Connectivity and Nitrate Uptake Potential of Intermittent Streams in the Northeast USA

Non-perennial streams dominate the extent of stream networks worldwide. Intermittent streams can provide ecosystem services to the entire network—including nitrate uptake to alleviate eutrophication of coastal waters—and are threatened by lack of legal protection. We examined 12 intermittent streams in the temperate, humid climate of the Northeast USA. Over 3 years of monitoring, continuous flow was observed a median of 277 d yr−1, with no-flow conditions from early summer into fall. Estimated median discharge was 2.9 L s−1 or 0.36mm d−1. All intermittent streams originated from source wetlands (median area: 0.27 ha) and the median length of the intermittent stream from the source wetland to the downstream perennial stream was 344m. Through regional geospatial analysis with high resolution orthophotography, we estimated that widely available, “high resolution” (1:24,000) hydrography databases (e.g., NHDPlus HR) only displayed 43% of the total number of intermittent streams. Whole-stream gross nitrate-N uptake rates were estimated at six intermittent streams during continuous flow conditions using pulse additions of nitrate and a conservative tracer. These rates displayed high temporal variability (range: no detect to over 6,000mg N m−1 d−1); hot moments were noted in nine of the 65 pulse additions. Whole-stream gross nitrate-N uptake rates were significantly inversely related to discharge, with no measurable rates above 7 L s−1. Temperature was significantly positively correlated with whole-stream gross nitrate-N uptake rates, with more hot moments in the spring. Microbial assays demonstrated that nitrate cycling in intermittent streams are consistent with results from low order, perennial forested streams and highlighted the importance of debris dams and pools—potential locations for transient storage. Our assessment suggests that intermittent streams in our region may annually contribute 24–47% of the flow to perennial streams and potentially remove 4.1 to 80.4 kg nitrate-N km−2 annually. If development in these areas continues, perennial streams are in danger of losing a portion of their headwaters and potential nitrate uptake areas may become nitrate sources to downstream areas. These results argue to manage fluvial systems with a holistic approach that couples intermittent and perennial components

Antibodies against endogenous retroviruses promote lung cancer immunotherapy

B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS). Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy response

Exploring Greenhouse Gas Emissions from Beaver Ponds in Southern Rhode Island

Climate change is one of the largest environmental issues facing humanity today, having the potential to alter fresh water availability, agricultural yields, forest productivity, and global sea levels. As climate change is likely to increase the intensity of extreme weather events, the potential for massive human and financial consequences is of further concern. The Intergovernmental Panel on Climate Change asserts that climate change is due to anthropogenic alterations of the atmosphere’s composition, with additional contributions from natural biochemical processes. In particular, the rapid increase in the concentrations of greenhouse gases (GHGs) in the atmosphere can trigger atmospheric warming as these GHGs absorb the heat radiated from the earth and re-emit it into the atmosphere. Much research has been directed at understanding the sources of GHGs to better assess how to reduce GHG emission rates. The study of biogeochemical cycling, particularly the cycling of carbon (C) and nitrogen (N), underlies our ability to predict GHG generation from natural environments. More scientific research is necessary to accurately derive estimates of GHG emission rates from different landscapes around the globe. These estimates will subsequently inform decisions in GHG management and climate change mitigation. Research to date has indicated that certain landscape features may function as “hotspots” for GHG emissions. Because it is estimated that natural wetlands account for nearly 30% of total methane emissions (Reddy and DeLaune 2008), it is important to better quantify the fluxes of methane and other GHGs from natural environments into the atmosphere. Studies (Naiman et al. 1994, Soumis et. al 2004) have shown that wetland environments, such as beaver ponds, may be sources of atmospheric carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) – all potent GHGs. Due to the resurgence of the North American beaver (Castor canadensis), there is an increasing interest in investigating beaver ponds as potential hotspots of GHG emission. Beaver dams impound natural stream flow, creating wetland environments that foster anaerobic conditions, trap sediments and nutrients, and accumulate organic matter. This organic matter serves as a C source for microbial activity to facilitate biogeochemical cycling. With these conditions, beaver ponds alter the cycling of C and N within the riverine environment via the processes of respiration, methanogenesis and denitrification (Naiman et al. 1994) – which generate CO2, CH4 and N2O. In this study, the diffusive flux of GHGs (CO2,CH4, N2O) from the air-water interface of three beaver ponds in Southern Rhode Island in the fall 2012 and spring 2013 seasons was determined via linear increase in concentration of gases in a static chamber over a defined sampling period (as described in St. Louis et al. 2000). Five floating gas chambers were launched on each beaver pond, sampled in 15-minute intervals over one hour, and the samples were processed on a gas chromatograph. An emission rate was derived for each gas from the linear regression of the change in concentration of the gas over time. Gas chamber sampling occurred three times per season on different dates at each of the three beaver ponds. Across sites, fall mean daily pond emissions ranged from 10 to 600 mg CH4 m-2 d-1 and 4,150 to 23,100 mg CO2 m-2d-1. Spring mean daily pond emissions ranged from 10 to 230 mg CH4 m-2 d-1 and 1,500 to 4,300 mg CO2 m-2 d-1. Emissions of N2O were negligible. Variability in GHG emissions may be due to varying levels of labile C, temperature, photosynthetic activity, and pH. Future research involves investigating environmental parameters, such as subaqueous sediment temperature and reduction-oxidation potential, which may influence GHG emission rates

