Coral Ba/Ca and Mn/Ca Ratios as Proxies of Precipitation and Terrestrial Input at the Eastern Offshore Area of Hainan Island

Geochemical ratios in coral reef skeletons could be used as proxies to reconstruct past climatological and environmental records in data-poor regions. Using a 103-year data set (1902 to 2005), the annual variations in Ba/Ca and Mn/Ca ratios of Porites lutea skeletons at an eastern offshore area of Hainan Island (19°12′28.4′′N, 110°37′38.8′′E) were analyzed using inductively coupled plasma-optic emission spectrometry (ICP-OES). The analysis results showed that Ba/Ca ratios varied from a minimum of 3.120 μmol mol?1 in 1903 to a maximum of 10.064 μmol mol?1 in 1944, with an average of 5.256 μmol mol?Mn/Ca ratios varied from 0.206 to 5.708 μmol mol?1 with an annual average of 1.234 μmol mol?1, with peak values in 2001, 1964 and 1932, that correlated with strong rainfall events caused by typhoons. Variation in Ba/Ca and Mn/Ca ratios were compared with available river discharge and precipitation records, providing insight into past climatological events. Human activities and their indirect effects could impact the strength of the relationship between Ba/Ca and Mn/Ca ratios and observed precipitation and terrestrial input in the future.