Tidally driven export of dissolved organic carbon, total mercury, and methylmercury from a mangrove-dominated estuary.
The flux of dissolved organic carbon (DOC) from mangrove swamps accounts for 10% of the global terrestrial flux of DOC to coastal oceans. Recent findings of high concentrations of mercury (Hg) and methylmercury (MeHg) in mangroves, in conjunction with the common co-occurrence of DOC and Hg species, have raised concerns that mercury fluxes may also be large. We used a novel approach to estimate export of DOC, Hg, and MeHg to coastal waters from a mangrove-dominated estuary in Everglades National Park (Florida, USA). Using in situ measurements of fluorescent dissolved organic matter as a proxy for DOC, filtered total Hg, and filtered MeHg, we estimated the DOC yield to be 180 (±12.6) g C m(-2) yr(-1), which is in the range of previously reported values. Although Hg and MeHg yields from tidal mangrove swamps have not been previously measured, our estimated yields of Hg species (28 ± 4.5 μg total Hg m(-2) yr(-1) and 3.1 ± 0.4 μg methyl Hg m(-2) yr(-1)) were five times greater than is typically reported for terrestrial wetlands. These results indicate that in addition to the well documented contributions of DOC, tidally driven export from mangroves represents a significant potential source of Hg and MeHg to nearby coastal waters.
United States Geological Survey California Water Science Center, Sacramento, California 95819, United States. bbergama@usgs.gov
Brian A
BA
Bergamaschi
David P
DP
Krabbenhoft
George R
GR
Aiken
Eduardo
E
Patino
Darren G
DG
Rumbold
William H
WH
Orem
D002244:Carbon / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D005431:Florida; D005453:Fluorescence; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D012044:Regression Analysis; D043982:Rhizophoraceae; D012623:Seawater / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D014872:Water Movements; D014877:Water Pollution, Chemical / Q000032:analysis*
D008767:Methylmercury Compounds; D002244:Carbon; D008628:Mercury