Bioaccumulation of heavy metals by brown trout (Salmo trutta) in the Arkansas River: importance of food chain transfer

December, 1992.Includes bibliographical references (pages 13-14).This study examined uptake and transfer of heavy metals form benthic invertebrates to brown trout in the Arkansas River. Metals in water, aufwuchs, benthic invertebrates, and fish were measured at stations upstream and downstream from California Gulch (GC). Aufwuchs and benthic invertebrates were highly contaminated by heavy metals downstream from California Gulch. The diet of brown trout at the Arkansas River was dominated by benthic invertebrates. These accounted for 40 to 95 percent of the diet of the brown trout. Differences in prey availability between upstream and downstream resulted in the differences. Ephemeroptera comprised a greater portion of the diet of the fish collected upstream from GC, whereas metal-tolerant organisms were more common in the diet of fish from downstream. Elevated metal levels in water and invertebrates downstream resulted in increased metals in gill and gut tissue; however, metal concentrations in brown trout liver and kidney tissue were generally similar both upstream and downstream. The data suggest that fish regulated metal accumulation. The implications of these findings for the recovery of brown trout populations at the Arkansas River are discussed.Grant no. 14-08-0001-2008, Project no. 10; financed in part by the U.S. Dept. of the Interior, Geological Survey, through the Colorado Water Resources Research Institute

Thresholds, breakpoints, and nonlinearity in freshwaters as related to management.

Nonlinear ecological responses to anthropogenic forcing are common, and in some cases, the ecosystem responds by assuming a new stable state. This article is an overview and serves as the introduction to several articles in this BRIDGES cluster that are directed toward managers interested in dealing with nonlinear responses in freshwaters, particularly streams. A threshold or breakpoint occurs where the system responds rapidly to a relatively small change in a driver. The existence of a threshold can signal a change in system configuration to an alternative stable state, although such a change does not occur with all thresholds. In general, a mechanistic understanding of ecological dynamics is required to predict thresholds, where they will occur, and if they are associated with the occurrence of alternative stable states. Thresholds are difficult to predict, although a variety of univariate methods has been used to indicate thresholds in ecological data. When we applied several methods to one type of response variable, the resulting threshold values varied 3-fold, indicating that more research on detection methods is necessary. Numerous case studies suggest that the threshold concept is important in all ecosystems. Managers should be aware that human actions might result in undesirable rapid changes and potentially an unwanted alternative stable state, and that recovery from that state might require far more resources and time than avoiding entering the state in the first place would have required. Given the difficulties in predicting thresholds and alternative states, the precautionary approach to ecosystem management is probably the most prudent

Response of stream ecosystem structure to heavy metal pollution: context-dependency of top-down control by fish

The stress-gradient hypothesis predicts that biotic interactions within food webs are context dependent, since environmental stressors can attenuate consumer-prey interactions. Yet, how heavy metal pollution influences the impacts of predatory fish on ecosystem structure is unknown. This study was conducted in the Osor stream (Spain), which features a metal (mainly Zn) pollution gradient. We aimed to determine how the responses of benthic communities to the presence and absence of predatory fish interact with environmental stress and to test whether the top-down control of top predators is context dependent. To address these questions, periphyton biomass and macroinvertebrate densities were determined throughout an exclosure/enclosure mesocosm experiment using the Mediterranean barbel (Barbus meridionalis) as a top predator. The monitoring study showed that metal accumulation in periphyton and macroinvertebrates reflected patterns observed in water. The mesocosm study showed that fish predation effects on larval chironomids were not context-dependent and that periphyton biomass was markedly lower in the presence of fish regardless of metal pollution levels. This strong top-down control on periphytic algae was attributed to the foraging behaviour of fish causing bioturbation. In contrast, the top predator removal revealed grazer-periphyton interactions, which were mediated by heavy metal pollution. That is, periphyton benefitted from a lower grazing pressure in the metal-polluted sites. Together, our results suggest that the top-down control by fishes depends more on functional traits (e.g. feeding behaviour) than on feeding guild, and demonstrate the capacity of top predators to modify anthropogenic stressor effects on stream food-web structure.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was supported by the Spanish Ministry of Science, Innovation and Universities (projects CGL2013-43822-R and CGL2016-80820-R, AEI/FEDER/EU) and the Government of Catalonia (ref. 2017 SGR 548 and CERCA Programme). F. Rubio-Gracia and M. Argudo benefitted from a predoctoral fellowship from the University of Girona (IFUdG2017) and the Agency for Management of University and Research Grants (AGAUR) of the Government of Catalonia (2016 FI-B 00284), respectively

