A discussion of the potential impacts of climate change on the shorelines of the Northeastern USA

An increase in the rate of sea-level rise and potential changes in storminess represent important components of global climate change that will likely affect the extensive coasts of the Northeastern USA. Raising sea level not only increases the likelihood of coastal flooding, but changes the template for waves and tides to sculpt the coast, which can lead to land loss orders of magnitude greater than that from direct inundation alone. There is little question that sea-level rise, and in particular an increased rate of rise, will result in permanent losses of coastal land. However, quantitative predictions of these future coastal change remains difficult due in part to the complexity of coastal systems and the influence of infrequent storm events, and is further confounded by coastal science’s insufficient understanding of the behavior of coastal systems over decadal timescales. Recently, dramatic improvements in technology have greatly improved our capabilities to investigate and characterize processes and sedimentary deposits in the coastal zone, allowing us, for the first time, to address some of the over-arching problems involved in shoreline change. Despite advances in many areas of coastal geology, our fundamental understanding of shoreline change has been limited by a lack of a broad and integrated scientific focus, a lack of resources, and a lack of willingness on the part of policymakers who make crucial decisions about human activity along the coast to support basic research in this area. Although quantitative predictions remain constrained, there remains little doubt that the predicted climates changes will have profound effects upon the Northeastern coast.     

Bromus tectorum invasion alters nitrogen dynamics in an undisturbed arid grassland ecosystem

The nonnative annual grass Bromus tectorum has successfully replaced native vegetation in many arid and semiarid ecosystems. Initial introductions accompanied grazing and agriculture, making it difficult to separate the effects of invasion from physical disturbance. This study examined N dynamics in two recently invaded, undisturbed vegetation associations (C3 and C4). The response of these communities was compared to an invaded/ disturbed grassland. The invaded/disturbed communities had higher surface NH4+ input in spring, whereas there were no differences for surface input of NO3-. Soil inorganic N was dominated by NH4+, but invaded sites had greater subsurface soil NO3-. Invaded sites had greater total soil N at the surface four years post-invasion in undisturbed communities, but total N was lower in the invaded/disturbed communities. Soil delta15N increased with depth in the noninvaded and recently invaded communities, whereas the invaded/disturbed communities exhibited the opposite pattern. Enriched foliar delta15N values suggest that Bromus assimilated subsurface NO3-, whereas the native grasses were restricted to surface N. A Rayleigh distillation model accurately described decomposition patterns in the noninvaded communities where soil N loss is accompanied by increasing soil delta15N; however, the invaded/ disturbed communities exhibited the opposite pattern, suggesting redistribution of N within the soil profile. This study suggests that invasion has altered the mechanisms driving nitrogen dynamics. Bromus litter decomposition and soil NO3- concentrations were greater in the invaded communities during periods of ample precipitation, and NO3- leached from the surface litter, where it was assimilated by Bromus. The primary source of N input in these communities is a biological soil crust that is removed with disturbance, and the lack of N input by the biological soil crust did not balance N loss, resulting in reduced total N in the invaded/disturbed communities. Bromus produced a positive feedback loop by leaching NO3- from decomposing Bromus litter to subsurface soil layers, accessing that deepsoil N pool with deep roots and returning that N to the surface as biomass and subsequent litter. Lack of new inputs combined with continued loss will result in lower total soil N, evidenced by the lower total soil N in the invaded/disturbed communities.     

Behavior of pesticides in sediment/water systems in outdoor mesocosms

The distribution of eight pesticides between sediment and water held in 1-m square outdoor stainless-steel mesocosms was studied, simulating both spring and autumn applications. Pesticide behavior was largely independent of rate of application, chosen in the first three experiments to be 4% or 40% of the normal field rate so as to simulate spray drift or partial overspray. Following application by spray to the water surface, all compounds were uniformly distributed in the 30 cm of overlying water within 24 h. The lipophilic pesticides (chlorpyrifos, pendimethalin, and permethrin) moved into the sediment within 30 d but with little penetration below 2.5 cm depth, and only chlorpyrifos persisted beyond 30 d. The mass balance of these lipophilic pesticides at 1 d was only 26.3% to 61%, with these initial losses attributed to processes such as volatilization. Isoproturon and chlorotoluron persisted for around 120 d, remaining largely in the overlying water with a maximum of 15% in the sediment. Permethrin and difenoconazole were much less persistent in these mesocosms, with very little ever found in the sediment in contrast to previous findings in laboratory-scale stirred systems as used in registration tests. The polar mecoprop remained almost entirely in the water phase and was rapidly degraded. Two further experiments examined also the influence of the submerged plant Lagarosiphon major in the mesocosms, the first experiment simulating a full-rate overspray with chlorpyrifos and linuron and the second a repeat in spring of the earlier main autumn experiment. Both chlorpyrifos and linuron applied in the autumn were quite persistent over the winter period, with about 20% still remaining after 152 d. Uptake into L. major was correlated with pesticide lipophilicity, but was only a small factor compared to uptake by sediment and degradation in these lightly vegetated systems.     

