«Received: 29th Feb-2012 Revised: 12th Mar-2012 Accepted: 16th Mar-2012 Research Article SEASONAL CHANGES OF HYDROGRAPHIC PROPERTIES IN SEA WATER OF ...»
Received: 29th Feb-2012 Revised: 12th Mar-2012 Accepted: 16th Mar-2012
SEASONAL CHANGES OF HYDROGRAPHIC PROPERTIES IN SEA WATER OF
CORAL REEF ISLANDS, GULF OF MANNAR, INDIA
J.S. Yogesh Kumar*, and S. Geetha1
Zoological Survey of India, Andaman and Nicobar Regional Centre, National Coral Reef Research
Institute, Port Blair- 744102, Andaman & Nicobar Islands, India.
1 Wetland Research and Development, Thoothukudi, Tamil Nadu, India *Corresponding Author mail ID – firstname.lastname@example.org
: The present investigation was carried out the hydrographic parameters of Thoothukudi and Vembar group, Gulf of Mannar. During the study period maximum rainfall was recorded during the monsoon season at Nallathanni Island and minimum was during the summer season at Kaswari Island. The maximum atmospheric temperature was observed in summer season at Nallathanni Island and the minimum atmospheric temperature was recorded during the monsoon season at Upputhanni and Nallathanni Islands. The surface water temperature (°C) ranges between 32.08 to 26.31°C and bottom water temperature (°C) ranges between 30.68 to 25.46°C. Sea water transparency (m) ranges were 3.27m to
0.59m at all the study station. The surface water salinity (‰) ranges from 35.09 ppt- 30.83 ppt and bottom water salinity ranges from 35.86 ppt – 32.51 ppt. The surface water pH values range from were 7.68 to 7.48 and bottom water pH values range from 7.88 to 7.49. The Dissolved oxygen (SW) concentration ranges from 5.12 ml/l to 4.36 ml/l and dissolved oxygen (BW) ranges from 4.57 ml/l to 4.08 ml/l at all the study stations respectively. The surface water inorganic nitrate concentration (mg/l) ranges from 0.63 to 0.06 and Bottom water nitrate (mg/l) range from 0.81 to 0.06. The surface water nitrite ranged from 0.059 to 0.002 at all the study locations. The Magnesium (mg/l) content on surface water varied between 1580 - 1052 and bottom water were 1537 to 1064 at all the stations. Organic phosphate (mg/l) ranges at surface water range from 1.88 to 0.18 and bottom water were 1.74 to 0.18. Dissolved calcium (mg/l) on surface water ranges from 518 to 293 at Thoothukudi and Vembar group of islands correspondingly.
Key wards: Physico-Chemical parameters, coral islands, Thoothukudi, Vembar, Gulf of Mannar Islandsr
INTRODUCTIONWater, the most vital resource for all kinds of life, is very much adversely affected by human activities. Man has rapidly advanced his efforts to counteract this to cope up with this scenario. Ever since the industrial revolution, natural and polluted waters have been studied in great detail all over the world [1 - 6].
Considerable data is now available on most kind of pollutants and their effect on the ecosystem as well as on the organism.
The marine hydrography is much complicated due to the dynamic nature of this ecosystem. Changes in the hydrographical parameters such as salinity, dissolved oxygen, dissolved carbon dioxide; nutrients and so on affect the activities and growth of the organisms in the ecosystem . Studies on the impact of abiotic variables of the aquatic ecosystem are very vital for any pollution monitoring evaluation. It is an accepted fact that in an aquatic environment, among the various abiotic factors, changes in salinity, temperature and pH can be considered as the three main variables which definitely pose a threat on the biota [8 – 11].
Corals are one of the most significant symbiotic associations in animal kingdom in which partnership between tiny unicellular algae and various marine animals together enable the formation of corals reefs .
Corals are made up of calcareous skeletons of millions of tiny marine organisms. The lower organisms lay down calcium. So that the reef growth beneath the cell layers builds the corals continuously over hundreds of thousands of years . The annual growth of corals is very slow. Based on environmental conditions, they may increase in size from a few mm to 5cm every year. Fresh corals have grown over 30cm within Tuticorin harbour where the break waters had only recently been constructed . Corals mainly grow in warm tropical areas (70°F-85°F) with shallow and clean waters.
