Long‐term nutrient addition increases respiration and nitrous oxide emissions in a New England salt marsh

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecology and Evolution 8 (2018): 4958-4966, doi:10.1002/ece3.3955.Salt marshes may act either as greenhouse gas (GHG) sources or sinks depending on hydrological conditions, vegetation communities, and nutrient availability. In recent decades, eutrophication has emerged as a major driver of change in salt marsh ecosystems. An ongoing fertilization experiment at the Great Sippewissett Marsh (Cape Cod, USA) allows for observation of the results of over four decades of nutrient addition. Here, nutrient enrichment stimulated changes to vegetation communities that, over time, have resulted in increased elevation of the marsh platform. In this study, we measured fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in dominant vegetation zones along elevation gradients of chronically fertilized (1,572 kg N ha−1 year−1) and unfertilized (12 kg N ha−1 year−1) experimental plots at Great Sippewissett Marsh. Flux measurements were performed using darkened chambers to focus on community respiration and excluded photosynthetic CO2 uptake. We hypothesized that N‐replete conditions in fertilized plots would result in larger N2O emissions relative to control plots and that higher elevations caused by nutrient enrichment would support increased CO2 and N2O and decreased CH4 emissions due to the potential for more oxygen diffusion into sediment. Patterns of GHG emission supported our hypotheses. Fertilized plots were substantially larger sources of N2O and had higher community respiration rates relative to control plots, due to large emissions of these GHGs at higher elevations. While CH4 emissions displayed a negative relationship with elevation, they were generally small across elevation gradients and nutrient enrichment treatments. Our results demonstrate that at decadal scales, vegetation community shifts and associated elevation changes driven by chronic eutrophication affect GHG emission from salt marshes. Results demonstrate the necessity of long‐term fertilization experiments to understand impacts of eutrophication on ecosystem function and have implications for how chronic eutrophication may impact the role that salt marshes play in sequestering C and N

Principles controlling boundaries and their application to the development of some of the European states 300 BC-1928 AD

Thesis (M.A.)--Boston University, 1937. This item was digitized by the Internet Archive

Artist Talk: Semio-Technical Traffics

A talk between artists Emily Rosamond and Kristoffer Ørum, with curator Iben Bach Elmstrom. SixtyEight Art Institute, Copenhagen 10 January, 202

Semio-Technical Traffics

Two-person exhibition: Emily Rosamond and Kristoffer Ørum Curated by Iben Bach Elmstrøm 10 January - 15 February, 2020 SixtyEight Art Institute, Gothersgade 167, Copenhage

Textural variations in Neogene pelagic carbonate ooze at DSDP Site 593, southern Tasman Sea, and their paleoceanographic implications

Changes in Neogene sediment texture in pelagic carbonate-rich oozes on the Challenger Plateau, southern Tasman Sea, are used to infer changes in depositional paleocurrent velocities. The most obvious record of textural change is in the mud:sand ratio. Increases in the sand content are inferred to indicate a general up-core trend towards increasing winnowing of sediments resulting from increasing flow velocity of Southern Component Intermediate Water (SCIW), the forerunner of Antarctic Intermediate Water. In particular, the intervals c. 19-14.5 Ma, c. 9.5-8 Ma, and after 5 Ma are suggested to be times of increased SCIW velocity and strong sediment winnowing. Within the mud fraction, the fine silt to coarse clay sizes from 15.6 to 2 µm make the greatest contribution to the sediments and are composed of nannofossil plates. During extreme winnowing events it is the fine silt to very coarse clay material (13-3 µm) within this range that is preferentially removed, suggesting the 10 µm cohesive silt boundary reported for siliciclastic sediments does not apply to calcitic skeletal grains. The winnowed sediment comprises coccolithophore placoliths and spheres, represented by a mode at 4-7 µm. Further support for seafloor winnowing is gained from the presence in Hole 593 of a condensed sedimentary section from c. 18 to 14 Ma where the sand content increases to c. 20% of the bulk sample. Associated with the condensed section is a 6 m thick orange unit representing sediments subjected to particularly oxygen-rich, late early to early middle Miocene SCIW. Together these are inferred to indicate increased SCIW velocity resulting in winnowed sediment associated with faster arrival of oxygen-rich surface water subducted to form SCIW. Glacial development of Antarctica has been recorded from many deep-sea sites, with extreme glacials providing the mechanism to increase watermass flow. Miocene glacial zones Mi1b-Mi6 are identified in an associated oxygen isotope record from Hole 593, and correspond with times of particularly invigorated paleocirculation, bottom winnowing, and sediment textural changes

Technical Memo: Incorporating Mixture Toxicity into Bayesian Networks to calculate risk to pesticides in the Upper San Francisco Estuary.

