Sea-level rise and storms alter soil carbon dynamics of southwest Florida mangrove forests
Abstract
The ability of mangrove ecosystems in southwest Florida to continue as net carbon sinks is directly dependent on rates of organic carbon (OC) burial, the primary driver of soil accretion in carbonate-platform mangrove forests. Over the past several millennia, equilibrium between regional sea-level rise (SLR) and vertical development of mangrove soils has produced extensive carbon stocks. However, increases in SLR and tropical cyclone intensity are likely to alter rates of accretion and OC burial including changes in organic matter production and /or preservation and the deposition of allochthonous material. We measured soil accretion and OC burial rates using 210Pb dating in soil cores along the southwestern Florida coast from Rookery Bay to Shark River in Everglades National Park. Accretion rates match (within uncertainty) the rate of SLR over the most recent 50- and 100-year periods for most of the region, but have not kept pace with the substantially higher rate of SLR in the last decade. Despite SLR outpacing accretion over the last decade, accretion and OC burial rates are typically greatest within this recent period. Stable isotopic and lignin data suggest the more recent accelerated rates in accretion and OC burial will contribute to a lasting increase in soil accretion. Hurricanes Wilma (2005) and Irma (2017) deposited a substantial marine carbonate storm layer throughout much of the forests in our study area, with spatially and temporally variable positive and negative effects on soil carbon. The storm layer reduced soil CO2 efflux by 30% in some areas and has the potential to enhance OC preservation through reduced respiratory losses. The suppression of respiration via storm layers and the acceleration in OC burial observed in the last decade both contribute to greater accretion rates and enhance the resilience of the mangrove forests to SLR. Elsewhere in the region, accretion and OC burial rates were substantially lower at the brackish ecotone. Salinity has increased at those sites and is potentially enhancing OC loss at the saline intrusion front into the freshwater wetlands of the region. Therefore, these sites are more vulnerable to SLR and potentially become open water in the future.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC51H0989S
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0490 Trace gases;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE