A Targeted Lipidomics and Compound- Specific Isotope Ratio Analysis Approach in Profiling Microbial Community in Submarine Groundwater Discharge in Southern Luzon, Philippines

Jihan Al-Shdifat, The Marine Science Institute, University of the Philippines - Diliman, Quezon City, Philippines, Caroline Marie Jaraula, Marine Science Institute, University of the Philippines, Metro Manila, Philippines, M. Bayani Cardenas, University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States, Aljon Francis Koji Elegado, The Marine Science Institute, University of the Philippines- Diliman, Philippines, Danie Mao-Chang Liang, Academia Sinica, Taiwan, Raymond Rodolfo, Ateneo de Manila University, Department of Environmental Science, Quezon City, Philippines and Mark Lapus, Ridge to Reef Solutions, Inc., Philippines
Submarine groundwater discharge (SGD), characterized by its distinctive biogeochemical profile is host to an array of microbial species. The persistence of SGD in an area within the Verde Island Passage Marine Corridor hosting “the center of the center of marine shorefish biodiversity”, is currently of interest due to the input of nutrients and trace metals to the oceans. Shallow hydrothermal vents, with temperatures measuring up to 50°C, in the area, host an array of microbial mats in various substrates. Bubble curtains, registering up to 90% carbon dioxide, play a role in creating a more alkaline seawater pH. They can be tapped as an opportunity to understand the influence of SGD micro-environments on corals, seagrass, and microbial communities that thrive in the area. Microbial groups are of interest due to their ability to adapt to dynamics of SGD fluxes, observed particularly in their lipid composition as an expressed trait. Lipids are recognized as an essential class of organic compounds as they provide insights on the organism’s metabolic function. They are also among the first means of adaptation to the environment as they form part of the cell membrane. Reports on the microbial communities in SGD sites is scarce. This study explores shallow vents and cold (23°C) seeps emitting carbon dioxide particularly in coral reef areas. White microbial communities and sediments around the vents and are collected and analyzed for their intact polar lipid profile and their compound-specific stable carbon and hydrogen isotope ratios using gas chromatography-mass spectrometry/ isotope ratio mass spectrometry (GCMS-IRMS). SGD is characterized by its nutrients, cation and anion composition, as well as stable hydrogen and oxygen isotope ratios. The study area is a natural analogue to ocean acidification and bears information on the adaptation of microbes and their link to their surrounding coral reefs.