ACCELERATED EROSION ON THE NORTH CAROLINA COASTAL PLAIN

The Atlantic Coastal Plain of the United States has long been considered to have negligible soil erosion owing to low relief and permeable soils. Several recent studies point to a need for reassessment. Post-settlement erosion on the North Carolina Coastal Plain was estimated at the regional scale based on soil-profile truncation of a representative upland soil (Norfolk series). Apparent post-settlement soil-profile truncation ranges from 2.5 to 30 cm (mean 14.5 cm), implying a minimum regional average rate of 0.55 mm/yr since the region was settled in the 1700s. This amounts to a conservative estimated average rate of 9.3 t/ha/yr, a rate of the same general magnitude as estimated erosion rates in the North Carolina Piedmont, long recognized as a problem erosion area. Results imply accelerated water erosion despite the low slopes and permeable soils, and suggest the possibility of significant eolian erosion in the region. This rapid erosion in an area noted for its geological stability is a testament to the importance of vegetation cover and human agency in landscape evolution in the Coastal Plain. [Key words: accelerated erosion, soil profile, geomorphology, coastal plain, North Carolina.]     

Investigations into a small fraction of volatile hydrocarbons: III. Two diatom cultures produce ectocarpene, a pheromone of brown algae

Ectocarpene was extracted from cultures of Skeletonema costatum and probably in traces from cultures of Lithodesmium undulatum shortly after a change in the light regime which is known to induce formation of gametes.     

The elephant in the room: The hidden costs of leasing individual transferable fishing quotas

Despite the increasingly positive reviews of individual transferable quotas (ITQs), few studies have considered how quota leasing activities can reduce the economic benefits to society and to fishermen operating under the ITQ fisheries system. This analysis reveals negative economic impacts of ITQs previously overlooked by examining the extent of quota leasing and the relationship between the catch value, the cost of fishing, and the quota lease price in the BC halibut fishery, long considered a poster child for ITQs. Findings challenge assumptions of economic theory used to promote the benefits of ITQs.     

Methane sources,sinks and fluxes in a temperate tidal Lagoon: The Arcachon lagoon (SW France)

The Arcachon lagoon is a 156 km² temperate mesotidal lagoon dominated by tidal flats (66% of the surface area). The methane (CH₄) sources, sinks and fluxes were estimated from water and pore water concentrations, from chamber flux measurements at the sediment–air (low tide), sediment–water and water–air (high tide) interfaces, and from potential oxidation and production rate measurements in sediments. CH₄ concentrations in waters were maximal (500–1000 nmol l⁻¹) in river waters and in tidal creeks at low tide, and minimal in the lagoon at high tide (<50 nmol l⁻¹). The major CH₄ sources are continental waters and the tidal pumping of sediment pore waters at low tide. Methanogenesis occurred in the tidal flat sediments, in which pore water concentrations were relatively high (2.5–8.0 μmol l⁻¹). Nevertheless, the sediment was a minor CH₄ source for the water column and the atmosphere because of a high degree of anaerobic and aerobic CH₄ oxidation in sediments. Atmospheric CH₄ fluxes at high and low tide were low compared to freshwater wetlands. Temperate tidal lagoons appear to be very minor contributor of CH₄ to global atmosphere and to open ocean.     

Ignoring market failure in quota leasing?

This short communication is, in part, a response to the Bruce Turris' rejoinder (Marine Policy…2010) to Pinkerton et al., The elephant in the room: The hidden costs of leasing individual transferable fishing quotas (Marine Policy, July 2009). In responding to this article on the unacknowledged problems of unregulated and even unrecorded leasing of individual transferable fishing quotas (ITQs), Turris illustrated the point of the original article well by minimizing the status of leasing as a major influence leading to problems with the fishery: an elephant in the room. Turris focused instead on relatively small and less relevant details, misrepresented the argument, and largely ignored or skirted our discussion of the absent structural conditions important for open competition and efficient outcomes. This response addresses several of his concerns, elaborates on some of the initial points in the original article and contributes some new ones.     

The missing Myopus: plugging the gaps in Late Pleistocene small mammal identification in western Europe with geometric morphometrics

Lemmus and Myopus are two lemming species with distinct habitat requirements but which show very similar dental morphologies. They are thus extremely difficult to distinguish from one another in the fossil record on the basis of their dental remains, leading to poor understanding of the palaeobiogeographical evolution of Myopus as well as inaccurate palaeoenvrionmental reconstructions. Currently, the presence of Myopus in the fossil register from the Pleistocene is still debated and no firm occurrence of this lemming in western Europe has yet been confirmed for the Late Pleistocene. In this paper, we used geometric morphometrics on modern material to establish morphological differences between Lemmus and Myopus teeth (first lower and third upper molars). Morphological data were then used to build a robust linear discriminant model able to confidently classify isolated teeth of these two genera, and finally, linear discriminant models were used on fossil remains of Lemmus/Myopus from two Late Pleistocene archaeological/palaeontological sites (Grotte des Gorges and Gully Cave). This study demonstrates, for the first time, the presence of Myopus schisticolor in west European Late Pleistocene sites between the end of Marine Isotope Stage 3 and the beginning of the Holocene, during climatic events that favoured the development of taiga forest of birch and pine in these regions.     

Influence of Shallow Geology on Volatile Organic Chemical Attenuation from Groundwater to Deep Soil Gas

Vapor intrusion pathway evaluations commonly begin with a comparison of volatile organic chemical (VOC) concentrations in groundwater to generic, or Tier 1, screening levels. These screening levels are typically quite low reflecting both a desired level of conservatism in a generic risk screening process as well as limitations in understanding of physical and chemical processes that impact vapor migration in the subsurface. To study the latter issue, we have collected detailed soil gas and groundwater vertical concentration profiles and evaluated soil characteristics at seven different sites overlying chlorinated solvent contaminant plumes. The goal of the study was to evaluate soil characteristics and their impacts on VOC attenuation from groundwater to deep soil gas (i.e., soil gas in the unsaturated zone within 2 feet of the water table). The study results suggest that generic screening levels can be adjusted by a factor of 100× at sites with fine‐grained soils above the water table, as identified by visual observations or soil air permeability measurements. For these fine‐grained soil sites, the upward‐adjusted screening levels maintain a level of conservatism while potentially eliminating the need for vapor intrusion investigations at sites that may not meet generic screening criteria.