Seasonal variation in paediatric blood lead levels in Syracuse,NY, USA

Venous blood lead values for 2,633 children aged 0–4 years in Syracuse, New York, collected between 1 April 1992 and 31 March 1993 were summarised by census tract for study of geographic variability. A demographic exposure model is presented showing housing stock and SES (socioeconomic status) parameters as the most significant predictor variables. A seasonal trend in blood lead levels was observed with late summer values about 40% higher than late winter values for census tracts with the highest geometric mean PbB levels. Seasonal variation is compared with a biokinetic uptake model to examine hypotheses about temporal variations in soil and dust lead exposure patterns.     

Comparing geographic boundaries in songbird demography data with vegetation boundaries: a new approach to evaluating habitat quality

To plan for the habitat needs of forest songbirds of conservation concern, managers need to understand how spatial heterogeneity in forest conditions influences habitat quality. I used difference boundary detection (wombling) and spatially constrained clustering to delineate boundaries in various combinations of four forest vegetation variables (understory height, understory density, percent deciduous vs. conifer understory, and percent canopy closure) in two Michigan northern hardwood forests. My goal was to identify vegetation boundaries that corresponded with boundaries in an understory-dependent songbird’s distribution, and with boundaries in demographic measures for this songbird that indicate habitat quality (e.g., occupancy by older vs. yearling males, reproductive success). Both forests were actively-managed, mature stands: The first site (78 ha) was heavily deer-browsed (HB), with many browse-resistant conifers in the understory, and the second (62 ha) was less-browsed (LB), with deciduous-dominated understory. I compared the vegetation difference and cluster boundaries to difference boundaries based on 6 years of distribution and demographic data for black-throated blue warblers (Dendroica caerulescens). At the HB site, warbler boundaries overlapped strongly with vegetation boundaries that included all four variables, and clustering effectively divided the habitat into areas with different warbler occupancy and demographic characteristics. At the LB site, warbler distribution showed high overlap with difference and cluster boundaries based on just the height and density of understory vegetation, and cluster boundaries again effectively partitioned the study area into sites that varied in habitat quality. Thus, geographic boundary analysis is likely to be a useful tool for identifying key vegetation variables for management, and for delineating clusters (habitat patches) within sites that capture differences in habitat quality.

How should surface elevation table data be analyzed? A comparison of several commonly used analysis methods and one newly proposed approach

Environmental and Ecological Statistics - The use of surface elevation table (SET) instruments to monitor elevation changes at low elevation coastal locations has steadily increased in recent...     

Biotic resistance via granivory: establishment by invasive, naturalized, and native asters reflects generalist preference

Escape from specialist natural enemies is frequently invoked to explain exotic plant invasions, but little attention has been paid to how generalist consumers in the recipient range may influence invasion. We examined how seed preferences of the widespread generalist granivore Peromyscus maniculatus related to recruitment of the strongly invasive exotic Centaurea stoebe and several weakly invasive exotics and natives by conducting laboratory feeding trials and seed addition experiments in the field. Laboratory feeding trials showed that P. maniculatus avoided consuming seeds of C. stoebe relative to the 12 other species tested, even when seeds of alternative species were 53-94% smaller than those of C. stoebe. Seed addition experiments conducted in and out of rodent exclosures revealed that weakly invasive exotics experienced relatively greater release from seed predation than C. stoebe, although this was not the case for natives. Seed mass explained 81% of the variation in recruitment associated with rodent exclusion for natives and weak invaders, with larger-seeded species benefiting most from protection from granivores. However, recruitment of C. stoebe was unaffected by rodent exclusion, even though the regression model predicted seeds of correspondingly large mass should experience substantial predation. These combined laboratory and field results suggest that generalist granivores can be an important biological filter in plant communities and that species-specific seed attributes that determine seed predation may help to explain variation in native plant recruitment and the success of exotic species invasions.     

