Examining the utility of coral Ba/Ca as a proxy for river discharge and hydroclimate variability at Coiba Island, Gulf of Chirquí, Panamá

Panamá's extreme hydroclimate seasonality is driven by Intertropical Convergence Zone rainfall and resulting runoff. River discharge (Q) carries terrestrially-derived barium to coastal waters that can be recorded in coral. We present a Ba/Ca record (1996-1917) generated from a Porites coral colony in the Gulf of Chiriquí near Coiba Island (Panamá) to understand regional hydroclimate. Here coral Ba/Ca is correlated to instrumental Q (R = 0.67, p < 0.001), producing a seasonally-resolved Reduced Major Axis regression of Ba/Ca (μmol/mol) = Q (m3/s) × 0.006 ± 0.001 (μmol/mol)(m3/s)− 1 + 4.579 ± 0.151. Our results support work in the neighboring Gulf of Panamá that determined seawater Ba/Ca, controlled by Q, is correlated to coral Ba/Ca (LaVigne et al., 2016). Additionally, the Coiba coral Ba/Ca records at least 5 El Niño events and identified 22 of the 37 wet seasons with below average precipitation. These data corroborate the Q proxy and provide insight into the use of coral Ba/Ca as an El Niño and drought indicator.