Movement ecology: size-specific behavioral response of an invasive snail to food availability

Immigration, emigration, migration, and redistribution describe processes that involve movement of individuals. These movements are an essential part of contemporary ecological models, and understanding how movement is affected by biotic and abiotic factors is important for effectively modeling ecological processes that depend on movement. We asked how phenotypic heterogeneity (body size) and environmental heterogeneity (food resource level) affect the movement behavior of an aquatic snail (Tarebia granifera), and whether including these phenotypic and environmental effects improves advection-diffusion models of movement. We postulated various elaborations of the basic advection diffusion model as a priori working hypotheses. To test our hypotheses we measured individual snail movements in experimental streams at high- and low-food resource treatments. Using these experimental movement data, we examined the dependency of model selection on resource level and body size using Akaike's Information Criterion (AIC). At low resources, large individuals moved faster than small individuals, producing a platykurtic movement distribution; including size dependency in the model improved model performance. In stark contrast, at high resources, individuals moved upstream together as a wave, and body size differences largely disappeared. The model selection exercise indicated that population heterogeneity is best described by the advection component of movement for this species, because the top-ranked model included size dependency in advection, but not diffusion. Also, all probable models included resource dependency. Thus population and environmental heterogeneities both influence individual movement behaviors and the population-level distribution kernels, and their interaction may drive variation in movement behaviors in terms of both advection rates and diffusion rates. A behaviorally informed modeling framework will integrate the sentient response of individuals in terms of movement and enhance our ability to accurately model ecological processes that depend on animal movement.     

A survey of pollutant emission levels in wastewaters and residuals from the petroleum refining industry

This paper summarizes the data made available during the last decade on the subject of emission levels of wastewaters and solid residuals from the petroleum refininf industry. The data for both traditional and priority pollutants from a number of studies are considered. Specific organic compounds which are not traditional pollutants and are not on the priority pollutant list are presented for some cases. A discussion of accuracy, precision, variance, and some causes of variance is presented. Types of wastewater and residual samples for which data are presented include raw waste loadings from Class A through E refineries, loadings of various pollutants across several process units such as dissolved air flotation, activated sludge processes, carbon columns (powdered and granular), and clarifiers, and oily solids (tank bottoms, crude oil, bunker C, and waxy product).