Examining the principal factors that limits the chlorophyll-a concentration across coastal waters of northern Maharashtra state using a robust Generalised Additive Model

Chlorophyll a (Chl-a) is a pigment found in phytoplankton which is often used as a proxy for primary productivity in the ocean. Chl-a concentrations can be influenced by various factors such as sea temperature, nutrient availability, and light availability. These influences can be complex in more dynamic coastal waters. Hence, the study tried to understand the impacts and relation of different environmental variables on Chl-a production in the coastal water of Greater Mumbai and Palghar Districts of Maharashtra, India. Simple descriptive statistical analysis and a more complex Generalised Additive Model (GAM) were used to study the relative impacts of Sea Surface Temperatures (SST), Euphotic layer Depth (ED), Particulate Inorganic Carbon (IC) and Total Precipitation (TP) on Chl-a production. The post-monsoon month of August to January from 2002 to 2021 were analysed when Chl-a concentrations were the highest. The results suggested a strong negative relation of ED and IC with Chl-a. ED has the most significant (p0.5) showed least to no association with Chl-a production for the study area despite its known impacts. The R2-adj value of 0.454 shows that the model has reasonable explanatory ability. Overall, the model explains around 52.3 % of the total deviance of Chl-a, indicating a moderate fit of the model. Such associations of controlling factors with Chl-a production locally can be essential to understand the complex dynamics of coastal ecosystems and managing the ecosystems against adverse impacts of climatic and non-climatic drivers. •Exploring the relationship between Chl-a and environmental factors using GAM.•The study region has a significant association between Chl-a and environmental factors.•GAM analysis shows a more complex relation between ED and Chl-a variability over the study region.