A three-coral Ba/Ca network provides a regional river discharge reconstruction in the Gulf of Chiriquí, Panama throughout the 20th century

The Ba/Ca ratio in stony corals (Ba/Ca cor ) has been shown in some settings to be a proxy for hydroclimate, specifically river discharge. While this relationship is well-established along the Pacific Coast of Panama, the degree to which temporal variations in Ba/Ca cor from different regions in the estuary replicate is still an area of uncertainity. Here, we present three near-monthly resolved Porites lobata Ba/Ca cor time-series from near-shore and off-shore locations in the Gulf of Chiriquí to illustrate how different corals can record gulf-wide hydroclimatic conditions. All three records are correlated ( r min = 0.48, r max = 0.92) and replicate one another at monthly, annual average, annual amplitude, wet season average, and dry season average resolutions. By averaging time-matched points, we generated a composite Ba/Ca cor record that yielded statistically significant river discharge calibrations. The Gulf of Chiriquí (GoC) is a prime location for the study of the Ba/Ca cor - river discharge relationship, as the region is not substantially impacted by seasonal upwelling or temperature variability due to the topographic blocking of the tradewinds and does not appear to be driven by barite formation in the water column. However, Ba originating from marsh sediment or mangrove forests might contribute to the signal recorded in the corals. Our reconstruction extends the instrumental discharge data by ~70 years and demonstrates the strong and consistent relationship between El Niño events and droughts in Panama with implications for understanding the functioning of the Panama Canal. Therefore, replicated Ba/Ca cor records in the GoC have the potential to not only improve our quantification of past river discharge, but also serve as a tool to supplement our understanding of paleo-ENSO and its impact on regional hydroclimate. • Three Ba/Ca coral records from the Gulf of Chiriquí replicate one another. • Coral Ba/Ca is correlated with river discharge, extending the instrumental record. • Anomalies in reconstructed river discharge can inform Panama Canal activities.