ALBERT

Description: Coastal environments of the early mid-Holocene provided challenges and opportunities for agriculturalists living in the Santa Elena Peninsula, Ecuador (Santa Elena Province, formerly southwestern Guayas Province). Cores extracted from swamps in three river outflows, namely, the Río Verde/Río Zapotal drainage (Chanduy estuary), the Río Grande (Punta Carnero locality), and the Río Valdivia, provided pollen, phytolith, sedimentary, and elemental sequences relevant to documenting vegetation and agriculture. The Chanduy record documented maize and other cultigens from 3200 to 500 cal. BC, providing evidence for intensive cultivation of alluvial lands. The Punta Carnero core provided the first evidence for occupation of the peninsula during the ‘hiatus’ between the Vegas and Valdivia periods, as maize was present in a stratum dating to 4857 cal. BC. Records documented mid-Holocene sea-level stabilization, development of low-energy depositional environments, and variation in rainfall attributable to El Niño-Southern Oscillation (ENSO) by 5000 cal. BC. There was no evidence that the region was either markedly wetter or drier in the early mid-Holocene, suggesting that climate controls similar to those of today were in place.

Description: Considerable variability in the seasonal patterns of streamwater nitrate (NO 3 - ) has been observed in forested watersheds throughout the world. While many forested headwater catchments exhibit winter and early spring peaks in NO 3 - concentrations, several watersheds have peak concentrations during the summer months. Pond Branch, a headwater catchment in Maryland monitored for over 10 years, exhibits recurrent and broad summer peaks in both NO 3 - concentrations and watershed export. Higher NO 3 - export from June to September is particularly surprising, given that these summer months typically have the year's lowest discharge. A key challenge is identifying the source(s) of NO 3 - and the mechanism(s) by which it is transported to the watershed outlet during the summer. In this study, we assessed multiple hypotheses (not mutually exclusive) that could account for the seasonal trend including proximal controls of groundwater-surface water interactions, in-stream processes, and riparian groundwater-N cycling interactions, as well as two distal controls: geochemical weathering and senescence of riparian vegetation. A combination of long-term weekly and limited duration high-frequency sensor data reveal the importance of riparian ecohydrologic processes during baseflow. In this watershed, patterns of seasonal streamwater NO 3 - concentrations and fluxes depend fundamentally on interactions between groundwater dynamics and nitrogen (N) cycling in the riparian zone. Groundwater tables control nitrification-denitrification dynamics as well as hydrologic transport. Our results suggest that in many watersheds, a more sophisticated exploration of NO 3 - production and NO 3 - transport mechanisms is required to identify critical points in the landscape and over time that disproportionately drive patterns of watershed NO 3 - export. This article is protected by copyright. All rights reserved.

Description: Knowledge of the incidence and levels of synthetic particles in large marine vertebrates is lacking. Here, we explore whether synthetic particles could be isolated from marine turtle ingesta and report the presence in every turtle subjected to investigation including individuals from all the seven species of marine turtle, sampled from three ocean basins. Most particles were fibres in lesser quantities were fragments/microbeads and were a range of synthetic materials. Synthetic particles isolated from species occupying different trophic levels suggest the possibility of multiple ingestion pathways. We assess the likelihood this presents a significant conservation problem at current levels. Abstract Despite concerns regarding the environmental impacts of microplastics, knowledge of the incidence and levels of synthetic particles in large marine vertebrates is lacking. Here, we utilize an optimized enzymatic digestion methodology, previously developed for zooplankton, to explore whether synthetic particles could be isolated from marine turtle ingesta. We report the presence of synthetic particles in every turtle subjected to investigation (n = 102) which included individuals from all seven species of marine turtle, sampled from three ocean basins (Atlantic [ATL]: n = 30, four species; Mediterranean (MED): n = 56, two species; Pacific (PAC): n = 16, five species). Most particles (n = 811) were fibres (ATL: 77.1% MED: 85.3% PAC: 64.8%) with blue and black being the dominant colours. In lesser quantities were fragments (ATL: 22.9%: MED: 14.7% PAC: 20.2%) and microbeads (4.8%; PAC only; to our knowledge the first isolation of microbeads from marine megavertebrates). Fourier transform infrared spectroscopy (FT‐IR) of a subsample of particles (n = 169) showed a range of synthetic materials such as elastomers (MED: 61.2%; PAC: 3.4%), thermoplastics (ATL: 36.8%: MED: 20.7% PAC: 27.7%) and synthetic regenerated cellulosic fibres (SRCF; ATL: 63.2%: MED: 5.8% PAC: 68.9%). Synthetic particles being isolated from species occupying different trophic levels suggest the possibility of multiple ingestion pathways. These include exposure from polluted seawater and sediments and/or additional trophic transfer from contaminated prey/forage items. We assess the likelihood that microplastic ingestion presents a significant conservation problem at current levels compared to other anthropogenic threats.

