CONTENTS-
Abstract
Introduction
Priority Actions
Materails and Methods
Results
Observations
Discussions
Acknowledgements
References

Aquatic ecosystem, which is very rich in the emergent, submerged or floating plants, is responsible for making the lake shallow. The present paper enumerates the common aquatic angiosperms (macrophytes) and pteridophytes, which are the components of lake bio-diversity and aquatic ecocystem.

Life on earth depends on fresh water. Our planet earth has a definite hydrological cycle, which sustains   life on earth. Continuously moving above and below the soil surface, water maintains and links the planet's ecosystem. Some is returned directly to the atmosphere, partly via plants. The rest flows into and over the ground, permeating soil, moving through organisms, recharging underground aquifers, replenishing rivers and lakes and   finally entering the oceans.

Earth summit's agenda for change and sustainable use, freshwater requires.

•  Better information

•  Better awareness of how the water cycle works, the effects of land use   on the water cycle, the importance of wet lands and other key ecosystems, and of how to use water and aquatic resources sustainably; and better training in these matters.

•  Management of water demands to ensure efficient and equitable allocation of water among competing uses.

•  Integrated management of all water   resources.

•  Improved institutional capacity to manage fresh waters.

•  Strength and capacity of communities to use water resources sustainably

•  Increased international co- operation on water.

•  Conservation of the diversity of issues - aquatic species and genetic stocks.

Water samples were collected and   the results of the analysis are included to   compare the growth of macrophytic vegetation   with reference to the physico-chemical parameters (Puttaiah and Somashekar, 1987; Durani and Rout, 1982; Kaul et al,1980). The parameters that affected the   distribution of macrophytes - calcium, nitrates, phosphates and pH, BOD, COD   are given for Kukkarahalli tank. Four water samples from four sides of the lake were collected and analysed. This lake is situated within the Mysore University campus. The algal vegetation was studied by Puttaiah and Somashekar (1987) .The macrophytic vegetation was studied by the conventional quadrant method in the periphery of lake whereas in the middle of the lake   point counting method (IVI value) was used.

Table-1; Detail of the Lake Morphology, Physiography

For our convenience the lake was divided into four parts - lake east, west, north and south.   From each site sample water and macrophytic vegetation was collected and analysed.

The sampling of aquatic macrophytes is the most important aspect   in the studies related with them as the distribution and biomass of aquatic macrophytes is highly variable. They are also prone to frequent disturbances. In general, some   precautions should be taken while sampling the aquatic macrophytes.

•  No sampling was done in disturbed area of the lake.

•  Sampling   was done over a period of six months and also   when maximum bio-mass was present. So that the phenological variations of the microphytes   can also be studied.

•  The macrophytes were selected because, they are normally   used to study the effect of a particular factor say a pollutant, which has effect on the indicator species.

Kukkarahalli lake varied from 18-9 feet depth. The lake also harboured a number of macrophytes. Water from this lake is mainly used for boating and fish farming and irrigation, in addition to recreation. Irrigation is now totally stopped. The results   of physico- chemical   analysis is given in Table-2

Table-2; Table explaining the water quality analysis results of North and south side of Kukkarahalli Lake over a 1980-82 and 2001-2002 (the average of certain related factors in mg/L in North and South point of the   Kukkarahalli lake).

Weed management and utilisation

The aquatic weeds whether they are emergent, submerged or floating are detrimental when present in excessive quantities. The emergent weeds like the coarse reed; rushes, sedges and grasses trap silt and debris and prevent access to   water, and in course of time make the water shallow. Submerged weeds such as “water mill soil” [Myriophyllum ] Hornwort   [Ceratophyllum ] and Hydrilla are equally damaging. The   high requirement of oxygen for respiration of these weeds at night causes oxygen deficiency in water and the fishes start dying. Weeds such as water lilies, “pond weeds”   [ Potomogeton ] duck weeds [ Lemna and wolfia ] water cabbage [ Pistia] water ferns [ Salvinia, Azolla , and the pestilential water hyacinth Eichornia crassipes ] cover the water surface cutting down the light necessary for photosynthesis and thus causing an acute oxygen deficiency in the water.

The weeds are cleared by manual or mechanical methods or they are killed chemically, or biologically. Manual or mechanical cutting is effective in certain situations and for controlling emergent weeds under water cutters are used. Sometimes chains or rolls of barbed wire are also dragged through the beds to entangle the weeds. Certain small and light floating weeds, viz. Spirodella, Lemna, Azolla and Wolfia are easily skimmed out by twisted straw ropes or small mesh nets.

