Nutrient Dynamics in the Coastal Waters Off Padubidri, Karnataka, West Coast of India

Abstract

Aim: Study of nutrient input into the Arabian sea in relation to various environmental parameters Study Design: A stratified random sampling technique was used to conduct monthly in-situ sampling at seven selected stations. Place and Duration of Study: Study was conducted along Padubidri coast from January, 2023 to December, 2024. Methodology: Surface water samples were collected monthly from the coastal waters of Padubidri to evaluate several physicochemical properties. Air and surface water temperatures and transparency were measured at the sampling location using a mercury-in-glass centigrade thermometer and Secchi disc, respectively. At the same time, the analysis of the remaining parameters was conducted in the laboratory according to standard procedures. Water samples for dissolved oxygen analysis were collected in 125-ml glass bottles and preserved on the field using Winkler's reagents. Surface water samples for nutrient analysis were collected in clean polythene bottles, promptly placed in an icebox and transferred to the laboratory for further analysis. Results: Surface water samples were collected monthly using a stratified random sampling method at seven stations and analysed for water temperature (28.39-33.24 oC), transparency (1.56-5.30 m), pH (7.37-8.20), salinity (26.64-38 psu), dissolved oxygen (4.43-7.43 mg/l), BOD (1.37-2.78 mg/l), TDS (31874.29-0525.71 mg/l) and TSS (131.14-577.14 mg/l) and nutrients including ammonia (1.49-13.73 µg-at/l), nitrite (0.56-2.72 µg-at/l), nitrate (0.73-3.81 µg-at/l), phosphate (0.87-4.35 µg-at/l) and silicate (13.07-82.80 µg-at/l). The findings underscore the influence of physicochemical dynamics on coastal water quality and provide a valuable baseline for assessing ecological health and managing coastal resources in monsoon-affected tropical regions. Correlation coefficient revealed positive as well as negative relationship between environmental variables and nutrient at 95 % (p<0.05) level of significance. Conclusion: Results revealed seasonal fluctuations in environmental and nutrient parameters, driven by natural climatic cycles and runoff patterns.