CHASING COASTAL CARBON: ORGANIC AND INORGANIC SOURCES AND SINKS ALONG SHIFTING FRESHWATER-MARINE GRADIENTS

Coastal wetlands are globally important stores of carbon (C), but rapid climate- and human-driven changes in fresh and marine water are affecting C cycling and storage capacity. The Florida Everglades is a model system to test how water management and rapid sea-level rise are changing C cycling along freshwater-to-marine gradients across diverse ecosystems that include peat and marl marshes, mangroves, and seagrass meadows. Upstream restoration of peat and marl marshes is increasing water depths and methane fluxes. Particulate organic matter nutrients increase and C decrease with water depths that elevate microbial respiration rates in marl but not peat marshes. Saltwater intrusion increases particulate organic C loss through higher electron acceptors and nutrients that prime microbial breakdown. Landscape-scale shifts in dissolved organic C concentrations and dissolved organic matter (DOM) composition illustrate how shifts in fresh and marine hydrology control sources and fluxes of C. Upstream freshwater restoration in peat drainages is mobilizing marsh C into downstream mangrove estuaries. Saltwater intrusion from sea-level rise is increasing and shifting marine and mangrove C inland in marl drainages, while upstream restoration in marl marshes is increasing humic DOM from allochthonous peat marshes. Carbonate seagrasses are net sources of atmospheric C despite being net autotrophic ecosystems. As climate and human changes continue to transform coastal ecosystems, integrated approaches that conserve and maximize C storage is critical.

Presentation Preference: Oral

Primary Presenter: John Kominoski, Florida International University (jkominos@fiu.edu)

Authors:

John Kominoski, Florida International University  (jkominos@fiu.edu)