Nutrient contribution of leaf litter in urban stormwater

This paper investigates the nutrient contribution from leaf litter in urban waterways, using data from a gross pollutant monitoring programme in a 50 ha catchment in an inner-city suburb of Melbourne, Australia. The data indicate that the potential nutrient contribution of stormwater leaf litter (greater than 5 mm) is about two orders of magnitude smaller than the typical nutrient loads in urban stormwater. The results suggest that removing leaf litter from urban waterways will do little to reduce the total stormwater nutrient load.1998 Academic Press     

Factors regulating annual mating success and reproductive success in spotted sandpipers (Actitis macularia)

Summary We investigated factors affecting annual mating success (MS) and reproductive success (RS) of spotted sandpipers (Actitis macularia) from 13 years of a 17-year study at Little Pelican Island, Leech Lake, Minnesota. Analyses were restricted to ages 1–3. Mean annual female MS varied from 1.3 to 2.7 mates, and the MS pattern was indistinguishable from random. However, female MS increased with age and was affected by arrival date, territory size, and beach size. Female RS also increased with age, and number of mates and year effects were the most significant explanatory variables in each age. Older female RS was increased by priority on a territory and presence of a previous mate. Territory size and beach size varied with population density and did not predictably affect RS. The strong year affect on RS was associated with annual variation in sex ratio and predation. Males produce only one successful clutch per year, so MS greater than one is a result of nest loss and does not increase RS. Neither male MS nor RS changed with age. Male reproductive failure rate varied by year. Given that a male produced young, the degree of RS was affected by year, arrival date, priority on a territory, territory size, and beach size. In years with early-season predation, late arrivals had higher RS; territory and beach size effects varied by year. Neither the presence, nor degree, of female care was associated with male RS. Male RS was more subject to annual environmental variability than was female RS, probably because of relatively low annual potential RS among males.Offprint requests to: L.W. Oring at the current address     

Modeling and source apportionment of diesel particulate matter

The fine and ultra fine sizes of diesel particulate matter (DPM) are of greatest health concern. The composition of these primary and secondary fine and ultra fine particles is principally elemental carbon (EC) with adsorbed organic compounds, sulfate, nitrate, ammonia, metals, and other trace elements. The purpose of this study was to use an advanced air quality modeling technique to predict and analyze the emissions and the primary and secondary aerosols concentrations that come from diesel-fueled sources (DFS). The National Emissions Inventory for 1999 and a severe southeast ozone episode that occurred between August and September 1999 were used as reference. Five urban areas and one rural area in the Southeastern US were selected to compare the main results. For urban emissions, results showed that DFS contributed (77.9%+/-8.0) of EC, (16.8%+/-8.2) of organic aerosols, (14.3%+/-6.2) of nitrate, and (8.3%+/-6.6) of sulfate during the selected episodes. For the rural site, these contributions were lower. The highest DFS contribution on EC emissions was allocated in Memphis, due mainly to diesel non-road sources (60.9%). For ambient concentrations, DFS contributed (69.5%+/-6.5) of EC and (10.8%+/-2.4) of primary anthropogenic organic aerosols, where the highest DFS contributions on EC were allocated in Nashville and Memphis on that episode. The DFS contributed (8.3%+/-1.2) of the total ambient PM(2.5) at the analyzed sites. The maximum primary DPM concentration occurred in Atlanta (1.44 microg/m(3)), which was 3.8 times higher than that from the rural site. Non-linearity issues were encountered and recommendations were made for further research. The results indicated significant geographic variability in the EC contribution from DFS, and the main DPM sources in the Southeastern U.S. were the non-road DFS. The results of this work will be helpful in addressing policy issues targeted at designing control strategies on DFS in the Southeastern U.S.     

Fatal and serious collisions involving pedal cyclists and trucks in London between 2007 and 2011

Objective: Increased numbers of people riding pedal cycles have led to a greater focus on pedal cycle safety. The aim of this article is to explore factors that are associated with fatal and a small number of serious-injury pedal cyclist crashes involving trucks that occurred in London between 2007 and 2011.

Methods: Data were collected from police collision files for 53 crashes, 27 of which involved a truck (≥3.5 tonnes) and a pedal cycle. A systematic case review approach was used to identify the infrastructure, vehicle road user, and management factors that contributed to these crashes and injuries and how these factors interacted.

Results: Trucks turning left conflicting with pedal cyclists traveling straight ahead was a common crash scenario. Key contributory factors identified included the pedal cyclists not being visible to the truck drivers, road narrowing, and inappropriate positioning of pedal cyclists.

Conclusions: Crashes involving trucks and pedal cyclists are complex events that are caused by multiple interacting factors; therefore, multiple measures are required to prevent them from occurring.     

Effects of temporary starvation on larvae of the sea star Asterina miniata

Patchy food distribution may force temporary starvation conditions on planktonic larvae. This potential food limitation may affect survivorship, duration of larval period, and post-metamorphic succes. In this study, larvae of the asteroid Asterina miniata were subjected to temporary food deprivation of several durations and at different stages. Developmental effects were documented by quantification of larval stage, total length, time to metamorphosis, initial juvenile radius, range of settling times, and percent survival to metamorphosis. All starved treatments were significantly affected in settling time and most in percent survival. However, larvae starved later in development demonstrated tremendous tolerance of food deprivation (e.g. the total number of settlers in the treatment starved for 28 d was not significantly different from the fed control). Survival was lower in treatments starved earlier in development than those starved later. Food is apparently required until late in larval development to facilitate metamorphosis. The range of settling times was large; for example, the continuously-fed control treatment produced juveniles from Days 58 through 136. Temporary starvation had no effect on initial juvenile radius.     