This memo presents the methods we have developed to calculate risk of mixtures of pesticides for the Upper San Francisco Estuary (USFE). We used curve fitting to estimate the exposure-response curves for each individual chemical and then the mixture. For the mixture the models were normalized for specific ECx values. In that way the curve fitting was optimized for effects that are similar to most threshold values. A Bayesian network was then built that incorporated four different pesticides and a specific mode of action. The input distributions of the pesticides were measured amounts from each of the six risk regions. Sensitivity analysis identified the components of the Bayesian network most important in determining the toxicity. We did demonstrate that curve fitting using additive models for mixtures can be used to estimate fish toxicity in this proof-of-concept model. Bifenthrin and the specific risk region were the two variables that were most important to the risk calculation. These techniques appear applicable to estimating risk due to the variety of chemicals and other stressors in the USFE and to the multiple endpoints under managemen

Transient coastal landscapes : rising sea level threatens salt marshes

© The Author(s), 2018. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science of The Total Environment 640-641 (2018): 1148-1156, doi:10.1016/j.scitotenv.2018.05.235.Salt marshes are important coastal environments that provide key ecological services. As sea level rise has accelerated globally, concerns about the ability of salt marshes to survive submergence are increasing. Previous estimates of likely survival of salt marshes were based on ratios of sea level rise to marsh platform accretion. Here we took advantage of an unusual, long-term (1979-2015), spatially detailed comparison of changes in a representative New England salt marsh to provide an empirical estimate of habitat losses based on actual measurements. We show prominent changes in habitat mosaic within the marsh, consistent and coincident with increased submergence and coastal erosion. Model results suggest that at current rates of sea level rise, marsh platform accretion, habitat loss, and with the limitation of the widespread “coastal squeeze”, the entire ecosystem might disappear by the beginning of the next century, a fate that might be likely for many salt marshes elsewhere.Ivan Valiela and Elizabeth Elmstrom were supported by Woods Hole Sea Grant, NOAA grant no. NA14OAR4170074. Javier Lloret was supported by a Rosenthal Postdoctoral Fellowship Award from the Marine Biological Laboratory, and by a Northeast Climate Science Center Fellowship. Tynan Bowyer was supported by a Metcalf Research Fellowship of the University of Chicago. David Remsen was supported by MBL Cox and Bernstein funds.2020-06-0

The Relative Contributions of Contaminants to Ecological Risk in the Upper San Francisco Estuary

This report presents the methods we developed to calculate risk of mixtures of pesticides for the Upper San Francisco Estuary (USFE). We used curve fitting to estimate the exposure-response curves for each individual chemical and then the mixture. For the mixtures, the models were normalized for specific ECx values. In that way, the curve fitting was optimized for effects that are comparable to most threshold values. A Bayesian network was built that incorporated five different pesticides and mercury. The input distributions of the contaminants were measured amounts from each of the six risk regions. We also explored three different methods of combining the results of the three pathways – additive, average, and expert judgement. The initial result was the BN model’s Predicted Fish Mortality (%). The Sensitivity analysis (mutual information) identified the most important components of the Bayesian network in determining the toxicity. The top two pathways were the Malathion/Diazinon Mortality pathway and the Mercury Mortality pathway. For the individual nodes Mercury, Bifenthrin and Season were key. Currently, we are completing the risk assessment network by adding Chinook salmon and Delta smelt population pathways to estimate risk to the six Risk Regions. A major accomplishment was the demonstration that curve fitting using additive models for mixtures can be used to estimate fish toxicity in this proof-of-concept model. Bifenthrin, the specific risk region, and season were the inputs that were most important to the calculation. Factors determining macroinvertebrate community structure were identified using multivariate tools. Water quality parameters were the most important in determining clusters of similar macrobenthic communities. Because contaminants were not statistically significant in determining these patterns, further analysis of macroinvertebrate community structure was not conducted. At this time, the techniques applied in this program appear applicable to estimating risk due to the variety of chemicals and other stressors to the multiple endpoints under management in the USFE