Ecological integrity and western water management: a Colorado perspective

Sept. 1995.Includes bibliographical references

Research Progress Reports: Fruit and Vegetable Processing and Technology Division, Department of Horticulture [1967]

Evaluation of snap bean varieties for processing / Wilbur A. Gould and William Hildebolt -- Evaluation of various grape cultivars for processing. I. Table wines ; Recommended fruit varieties for canning and freezing / J. F. Gallander -- Evaluation of tomato varieties for processing / W. A. Gould, J. R. Geisman, C. S. Parrott, J. H. McClelland and W. N. Brown -- The effect of different levels of sugar and acid on the quality of apple fruit juice blends / James Gallander and Harold Stammer -- Epidermal sloughing of snap beans as influenced by processing variables / William Hildebolt and W. A. Gould -- Effect of stannous chloride on the color of glass packed kraut / J. R. Geisman -- Proteins and enzymes in the apple fruit in relation to variety and maturation ; Proteins and enzymes in tomato fruits / Robert L. Clements -- Effect of food additives on quality of canned tomatoes / Wilbur A. Gould -- Effects of selective herbicides on the composition and quality of tomatoes / W. A. Gould, J. R. Geisman, E. K. Alban and John Deppen -- Trace levels of pesticide residues in agricultural commodities in marketing channels / W. A. Gould, J. R. Geisman, E. K. Alban, John Deppen, and P. van Pottlesberghe -- Removal of DDT residues by unit operations in preparing and processing spinach / J. R. Geisman, John Deppen and Benita Yao -- The use of chlorine dioxide in handling and holding mechanically harvested tomatoes / J. R. Geisman, Winston D. Bash, Edwin Schmidt, Jr., Linda Hamrick and W. A. Gould -- Effect of mechanical harvesting and handling of tomatoes on quality of canned tomatoes / Wilbur A. Gould, J. R. Geisman, Edwin Schmidt, Jr., John McClelland and W. N. Brow

Communications Biophysics

Contains reports on four research projects.National Institutes of Health (Grant 5 P01 NS13126-02)National Institutes of Health (Grant 5 K04 NS00113-03)National Institutes of Health (Grant 2 ROI NS11153-02A1)National Science Foundation (Grant BNS77-16861)National Institutes of Health (Grant 5 RO1 NS10916-03)National Institutes of Health (Fellowship 1 F32 NS05327)National Institutes of Health (Grant 5 ROI NS12846-02)National Institutes of Health (Fellowship 1 F32 NS05266)Edith E. Sturgis FoundationNational Institutes of Health (Grant 1 R01 NS11680-01)National Institutes of Health (Grant 2 RO1 NS11080-04)National Institutes of Health (Grant 5 T32 GIM107301-03)National Institutes of Health (Grant 5 TOI GM01555-10

Communications Biophysics

Contains research objectives and summary of research on nine research projects split into four sections.National Institutes of Health (Grant 5 ROI NS11000-03)National Institutes of Health (Grant 1 P01 NS13126-01)National Institutes of Health (Grant 1 RO1 NS11153-01)National Institutes of Health (Grant 2 R01 NS10916-02)Harvard-M.I.T. Rehabilitation Engineering CenterU. S. Department of Health, Education, and Welfare (Grant 23-P-55854)National Institutes of Health (Grant 1 ROl NS11680-01)National Institutes of Health (Grant 5 ROI NS11080-03)M.I.T. Health Sciences Fund (Grant 76-07)National Institutes of Health (Grant 5 T32 GM07301-02)National Institutes of Health (Grant 5 TO1 GM01555-10