7 research outputs found
Snail Kite Use of a Drought-related Habitat and Communal Roost in West Palm Beach, Florida 1987-1991
Snail Kite Use of a Drought-related Habitat and Communal Roost in West Palm Beach, Florida 1987-1991
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Feather mercury concentrations and physiological condition of great egret and white ibis nestlings in the Florida Everglades
Mercury contamination in the Florida Everglades has reportedly played a role in the recent decline of wading birds, although no studies have identified a mechanism leading to population-level effects. We assessed feather mercury levels in great egret (Ardea alba; n = 91) and white ibis (Eudocimus albus; n = 46) nestlings at breeding colonies in the Florida Everglades during a year (2006) with excellent breeding conditions (characterized by hydrology leading to concentrated prey) and a year with below average breeding conditions (2007). We also assessed the physiological condition of those nestlings based on levels of plasma and fecal corticosterone metabolites, and stress proteins 60 and 70. Mercury levels were higher in both species during the good breeding condition year (great egret = 6.25 μg/g ± 0.81 SE, white ibis = 1.47 μg/g ± 0.41 SE) and lower in the below average breeding year (great egret = 1.60 μg/g ± 0.11 SE, white ibis = 0.20 μg/g ± 0.03 SE). Nestlings were in better physiological condition in 2006, the year with higher feather mercury levels. These results support the hypothesis that nestlings are protected from the harmful effects of mercury through deposition of mercury in growing feathers. We found evidence to suggest shifts in diets of the two species, as a function of prey availability, thus altering their exposure profiles. However, we found no evidence to suggest they respond differently to mercury exposure
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<sup>–2</sup> yr<sup>–1</sup>, 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<sup>–2</sup> yr<sup>–1</sup> and 3.1 ± 0.4 μg
methyl Hg m<sup>–2</sup> yr<sup>–1</sup>) 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