Surface-mediated formation of PBDD/Fs from the high-temperature oxidation of 2-bromophenol on a CuO/silica surface

As a model brominated hydrocarbon that may form brominated dioxins, we studied the surface-mediated, oxidative thermal degradation of 2-bromophenol on a supported copper oxide catalyst in a 1 mm i.d., fused silica flow reactor at a constant concentration of 90 ppm over a temperature range from 250 to 550 degrees C. Observed products included: dibenzo-p-dioxin (DD), 1-monobromodibenzo-p-dioxin (1-MBDD), dibromodibenzo-p-dioxin (DBDD), tribromodibenzo-p-dioxin (TrBDD), 4-monobromodibenzofuran (4-MBDF), 2,4,6-tribromophenol, 2,4- and 2,6-dibromophenol, and polybrominated benzenes. The results are compared and contrasted with previous work on surface catalyzed oxidative thermal degradation of 2-chlorophenol as well as our own work with the surface-catalyzed pyrolytic thermal degradation of 2-bromophenol. Typically 20 to 200x higher yields of PBDDs are observed for 2-bromophenol than for the analogous PCDDs for 2-chlorophenol. However the anticipated PBDF, 4,6-DBDF, was not observed and 4-MBDF was observed at very low yields. Surprisingly, the maximum yields of PBDDs were observed at higher temperatures than under pyrolytic conditions. This is attributed to regeneration of the catalytic surface due to the presence of oxygen. Higher yields of polybrominated phenols and polybrominated benzenes were also observed than for the analogous chlorinated phenols and benzenes from the oxidation of 2-chlorophenol. This can be attributed to the ease of bromination over chlorination based on the higher abundance of bromine atoms present for 2-bromophenol than chlorine atoms present for 2-chlorophenol.     

Assessing Potential Removal of Low-Head Dams in Urban Settings: An Example from the Ottawa River,NW Ohio

This is a study of the scientific component of an effort to restore an urban river by removing a low-head dam. The Secor Dam is owned by a local government entity near Toledo, Ohio. The proposed removal of the last structure impeding flow on the Ottawa River has broad appeal, but the owner is concerned about liability issues, particularly potential changes to the flood regime, the presence of contaminated sediments behind the dam, and possible downstream transport of reservoir sediments. Assessing sediment contamination involved sediment sampling and analysis of trace metals and organic contaminants. Forecasting sediment transport involved field methods to determine the volume and textural properties of reservoir and upstream sediment and calculations to determine the fate of reservoir sediments. Forecasting changes in the flood regime involved HEC-RAS hydrological models to determine before and after dam removal flood scenarios using LiDAR data imported into an ArcGIS database. The resulting assessment found potential sediment contamination to be minor, and modeling showed that the removal of the dam would have minimal impacts on sediment transport and flood hazards. Based on the assessment, the removal of the dam has been approved by its owners.     

Towards a sustainable food production: modelling the impacts of climate change on maize and soybean production in Ghana

Environmental Science and Pollution Research - The Ghanaian economy relies heavily on maize and soybean production. The entire maize and soybean production system is low-tech, making it extremely...     

Conserving alpha and beta diversity in wood-production landscapes

International demand for wood and other forest products continues to grow rapidly, and uncertainties remain about how animal communities will respond to intensifying resource extraction associated with woody bioenergy production. We examined changes in alpha and beta diversity of bats, bees, birds, and reptiles across wood production landscapes in the southeastern United States, a biodiversity hotspot that is one of the principal sources of woody biomass globally. We sampled across a spatial gradient of paired forest land-uses (representing pre and postharvest) that allowed us to evaluate biological community changes resulting from several types of biomass harvest. Short-rotation practices and residue removal following clearcuts were associated with reduced alpha diversity (−14.1 and −13.9 species, respectively) and lower beta diversity (i.e., Jaccard dissimilarity) between land-use pairs (0.46 and 0.50, respectively), whereas midrotation thinning increased alpha (+3.5 species) and beta diversity (0.59). Over the course of a stand rotation in a single location, biomass harvesting generally led to less biodiversity. Cross-taxa responses to resource extraction were poorly predicted by alpha diversity: correlations in responses between taxonomic groups were highly variable (−0.2 to 0.4) with large uncertainties. In contrast, beta diversity patterns were highly consistent and predictable across taxa, where correlations in responses between taxonomic groups were all positive (0.05–0.4) with more narrow uncertainties. Beta diversity may, therefore, be a more reliable and information-rich indicator than alpha diversity in understanding animal community response to landscape change. Patterns in beta diversity were primarily driven by turnover instead of species loss or gain, indicating that wood extraction generates habitats that support different biological communities.