Macrobenthic Fauna of a Local Stream , Ghomanhasan ( Jammu )

Stream Gho-Manhasan is analysed for physical, chemical and biological status of its water. Variations both in water and benthic life inhabiting the stream were noted down.

Soil samples were taken from 3 different stations with a sieve of known mesh size and brought to laboratory.Samples were washed and macrobenthos were taken out with the help of brush and preserved in 5% formalin.These organisms were then identified following Ward and Whipple (1959), Needham and Needham (1962), Adoni (1985) and Pennak (1989).

Water Quality
Water sample has been analysed for temperature, speed, depth, Dissolved Oxygen, Free Carbondioxide, Calcium, Magnesium, Bicarbondate, Carbonate and Chloride.The results as presented in Table I show minor variations in their mean value at different stations.Station I experiences highest speed and lowest depth while its speed goes on declining with an increase in depth downstream.pH does not show much fluctuation, CO 3 2-remains absent throughout study period.Other parameters like HCO 3 -, Mg ++ , Ca ++ and Cl -experience slightly increased values downstream and their highest concentration is recorded at station III.

Macrobenthic community
The stream is populated mainly by Annelida, Arthropoda & Mollusca.Among the three groups, Arthropods dominated qualitatively and Annelids quantitatively.Different stations of the stream exhibit varied diversity at the sps.level (Table 2).
The seasonal variation in macrobenthic community along with maxima & minima has been depicted in the Table 3.

Oligochaetes
Highest number of oligochaetes (Table 3) in summer months may be associated with organically rich bottom and increased temperature which enhances organic production.Sunder and Subla (1986) also linked their abundance with rising temperature.Its decline in winter months may be attributed to the low temperature (Pennak, 1989).
In stream Gho-Manhasan, three sps. of oligochaetes have been reported viz, Tubifex, Lumbriculus and Chaetogaster.Tubifex and Lumbriculus are found abundantly at station III (Table 4) through out the study period that may be attributed to the organically rich bottom.Moreover this station is also under the influence of anthropogenic factors which lead to the increase in the apparent pollution level.These observation are also supported by Gopal and Sah (1993) and Sharma (1999) who also reported their abundance in polluted zone.

Diptera
The summer peak of dipterans (Table 3) can be attributed to the reduced flow and high water temperature.Present findings are supported by Stehr and Branson (1938) and Gopal and Sah (1993).The winter rains during February are found responsible for their less number as they wash away  4).The water quality of the station favour their abundance as the water receives effluents from various sources and pollutants get stranded on its bank thereby making it rich in organic matter and Carbondioxide and poor in Oxygen.A decline in DO level also favours the healthy growth of Chironomus sps (Sharma 1999 andSawhney 2004).

Odonata
The maximum production of odonates during winter months (Table 3) can be attributed to low temperature as it favours the abundance of their larvae by inhibiting metamorphosis.Such finding are in concordance with Anwar and Siddiqui (1988) and Chopra et al. (1993).

Molluscs
Summer peak of molluscs show direct relationship with high concentration of bicarbonate and calcium (Table 1).Increasing water temperature during summers is also advantageous to the rich population of molluscs.Present findings also get support from the observation already recorded by Stout and Vandermeer (1978), King (1983) and Rosillion (1985).
Their minimum density can be attributed to low temperature as has already been discussed by Dutta and Malhotra (1986) and Thakial (1997).
Molluscs are represented by three species with their maximum abundance at station III, their increase in number can be related to increasing concentration of bicarbonate, calcium and chloride which favour high population of Molluscs.Present findings are also in concordance with the findings made by David and Ray (1968) and Sunder and Subla (1986).In addition to these factors low speed and high depth at Station III also lead toward its pooled nature and there by supporting the rich population of molluscs.
On the basis of the above discussion it can be concluded that pollution has direct effects on physico-chemical quality of water which ultimately affect the benthic life thereby causing their population to appear or disappear from a water body.