Adaptations in a hierarchical food web of southeastern Lake Michigan

Two issues in ecological network theory are: (1) how to construct an ecological network model and (2) how do entire networks (as opposed to individual species) adapt to changing conditions? We present a novel method for constructing an ecological network model for the food web of southeastern Lake Michigan (USA) and we identify changes in key system properties that are large relative to their uncertainty as this ecological network adapts from one time point to a second time point in response to multiple perturbations. To construct our food web for southeastern Lake Michigan, we followed the list of seven recommendations outlined in Cohen et al. [Cohen, J.E., et al., 1993. Improving food webs. Ecology 74, 252–258] for improving food webs. We explored two inter-related extensions of hierarchical system theory with our food web; the first one was that subsystems react to perturbations independently in the short-term and the second one was that a system's properties change at a slower rate than its subsystems’ properties. We used Shannon's equations to provide quantitative versions of the basic food web properties: number of prey, number of predators, number of feeding links, and connectance (or density). We then compared these properties between the two time-periods by developing distributions of each property for each time period that took uncertainty about the property into account. We compared these distributions, and concluded that non-overlapping distributions indicated changes in these properties that were large relative to their uncertainty. Two subsystems were identified within our food web system structure (p < 0.001). One subsystem had more non-overlapping distributions in food web properties between Time 1 and Time 2 than the other subsystem. The overall system had all overlapping distributions in food web properties between Time 1 and Time 2. These results supported both extensions of hierarchical systems theory. Interestingly, the subsystem with more non-overlapping distributions in food web properties was the subsystem that contained primarily benthic taxa, contrary to expectations that the identified major perturbations (lower phosphorous inputs and invasive species) would more greatly affect the subsystem containing primarily pelagic taxa. Future food-web research should employ rigorous statistical analysis and incorporate uncertainty in food web properties for a better understanding of how ecological networks adapt.     

Round herring (genus Etrumeus) contain distinct evolutionary lineages coincident with a biogeographic barrier along Australia’s southern temperate coastline

Molecular genetic surveys of marine fishes have revealed that some widely distributed species are actually a composite of multiple evolutionary lineages. This is apparent in the round herrings (genus Etrumeus), wherein a globally distributed taxon (Etrumeus sadina Mitchill 1814) has proven to contain at least seven valid taxa, with more likely awaiting discovery. Here, we survey evolutionary lineages of the nominal E. sadina (formerly E. teres, a junior synonym) across the southern temperate zone of Australia, a marine region divided into three biogeographic provinces based primarily on the distribution of intertidal faunas. Results from morphological and mitochondrial DNA data reveal two evolutionary lineages corresponding to eastern and southwestern provinces (d = 0.007 for cytochrome c oxidase subunit I and d = 0.017 for cytochrome b), possibly initiated by the Bassian Isthmus between Australia and Tasmania during low sea-level stands. The Australian round herring is also genetically distinct from the nearest congeneric forms in the Indian and Pacific Oceans, with a corresponding modal difference in gill-raker counts in most cases. Based on these data, we resurrect the title Etrumeus jacksoniensis for the Australian round herring. While the Bassian Isthmus may have initiated the partition of evolutionary lineages within Australia, additional oceanographic and ecological factors must reinforce this separation in order to maintain diagnostic genetic differences along a continuous temperate coastline.     

Moisture as a determinant of habitat quality for a nonbreeding neotropical migratory songbird

Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satellite-derived measure of habitat moisture, we identified a moisture gradient across home ranges of radio-tracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the late-winter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable season-long declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that high-quality habitats may be limited and that there may be competition for them. The habitat-linked variation in performance we observed suggests that habitat limitation could impact individual and population-level processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of high-quality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted.     

Geochemical provenance and spatial distribution of fluoride in groundwater of Mayo Tsanaga River Basin, Far North Region, Cameroon: implications for incidence of fluorosis and optimal consumption dose

The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO₃ signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO₃ type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods.     

