CTD Deployment Water Sampling

2 APPROACH AND METHODOLOGY 2.1 Water Quality

2.1.1 CTD Deployment

A CTD model ACL 1180-PDK, Alec Elcetronics, Japan was used in sampling in situ parameters conductivity, temperature, salinity, turbidity and depth at 3 different locations in the Belibangara and Amansuri lagoons to study the variations in conductivity, temperature, salinity and turbidity with depth in each lagoon. During deployment, the CTD was allowed to equilibrate at the surface at each station and then was lowered at a drop rate of 0.5 ms -1 till the CTD touched the bottom. The depth of the water was recorded with the aid of an on-board echo sounder. The data collected, which was logged in the CTD at every 0.1 m, was uploaded to a computer at the end of each sampling.

2.1.2 Water Sampling

Water samples were collected for dissolved oxygen DO and biochemical oxygen demand BOD 5 determination using the iodometric titrimetric method APHA, 1995. Water samples for DO analysis were fixed in DO bottles on the field using the Winkler reagents Winkler I and II. Both samples for DO and BOD were kept on ice and sent to the laboratory for analysis. For turbidity measurements, water samples were collected in 100ml plastic bottles and capped. For nutrients analysis, 100ml plastic bottles were filled with water samples, capped and kept on ice. For chlorophyll analysis, one litre 1L water samples were filtered through a 0.45µm filter paper 47mm -diameter Whatman GFC and the residue kept on ice. Water samples for trace metals As, Cd, Cu, Pb, Hg, Fe, Mn and Zn analysis were taken into 1L high-density polypropylene bottles previously washed and soaked in analytical grade nitric acid solution. The water samples were then fixed in situwith dilute analytical grade nitric acid to prevent metal oxidation and kept on ice. For microbial analysis, water samples were collected into 100ml sterile plastic containers, capped and placed on ice. All the samples were then transported to the laboratory for analysis. Prior to sampling, all sampling containers were pre-conditioned by rinsing three times with field water sample.

2.1.3 Water Analyses