Terrestrial arthropods from the Late Pleistocene of Jamaica: systematics,palaeoecology and taphonomy

The Red Hills Road Cave, Jamaica, is the most important site for terrestrial arthropods in the post‐Miocene of the Greater Antilles. Its fauna includes millipedes, isopods, crabs and insects, in addition to land snails and vertebrates. Arthropods are preserved in three dimensions and delicate structures such as limbs can be recognized. This unusual preservation was favoured by acidic groundwater rich in dissolved calcium carbonate; periods of high rainfall during which the bottle‐shaped cave was filled with water; and any arthropod washed in would have drowned. The absence of spiders, centipedes and most insects is due to the absence of carbonate in their exoskeletons. Millipedes and isopods possess a potential for preservation by carbonate mineralization that does not occur in other groups; they secrete calcium carbonate in the exoskeleton which hardens the cuticle and is water permeable, bringing about mineral replacement of the original structures. Within the cave, fossil millipede taxa include Rhinocricus sp. or spp., Chondrotropis sp., Caraibodesmus verrucosus (Pocock) and Cyclodesmus sp. cf. C. porcellanus Pocock. The isopod fauna includes Pseudarmadillo sp., Venezillo boonae Van Name, and Philoscia spp. 1 and 2. Crab claws belong to Sesarma sp. cf. S. cookei Hartnoll. Millipedes and isopods are particularly complete, representing drowned individuals fossilized soon after death; land crabs occur as fingers and rare chelae, suggesting that they may be exuviae. Only the most robust parts of insects have been discovered, but are particularly rare, consisting of three taxa of fly puparia and one possible beetle elytra. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of Two Tropical Storms on the Residual Flow in a Subtropical Tidal Inlet

The mechanisms responsible for the modulation of laterally sheared non-tidal (residual) exchange flow in a subtropical inlet, with special emphasis on tropical storm influence, are studied using a combination of current velocity profiles and hydrographic and meteorological data. The mouth of the inlet, St. Augustine Inlet in northeast Florida, is characterized by a 15-m-deep channel flanked by shoals (<6 m deep). Residual flows across the inlet mouth were laterally sheared with inflow in the channel and outflow over the shoals. This pattern persisted during four separate semi-diurnal tidal cycle surveys effected over 3 years. During spring tides, residual exchange flows intensified relative to neap tides. Residual inflow in the channel only reversed immediately after tropical storms because of their extreme winds and major temporal changes in water level. After the residual flow reversed in the channel, along-channel baroclinicity drove gravitational circulation that persisted for 4.5 days and was enhanced by offshore winds. A depth-averaged along-basin momentum budget highlighted the importance of bottom friction to help balance the barotropic pressure gradient. The rest of the momentum budget was likely provided by advective terms. During and after tropical storms, accelerations from wind stress and baroclinic pressure gradients also became influential in the along-basin momentum budget.     

Toxicities of antifouling biocide Irgarol 1051 and its major degraded product to marine primary producers

Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 microug L(-1) Irgarol vs. > 200 microg L(-1) M1; S. costatum, 0.29 microg L(-1) Irgarol vs. 11.32 microg L(-1)M1; and T. pseudonana, 0.41 microg L(-1) Irgarol vs. 16.50 microg L(-1)M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.     

Cobble cam: grain‐size measurements of sand to boulder from digital photographs and autocorrelation analyses

A new application of the autocorrelation grain size analysis technique for mixed to coarse sediment settings has been investigated. Photographs of sand‐ to boulder‐sized sediment along the Elwha River delta beach were taken from approximately 1·2 m above the ground surface, and detailed grain size measurements were made from 32 of these sites for calibration and validation. Digital photographs were found to provide accurate estimates of the long and intermediate axes of the surface sediment (r² > 0·98), but poor estimates of the short axes (r² = 0·68), suggesting that these short axes were naturally oriented in the vertical dimension. The autocorrelation method was successfully applied resulting in total irreducible error of 14% over a range of mean grain sizes of 1 to 200 mm. Compared with reported edge and object‐detection results, it is noted that the autocorrelation method presented here has lower error and can be applied to a much broader range of mean grain sizes without altering the physical set‐up of the camera (～200‐fold versus ～6‐fold). The approach is considerably less sensitive to lighting conditions than object‐detection methods, although autocorrelation estimates do improve when measures are taken to shade sediments from direct sunlight. The effects of wet and dry conditions are also evaluated and discussed. The technique provides an estimate of grain size sorting from the easily calculated autocorrelation standard error, which is correlated with the graphical standard deviation at an r² of 0·69. The technique is transferable to other sites when calibrated with linear corrections based on photo‐based measurements, as shown by excellent grain‐size analysis results (r² = 0·97, irreducible error = 16%) from samples from the mixed grain size beaches of Kachemak Bay, Alaska. Thus, a method has been developed to measure mean grain size and sorting properties of coarse sediments. Copyright © 2009 John Wiley & Sons, Ltd.     

Vulnerability and adaptation to climate-related fire impacts in rural and urban interior Alaska

This paper explores whether fundamental differences exist between urban and rural vulnerability to climate-induced changes in the fire regime of interior Alaska. We further examine how communities and fire managers have responded to these changes and what additional adaptations could be put in place. We engage a variety of social science methods, including demographic analysis, semi-structured interviews, surveys, workshops and observations of public meetings. This work is part of an interdisciplinary study of feedback and interactions between climate, vegetation, fire and human components of the Boreal forest social–ecological system of interior Alaska. We have learned that although urban and rural communities in interior Alaska face similar increased exposure to wildfire as a result of climate change, important differences exist in their sensitivity to these biophysical, climate-induced changes. In particular, reliance on wild foods, delayed suppression response, financial resources and institutional connections vary between urban and rural communities. These differences depend largely on social, economic and institutional factors, and are not necessarily related to biophysical climate impacts per se. Fire management and suppression action motivated by political, economic or other pressures can serve as unintentional or indirect adaptation to climate change. However, this indirect response alone may not sufficiently reduce vulnerability to a changing fire regime. More deliberate and strategic responses may be required, given the magnitude of the expected climate change and the likelihood of an intensification of the fire regime in interior Alaska.     

Urban geology: modelling Coal Measures strata in the nineteenth and twenty‐first centuries

Displays of artificial geological artefacts may be accurate, but not always. Examination of restorations of Coal Measure (Upper Carboniferous, Pennsylvanian) strata in two public displays shows how standards vary. In Crystal Palace Park, London (opened 1854), Coal Measures are accurately displayed and explained in detail. These beds are faulted, and associated features such as nodular mudrocks are displayed, although the density of nodules may be inaccurate. In contrast, in the Dutch National Railway Museum, Het Spoorwegmuseum, Utrecht, the Netherlands (reopened 2005), the portrayal of Pennsylvanian strata (sandstones?) of north‐east England gives them a uniform colour and poor bedding. Although there is a reconstruction of part of a coal mine, coal(?) forms lenses, not beds, and is the same brown hue as the sandstone. Museums and theme parks need to pursue the expertise of knowledgeable local geologists if they are to accurately model geological phenomena.