Ocean acidification is driven by elevated atmospheric CO2. Coastal acidification is primarily driven by regional factors such as freshwater inflows, coastal upwelling (high CO2, low pH water), and eutrophication in addition to increased atmospheric CO2. Previous studies have demonstrated that acidification of estuaries, coastal and open surface waters, and subsurface waters in the Gulf of Mexico (GOM) has occurred over the past 10 to 40 years. However, rates of acidification and the processes driving it are highly variable, and studies of local impacts of acidification to coastal ecosystems and habitats are limited.

This study builds on the recent data collection activities within GUIS and PAIS. The study will analyze existing NPS monitoring data evaluate if they can be used to characterize acidification conditions in the parks. The data synthesis and analysis will include characterization of coastal acidification conditions at GUIS and PAIS, potential drivers, and comparison of results to other GOM ocean and coastal acidification monitoring efforts.

Data analyses will be conducted to answer the following science questions:

• What is the seasonal and spatial variability of the carbonate system and related environmental variables relative to nearby offshore conditions, and can the current monitoring approach help identify acidification events along the GUIS and PAIS coastal boundaries?
• What is the potential influence of freshwater inflow, temperature, and other environmental drivers on the carbonate system within GUIS and PAIS National Seashores in the context of coastal acidification?
• How are carbonate system variability, and coastal acidification drivers and conditions at GUIS and PAIS similar (or different) to conditions and drivers in other Gulf of Mexico estuaries and coastal systems?

Results will provide key information for broader, multi-agency ocean and coastal monitoring efforts in the GOM by USGS, NPS, NOAA, and EPA. The results will help identify monitoring gaps, identify approaches for continued and/or potential expanded monitoring, and better inform park management strategies for adaptation or mitigation of acidification impacts.