Feedbacks between bivalve density, flow, and suspended sediment concentration on patch stable states

We explore the role of biophysical feedbacks occurring at the patch scale (spatial scale of tens of meters) that influence bivalve physiological condition and affect patch stability by developing a numerical model for the pinnid bivalve, Atrina zelandica, in cohesive sediments. Simulated feedbacks involve bivalve density, flow conditions (assumed to be primarily influenced by local water depth and peak current speed), suspended sediment concentration (evaluated through a balance between background concentration, deposition, and erosion), and changes in the physiology of Atrina derived from empirical study. The model demonstrates that high bivalve density can lead to skimming flow and to a concomitant decrease in resuspension that will affect suspended sediment concentration over the patch directly feeding back on bivalve physiology. Consequently, for a given flow and background suspended sediment load, the stability of a patch directly depends on the size and density of bivalves in the patch. Although under a range of conditions patch stability is ensured independently of bivalve density, simulations clearly indicate that sudden changes in bivalve density or suspended sediment concentration can substantially affect patch structure and lead to different stable states. The model highlights the role of interactions between organisms, flow, and broader scale environmental conditions in providing a mechanistic explanation for the patchy occurrence of benthic suspension feeders.     

Range-restricted, specialist Bornean butterflies are less likely to recover from ENSO-induced disturbance

The forest fires induced by the El Ni?o Southern Oscillation (ENSO) in 1997-1998 resulted in the temporary extirpation of more than 100 lowland butterfly species at a forest site in Borneo. Species with more restricted ranges were less likely to recover over the following four years. Matched-pair analyses revealed that species with lower initial abundances, restricted geographic ranges, and more specialized larvae were less likely to return. Specialization differed predictably between the (more generalist) wide-range and (more specialized) restricted-range species in our data set, and both geographic range and level of specialization were important in multivariate models. These are the first observations directly linking extent of occurrence, ecological specialization, and observed recovery following local extirpation. If recovery time exceeds the frequency of disturbance, local extirpation can lead to local extinction. Given that ENSO-induced disturbances are increasing in frequency, in severity, and in geographic scale, these results suggest that specialist species with restricted geographic ranges could be at particularly high risk of global extinction.     

The fitting of general force-of-infection models to wildlife disease prevalence data

Researchers and wildlife managers increasingly find themselves in situations where they must deal with infectious wildlife diseases such as chronic wasting disease, brucellosis, tuberculosis, and West Nile virus. Managers are often charged with designing and implementing control strategies, and researchers often seek to determine factors that influence and control the disease process. All of these activities require the ability to measure some indication of a disease's foothold in a population and evaluate factors affecting that foothold. The most common type of data available to managers and researchers is apparent prevalence data. Apparent disease prevalence, the proportion of animals in a sample that are positive for the disease, might seem like a natural measure of disease's foothold, but several properties, in particular, its dependency on age structure and the biasing effects of disease-associated mortality, make it less than ideal. In quantitative epidemiology, the "force of infection," or infection hazard, is generally the preferred parameter for measuring a disease's foothold, and it can be viewed as the most appropriate way to "adjust" apparent prevalence for age structure. The typical ecology curriculum includes little exposure to quantitative epidemiological concepts such as cumulative incidence, apparent prevalence, and the force of infection. The goal of this paper is to present these basic epidemiological concepts and resulting models in an ecological context and to illustrate how they can be applied to understand and address basic epidemiological questions. We demonstrate a practical approach to solving the heretofore intractable problem of fitting general force-of-infection models to wildlife prevalence data using a generalized regression approach. We apply the procedures to Mycobacterium bovis (bovine tuberculosis) prevalence in bison (Bison bison) in Wood Buffalo National Park, Canada, and demonstrate strong age dependency in the force of infection as well as an increased mortality hazard in positive animals.     

Natural and anthropogenic metal inputs to soils in urban Uppsala, Sweden

Urban soils are complex systems due to human activities that disturb the natural development of the soil horizons and add hazardous elements. Remediation projects are common in urban areas and guideline values are set to represent a desired level of elements. However, the natural content of trace elements may not always equal the desired levels. In this study, an attempt is made to distinguish between metals that are present in the soil due to natural origins and to anthropogenic origins. Seventy-five soil samples of the 0–5, 5–10 and 10–20 cm layers were collected from 25 sites in urban areas of Uppsala City and analysed for aluminium (Al), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), tungsten (W) and zinc (Zn) using aqua regia for digestion. In order to highlight elements of geological origin, the results were compared to a similar study carried out in Gothenburg City, which has about three times as many inhabitants as Uppsala and has a more industrial history. A cluster analysis was also performed to distinguish between elements of natural and anthropogenic origin. Contents of As, Al, Fe, Cr, Ni, Mn and W in Uppsala were concluded to be of mainly geological origin, while contents of Cd, Cu, Zn, Pb and Hg seemed to have been impacted upon by mainly urban activities.     

