Evaluating the reproducibility and paleo-hydroclimate potential of coral skeletal Ba/Ca in the Gulf of Chiriquí, Panama

Abstract

Coral skeletal Ba/Ca (Ba/Cacor) has been found to be highly correlated with river discharge in some coastal settings. However, any hydrologic interpretation of Ba/Cacor time-series requires thorough evaluation of regional climate, even at sites in close proximity to one another. Here we explore how two corals can be used to provide insight into hydroclimate in the Gulf of Chiriquí, Panama (GoC) using Ba/Cacor, a region whose climate is dictated by seasonal and lower frequency shifts in the Intertropical Convergence Zone. The main purpose of this study is to provide a preliminary assessment of Ba/Cacor replication in pursuit of a regional geochemical network. The two corals analyzed in this study (Secas Island, S1 and Coiba, IC4A-2) were collected ∼74 km apart and grew in different reef settings at vastly different distances from the main river discharge points. Analytical uncertainty prevents complete confidence determining whether a small geochemical offset Ba/Cacor exists between our two records. However, temporal variability in S1 and IC4A-2 are well correlated at all examined temporal scales (rmonthly = 0.70, rannual = 0.65, rwet season = 0.67, rdry season = 0.55, rannual amplitude = 0.77). Considering a potential geochemical offset may exist between the two corals, we took a conservative approach and examined S1 and IC4A-2 separately to establish a relationship with river discharge. Both corals, barring IC4A-2 dry season averages, are statistically significantly correlated to river discharge, permitting the creation of Reduced Major Axis regressions to quantify the relationship. Ultimately, in regions where river discharge dominates, a network of Ba/Cacor records may assist in reconstructing regional variability or notable deviations in hydroclimate. With additional and temporally longer Ba/Cacor records, we will be able to apply our framework to more clearly reconstruct river discharge variability throughout the GoC.