INTRODUCTION
The rapid industrialization and aquaculture practices along the river
systems and the coastal areas have brought considerable decline in the
water quality of brackish waters and the estuaries. Coastal zones and
estuaries are important ecological systems and a resource for a variety
of uses. Such areas are subjected to a variety of socio-economic drivers,
producing increased pressures and impacts, which can lead to environmental
stress or even affect public health (Cave et al., 2003; Belzunce
et al., 2004). With the sudden increase of population and rapid
economic development, these areas are facing many ecological problems.
Such problems have been assigned mostly to an excess of nutrients, associated
with industrial and municipal wastewater (Balls, 1992) forestry and agriculture
(Bell, 1991). The subsequent increase in nutrient loads produces an ecological
impact over biological communities (Karlson et al., 2002), associated
mostly with eutrophication processes (Wang et al., 1999; Hanninen
et al., 2000).
The hydrobiological study is a pre-requisite in any aquatic system for
the assessment of its potentialities and to understand the realities between
its different trophic levels and food webs. Further, the environmental
conditions such as topography, water movement, salinity, oxygen, temperature
and nutrients characterizing a particular water mass also determine the
composition of its biota. Thus, the nature and distribution of the flora
and fauna in the aquatic system are mainly controlled by the fluctuations
in the physical and chemical characteristics of the water body. In Indian
estuaries and seas the physico-chemical characteristics had been carried
out by many workers (Ramaraju et al., 1987; Gouda and Panigrahy,
1996; Satpathy, 1996; Vijayalakshmi, 1999; Rajasegar, 2003).
The present study has been carried out in variation of physico-chemical
parameter in two different estuaries and coastal environments (Fig.
1). Among the two environments, Parangipettai coast is not polluted,
receiving only the land drainage through the Vellar estuary Parangipettai
situated along the southeast coast of India has a unique potential for
marine and brackish water resources, being endowed with various aquatic
biotopes viz., neritic, estuarine, backwaters and mangroves and it is
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Fig. 1: |
The study area connected to the Bay of Bengal at Parangipettai.
While the Cuddalore coast is polluted due to mainly the industrial discharges
in to the Uppanar estuary. Therefore, in the present investigations were
carried out in both the estuarine and coastal environment of Cuddalore
and Parangipettai waters for the period of two years to determine the
level of nutrients and other Physico-chemical parameters in both the estuarine
and coastal environment. |
Station 1 (Lat. 11° 31` 07` N” and Long. 79° 46`
67” E) is located in the marine zone of Vellar estuary (mouth region),
which is influenced by both neritic waters of Bay of Bengal and the fresh
water flow of the river Vellar.
Station 2 (Lat. 11°30` 79” N and Long. 79°47` 92”
E) is situated on the 5 fathom line in the near shore waters of the Bay
of Bengal at Parangipettai and is about 2 km away from the mouth of Vellar
estuary.
Station 3 (Lat. 11° 42` 31” N: Long. 79° 47` 80”
E) is located on the 5 fathom line in the near shore waters of the Bay
of Bengal at Cuddalore fishing harbour and is about 2 km away from the
Cuddalore harbour.
Station 4 (Lat. 11° 42` 34” N: Long. 79° 46` 88”
E) is located in the marine zone of Uppanar estuary the Gadilam estuary
is also joined near this station and most of the industries are located
near the station and hence selected for sampling (Fig. 1).
MATERIALS AND METHODS
Surface water samples were collected at monthly intervals from all the
stations for a period of two years from October 2000 to September 2002
for the estimation of various physico-chemical parameters. Rainfall data
for Parangipettai and Cuddalore coast were obtained from the meteorological
department. Temperature of air and surface water was recorded by using
a standard Centigrade thermometer. The hydrogen ion concentration (pH)
was estimated by using Elico-model (L1-10) pH meter. Salinity
was measured by using hand Refractometer (Atago, Japan). Dissolved oxygen
concentrations were analyzed immediately by adopting the Winkler`s method
as described by Strickland and Parsons (1972).
For the analysis of nutrients, surface water samples were collected in
a clean polythene bottle and kept in an icebox and transported to the
laboratory immediately. The water sample was then filtered using a Millipore
filtration unit using 4.7 cm Whatman Glass Filter paper (GF/C) and analyzed
for inorganic phosphate, nitrite, reactive silicate and ammonia adopting
the standard methods described by Strickland and Parsons (1972) and are
expressed in μM L-1.
