Abstract
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR rate of 0.67 ± 0.1 mm yr−1 between ~4.2–2.8 ka, 4–6 times lower than current rates. Despite low RSLR rates, the rapid mangrove to estuarine transgression was facilitated by a period of prolonged droughts and frequent storms. These findings suggest that with higher and accelerating RSLR today, enhanced climate variability could further hasten the loss of mangrove-lined coastlines, compounded by the reductions in natural flow to the coast caused by water management. Climate variability is nonlinear, and when superimposed on increases in RSLR, can complicate estimated trajectories of coastal inundation for resource management and urban planning.
Highlights
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene
We show that the mangrove to estuarine (MET) occurs during a period of high climate variability, suggesting that transitions between droughts and storms sufficiently stressed the mangrove ecosystems, limiting their ability to keep pace with RSLR
The rate of eustatic sea-level change in the Holocene is associated with northern hemisphere deglaciation, which decreased following the final collapse of the Laurentide ice sheet after 7 ka[25]
Summary
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. Previous studies from Florida Bay and Ten Thousand Islands broadly show a transition to mangrove and estuarine environments ~4–3 ka[4,6] at a time when the rate of sea-level rise was slowing, but low dating resolution on continuous core records prevented careful examination of rates, nature, and drivers of these transitions. We determine the timing of transitions from freshwater marsh to mangrove (FMT) and mangrove to estuarine (MET) environments using pollen, stable carbon isotope and nitrogen isotope, and molluscan analyses from four well-dated (n = 8–10 14C dates/~2.5 -m core) cores in central Florida Bay. We show that the MET occurs during a period of high climate variability, suggesting that transitions between droughts and storms sufficiently stressed the mangrove ecosystems, limiting their ability to keep pace with RSLR
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