Understanding effects of changes in land use, environmental parameters, habitat characteristics on the Great Basin aquatic invertebrates using ecological stoichiometric theory

Land use and land cover change affects the ecological health of aquatic organisms. Such changes have been explained using ecological stoichiometric theories in temperate and humid ecosystems, but not on aquatic organisms in semi-arid watersheds. Semi-arid streams in the Great Basin are characterized by high gradients in water temperature, discharge and land use. This can result in a high variability of nutrient loading, which likely alters the elemental composition of food web components. In eight sub-watersheds differing in land use, we used multiple regression analysis followed by Akaike’s Information Criterion (AIC) to determine which predictor variable(s) best explains the variability in two basal food resources, seston and periphyton and BMIalong Walker River in California and Nevada. We have shown that elemental composition of basal food resources are best explained by land use and associated differences in SRP, DOC, and stream water N:P ratios. In contrast, BMI elemental stoichiometry was rather related to taxonomic identity and body mass. Therefore both parameters should always be taken into account when addressing land use effects on resource-consumer stoichiometry. Food-related differences in some of the BMI taxa support previous studies that consumer can deviate from strict homeostasis. Consumer-resource imbalances were related to feeding mode and were higher for collector-gatherer than for scraper and collector-