SPATIAL AND TEMPORAL VARIATIONS IN THE GROWTH AND PHOTOSYNTHESIS OF SUBMERGED MACROPHYTES IN SONGKHLA LAGOON

Increases in organic matter and temperature are major threats to benthic vegetation survival in the Songkhla Lagoon in Southern Thailand, leading to a loss of ecosystem functions and altered biodiversity. This project aimed to investigate the spatial and temporal variations in photosynthesis, growth, and carbon capture potential of submerged macrophytes in Songkhla Lagoon, including potential inhibitory effects of macrophytes on phytoplankton bloom. Percentage cover, photosynthetic performance, morphology and organic content of submerged macrophytes were investigated in situ bimonthly for a year. Environmental parameters such as organic matter content and carbon and nitrogen contents in sediment, nutrients, water temperature, and light were assessed. Free floating macrophytes, submerged macrophytes and macroalgae were observed from May 2017 to May 2018. CCA indicates that the main factors influencing submerged macrophytes were chlorophyll a concentration and dissolved oxygen concentration in the water, depth, organic carbon in sediment, and phosphate concentration in water. This project suggests that the relationship between environmental parameters and composition of macrophytes can be a helpful tool for predicting ecosystem processes under future climate change scenarios. This study further suggests that there is a potential role for macrophytes as bioindicators for the ecological status of Songkhla Lagoon that contributes to the development of a sustainable lake management plan.