Algal blooms and Diatoms

Due to overdose of fertiliser in pond/lake water or   due to treated sewage or agricultural fertiliser flowing into the lake, the minute algal cells reach the water body and then multiply fast turning the pond water bright green or sometimes brick red in colour. Some of the most common and harmful algal cells are Microcystsis aeruginosa, Anabaena spiroides and Euglena spp. To the collected pond water (100 ml bottle), 1ml of manganese sulphate solution [48% aqueous solution] should be added first and then 1ml of alkaline iodide [50gNaoH + 13.5g KI/100ml distilled water] solution. The intensity of colour developed   indicates the concentration of dissolved oxygen, a whitish precipitate indicating paucity and brownish precipitate indicating higher levels of dissolved oxygen. The lake desmid bio-diversity was   worked out by Puttaiah and Somashekar (1987). In the microphytic flora, the dominant desmids were Penium, Staurastrum, Euastrum, Closterium, Cosmarium, etc.

The algal samples were analysed from both North and South zone of the lake and the following algal genera was reported from Kukkarahalli Lake, along with their pollution index (Table 3).

The above table explains greater the number of the pollution index value of the species, common is their occurrence. But however, some common desmids and microphytic as well as the macrophytic algae are seen in Kukkarahalli lake which are pollution tolerant species.   

Aquatic Macrophytes:

Aquatic macrophytes are large, predominantly angiosperm plants, inhabiting various sections of aquatic ecosystems and are of considerable importance from the productivity point of view in shallow water bodies or in the littoral zones of the deep water bodies. They play an important role in providing food to fish and other aquatic animals, provide shelter to algae and some animals and also play an important role in cycling of nutrients in the given water body.

The study of macrophytes is important to limnologists in   order to understand the functioning of aquatic ecosystems. Most of the aquatic macrophytes may become a nuisance, when growing profusely. They are then termed as aquatic weeds and become a concern   for water management. They impede flow of water, harbour mosquitoes, cause loss of water and rapidly eutrophicate the lake or water bodies. They however possess tremendous, capacity to absorb nutrients and have also been used for the treatment of sewage and industrial wastes. Types of aquatic macrophytes in   Kukkarahalli (2/8/2002 to 2/9/2002) are Submerged macrophytes, Emergent macrophytes, Floating leaves emergent plants, Hydrophytes in the edges of the lake and Mesophytic plants found on the edges of the lakes:

Table 4: Macrophytic flora and their distribution in Kukkarahalli Lake and surroundings

In this above table certain abbreviations are used for demarcating the distribution of the macrophytes in the Lake

F–For, E-Edge only, S–Surface, M-Middle, Fl–Floating and Su-Submerged.

Plants in any ecosystem remain in constant interaction with their physical environment. The physical environment of the plants regulates their growth and in turn affects the chemical composition. The chemical analysis of the plants emerged as an important tool for an ecologist to understand nutritional budgets of a ecosystem or in other words the pollution or accumulation of difference in chemicals accumulated in that area, which are fostering or triggering a specific kind of macro or microphytic vegetation.   Popularly the analysis is used as a tool to study the ecological pattern and distribution of the chemical pollutants (Piper (1950), Chapman and Pratt (1961) and Allen et.al. (1974)).   For any lake biodiversity, three major things are responsible for luxuriant growth of macro/microphytic vegetation   - pollution,   sedimentation   and   depth of water level. . These   change the pH of the water body as evident from Kukkarahalli lake where   the pH ranged   from 9.3 to 9.6. .

The aquatic weeds, which are a common sight   in any aquatic ecosystem, become   a menace for water bodies.   In many places deweeding is a big programme, so in such a situation, if we can harness the potential   of the   weeds   for better utility, we can conserve   the diversity of macrophytic plant population .

The author is thankful to Principal Dr. G. Ravindra for his constant encouragement and to Prof A.L.N.Sharma for his constant and continuous encouragement.

Allen, S.E., Grimshaw, H.M. Parkinson, J.A. and Christopher, O. (1974).   Chemical analysis of ecological materials. Blackwell Scientific Publication. Oxford.

Chapman, H.D. and Pratt, P.F. (1961). Methods of analysis of soils, plants and waters. University of California.

Durani. P.K. and Rout. D.K. (1982) Phytosociological and production of Nandankanan Lake in Orissa GeoBios 9:25-29.

Kaul. V, Trisal. C.L and Hondoo.J.K. (1980)   Distribution and production of macrophytes in some water bodies of Kashmir. Glimpses of Ecology. Prof. Mishra commem. R. vol (edt) J.S. Single B. Gopal.. pp 313-334.

Piper, C.S. (1950). Soil and Plant Analysis. University of Adelaide, Australia.

Puttaiah.E.T.   and Somashekar.R.K. (1987) On the Ecology of Desmids in Lakes of Mysore City.     Geobios new Reports 6:132-137.

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