RESULTS
Monthly variations in meteorological and physico-chemical parameters
viz. rainfall, air and surface water temperature, salinity, pH, dissolved
oxygen, inorganic phosphate, nitrite, reactive silicate and ammonia in
water were recorded for a period of two years from October 2000 to September
2002.
Rainfall
The total annual rainfall recorded from Parangipettai (station 1 and
2) was 870.5 (2000 to 2001) and 966.4 mm (2001 to 2002). Maximum (294.6
mm) rainfall was recorded during November 2000. The monthly mean rainfall
was 77.5 mm, respectively. However at Cuddalore, the total annual rainfall
recorded for the year 2000 to 2001 was 882.3 and 953.8 mm in 2001 to 2002.
Maximum rainfall (296 mm) was recorded during November 2000. The monthly
mean rainfall for the year 2000 to 2001 and 2001 to 2002 was 73.52 and
79.48 mm, respectively (Fig. 2).
Temperature
During the study period air temperature varied from 24.1 to 33.8°C.
The minimum was recorded during monsoon season (October, 2001) at station
3 and maximum during the summer season (April, 2002) at station 1 (Fig.
3). In general, all the four stations showed similar seasonal changes.
Surface water temperature showed similar trend to that of air temperature.
The surface water
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| Fig. 2: |
Monthly variations in rainfall recorded during October 2000
to September 2002 from Parangipettai and Cuddalore |
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| Fig. 3: |
Monthly variations in air temperature recorded during October
2000 to September 2002 from stations 1, 2, 3 and 4 |
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| Fig. 4: |
Monthly variations in surface water temperature recorded during
October 2000 to September 2002 from stations 1, 2, 3 and 4 |
temperature was varied from 24.5 to 34.2°C. The minimum surface water
temperature was recorded during monsoon season (October, 2001) at station
2 and maximum was recorded during the summer season (April, 2002) at station
1 (Fig. 4). In general, all the four stations showed
similar seasonal changes.
Salinity, pH and Dissolved oxygen
Salinity range was varied from 15.3 to 35.5‰. All the stations
showed similar seasonal pattern in salinity distribution and registering
low values during monsoon season and high values during the summer season
(Fig. 5). Seasonal fluctuations in the pH followed the
trend similar to that of salinity (Fig. 6). Dissolved
oxygen concentration was varied from 3.14 to 7.02 ml L-1. minimum
was recorded in the premonsoon season at station 4 and the maximum during
monsoon season at station 1 (Fig. 7).
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| Fig. 5: |
Monthly variations in salinity recorded during October
2000 to September 2002 from stations 1, 2, 3 and 4 |
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| Fig. 6: |
Monthly variations in pH recorded during October 2000 to September
2002 from stations 1, 2, 3 and 4 |
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| Fig. 7: |
Monthly variations in dissolved oxygen concentration recorded
during October 2000 to September 2002 from stations 1, 2, 3 and 4 |
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| Fig. 8: |
Monthly variations in nitrite concentration during October
2000 to September 2002 from stations 1 2, 3 and 4 |
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| Fig. 9: |
Monthly variations in dissolved inorganic silicate concentration
during October 2000 to September 2002 from stations 1, 2, 3 and 4 |
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| Fig. 10: |
Monthly variations in inorganic phosphate concentration during
October 2000 to September 2002 from stations 1, 2, 3 and |
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| Fig . 11: |
Monthly variations in ammonia during October 2000 to September
2002 from stations 1, 2, 3 and 4 |
Nitrite, Silicate, Inorganic phosphate and Ammonia
The nitrite concentration was varied from 0.205 to 2.68 μM L-1.
Minimum was recorded during premonsoon season at station 2 and the maximum
during monsoon season at station 4 (Fig. 8). Silicate
values was ranged from 4.83 to 52.32 μM L-1 concentration
it also shows the similar trend like nitrite minimum was recorded during
premonsoon at station 3 and the maximum during the monsoon season at station
4 (Fig. 9). Inorganic phosphate concentration was varied
from 0.186 to 2.48 μM L-1. Minimum was recorded during
the postmonsoon at station 2 and the maximum during the monsoon at station
4 (Fig. 10). Ammonia level was varied from 0.0111 to
0.461 μM L-1. Minimum was recorded during premonsoon season
at station 1 and the maximum during the summer season (Fig.
