The PIs will conduct two bodies of field work detailed below.

1. Characterization of dynamic beach features, wrack, and vegetation to investigate ecosystem dynamics and recovery of features including climbing dunes and vegetation following a strong erosion event in 2023 and to develop time series of long-term changes on Percos, North, and Cojo Beaches. PIs will continue to utilize new approaches to quantify the elevations and extent of beach features and the dynamics and distribution of wrack subsidies to the beaches as well as coastal strand and dune vegetation using drone and ground-based transect surveys. The unique combination of intense physical dynamics and processes and high subsidies found on the Dangermond Preserve beaches make these three beaches ideal study sites for this research which can be expanded to other beaches on the Preserve.

• PIs will use a multispectral drone in conjunction with our transect surveys to collect additional data and calibrate and ground truth these methods and observations at Percos, North, and Cojo beaches, providing needed data from pristine, wild mainland beaches. They will also incorporate these data into models being developed to automatically detect and quantify wrack and dune vegetation cover. In addition, they will use the resulting data to train a different model for the identification of coastal strand and dune plant species. These surveys will produce orthomosaics of the site which can be used in additional spatial analyses.
• PIs will also use a mobile, RTK-enabled GPS unit to collect ground control point position and elevation data on dynamic beach features and elevations. Using the elevation data from the drone and this GPS unit they will construct site-wide digital elevation models (DEMs) for each survey. The elevation data will be available to refine predictions and modelling for projecting the effects of sea level rise and storm impacts on biodiverse Dangermond Preserve beaches.
• To ground truth the drone surveys PIs will conduct transect-based surveys of dune vegetation cover, wrack cover, and physical features of the beaches and dunes (dune crest, dune toe, vegetation toe, high tide strandline, berms, water table outcrop, etc.). They will also collect RTK GPS data on the position and elevation of these features.

2. Surfperch diet and food web connections: PIs have completed the sample processing and stable isotope analysis for our study of barred surfperch diet. In this next stage they will conduct additional data analysis and synthesis of these diet results to compare fish diet in an MPA (Percos) and at a reference beach (Refugio) to identify patterns in resource use based on season and fish maturity (size). These results will be part of a manuscript detailing the drivers of surfperch prey resources and use of sandy beach resources inside (Percos) and outside (Refugio State Beach) of a Marine Protected Area.
3. Talitrid amphipod population surveys: Taltrid amphipods are sensitive indicators of injury from oil spills and other impacts, including winter storm and wave-driven disturbances. The PIs will initiate semi-annual surveys of talitrid amphipods at Percos, North, and Cojo Beaches to provide a time series on these indicator taxa that can be used to track condition of the beach ecosystem.