Acetylcholinesterase activity in Corbicula fluminea Mull., as a biomarker of organophosphate pesticide pollution in Pinacanauan River, Philippines

Organophosphates are known to inhibit the enzyme acetylcholinesterase. In this study, the AChE activity from the total soft tissues of Corbicula fluminea Mull. was used as a biomarker of organophosphate pollution in Pinacanauan River. Clams were collected from two different sites and at different seasons of the year. A colorimetric assay on the total soft tissues of the clams showed a directly proportional relationship between enzyme activity and condition of the riverine system. In vitro experiments on the total soft tissue, adductor muscles, digestive glands, and gills were conducted to assess the degree of localization of AChE as well as the sensitivity and tolerance of the enzymes in these tissues to varying concentrations of malathion. The degree of enzyme localization from highest to lowest is as follows: adductor muscle > gills > digestive gland whereas sensitivity to OP from greatest to least is: gills > adductor muscles > digestive gland.     

Diets of some deep-sea brittle stars in the Rockall Trough

The stomachs of 1 165 individuals of the species Ophiacantha bidentata (Retzius), Ophiactis abyssicola (M. Sars), Ophiocten gracilis (O. Sars), Ophiura irrorata (Lyman), O. ljungmani (Lyman) and Ophiomusium lymani Wyville Thomson, collected from the general area of the Rockall Trough from 1973 to 1983, were examined; 47% contained material. This varied in nature and in volume between individuals, but overall, the diets of the 6 species showed quite high similarity. The few differences evident are interpreted as reflecting different lifestyles. Except for Ophiocten gracilis, the probably motile, epifaunal species (Ophiura irrorata, O. ljungmani and Ophiomusium lymani) showed the greatest variety in items, and the lowest similarity with the remaining species; they are probably unselective omnivores, eating whatever small prey or organic detritus they are able to find. Ophiacantha bidentata and Ophiactis abyssicola showed both the least dietary variety, and the highest similarity to each other. This probably reflects their more sedentary lifestyle, feeding on current-borne particles and small prey from perches on sessile fauna. The stomach contents of Ophiocten gracilis consisted mainly of amorphous organic material and mineral particles, indicating a microphagous feeding mechanism. With O. gracilis, the proportion of stomachs with food decreased markedly in summer, this coinciding with seasonal gonadal development when stomachs frequently appeared ruptured or compressed. The possible importance of seasonal sedimentation of fast-sinking particulates from the surface is discussed in relation to finds of flocculent organic material, often containing diatom frustules, in stomachs of all 6 species. Some doubts remain as to whether our results are biased by specimens egesting stomach contents on capture. As in shallow water, deep-sea ophiuroids seem to be trophic generalists lacking in dietary specialization. Brief notes on parasites encountered are also given.     

Response of hydrothermal vent vestimentiferan <Emphasis Type="Italic">Riftia pachyptila</Emphasis> to differences in habitat chemistry

Vestimentiferan tubeworms, which rely on intracellular sulfide-oxidizing autotrophic bacteria for organic carbon, flourish at deep-sea hydrothermal vents despite the erratic nature of their habitat. To assess the degree to which differences in habitat chemistry (sulfide, pH/CO₂) might impact host and symbiont metabolic activity, Riftia pachyptila tubeworms were collected from habitats with low (H₂S < 0.0001 mM) and high (up to 0.7 mM) sulfide concentrations. The elemental sulfur content of the symbiont-containing trophosome organ was lower in specimens collected from the low-sulfide site. Symbiont abundance, RubisCO activity, and trophosome carbon fixation rates were not significantly different for individuals collected from low- versus high-sulfide habitats. Carbonic anhydrase activities were higher in the anterior gas exchange organs of R. pachyptila from the low-sulfide habitat. Despite large differences in habitat chemistry, symbiont abundance and autotrophic potential were consistent, while the host appears to tailor carbonic anhydrase activity to environmental CO₂ availability.