Abstract

In recent years, fishery harbours have become places with high levels of pollution due to fishing and related activities. Studies have been conducted in the southern and western parts of the country to determine the pollution status of harbours, but little is known in the northern part of the island. Thus, the study was conducted at the Myliddy fishery harbour, in order to analyse the spatial and temporal variations of the physical, chemical and biological parameters, to assess the pollution level of the fishery harbour using the Store et Retrieval method (STORET method) and to identify the possible sources of the pollution. The survey was carried out during a six-month period from January 2022 to June 2022 at three sampling sites at the harbour. A SmarTROLL multiparameter was used to collect on-site measurements of the water temperature, pH, actual conductivity, salinity, dissolved oxygen (DO), density, total dissolved solids (TDS), pressure and air temperature. Total coliform, chlorophyll a, turbidity, nitrate, phosphate, biochemical oxygen demand (BOD), chemical oxygen demand (COD) and oil and grease content were measured at the laboratory using standard methods. Results showed that BOD, salinity, TDS, actual conductivity, water temperature, air temperature, phosphorous, phosphorous pentoxide and phosphate have a significant difference among sampling months (p<0.05). Phosphorous, phosphorous pentoxide and phosphate showed a significant difference among sampling sites (p<0.05). The acceptable limit was exceeded by the MPN value for total coliforms (per 100 ml), which ranged between 6.1 and 1600. COD ranges between 75 and 185 mg/L, which is over the limits. Oil and grease concentration is below average, ranging from 0.3 to 2.5 mg/L. The pH value is between 7.74 and 8.19, which is within acceptable limits. The DO ranges from 3.265 to 6.528 ppm, exceeding the recommended amount. The BOD concentration in the harbour water ranges from 0.407 to 4.896 ppm, which is below the recommended level. According to the STORET method, this fishery harbour is moderately polluted [class C – score (-24)]. The study revealed that Myliddy fishery harbour is subjected to chemical and microbial pollution.

Keywords- Chemical oxygen demand, STORET method, Total coliforms