Resurgent beaver ponds in the northeastern United States: Implications for greenhouse gas emissions

Beaver ponds, a wetland type of increasing density in the northeastern United States, vary spatially and temporally, creating high uncertainty in their impact to greenhouse gas (GHG) emissions. We used floating static gas chambers to assess diffusive fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) from the air-water interface of three beaver ponds (0.05-8 ha) in Rhode Island from fall 2012 to summer 2013. Gas flux was based on linear changes of gas concentrations in chambers over 1 h. Our results show that these beaver ponds generated considerable CH4 and CO2 emissions. Methane flux (18-556 mg m-2 d-1) showed no significant seasonal differences, but the shallowest pond generated significantly higher CH4 flux than the other ponds. Carbon dioxide flux (0.5-22.0 g m-2 d-1) was not significantly different between sites, but it was significantly higher in the fall, possibly due to the degradation of fresh leaves. Nitrous oxide flux was low (0-2.4 mg m-2 d-1). Overall, CH4 and CO2 comprised most of the global warming potential, 61 and 38%, respectively. The shallowness of the beaver ponds may have limited the time needed for CH4 oxidation to CO2 before CH4 escaped to the atmosphere. Beaver dams also increase the aerial extent of hydric soils, which may transform riparian areas from upland GHG sinks to wetland GHG sources thereby changing the net global warming potential. Further studies tracking the pattern and conditions of beaver pond creation and abandonment will be essential to understanding their role as GHG sources

(Supplementary Table 1) Iceberg-rafted debris (IBRD) mass accumulation rates (MAR) of IODP site 318-U1361

The Pliocene and Early Pleistocene, between 5.3 and 0.8 million years ago, span a transition from a global climate state that was 2-3 °C warmer than present with limited ice sheets in the Northern Hemisphere to one that was characterized by continental-scale glaciations at both poles. Growth and decay of these ice sheets was paced by variations in the Earth's orbit around the Sun. However, the nature of the influence of orbital forcing on the ice sheets is unclear, particularly in light of the absence of a strong 20,000-year precession signal in geologic records of global ice volume and sea level. Here we present a record of the rate of accumulation of iceberg-rafted debris offshore from the East Antarctic ice sheet, adjacent to the Wilkes Subglacial Basin, between 4.3 and 2.2 million years ago. We infer that maximum iceberg debris accumulation is associated with the enhanced calving of icebergs during ice-sheet margin retreat. In the warmer part of the record, between 4.3 and 3.5 million years ago, spectral analyses show a dominant periodicity of about 40,000 years. Subsequently, the powers of the 100,000-year and 20,000-year signals strengthen. We suggest that, as the Southern Ocean cooled between 3.5 and 2.5 million years ago, the development of a perennial sea-ice field limited the oceanic forcing of the ice sheet. After this threshold was crossed, substantial retreat of the East Antarctic ice sheet occurred only during austral summer insolation maxima, as controlled by the precession cycle

Nd-Sr isotopes, diatom and biogenic opal content of Pliocene sediments from IODP Site 318-U1361

Warm intervals within the Pliocene epoch (5.33-2.58 million years ago) were characterized by global temperatures comparable to those predicted for the end of this century (Haywood and Valdes, doi:10.1016/S0012-821X(03)00685-X) and atmospheric CO2 concentrations similar to today (Seki et al., 2010, doi:10.1016/j.epsl.2010.01.037; Bartoli et al., 2011, doi:10.1029/2010PA002055; Pagani et al., 2010, doi:10.1038/ngeo724). Estimates for global sea level highstands during these times (Miller et al., 2012, doi:10.1130/G32869.1) imply possible retreat of the East Antarctic ice sheet, but ice-proximal evidence from the Antarctic margin is scarce. Here we present new data from Pliocene marine sediments recovered offshore of Adélie Land, East Antarctica, that reveal dynamic behaviour of the East Antarctic ice sheet in the vicinity of the low-lying Wilkes Subglacial Basin during times of past climatic warmth. Sedimentary sequences deposited between 5.3 and 3.3 million years ago indicate increases in Southern Ocean surface water productivity, associated with elevated circum-Antarctic temperatures. The geochemical provenance of detrital material deposited during these warm intervals suggests active erosion of continental bedrock from within the Wilkes Subglacial Basin, an area today buried beneath the East Antarctic ice sheet. We interpret this erosion to be associated with retreat of the ice sheet margin several hundreds of kilometres inland and conclude that the East Antarctic ice sheet was sensitive to climatic warmth during the Pliocene