Evaluating the Illinois Stream Valley Segment Model as an Effective Management Tool

Stream habitat assessments are conducted to evaluate biological potential, determine anthropogenic impacts, and guide restoration projects. Utilizing these procedures, managers must first select a representative stream reach, which is typically selected based on several criteria. To develop a consistent and unbiased procedure for choosing sampling locations, the Illinois Department of Natural Resources and the Illinois Natural History Survey have proposed a technique by which watersheds are divided into homogeneous stream segments called valley segments. Valley segments are determined by GIS parameters including surficial geology, predicted flow, slope, and drainage area. To date, no research has been conducted to determine if the stream habitat within a valley segment is homogeneous and if different valley segments have varying habitat variables. Two abutting valley segments were randomly selected within 13 streams in the Embarras River watershed, located in east-central Illinois. One hundred meter reaches were randomly selected within each valley segment, and a transect method was used to quantify habitat characteristics of the stream channel. Habitat variables for each stream were combined through a principal components analysis (PCA) to measure environmental variation between abutting valley segments. A multivariate analysis of variance (MANOVA) was performed on PCA axes 1–3. The majority of abutting valley segments were significantly different from each other indicating that habitat variability within each valley segment was less than variability between valley segments (5.37 ≤ F ≤ 245.13; P ≤ 0.002). This comparison supports the use of the valley segment model as an effective management tool for identifying representative sampling locations and extrapolating reach-specific information.     

Short-Run Allocation of Emissions Allowances and Long-Term Goals for Climate Policy

We summarize the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent had been shrinking at a relatively modest rate of 3–4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million km². Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that the trends towards retreat and thinning will inevitably lead to an eventual loss of all ice in summer, which can be described as a ‘tipping point’ in that the former situation, of an Arctic covered with mainly multi-year ice, cannot be retrieved.     

Influence of global change on phytoplankton and nutrient cycling in the Elbe River

The effects of changing climatic and socioeconomic conditions on the water quality of the Elbe River were investigated using the deterministic model QSim. Since the impact of global change on river water quality marks the endpoint of various processes in the catchment and in the atmosphere, this study was performed within a network of interacting models that determined input parameters for water quality simulations. The development of phytoplankton and nutrient concentrations under conditions of global change was modeled along a 700 km stretch of the river. The simulations revealed a strong, scale-dependent effect of climate change on phytoplankton biomass, leading to a longitudinal shift of the dominating processes (primary productivity vs. respiration) along the river continuum. Under reduced flow, combined with increasing temperature and global radiation, phytoplankton biomass increased and phytoplankton maxima shifted in upstream direction, followed by higher system respiration rates in the adjacent downstream sections. In contrast, higher flow shifted the phytoplankton maximum toward the downstream sections. Even a drastic reduction of phosphorus inputs from anthropogenic sources had only limited influence on algal biomass, due to the ability of algal cells to store phosphorus. A strong reduction in P-inputs especially in the headwaters would be necessary to counterbalance the possible climate-induced effects on algal biomass.     

Evaluation of a novel high throughput screening tool for relative emissions of industrial chemicals used in chemical products

Tens of thousands of chemicals are currently marketed worldwide, but only a small number of these compounds has been measured in effluents or the environment to date. The need for screening methodologies to select candidates for environmental monitoring is therefore significant. To meet this need, the Swedish Chemicals Agency developed the Exposure Index (EI), a model for ranking emissions to a number of environmental matrices based on chemical quantity used and use pattern. Here we evaluate the EI. Data on measured concentrations of organic chemicals in sewage treatment plants, one of the recipients considered in the EI model, were compiled from the literature, and the correlation between predicted emission levels and observed concentrations was assessed by linear regression analysis. The adequacy of the parameters employed in the EI was further explored by calibration of the model to measured concentrations. The EI was found to be of limited use for ranking contaminant levels in STPs; the r² values for the regressions between predicted and observed values ranged from 0.02 (p = 0.243) to 0.14 (p = 0.007) depending on the dataset. The calibrated version of the model produced only slightly better predictions although it was fitted to the experimental data. However, the model is a valuable first step in developing a high throughput screening tool for organic contaminants, and there is potential for improving the EI algorithm.     

Sex-specific nest defense in house sparrows (Passer domesticus) varies with badge size of males

According to indicator models of sexual selection, females can benefit from choosing males with above average epigamic traits, but empirical evidence for such benefits is scarce. Here, we report results from an experiment with 29 pairs of house sparrows (Passer domesticus) where the intensity of nest defense against a mounted mustelid predator was related to the size of the black throat and breast patch (“badge”) in males. Using principal components analysis (PCA), original response variables of both sexes were reduced to two factors: “Approach” to the predator and “Distant warning”. “Approach”, the more risky behavior, increased from small- through medium- to large-badged males and decreased in their females. Since large-badged males have a higher certainty of paternity (i.e. greater benefits from defense) and may be older and more experienced (i.e. incur lower costs), the most likely explanation for male defense intensity increasing with badge size is an improving benefit/cost ratio. The resulting optimal response of their females and evolutionarily stable participation in joint parental care is illustrated by a graphical model. It shows that females would, indeed, benefit directly from choosing large-badged males. This, however, is no proof of a direct evolutionary tie between badge size and paternal behavior, as assumed by indicator models of sexual selection. It may simply represent a spurious relationship, originating from the correlation of badge size and defense with confidence of paternity. Received: 22 September 1997 / Accepted after revision: 3 November 1997