11).
DISCUSSION
The physico-chemical variables of the present study areas are subjected
to wide spatial temporal variations. Rainfall is the most important cyclic
phenomenon in tropical countries as it brings about important changes
in the physical and chemical characteristics of the coastal and estuarine
environments. In the present study, bulk quantities of rainfall were received
during the monsoon months (November, 2000 and October, 2001) due to northeast
monsoon.
Temperature variation is another important factor in the coastal and
estuarine ecosystems, which influences the physico-chemical characters
of coastal and estuarine waters to a greater extend triggering the breeding
and spawning of marine fishes. Seasonal variations were observed in atmospheric
and water temperature showed the distinct biomodel oscillations at all
the three stations. The maximum temperature was recorded during the summer
season and minimum was recorded monsoon could be ascribed to the effect
of atmospheric cooling. In the present study temperature showed that atmospheric
variation including insolation play major role governing temperature and
water exchange between the sea and the estuary is of less significance.
Similar conclusion has also been drawn from this estuary (Chandran and
Ramamoorthy, 1984; Rajasegar, 2003).
Salinity is considered to be the prime factor among the environmental
variables influencing the dynamic nature of the estuarine and coastal
waters by the freshwater inflow and the prevailing temperature. Among
the four stations, the salinity values ranged from 18.5 to 35.5‰
during the two years of study period. The maximum salinity was recorded
at station 2 during the summer season (April, 2002) and the minimum at
station 1 during the monsoon season (November, 2001). The higher values
recorded in summer season could be attributed to the high degree of evaporation
of surface water in the shallow areas and less wave and tidal action with
decreased freshwater inflow and drainage. During the monsoon season, all
the stations received bulk rainfall and the freshwater input in turn greatly
reduces the salinity values. Moderate salinity values were observed during
the pre and postmonsoon periods, which represent a transition period between
monsoon and summer. Similar observations were made by Rajasegar (2003).
The hydrogen-ion concentration (pH) gets changed with time due to the
changes in temperature, salinity and biological activity. The pH remained
alkaline throughout the study period at all stations registering a maximum
during summer season, which could be attributed to the high salinity of
water. Most of the natural waters are generally alkaline due to the presence
of sufficient quantities of carbonate. Higher value of pH was recorded
at coastal stations (2 and 3) than in estuarine stations (1 and 4). pH
was low during the monsoon (7.7 at station 1 and 3, 7.8 at station 2 and
7 at station 4) and this was associated with lesser salinity region. pH
was also quite low during floods in the peak monsoon season due to the
influence of freshwater influx, dilution of saline water, reduction of
salinity and temperature and decomposition of organic matter, as suggested
by several authors (Zingde et al., 1985).
Dissolved oxygen concentration shows a wide range of variation throughout
the study period. Dissolved oxygen concentration was low during the premonsoon
season but increased during summer and monsoon seasons. The low dissolved
oxygen concentration observed during the premonsoon season could be attributed
to the lesser input of freshwater into the study area. Higher value of
dissolved oxygen concentration observed in the monsoon season was due
to heavy rainfall and the result of freshwater mixing (Ramaraju et
al., 1987; Zingdge et al., 1985)., Mitra et al., (1990);
Nandan and Abdul Azis (1993) and Rajasegar (2003) have also opined that
the monsoonal maximum of dissolved oxygen content was due to the consequent
renewal of freshwater flow.
From the present study it is evident that relatively higher concentration
of ammonia was recorded in water samples of Uppanar estuary, which receives
the contaminants directly through the discharge of untreated domestic
sewage from Cuddalore town area and the disposal of waste from well established
industrial area. But along Parangipettai coast, at station 1 is apparently
unpolluted due to limited inflow of domestic sewage and the absence of
major industrial complex in the nearby areas. The main source of contaminants
might be through the aquaculture activities.
