[1] Wetlands represent the largest component of the terrestrial biological carbon pool and thus play an important role in global carbon cycles. Most global carbon budgets, however, have focused on dry land ecosystems that extend over large areas and have not accounted for the many small, scattered carbon-storing ecosystems such as tidal saline wetlands. We compiled data for 154 sites in mangroves and salt marshes from the western and eastern Atlantic and Pacific coasts, as well as the Indian Ocean, Mediterranean Ocean, and Gulf of Mexico. The set of sites spans a latitudinal range from 22.4°S in the Indian Ocean to 55.5°N in the northeastern Atlantic. The average soil carbon density of mangrove swamps (0.055 ± 0.004 g cm À3 ) is significantly higher than the salt marsh average (0.039 ± 0.003 g cm À3 ). Soil carbon density in mangrove swamps and Spartina patens marshes declines with increasing average annual temperature, probably due to increased decay rates at higher temperatures. In contrast, carbon sequestration rates were not significantly different between mangrove swamps and salt marshes. Variability in sediment accumulation rates within marshes is a major control of carbon sequestration rates masking any relationship with climatic parameters. Globally, these combined wetlands store at least 44.6 Tg C yr À1 and probably more, as detailed areal inventories are not available for salt marshes in China and South America. Much attention has been given to the role of freshwater wetlands, particularly northern peatlands, as carbon sinks. In contrast to peatlands, salt marshes and mangroves release negligible amounts of greenhouse gases and store more carbon per unit area.

18Relative sea-level changes during the last ~2500 years in New Jersey, USA were reconstructed to test if 19 late Holocene sea level was stable or included persistent and distinctive phases of variability. 20Foraminifera and bulk-sediment δ 13 C values were combined to reconstruct paleomarsh elevation with 21 decimeter precision from sequences of salt-marsh sediment at two sites using a multi-proxy approach. 22The history of sediment deposition was constrained by a composite chronology. An age-depth model 23 developed for each core enabled reconstruction of sea level with multi-decadal resolution. Following 24 correction for land-level change (1.4mm/yr), four successive and sustained (multi-centennial) sea-level 25 trends were objectively identified and quantified using error-in-variables change point analysis to account 26 for age and sea-level uncertainties. From at least 500BC to 250AD sea-level fell at 0.11mm/yr. The 27 second period saw sea-level rise at 0.62mm/yr from 250AD to 733AD. Between 733AD and 1850AD sea 28 level fell at 0.12mm/yr. The reconstructed rate of sea-level rise since ~1850AD was 3.1mm/yr and 29 represents the most rapid period of change for at least 2500 years. This trend began between 1830AD and 30 1873AD and its onset is synchronous with other locations on the U.S. Atlantic coast. Since this change 31 point, reconstructed sea-level rise is in agreement with regional tide-gauge records and exceeds the global 32 average estimate for the 20 th century. These positive and negative departures from background rates 33 demonstrate that the late Holocene sea level was not stable in New Jersey. 34 35

During sea level rise, salt marshes transgress inland invading low-lying forests, agricultural fields, and suburban areas. This transgression is a complex process regulated by infrequent storms that flood upland ecosystems increasing soil salinity. As a result upland vegetation is replaced by halophyte marsh plants. Here we present a review of the main processes and feedbacks regulating the transition from upland ecosystems to salt marshes. The goal is to provide a process-based framework that enables the development of quantitative models for the dynamics of the marsh-upland boundary. Particular emphasis is given to the concept of ecological ratchet, combining the press disturbance of sea level rise with the pulse disturbance of storms.

We report the results of a 5-year fertilization experiment in a central Long Island Sound salt marsh, aimed at understanding the impacts of high nutrient loads on marsh elevational processes. Fertilization with nitrogen led to some significant changes in marsh processes, specifically increases in aboveground primary production and in CO 2 fluxes from the soil. However, neither nitrogen nor phosphorus fertilization led to elevation loss (relative to controls), reduced soil carbon, or a decrease in belowground primary production, all of which have been proposed as links between elevated nutrient loads and marsh drowning. Our data suggest that high nutrient levels increase gross carbon loss from the sediment, but that this is compensated for by other processes, leading to no net deleterious effect of nutrient loading on carbon storage or on marsh stability with respect to sea level rise.

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We used the dual isotope approach to identify sources of nitrate (NO3-) to two mixed land-use watersheds draining to Long Island Sound. In contrastto previous work, we found that sewage effluent NO3- was not consistently enriched in 15N. However, these effluents followed a characteristic denitrification line in delta15N-delta18O space, which could be used as a source signature. We used this signature, together with those of atmospheric deposition and microbial nitrification, to calculate ranges of possible contributions from each of these sources. These estimates are unaffected by any denitrification that may have taken place in soils or streams. Our estimates for atmospheric nitrogen only include unprocessed atmospheric deposition, i.e., NO3-that is not taken up in watershed soils before being delivered to rivers. Using this method, the contribution of atmospheric NO3- could be assessed with good precision and was found to be very low at all our sampling sites during baseflow. During a moderate storm event, atmospheric deposition contributed up to approximately 50% of stream NO3-, depending on the site, with the sites that experienced more stormflow showing a greater contribution of atmospheric NO3-. Our estimates of sewage contribution generally had too large a range to be useful.

Hydraulic fracturing of shale for gas production in Pennsylvania generates large quantities of wastewater, the composition of which has been inadequately characterized. We compiled a unique data set from state-required wastewater generator reports filed in 2009-2011. The resulting data set, comprising 160 samples of flowback, produced water, and drilling wastes, analyzed for 84 different chemicals, is the most comprehensive available to date for Marcellus Shale wastewater. We analyzed the data set using the Kaplan-Meier method to deal with the high prevalence of nondetects for some analytes, and compared wastewater characteristics with permitted effluent limits and ambient monitoring limits and capacity. Major-ion concentrations suggested that most wastewater samples originated from dilution of brines, although some of our samples were more concentrated than any Marcellus brines previously reported. One problematic aspect of this wastewater was the very high concentrations of soluble constituents such as chloride, which are poorly removed by wastewater treatment plants; the vast majority of samples exceeded relevant water quality thresholds, generally by 2-3 orders of magnitude. We also examine the capacity of regional regulatory monitoring to assess and control these risks.

We present an expanded training set of salt‐marsh foraminifera for reconstructing Holocene relative sea‐level change from 12 sites in New Jersey that represent varied physiographic environments. Seven groups of foraminifera are recognized, including four high‐ or transitional‐marsh assemblages and a low‐salinity assemblage. A weighted‐averaging transfer function trained on this dataset was applied to a dated core from Barnegat Bay to reconstruct sea level with uncertainties of ± 14% of tidal range. We evaluate the transfer function using seven tests. (1) Leave‐one‐site‐out cross validation suggests that training sets of salt‐marsh foraminifera are robust to spatial autocorrelation caused by sampling along transects. (2) Segment‐wise analysis shows that the transfer function performs best at densely sampled elevations and overall estimates of model performance are over optimistic. (3) Dissimilarity and (4) non‐metric multi‐dimensional scaling evaluated the analogy between modern and core samples. The closest modern analogues for core samples were drawn from six sites demonstrating the necessity of a multi‐site training set. (5) Goodness‐of‐fit statistics assessed the validity of reconstructions. (6) The transfer function failed a test of significance because of the unusual properties of some cores selected for sea‐level reconstruction. (7) Agreement between reconstructed sea level and tide‐gauge measurements demonstrates the transfer function's utility. Copyright © 2013 John Wiley & Sons, Ltd.