Phosphorus cycling in wetland soils: the importance of phosphate diesters

Productivity in P limited peatlands is regulated in part by the turnover of organic phosphates, which is influenced by the chemical nature of the compounds involved. We used solution 31P nuclear magnetic resonance (NMR) spectroscopy to quantify organic and inorganic phosphates in benthic floc (a mixture of plant detritus and algae) and underlying soil from sites along P gradients in hard water and soft water areas of the northern Florida Everglades, USA. Phosphorus-enriched sites were dominated by cattail (Typha spp.), while unenriched sites included sawgrass (Cladium jamaicense Crantz) ridges and open-water sloughs. Phosphorus extracted in a solution containing 0.25 M NaOH and 50 mM EDTA (ethylenediaminetetraacetate) included phosphate, phosphate monoesters, DNA, and pyrophosphate. Signals from phosphate monoesters were consistent with those from alkaline hydrolysis products of RNA and phospholipids formed during extraction and analysis, whereas phytic acid (myo-inositol hexakisphosphate), the most abundant organic phosphate in most soils, was not detected. Phosphorus composition was similar among sites, although neither DNA nor pyrophosphate were detected in extracts of benthic floc from a calcareous slough. DNA was a greater proportion of the P extracted from soil compared to benthic floc, while the opposite was true for pyrophosphate. Research on the cycling of organic phosphates in wetlands focuses conventionally on the turnover of phosphate monoesters, but our results suggest strongly that greater emphasis should be given to understanding the role of phosphate diesters and phosphodiesterase activity.     

The role of sales of new motorcycles in a recent increase in motorcycle mortality rates

INTRODUCTION: The National Highway Traffic Safety Administration (NHTSA) has reported that mortality rates from crashes among motorcycle riders in the United States increased from 21.0 per 100 million motorcycle miles traveled in 1997 to 38.4 per 100 million motorcycle miles traveled in 2003. At the same time, annual domestic sales of new, on-road motorcycles increased from 247,000 in 1997 to 648,000 in 2003. METHOD: This study used data from the NHTSA Fatality Analysis Reporting System and annual sales figures for on-road motorcycles to determine if newer motorcycles were more likely to be involved in fatal crashes and if fatal crashes involving newer motorcycles could account for the mortality increase after 1997. RESULTS: Mortality rates were 7.9, 8.1, 5.4, and 2.9 per 10,000 motorcycles sold for motorcycles <1, 1-3, 4-6, and 7-11 years old, respectively, from 1994 to 2003. Assuming complete registration, the number of motorcycles sold during the 2000-2003 time period accounted for 42.4% of the total number of motorcycles registered in 2003. Motorcycles sold during 2000-2003 were associated with 52.5% of all motorcycle deaths in 2003. The increase in the number of deaths associated with motorcycles less than four years old between 1997 and 2003 accounted for 78.1% of the total increase in motorcyclist deaths over this time period. CONCLUSIONS: Two possible explanations for the association between high sales volumes and mortality rates are: (a) increased exposure from more extensive use of motorcycles when they are new; and (b) inexperience with motorcycle riding or with specific motorcycles. IMPACT ON INDUSTRY: This study suggests that the deaths of growing numbers of motorcyclists are a consequence of the financial success of the motorcycle industry.     