Nitrite concentration was higher during the monsoon season and low during
the summer season. The peak values of nitrite observed during the monsoon
season could be attributed to the influence of seasonal floods. The higher
concentration of nitrite and seasonal variation could also be attributed
to the variation in phytoplankton excretion, oxidation of ammonia and
reduction of nitrite (Kannan and Kannan, 1996). In addition to this increase
in nitrite content at the surface water layer might also be due to denitrification
and by air-sea interaction of exchange of chemical elements (Mathew and
Pillai, 1990). Low values of NO2 observed during the summer
seasons might be due to the lesser amount of freshwater inflow and higher
salinity. The observed increase in nitrite at station 1 and 4, may be
due to the increased bacterial activity which is more in a silty-clayey
substratum prevailing at station 1 and 4 rather than the sandy substratum
at station 2 and 3 (Segar and Hariharan, 1989). Similarly maximum value
in monsoon and minimum value in summer season were also recorded by Chandran
and Ramamurthi (1984) from Vellar estuary, Edward and Ayyakkannu (1991)
from Kollidam estuary, Kannan and Kannan (1996) from Palk Bay, Satpathy
(1996) from coastal waters of Kalpakkam and Vijayalakshmi (1999) from
Parangipettai and Cuddalore waters.
In the present investigation, the reactive silicate concentration was
found to be much higher than inorganic phosphate and nitrite. Station
1 and 4 recorded more silicate concentration than the station 2 and 3.
High silicate concentration recorded during monsoon season may be due
to the addition of silica material by land run-off caused by flooding
during the monsoon season. Further more silicate available at the bottom
sediments might go into the upper water layers when the bottom is agitated
by wind action during the monsoon season.
Low values of silicate recorded during the premonsoon season may be due
to the sizeable reduction in the freshwater input and greater utilization
of the nutrient by the abundantly available phytoplankton for their biological
activity (Gouda and Panigrahy, 1992). In addition to phytoplankton uptake,
some other processes like absorption and co-precipitation of soluble silicon
might also govern the distribution of dissolved silicate in the marine
environment (Choudhury and Panigrahy, 1991; Gouda and Panigrahy, 1992).
In the present study, the inorganic phosphate registered its peak values
during the monsoon season and decreased concentration during the postmonsoon
season. Inorganic phosphate concentration was high in both the estuary
and coastal waters during the monsoon season due to heavy rainfall, input
of domestic sewage and fertilizers from the agricultural discharges from
the adjacent lands. Low concentration of inorganic phosphate observed
during the postmonsoon seasons was due to the decreased land drainage,
sewage and fertilizer disposal from the land drainage. Such monsoonal
maximum and postmonsoonal minimum in the inorganic phosphate concentration
was also reported from Arasalar and Kaveri estuary (Saraswathi, 1993),
Tranquebar-Nagappattinam coast (Sampathkumar, 1992).
Station 1 and 4 registered more concentration of inorganic phosphate
than the station 2 and 3. The high inorganic phosphate concentration is
an important feature associated with sewage pollution in the estuarine
environment and hence the inorganic phosphate concentration could be taken
as an index to identify the extend of pollution in the estuarine environment
and compare with coastal environment.
Higher concentration of ammonia was observed during the postmonsoon and
summer seasons. Higher concentrations could be partly due to death and
subsequent decomposition of phytoplankton. Further, the peak concentrations
of ammonia during the postmonsoon and summer seasons coincided with the
high zooplankton production that could be related to the excretion of
ammonia by planktonic organisms (Segar and Hariharan, 1989).
The present observation on nutrients, agree well with the statement of
Choudhury and Panigrahy (1991) as the distribution and behaviour of nutrient
in the coastal environment particularly in the near shore water and estuaries
may exhibit considerable seasonal variation depending upon the local condition
like rainfall, quantum of freshwater inflow, tidal incursion and some
biological activity like phytoplankton uptake and regeneration.
The Cuddalore coast and Uppanar estuary shows the higher concentration
of nutrients when compared with The Vellar estuary and Parangipettai coastal
waters. Particularly the less DO and pH values and higher ammonia level
was observed in Uppanar estuary which may perhaps be due to the heavy
discharge of industrial effluents from the SIPCOT industry causing the
estuarine environment to become polluted one.
CONCLUSION
The physico-chemical status of the estuarine and coastal waters of Parangipettai,
using this methodology, is good in general. However, in the Cuddalore
coast, the Uppanar estuary, the water quality parameters are not good
enough because of the discharges from the associated industry and municipal
drainage.
ACKNOWLEDGMENTS
Authors wish to thank the Director of centre professor T. Balasubramanian
for providing facilities and Professor T. Kannupandi and Professor V.
Ramaiyan Centre of Advanced Study in Marine Biology, Annamalai University,
for their valuable suggestions and support.
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