Visualization of Water quality parameters off the Saint Martin’s Island, Bangladesh

Abstract

Bay of Bengal (BoB), where numerous rivers connect and have the world’s most significant delta, faces a high influx of toxic substances through industrial runoff, agricultural pesticides, and untreated sewage due to the dense inhabitants along its coast. As a result, Saint Martin's Island (SMI), situated in the northeastern of BoB, experiences a significant flow of sediments and various upstream wastes. This influx makes this Island vulnerable by altering the water quality, affecting marine organisms. Therefore, this study focuses on visualizing water quality parameters to observe the monthly distributional pattern around SMI. From July 2022 to June 2023, monthly monitoring of various water quality metrics was conducted, including temperature, salinity, dissolved oxygen (DO), density, and nutrients (nitrite, phosphate, and silicate) and counted phytoplankton to gain a deeper understanding of the water quality in the area. Chlorophyll-A and DO concentrations were highest during winter, indicating a post-monsoon phytoplankton bloom. Nitrite concentration was lower around the island than in the adjacent Naf River. The phosphate level fluctuated monthly, whereas the silicate level was consistently higher around the Island than the Naf River. These variations of nitrite and phosphate could be influenced by agricultural runoff and freshwater influx, while sediment influx from terrestrial drainage could affect the silicate levels. This study will help understand the monthly variability of coastal water quality around the Island and the sources behind these variations. This study is also expected to provide perspectives for observing aquatic health and understanding the impacts of nutrients on the growth of organisms.