and Dutka, 1971) and Rhode river estuary of Maryland (Rublee and Dornseif, 1978). It
fluctuated widely between months and no similar pattern of distribution was noticed in all
the stations. The maximum counts were obtained in station 4 and peak values in all
stations were encountered in November when salinity was found to be very low except at
station 1. A reduction in the microbial fractions from station 4 to station 1 was well
pronounced in November. However such decrease was not noticed during other months.
The maximum extinction of fresh water forms was observed in station 1 which is situated
at the mouth of the estuary. Also salinity of the station 1 was above 24 ‰ during flood
condition and this could be detrimental to freshwater bacteria. According to Larsen
(1962), various true marine bacteria did not find optimal living conditions in brackish
water areas and many fresh water bacteria were inhibited by salinities of over 5 ‰.
Similar pattern of reduction in fresh water bacteria was reported in Schwentine river
mouth region (Rheinheimer, 1984). The antimicrobial activity of seawater and the salt
concentration of the overlying water and sediment might have inhibited the freshwater
bacteria. The annual mean values varied from 30.7 to 61.47 x 10 6 /g and the maximum
bacterial counts were observed in monsoon season (Fig. 6). The high population recorded
during monsoon season may be attributed to the increasing quantity of flood by monsoon
rains. A similar increase in total bacterial content of water run off was also observed
during flooding of northern German rivers (Muller-Haeckel and Rheinheimer, 1983) The
other peaks observed in post monsoon period coincides with the primary production
(Santhanam, 1976) and also might be due to nutrient content (Walker and Colwell, 1975 ;
Rublee, 1982).
Annual curves for actinomycetes also exhibited a completely different pattern than to the
curves of bacteria which demonstrated a peak in November in all stations. In general, a
bimodel distribution could be found. In station 2 and station 3, primary peaks and
secondary peaks were recorded in May and November respectively. But in station 1 and 4
primary peaks were recorded in november and secondary peaks in april and may respectively. A similar bimodel periodicity was noticed showing peak with greatest incidence in
March and November in Eastern Bay sediments (Walker and Colwell, 1975). However,
the shifting of peaks in station 1 and station 4 here may be due to non-static conditions
prevailing there. The number varied form log 4 to log 6/g and maximum occurred in
station 2 during May. Mean values fluctuated between 4.37 to 15.58 x 10 4 /g and unlike
bacteria maximum were recovered in summer followed by monsoon season. The population reported here is higher than the number of actinomycetes reported in Chesapeake
Bay estuarine sediments (Walker and Colwell, 1975) and Weser estuarine sediments
(Weyland, 1969). The higher numbers in summer may be due to stable conditions of
available nutrients.
The population of fungi varied from log 3 to log 6/g and maximum was recorded in
station 2. The annual mean value ranged between 15.36 to 33.19 x 10 3 /g. Higher numbers
were encoutered in the monsoon season. Monthly fluctuations vary widely and did not
show any common pattern of distribution in all stations. Also, no uniformity could be
observed in the distribution pattern of fungi with actinomycetes and bacteria in estuarine
sediments.
Influence of environmental parameters
The distribution of microbial populations in sediment is known to be controlled by
physico-chemical and biological characteristics of the sediment. To understand their
influences on bacteria, actinomycetes, fungi and total microbial load of the sediments, a
number of factors such as temperature, salinity, pH, organic carbon, total nitrogen, total
46
fluctuated widely between months and no similar pattern of distribution was noticed in all
the stations. The maximum counts were obtained in station 4 and peak values in all
stations were encountered in November when salinity was found to be very low except at
station 1. A reduction in the microbial fractions from station 4 to station 1 was well
pronounced in November. However such decrease was not noticed during other months.
The maximum extinction of fresh water forms was observed in station 1 which is situated
at the mouth of the estuary. Also salinity of the station 1 was above 24 ‰ during flood
condition and this could be detrimental to freshwater bacteria. According to Larsen
(1962), various true marine bacteria did not find optimal living conditions in brackish
water areas and many fresh water bacteria were inhibited by salinities of over 5 ‰.
Similar pattern of reduction in fresh water bacteria was reported in Schwentine river
mouth region (Rheinheimer, 1984). The antimicrobial activity of seawater and the salt
concentration of the overlying water and sediment might have inhibited the freshwater
bacteria. The annual mean values varied from 30.7 to 61.47 x 10 6 /g and the maximum
bacterial counts were observed in monsoon season (Fig. 6). The high population recorded
during monsoon season may be attributed to the increasing quantity of flood by monsoon
rains. A similar increase in total bacterial content of water run off was also observed
during flooding of northern German rivers (Muller-Haeckel and Rheinheimer, 1983) The
other peaks observed in post monsoon period coincides with the primary production
(Santhanam, 1976) and also might be due to nutrient content (Walker and Colwell, 1975 ;
Rublee, 1982).
Annual curves for actinomycetes also exhibited a completely different pattern than to the
curves of bacteria which demonstrated a peak in November in all stations. In general, a
bimodel distribution could be found. In station 2 and station 3, primary peaks and
secondary peaks were recorded in May and November respectively. But in station 1 and 4
primary peaks were recorded in november and secondary peaks in april and may respectively. A similar bimodel periodicity was noticed showing peak with greatest incidence in
March and November in Eastern Bay sediments (Walker and Colwell, 1975). However,
the shifting of peaks in station 1 and station 4 here may be due to non-static conditions
prevailing there. The number varied form log 4 to log 6/g and maximum occurred in
station 2 during May. Mean values fluctuated between 4.37 to 15.58 x 10 4 /g and unlike
bacteria maximum were recovered in summer followed by monsoon season. The population reported here is higher than the number of actinomycetes reported in Chesapeake
Bay estuarine sediments (Walker and Colwell, 1975) and Weser estuarine sediments
(Weyland, 1969). The higher numbers in summer may be due to stable conditions of
available nutrients.
The population of fungi varied from log 3 to log 6/g and maximum was recorded in
station 2. The annual mean value ranged between 15.36 to 33.19 x 10 3 /g. Higher numbers
were encoutered in the monsoon season. Monthly fluctuations vary widely and did not
show any common pattern of distribution in all stations. Also, no uniformity could be
observed in the distribution pattern of fungi with actinomycetes and bacteria in estuarine
sediments.
Influence of environmental parameters
The distribution of microbial populations in sediment is known to be controlled by
physico-chemical and biological characteristics of the sediment. To understand their
influences on bacteria, actinomycetes, fungi and total microbial load of the sediments, a
number of factors such as temperature, salinity, pH, organic carbon, total nitrogen, total
46