International Journal of Plant, Animal and Environmental Sciences Page: 135 Available online at www.ijpaes.com Yogesh Kumar and S. Geetha Copyrights@2012 IJPAES ISSN 2231-4490 Corals do not grow beyond 150 feet  even minor pollutants present in the sea that prevent sun light reaching the sea bed alter the growth of corals. Coral reefs are extremely sensitive to changes in the environment. Even slight changes in the reef environment may have detrimental effect on the health of entire coral colonies. These changes may be due to a variety of factors. But they generally fall within two categories viz., natural disturbance and anthropogenic disturbances have been linked to vast majority of decreases in coral cover and general health, when coral reefs and humans occur together . The seasonal changes of sea water temperature was affected the coral reproduction and metabolic activities .
The present study was designed to know the complete ecology and pollution monitoring aspects of a water body in the Thoothukudi and Vembar group of coral Islands in the Gulf of Mannar. An attempt has been made to collect data on the water quality parameters including the nutrients of the entire system. The samples were collected for a period of one year (2007 – 2008) at different points in the selected sites of the island.
MATERIALS AND METHODSSurface water samples were collected at monthly intervals from Thoothukudi and Vembar group of Islands for a period of one year from July 2007 to June 2008. Rain fall data were obtained from the meteorological department located at Kadaladi of Ramanathapuram district, from this the rain fall data of Kadaladi and Vallinokkam were obtained. Since these two stations are very close to the Vembar group of islands, the rainfall data of this area was considered as the data of the Vembar group of islands. From Vilathikulam block of Thoothukudi district, the data for Surankudi and Vippar were obtained. Since these two stations are very close to Thoothukudi group of islands, the data was taken into consideration as the rainfall data of Thoothukudi group of islands. Temperature was measured using a standard centigrade thermometer. Salinity was estimated standard titration method of the Mohr- Knudsen  and pH was measured using an ELICO Grip pH meter. Dissoved Oxygen was estimated by the modified Wrinkler’s method  and expressed as ml/l. For the analysis of nutrients, surface water samples were collected in clean polyethylene bottles and kept immediately in an ice box and transported to the laboratory. The water samples were then filtered using Millipore filtering system and analysed for phosphate, Calcium, Magnesium, dissolved organic nitrate and nitrite adopting the standard procedures described by  and expressed in iμ. Simple correlation co-efficient (r) analysis between different parameters and the Analysis of Variance (ANOVA) have been employed for the statistical interpretation of data obtained from the study is discussed.
RESULTS Monthly variations in metrological and Physico-chemical (Hydrographic) parameters viz., rainfall, atmospheric temperature, surface water temperature, bottom water temperature, salinity, transparency, pH, dissolved oxygen, nitrite, nitrate, Calcium, Magnesium, Inorganic phosphate. Rainfall recorded in the study area was given in the Figure 1. The annual rainfall in Van, Koswari and Kariyachalli of Thoothukudi group of islands were 35.8mm, 33.2 mm and 56.8 mm/yr respectively. Among the three islands maximum rainfall was recorded in Kariyachalli Island only during the study period. Monthwise record showed that in Thoothukudi group of islands the maximum rainfall was recorded during rainy season only, whereas during other months very scanty rain or totally nil rain was recorded. As for as Vembar group of islands were concerned the annual rainfall recorded was more or less equal in all islands and the rainfall recorded was 68mm, 94mm, 76mm/yr in Upputhanni, Pulivinichalli and Nallathanni island respectively.
The monthwise data showed that the Vembar group of islands received rainfall throughout the year except certain months. When compare to the Vembar group of islands the Thoothukudi group of islands received a less quantum of rainfall during the study period.
Atmospheric temperature Figure 2, shows the atmospheric temperature recorded at each station in Thoothukudi and Vembar group of islands. Average air temperature varied from 26.9 0C to 31.90C in Van Island, 26.50C to 32.30C in Kaswary Island, 26.40C to 32.20C at Kariyachalli Island, 26.7 0C to 32.90C in Upputhanni Island, 26.9 0C to 32.10C in Pulivinichally Island and 26.40C to 32.30C at Nallathanni Island. In almost all stations the least atmospheric temperature (28.30C to 28.90C) was observed during the monsoon season while the highest temperature (31 0C to 32.90C) was observed during summer season.
Water temperature Monthly variations in the surface and bottom water temperature in the six islands at Thoothukudi and Vembar group in Gulf of Mannar region are depicted in Figure 3. Surface water Temperature of Van Island ranged from 24.50C to 30.50C, Koswari Island from 24.30C to 31.40C and Kariyachalli Island ranged from
24.40C to 29.80C of Thoothukudi group of islands and 24.3 0C to 30.50C at Upputhanni Island, 25.70C to
32.130C at Pulivinichalli Island and 24.50C to 33.90C at Nallathanni Island of Vembar group, Gulf of Mannar.
