primary production of the fringing compartment of the aquatic
system is high or often could be very high.
9.5
Benthos
The organisms of the solid–water interface are
the ‘benthos’. The following terms appear to be
useful in characterising this assemblage. Benthos
could be classifi ed into the following types:
(a) Rhizobenthos: These are rooted in substratum.
(b) Haptobenthos: These are adnate to the solid
surfaces.
(c) Herpobenthos: These grow or move through
mud.
(d) Psammon: These grow or move through sand.
(e) Endobenthos: These penetrate a solid
substratum.
When the haptobenthos is well developed,
particularly on objects projecting into the free
water, it is called ‘lesion ’, fouling or ‘Bewuchs’.
Many merobenthic animals may also be
meroplanktonic.
The assemblage of organisms at the surface
fi lm is called ‘pleuston’; the ‘micro-pleuston’ is
often designated as ‘neuston’ and may be
‘hyponeuston’ below the fi lm or ‘epineuston’
above it. Some large organisms living in air
above the fi lm on which they walk or run are
best termed as ‘epipleuston’. Many meropleustonic animals which reach the surface fi lm from
below are adapted to live at the surface for part
of their lives.
The bottom area in contact with the water
exhibits striking zonation .
The following terms are recommended to
describe the zones ordinarily present:
(a) Epilittoral: This zone is completely above the
infl uence of the water.
(b) Supralittoral: This zone is above the water
but receives spray.
(c) Eulittoral: This zone lies between the high
and low seasonal levels.
(d) Infralittoral: This zone is permanently covered but with rooted or adnate macroscopic
vegetation, often divisible into upper (emergent
vegetation), middle (fl oating vegetation) and
lower (submerged vegetation).
(e) Littori-profundal: This is a transition zone
with scattered adnate algae.
(f) Profundal: This zone is the bared sediment
below biogeochemical compensation point.
In the terminology of seasonal change, if a
population rises to a maximum and declines once
in an annual cycle, it is monacmic ; if twice, diacmic ; and if many times, polyacmic .
If a species has a single generation per year, it
is called univoltine ; if two bivoltine ; and if many,
multivoltine .
If a generation takes two or more years, the
ordinary terms biennial or perennial will be used.
If a bivoltine or multivoltine species changes
its mode of reproduction, ordinarily to produce
resting stages, once in a year, it is monocyclic ;
if twice, dicyclic , etc. If no changes occur, it is
acyclic .
9 Other Organisms in the Lakes
9.3
Tripton
It may be of autochthonous or allochthonous
origins, termed ‘eutripton’ and ‘pseudotripton’,
respectively.
9.4
Fringing Communities
In marginal and other shallow regions of aquatic
habitats, a second input of photosynthetically
fi xed materials is provided by the fringing fl ora.
This fl oral set-up may assume different forms as
given below:
(a) These could be dense strands of vegetation of
basically terrestrial ancestry rooted and
sometimes submerged.
(b) Somewhat equivalent strands of essentially
aquatic macro-algae, which could be temporarily exposed to the air or could be permanently submerged in shallow water.
(c) Simple or colonial micro-algae forming mats
on the bottom sediments or rocks.
The importance of these larger plants to the
aquatic systems, which they fringe, lies in the
smaller epiphytic algae for which they provide an
attachment site. The litter and the detritus, on
their decomposition, are supplied to the water
and to the sediments. However, primary production of the fringing compartment of the aquatic
system is high or often could be very high.
9.5
Benthos
The organisms of the solid–water interface are
the ‘benthos’. The following terms appear to be
useful in characterising this assemblage. Benthos
could be classifi ed into the following types:
(a) Rhizobenthos: These are rooted in substratum.
(b) Haptobenthos: These are adnate to the solid
surfaces.
(c) Herpobenthos: These grow or move through
mud.
(d) Psammon: These grow or move through sand.
(e) Endobenthos: These penetrate a solid
substratum.
When the haptobenthos is well developed,
particularly on objects projecting into the free
water, it is called ‘lesion ’, fouling or ‘Bewuchs’.
Many merobenthic animals may also be
meroplanktonic.
The assemblage of organisms at the surface
fi lm is called ‘pleuston’; the ‘micro-pleuston’ is
often designated as ‘neuston’ and may be
‘hyponeuston’ below the fi lm or ‘epineuston’
above it. Some large organisms living in air
above the fi lm on which they walk or run are
best termed as ‘epipleuston’. Many meropleustonic animals which reach the surface fi lm from
below are adapted to live at the surface for part
of their lives.
The bottom area in contact with the water
exhibits striking zonation .
The following terms are recommended to
describe the zones ordinarily present:
(a) Epilittoral: This zone is completely above the
infl uence of the water.
(b) Supralittoral: This zone is above the water
but receives spray.
(c) Eulittoral: This zone lies between the high
and low seasonal levels.
(d) Infralittoral: This zone is permanently covered but with rooted or adnate macroscopic
vegetation, often divisible into upper (emergent
vegetation), middle (fl oating vegetation) and
lower (submerged vegetation).
(e) Littori-profundal: This is a transition zone
with scattered adnate algae.
(f) Profundal: This zone is the bared sediment
below biogeochemical compensation point.
In the terminology of seasonal change, if a
population rises to a maximum and declines once
in an annual cycle, it is monacmic ; if twice, diacmic ; and if many times, polyacmic .
If a species has a single generation per year, it
is called univoltine ; if two bivoltine ; and if many,
multivoltine .
If a generation takes two or more years, the
ordinary terms biennial or perennial will be used.
If a bivoltine or multivoltine species changes
its mode of reproduction, ordinarily to produce
resting stages, once in a year, it is monocyclic ;
if twice, dicyclic , etc. If no changes occur, it is
acyclic .
9 Other Organisms in the Lakes