Application of a magnetic extraction technique to assess radionuclide-mineral association in Cumbrian shoreline sediments

An assessment has been made of the association of (239+240)Pu, 241Am and 210Po (in secular equilibrium with 210Pb) with iron minerals using a magnetic extraction technique. Grab samples of beach sand from the Cumbrian (UK) coastline were subjected to successive extractions with an approximately 0.1 T ferrite magnet and an approximately 0.3 T rare-earth magnet procedure to separate magnetic iron oxide minerals. Radionuclide concentrations in the magnetic extracts were enhanced (by approximately 4-6-fold) relative to the residue. Those in the approximately 0.1 T magnet extracts were broadly similar to those in the antiferromagnetic material extracted by the approximately 0.3 T magnet, despite the very large differences in magnetic property values between the two fractions (one to two orders of magnitude). The percentage of magnetic material in terms of mass was small and therefore, the majority of these radionuclides (on average 88%) were associated with the residue. Removal of stable Fe was incomplete. Given that the radionuclides may also bind to paramagnetic (nonmagnetic) Fe minerals, the data were extrapolated by normalising the results to quantitative Fe removal. This yielded average values of 37%, 45% and 46% for (239+240)Pu, 241Am and 210Po(210Pb), respectively, as upper limits for the fraction associated with magnetic + nonmagnetic Fe minerals. There are significant uncertainties inherent in quantifying data from this extraction technique. Nevertheless, it seems reasonable to conclude that radionuclide association with Fe minerals is unlikely to have a significant impact upon the physical dispersion of sediment contaminated by Sellafield discharges in the Irish Sea. However, it may be an important factor in governing Pu redox and redissolution behaviour.     

Comparative analysis of health risk assessments for municipal waste combustors

Quantitative health risk assessments have been performed for a number of proposed municipal waste combustor (MWC) facilities over the past several years. This article presents the results of a comparative analysis of a total of 21 risk assessments, focusing on seven of the most comprehensive methodologies. The analysis concentrates on stack emissions of noncriteria pollutants and is comparative rather than critical in nature. Overall, the risk assessment methodologies used were similar whereas the assumptions and input values used varied from study to study. Some of this variability results directly from differences in site-specific characteristics, but much of it is due to absence of data, lack of field validation, lack of specific guidelines from regulatory agencies, and reliance on professional judgment. The results indicate that carcinogenic risks are more significant than chronic non-carcinogenic risks. In most instances polychlorodibenzodioxins, polychlorodibenzofurans, and cadmium contribute more significantly to the total carcinogenic risk from MWC stack emissions than other contaminants. In addition, the contribution to total risk of all indirect routes of exposure (ingestion and dermal contact) exceeds that of the direct inhalation route for most studies reviewed.     

Environmental impact assessment in the Philippines: 1977–1985

During 1977 a Philippine environmental impact statement (EIS) system was established and the National Environmental Protection Council (NEPC) was formed to develop environmental policy. Several months after its creation, NEPC was given responsibility to certify that proposed projects met EIS system regulations. With few exceptions, this requirement to gain NEPC's approval was not taken seriously by agencies. The poor record of agency compliance with the EIS system is explained by the absence of ‘controls’ to force thorough assessments. Judicial controls are absent. Procedural and evaluative controls are in place, but NEPC has neither the budget nor the political power to enforce them. Although the national EIS system is ineffective, agencies sometimes conduct informal, ad hoc environmental assessments in response to instrumental controls exercised by international funding organizations, professional controls exerted by planners, and public controls brought about by individuals and groups who would be adversely affected by projects.     

CONSIDERATIONS IN CHOOSING THE APPROPRIATE MIX OF URBAN AND AGRICULTURAL NONPOINT POLLUTION CONTROL1

ABSTRACT: In developing strategies for nonpoint pollution control in designated 208 areas, one of the issues facing planners is the relative emphasis which should be placed upon urban versus agricultural non-point control. Five criteria which should be considered in designing an appropriate BMP strategy mix are discussed: 1) BMP cost effectiveness; 2) information and administrative cost; 3) flexibility, which relates to the cost of reversibility given substantial uncertainties; 4) associated effects, both direct and indirect; and 5) acceptability to local jurisdictions and groups. Whatever an evaluation on the basis of the first four criteria may suggest, acceptance of agricultural BMPs will be difficult to achieve, thus favoring urban oriented strategies, unless local revenue sources are developed to offer payments to farmers for BMP adoption.