Retrospective analysis of the impacts of major hurricanes on sediments in the lower Everglades and Florida Bay

A record of the impacts of major hurricanes on sediment stratigraphy and composition in subtropical ecosystems has been preserved in the lower Everglades and Florida Bay. These impacts were observed in discontinuous layers of sediment that were identified from high-resolution, vertical profiles of excess ²¹⁰Pb and ¹³⁷Cs. Discontinuities were found at different geographic locations and at two to three different depths in the sediment column; however, the layers were each deposited within time periods that corresponded with the passing of category 3–5 hurricanes during 1960, 1948 and 1935. A simple mass balance model for excess ²¹⁰Pb was used to show net changes of ±20–100% in excess ²¹⁰Pb inventory that resulted from sediment disturbances of <1 to >22 cm. Abrupt shifts in sediment composition were often observed in hurricane-impacted layers. Ratios of organic (C/P) were four- to fivefold higher than normal in post-hurricane layers of sediment at open bay sites. These layers are phosphorus poor and seem to reflect preferential decomposition of organic P relative to organic C in association with hurricanes. The net effect is for major hurricanes to redistribute sediment, organic matter and nutrients.This revised version was published online in July 2003.