Physiological responses of Nodularia harveyana to osmotic stress

The effects of salinity stress on biomass yield, photosynthetic O₂ evolution and nitrogenase activity were investigated using axenic cultures of Nodularia harveyana (Thwaites) Thuret originally isolated from a salt marsh at Gibraltar Point, Lincolnshire, UK in 1971 and studied in this laboratory in 1983. Biomass yields, as chlorophyll a per culture, were highest in the 0 to 100% seawater (0 to 35 sea salt) range with negligible growth in 200% seawater; growth on NH ₄ ⁺ was greater than on N₂ and NO ₃ ^- , which did not differ significantly from each other. In short-term experiments, photosynthetic O₂ evolution remained high at salinities up to 150% seawater (52.5 sea salt); nitrogenase activity remained high at salinities up to 100% seawater (35 sea salt). The major internal low molecular weight carbohydrate which accumulated in response to increased salinity was sucrose, the levels of which fluctuated markedly and rapidly in response to salinity change.     

A multidimensional continuum model of fish behavior

A numerical model for the simulation and study of fish behavior is presented. The model, based on continuous representations in both biological and spatial dimensions, has been developed as part of a large Norwegian arctic ecosystems modeling project directed by Professor Jens G. Balchen of the University of Trondheim, Norway. The model describes the migratory behavior of fish, and is capable of incorporating a variety of hypothesized driving forces, such as food density, temperature, light, direction and magnitude of ocean currents, and local fish density. The model relies on standard finite difference numerical methods for solution of the continuum transport equations, and a gradient search conceptualization to determine fish taxis. Two driving forces, food and temperature fields, are used to provide a demonstration of the potentials of the proposed modeling methodology.     

Contribution of Roads to Forest Fragmentation in the Rocky Mountains

The contribution of roads to forest fragmentation has not been adequately analyzed. We quantified fragmentation due to roads in a 30,213-ha section of the Medicine Bow-Routt National Forest in sout heastern Wyoming with several indices of landscape structure using a geographic information system. The number of patches, mean patch area, mean interior area, mean area of edge influence, mean patch perimeter, total perimeter, and mean patch shape identified patch- and edge-related landscape changes. Shannon-Wiener diversity, dominance, contagion, contrast, and angular second moment indicated effects on landscape diversity and texture. Roads added to forest fragmentation more than clearcuts by dissecting large patches into smaller pieces and by converting forest interior habitat into edge habitat. Edge habitat created by roads was 1.54–1.98 times the edge habitat created by clearcuts. The total landscape area affected by clearcuts and roads was 2.5–3.5 times the actual area occupied by these disturbances. Fragmentation due to roads could be minimized if road construction is minimized or rerouted so that its fragmentation effects are reduced. Geographic information system technology can be used to quantify the potential fragmentation effects of individual roads and the cumulative effects of a road network on landscape structure.     

Osmoacclimation in Enteromorpha intestinalis: long-term effects of osmotic stress on organic solute accumulation

The fate of the protease trypsin in intestines of individual herring larvae Clupea harengus L. was studied following digestion of the copepod Acartia tonsa. Trypsin was retained in the intestine during two consecutive pulses of feeding and defaecation of copepods. Quantification of herring trypsin in digested, defaecated copepods showed that ca. 1% of larval intestinal enzyme was defaecated along with 1 to 3 copepods. Following ingestion of a single meal, the level of intestinal trypsin post-ingestion declined to pre-ingestion levels within 1 to 2 d of starvation. All enzyme data thus indicated that trypsin, released in response to ingestion of a meal, was retained. In addition, analysis of fed subgroups of starved larvae clearly indicated that release of trypsin from the pancreas stopped after 6 to 8 d of starvation. As the fish still contained substantial amounts of trypsinogen, the underlying cause might be defective release mechanisms. Daily secretion of trypsin and processes responsible for enzyme retention in the gut are discussed. Assimilation efficiency in herring larvae was estimated for copepodite prey. Average carbon assimilation was 90%.     

Consequences of ignoring dispersal variation in network models for landscape connectivity

Habitat loss and fragmentation can negatively influence population persistence and biodiversity, but the effects can be mitigated if species successfully disperse between isolated habitat patches. Network models are the primary tool for quantifying landscape connectivity, yet in practice, an overly simplistic view of species dispersal is applied. These models often ignore individual variation in dispersal ability under the assumption that all individuals move the same fixed distance with equal probability. We developed a modeling approach to address this problem. We incorporated dispersal kernels into network models to determine how individual variation in dispersal alters understanding of landscape-level connectivity and implemented our approach on a fragmented grassland landscape in Minnesota. Ignoring dispersal variation consistently overestimated a population's robustness to local extinctions and underestimated its robustness to local habitat loss. Furthermore, a simplified view of dispersal underestimated the amount of habitat substructure for small populations but overestimated habitat substructure for large populations. Our results demonstrate that considering biologically realistic dispersal alters understanding of landscape connectivity in ecological theory and conservation practice.