Description: Laser spectroscopy is an emerging technology for measuring nitrous oxide (N 2 O) dynamics in the environment, but most studies have focused on atmospheric applications. We have coupled a commercially available cavity ring-down spectroscope (CRDS) (Picarro G5101- I isotopic N 2 O analyzer) to an air/water gas equilibration device to collect continuous in situ dissolved N 2 O molar concentration and bulk nitrogen isotopic (δ 15 N-N 2 O) data. The δ 15 N-N 2 O values measured by the CRDS unit were found to be significantly affected by changes in the mixing ratios of O 2 , CO, CH 4 , and CO 2 . There was also an effect of N 2 O mixing ratio on δ 15 N-N 2 O. A series of equations was developed to correct for the matrix effect of O 2 and the spectral interference by CH 4 . Chemical traps effectively prevented interferences by CO and CO 2 . The maximum corrections required for N 2 O mixing ratio and O 2 matrix effects, were 1‰ (at a mixing ratio of 1.2 ppmv), and 11‰ (at 0% O 2 content), respectively. The CH 4 correction only became important at mixing ratios greater than 500 ppmv (〉0.5‰). Measurements of N 2 O molar concentration and δ 15 N-N 2 O from the CRDS isotopic N 2 O analyzer were similar to those measured with isotope ratio mass spectrometry. We demonstrated the utility of the laser-based system with field deployments in three estuarine tidal creeks in subtropical Australia. Future work in this field should focus on the application of the laser-based system to the measurement of N 2 O isotopologues in aquatic habitats, allowing for further constraints to be placed on the pathways of N 2 O cycling in aquatic system.

Description: Journal of the American Chemical Society DOI: 10.1021/ja311910h

Description: High‐frequency measurements of NO3− in rivers are improving understanding of the influence of hydrological and biogeochemical processes during high flow and within stream channels. Abstract Widespread deployment of sensors that measure river nitrate (NO3−) concentrations has led to many recent publications in water resources journals including review papers focused on data quality assurance, improved load calculations, and better nutrient management. The principal objective of this study is to review and synthesize studies of high‐frequency NO3− data that have aimed to improve understanding of the hydrologic and biogeochemical processes underlying episodic, diel, and long‐term stream NO3− dynamics. Investigations have provided unprecedented detail on hysteresis and flushing patterns during high flow, seasonal variation during baseflow, and responses to multiyear climate variation. Analyses of high‐frequency data have led to notable advances in understanding how climate variation affects spatial and temporal NO3− patterns, especially dry–wet cycles and antecedent moisture. Further advances have been limited by few investigations that include high‐frequency measurements outside the channel and the short duration of many records. High‐frequency data for multiple constituents have provided new insight to the relative roles of hydrology and biogeochemistry as highlighted by studies of the roles of autotrophic uptake, denitrification, riparian evapotranspiration, and temperature‐driven changes in viscosity as drivers of diel patterns. Comparisons of short duration high‐frequency data with long duration low‐frequency data have described similarities and differences in concentration–discharge patterns and highlighted the role of legacy stores. Investigators have applied innovative analysis approaches not previously possible with low‐frequency or temporally irregular data. Future availability of long duration high‐frequency data will provide new insight to processes, resulting in improved conceptual models and a deeper understanding of the role of climate variation. This article is categorized under: Science of Water 〉 Water Quality Science of Water 〉 Methods Water and Life 〉 Nature of Freshwater Ecosystems

Description: Energy & Fuels DOI: 10.1021/ef3012068

Description: : Floods frequently produce deoxygenation and acidification in waters of artificially drained coastal acid sulfate soil (CASS) wetlands. These conditions are ideal for carbon dioxide and methane production. We investigated CO 2 and CH 4 dynamics and quantified carbon loss within an artificially drained CASS wetland during and after a flood. We separated the system into wetland soils (inundated soil during flood and exposed soil during post flood period), drain water and creek water and performed measurements of free CO 2 ([CO 2 *]), CH 4 , dissolved inorganic and organic carbon (DIC and DOC), stable carbon isotopes, and radon ( 222 Rn: natural tracer for groundwater discharge) to determine aquatic carbon loss pathways. [CO 2 *] and CH 4 values in the creek reached 721 μM and 81 μM respectively two weeks following a flood during a severe deoxygenation phase (dissolved oxygen ~ 0% saturation). CO 2 and CH 4 emissions from the floodplain to the atmosphere were 17-fold and 170-fold higher during the flooded period compared to the post-flood period, respectively. CO 2 emissions accounted for about 90% of total floodplain mass carbon losses during both the flooded and post-flood periods. Assuming a 20- and 100-year global warming potential (GWP) for CH 4 of 105 and 27, CH 4 emission contributed to 85% and 60% of total floodplain CO 2− equivalent emissions respectively. Stable carbon isotopes (δ 13 C in dissolved CO 2 and CH 4 ) and 222 Rn indicated that carbon dynamics within the creek were more likely driven by drainage of surface floodwaters from the CASS wetland rather than groundwater seepage. This study demonstrated that 〉90% of CO 2 and CH 4 emissions from the wetland system occurred during the flood period and that the inundated wetland was responsible for ~95% of CO 2 -equivalent emissions over the floodplain.