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Physico-chemical Status of Water at the Vicinity of St. Martin’s Island, Bay of Bengal, Bangladesh

M.Y. Mehedi*
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

S. Islam
Institute of Marine Sciences, University of Chittagong, Chittagong 4331, Bangladesh

K. Azam
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

D. Kamal
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

Abstract/ Executive Summary:

Surface water around two stations of the St. Martin’s Island stretching 12 km south from southern most part of main land located in Ukhia and Teknaf were collected monthly during low tide and were analyzed for different hydrological parameters. The maximum and minimum values of water temperature, salinity, dissolved oxygen (DO), pH, water transparency, phosphate-phosphorous (PO4-P), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), ammonia-nitrogen (NH3-N) were noted as 27.9 and 25.6°C, 34.93 and 31.40 ppt., 8.71 and 6.35 mg l-1, pH 9.39 and 7.2, 74.86 and 52.40 cm, 18.02 and 7.28 mg l-1, 3.61 and 0.72 mg l-1, 1.88 and 0.07 mg l-1, and 1.92 and 0.08 mg l-1 respectively. During the period of investigation, the values of DO showed inverse relationship with salinity and water temperature. Nutrient contents in the investigated areas were much higher.

Keywords: Physico-chemical parameter; Nutrients; St. Martin’s Island; Bay of Bengal

Location: Bay of Bengal, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Water quality

Objectives:

There is also rich aquatic fauna inhabiting in water dominating the island. However, scanty information is available on the water quality in this area. The present investigation is undertaken to assess hydrological parameters so as to find out the ecological status of the studied area as well as the contribution of each factor on the growth and distribution of aquatic weeds.

Methodology:

St. Martin's Island is situated in between 92°18'-92°21' E and 20°34'-20°38' N and is about 12 km south from southern most part of the mainland. It is stretched North to South. To the East of this island Myanmar boundary line is about 5km away while to the West and South-west it faces the open sea. It is a group of several small and big islets but broadly three or four of this are recognized at high tide. Two stations, namely Dakshin para and Jingira, were selected around the St. Martin’s Island and the stations were treated as station 1 and station 2 respectively. Station 1 is situated at the southern part of the western coast. The shore slope of this station area is gradually slanting. The coast is made up of compactly stacked boulders of different shapes and sizes. Station 2 is situated at the Northern part of the western coast. The shore slope of area is gradually slanting. The coast is composed of large rock boulders.

Water samples were collected from the two stations around the St. Martin’s Island during the period of November to April at low tide. The samples were collected in clean plastic buckets of one-liter capacity each for measuring all the Physico-chemical parameters except DO and water transparency. For measuring DO, samples were collected in BOD bottles (300 ml) and treated with 2 ml of alkali-iodide azide reagents in the field. The bottles were turned upside down several times to allow thorough mixing. The bottles were closed with stoppers in such a way so that no air bubbles were formed.

All the bottles with samples were placed in wooden boxes to avoid direct sunlight. Samples were then transferred to the laboratory and preserved at 4°C before analysis (WHO, 1982). Water temperature was measured by thermometer (centigrade) by dipping in the water for three minutes. The value of pH was determined with the help of digital pH meter (Model PW 9409 Philips). Salinity was determined by following Mohr’s titration method (Strickland and Parson, 1965). DO, Phosphate-phosphorous, Nitratenitrogen, Nitrite-nitrogen, Ammonia-nitrogen were measured according to the procedure of APHA (1976). To obtain transparency, a secchi disc was lowered in to the water, in the shade until it disappeared and a depth measurement at this point was taken. Then the disc was raised until it reappeared and another depth measurement was taken. This process was repeated three times and the over all average was considered as the proper secehi disc reading or value of water transparency.

Source of Information: Khulna University Studies 2(1): 71-77

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The values of pH during the studied period were within the limit of EQS (6-9) for coastal water that was also responsible for the growth of seaweeds with an exception in February 1995. Nutrients (PO4-P, NO3-N, NO2-N, NH3-N) content around the St. Martin's Island water very high, which were essential for the growth of seaweeds. The findings of the present investigation will add to our understanding about the ecological status of St. Martin’s Island.

Knowledge Management: Journal