Bottom temperature of Van Island ranged from 23.9 0C to 29.20C, Koswari from 23.5 0C to 30.10C and in Kariyachalli Island from 24.10C to 28.40C at Thoothukudi group of Islands. In Vembar group of Islands the minimum observed bottom temperature was 23.8 0C and maximum temperature was 30.9 0C. Bottom water temperature observed in Upputhanni Island ranged from 23.8 0C to 29.10C, at Pulivinichalli Island 25.1 0C to
30.20C and at Nallathanni Island as 24.50C to 30.90C.
Figure 3 Seasonal mean variation of water temperature obtained at different stations studied during the study period (July 2007 to June 2008).
The month wise observation showed that the maximum temperature (27.91 0C to 32.080C) was noted during April to June (summer season) while the minimum value (25.47 0C to 27.440C) were observed during October to December (monsoon season) in most of the study area. The highest surface and bottom water temperature was recorded during the month of June to August (pre-monsoon) in all islands. During all seasons both the surface and bottom water temperatures showed very slight variations (0.5 0C to 1.30C) in almost all stations. In almost all stations the surface water temperature correlates with the atmospheric temperature to a greater extent. In almost all study area the minimum water temperature (25 0C-270C) was noted during the monsoon season and maximum (270C and 320C) during the summer season. While during the pre-monsoon and postmonsoon season in almost all stations the temperature level falls between 27 0C-300C.
Transparency Transparency and the level of light penetration of the study area are reported in the Figure 4.
Maximum light penetration was noticed in Van, Kaswari, Kariyachalli and Upputhanni island during the month of September (3.4, 5.2, 3.3 and 3.1 meter) and in Pulivinichalli and Nallathanni islands during January and February (3.5 and 3.4 meter).
Minimum transparency of sea water noticed during the month of March to June in Van, Kaswari and Kariyachalli, March in Upputhanni island (0.5m-0.7m), In Pulivinichalli island (1.1m) the minimum transparency was observed during the month of August and in Nallathanni island, the minimum transparency (1.2) was noted during the month of may.
During the month of August, September, December and January high values of water transparency observed in Van, Kaswari, Kariyachalli and Upputhanni. From October onwards up to April a drastic decline in the light penetration level was noticed which revealed the turbid nature of the water in these two islands (Pulivinichalli and Nallathanni Island). In the months of July and August the water showed slight decline in transparency in Pulivinichalli and Nallathanni Islands.
Maximum transparency was noted during in almost all stations during the pre- monsoon period except in Pulivinichalli and Nallathanni Island. Here the maximum transparency was noted during the post-monsoon season. The minimum transparency was recorded in all stations during the summer season.
Salinity The surface and bottom water salinity in Thoothukudi and Vembar group of Islands are shown in Figure 5.
Surface water salinity of Van Island ranged from 31.7 to 34.9ppt, Koswari 31.17 to 34.7ppt, Kariyachalli 31.1 to 36.4ppt, Upputhanni 32.1 to 35ppt, Pulivinichalli 30.1 to 34.6ppt and Nallathanni Island 31.1 to 35ppt.
Bottom water salinity of Van Island ranged from 32.2 to 35.3 ppt, Koswari 32.1 to 35.1ppt, Kariyachalli ranged from 32.2 to 37.2ppt, Upputhanni 33.1 to 35.6ppt, Pulivinichalli 32.2 to 35.3ppt and Nallathanni Island ranged from 32.3 to 35.6ppt.
The monthwise report on salinity showed that the highest surface and bottom water salinity was observed during the month of April to June (summer season) whereas the lowest surface water salinity was observed during the month of October to December (monsoon season) in all the six islands studied.
Hydrogen ion concentration (pH) The monthly variations of pH in the surface and bottom waters of the six islands are presented in Figure 6.
There was no much variation observed in the pH value in almost all seasons in all studied stations. There was no much deviation in the surface and bottom water pH. The range of pH falls between 7.1 to 8 in almost all stations. Surface water pH in Van Island ranged from 7.4 to 7.8, in Kaswari Island from 7.5 to 7.9, Kariyachalli Island ranged from 7.5 to 7.6, Upputhanni Island average 7.5, Pulivinichalli Island 7.1 to 8 and Nallathanni Island 7.5 to 7.9 respectively.