Spatio-temporal dynamics of water spread area and its implications on the ecosystem services of a tropical hypersaline lagoon

Abstract

Pulicat Lagoon, a tropical lagoon on India's southeast coast, has undergone substantial changes in its water spread area and salinity levels over decades. This study employs Landsat satellite imagery to analyze both long-term trends from 1991, 2001, and 2019 and short-term seasonal variations between September 2018 and July 2019. The long-term changes in water spread area in summer were estimated by the Normalized Difference Water Index, which varied from 311.1 sq. km to 389.2 sq. km. During 1991 and 2001, normal to excess rainfall in the northeast monsoon increased water spread area and salinity reduction. The seasonal analysis during 2018–2019 varied from a maximum of 491 sq. km during the North-East Monsoon to a minimum of 309 sq. km during the summer season. Findings indicate that Pulicat Lagoon is undergoing significant ecological changes marked by reduced water area and altered salinity. These transformations impact provisioning, regulating, and cultural ecosystem services. Challenges include economic and food security issues, vulnerability to climate-related disasters, cultural disruption, and ecological health. To address these challenges, comprehensive strategies are essential, including sustainable water management, preserving freshwater inflow, and ongoing salinity monitoring. These efforts are critical to safeguard the unique biodiversity of Pulicat Lagoon and maintain its ecological equilibrium.