Relative toxicity of spent lubricant oil and detergent against benthic macro-invertebrates of a west African estuarine lagoon

The relative acute toxicity of spent lubricant oil and detergent was evaluated against hermit crab, Clibanarius africanus (Aurivillus) and periwinkle, Tympanotonus fuscatus (L) from the Lagos lagoon in laboratory bioassays. Based on the derived toxicity indices, the detergent (96 hr LC50 = 5.77ml/l) was found to be 1.73 times more toxic than spent engine oil (96 hr LC50 = 10.01 ml/l) when acting singly against C africanus and 18.73 times (96 hr LC50-48.67 ml/l) more toxic (96 hr LC50 = 911.57 ml/l) when acting singly against T. fuscatus. On the basis of the computed susceptibility factors, C. africanus was found to be about eight times and ninety-one times more susceptible to the toxic effect of detergent and spent lubricant oil respectively. The randomized analysis of variance (ANOVA) showed that there was significant difference (Fcal 58.83 Ftab 3.87; DF 13; p > 0.05) between all treatments of spent lubricant oil and detergent during the 96 hr exposure period of test animals. At 5% level of significance the Student Neuman-Keuls (SNK) test further revealed significant differences in the mean mortality response of test animals exposed to toxicants at all concentrations and untreated control. The results obtained in this study suggest that the estuarine benthic macroinvertebrates, which play key roles in the environment, may serve as useful in-situ sentinels for biomonitoring studies of petroleum pollutants in fragile aquatic ecosystems such as the Lagos lagoon.     

First Jurassic Choristodera from Asia

Although choristoderes have a good Lower Cretaceous record in Asia, they have never previously been recorded from Jurassic deposits. Here we describe fragmentary vertebral material referable to Choristodera indet. from the Middle Jurassic Balabansai Svita of the Fergana Valley, Kyrgyzstan. This provides a significant range extension for the group in Asia and shows that choristoderes already had a Pan-Laurasian distribution in the Jurassic.     

Occurrence and accumulation of organochlorine contaminants in swordfish from Mediterranean Sea: a case study

Polychlorinated biphenyls including coplanar congeners and DDT compounds were measured in the liver of a teleost species: namely, Xiphias gladius. PCB concentrations (median: 1121 ng/g lipid wt) were comparable with DDT levels (median: 1236 ng/g lipid wt). PCBs revealed a profile dominated by hexa-, penta- and heptachlorinated congeners. Among DDTs, the compound in the greatest concentration was p,p'-DDE, representing 70% of the total DDT burden, followed by o,p'-DDT>p,p'-DDT>p,p'-DDD=o,p'-DDD. Mean total 2,3,7,8-TCDD equivalent of five coplanar PCBs was 8.83 pg/g lipid weight. The isomers with higher TEQs values were non-ortho congeners than mono-ortho ones.     

Accumulation of chromium (VI) from aqueous solutions using water lilies (Nymphaea spontanea)

This study describes an investigation using tropical water lilies (Nymphaea spontanea) to remove hexavalent chromium from aqueous solutions and electroplating waste. The results show that water lilies are capable of accumulating substantial amount of Cr(VI), up to 2.119 mg g(-1) from a 10 mg l(-1) solution. The roots of the plant accumulated the highest amount of Cr(VI) followed by leaves and petioles, indicating that roots play an important role in the bioremediation process. The maturity of the plant exerts a great effect on the removal and accumulation of Cr(VI). Plants of 9 weeks old accumulated the most Cr(VI) followed by those of 6 and 3 weeks old. The results also show that removal of Cr(VI) by water lilies is more efficient when the metal is present singly than in the presence of Cu(II) or in waste solution. This may be largely associated with more pronounced phytotoxicity effect on the biochemical changes in the plants and saturation of binding sites. Significant toxicity effect on the plant was evident as shown in the reduction of chlorophyll, protein and sugar contents in plants exposed to Cr(VI) in this investigation.     

Brominated flame retardant concentrations and trends in abiotic media

BFR burdens in abiotic media have been less studied than in biota, despite their essential value as an aide to identifying sources, temporal and geographic trends and exposure routes. Many polymer products consist of several percent by weight of BFRs. Global trade in these can result in rapid and wholesale BFR movement. Loss from in-use products of nonreactive BFRs may be important, particularly in respect to indoor exposure. In the case of BDE-209, discharges from publicly owned treatment works may be substantial. BFR burdens in air, water and sewage sludge respond rapidly to changes in environmental BFR inputs. PBDEs have been the most widely studied. In many locales PBDE burdens in these media now surpass those of PCBs. Air and water near sources and urban areas are typically enriched relative to rural locales. The more volatile PBDEs dominate in the vapor phase, while BDE-209 typically predominates on particulates. Evidence exists for long-range transport of the more volatile PBDEs. A greater diversity of BFRs (mostly PBDEs, HBCD and TBBP-A) has been detected in sewage sludges. Land application of these sludges on agricultural fields is one conduit for soil contamination. In general, environmental concentrations of BDE-209 appear to be increasing, while penta-BDE burdens in Europe may have peaked. Sediments function as longer-term integrators of environmental burdens. Concentrations of common BFRs therein may be substantial near point sources. Evidence for debromination in the environment has been limited to date. However, some laboratory and field observations suggest it is possible to a limited extent.