Swanson sm (41 resultados)

Filtrar la búsqueda

  • Libros (41)

a

Intervalo de precios personalizado (EUR)

a

  • Idioma: Inglés

    Editorial: Glimmer Train Press, Inc., 2016

    1595530452 / 9781595530455

    • Tapa blanda

    Librería: ThriftBooks-Atlanta, AUSTELL, GA, Estados Unidos de AmericaThriftBooks-Atlanta

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Usado - Aceptable

    EUR 14,72

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 1 disponible

    Paperback. Condición: Good. No Jacket. Pages can have notes/highlighting. Spine may show signs of wear. ~ ThriftBooks: Read More, Spend Less. Jane Zwinger (ilustrador).

  • Idioma: Inglés

    Editorial: Glimmer Train Press, Inc., 2016

    1595530452 / 9781595530455

    • Tapa blanda

    Librería: Arbor Scout, Ann Arbor, MI, Estados Unidos de AmericaArbor Scout

    Vendedor de 4 estrellas
    Contactar con el vendedor

    Condición: Usado - Bueno

    EUR 17,39

    Envío por EUR 5,33 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 1 disponible

    Condición: Used: Very Good. Jane Zwinger (ilustrador).

  • Condición: Usado

    EUR 45,74

    Envío por EUR 11,55 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 1 disponible

    Añadir al carrito

    Soft cover. Condición: Good, Vintage. No Dust Jacket. -- 89 Pages. Firmly Readable. Paperback : Vintage Soft Cover Edition In Good Clean Condition, A Typical Used Book With Some Slight Wear To Edges And Spine. Used, Good Over All. Has Sale Sticker Inside Back Cover. As To Be Expected With Used Books, There May Be Some Minor Bumping, Creases, And/Or Scuffs. Overall A Good Copy, Excellent Resource And Reading Enjoyment. ~ We Appreciate Your Consideration Of One Of Our Books, Art Prints Or Novelty Items. We Strive To Offer Fast, Courteous And Professional Service To All Our Patrons. Reading Is One Of Life's Great Pleasures. Please Inquire For Further Details, Our Items Arrive Shrink Wrapped And Well Packed. ~ Thank You For Viewing And Stopping By. Book.…

  • Idioma: Italiano

    Editorial: IL LEONE VERDE, 2025

    8865805404 / 9788865805404

    • Tapa dura

    Librería: Libreria della Natura, Milano, MI, ItaliaLibreria della Natura

    Vendedor de 4 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 18,00

    Envío por EUR 36,00 
    Se envía de Italia a Estados Unidos de America

    Cantidad disponible: 1 disponible

    LEGATURA EDITORIALE. Condición: NUOVO. Il libro è illustrato in maniera originalissima ed estremamente suggestiva usando solo il bianco/nero e il giallo oro; presenta una successione di quadri ambientali incatenati da una filastrocca che inizia con Ecco la chiave di casa e riprende una notissima filastrocca tradizionale inglese. I diversi ambienti si allargano in successione partendo dalla camera da letto per giungere al sole e al cielo, in un crescendo di luce che inonda la casa. E la notte non fa più paura. Età di lettura: da 4 anni. Krommes, Beth (ilustrador).…

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: PBShop.store UK, Fairford, GLOS, Reino UnidoPBShop.store UK

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 148,35

    Envío por EUR 4,88 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 9 disponibles

    PAP. Condición: New. New Book. Shipped from UK. Established seller since 2000.

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: PBShop.store UK, Fairford, GLOS, Reino UnidoPBShop.store UK

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 148,35

    Envío por EUR 4,88 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 7 disponibles

    PAP. Condición: New. New Book. Shipped from UK. Established seller since 2000.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: GreatBookPrices, Columbia, MD, Estados Unidos de AmericaGreatBookPrices

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 151,52

    Envío por EUR 2,35 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 10 disponibles

    Condición: New.

  • Idioma: Inglés

    Editorial: IWA Publishing, London, 2004

    1843397196 / 9781843397199

    • Tapa blanda
    • Primera edición

    Librería: Grand Eagle Retail, Bensenville, IL, Estados Unidos de AmericaGrand Eagle Retail

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 153,95

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 1 disponible

    Paperback. Condición: new. Paperback. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study, which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives addressed in this report are: (1) review and critique the existing body of knowledge for multiple stressors; (2) develop a searchable, annotated bibliography of multiple stressor research; and, (3) identify gaps in the body of knowledge. A rigorous, theoretical basis for the prediction of multiple stressor effects could not be developed from the literature on experimental studies of multiple stressor effects in aquatic ecosystems. Despite the wealth of observational data, the existence of several useful tools for interpretation of cause/effect relationships (including formal Stressor Identification methods), and the studies reviewed in this report, there are no tools that allow a confident, a priori, prediction of ecosystem response to multiple stressors. The current literature provides, at best, a series of site-specific glimpses of the response of ecological communities and ecosystems to multiple stressors. There is seldom, if ever, any reference to a more generalized model of multiple stressor effects apart from the discussion of the expectations regarding additivity versus synergism. Many articles that purport to be multiple stressor studies do not go beyond an inventory of the various stresses and upsets affecting the ecosystem, without attempting to assess the interactions among them. The objectives addressed in this report are: review and critique the body of knowledge for multiple stressors; develop a searchable, annotated bibliography of multiple stressor research; and, identify gaps in the body of knowledge. Shipping may be from multiple locations in the US or from the UK, depending on stock availability. …

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: PBShop.store US, Wood Dale, IL, Estados Unidos de AmericaPBShop.store US

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 154,04

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 9 disponibles

    PAP. Condición: New. New Book. Shipped from UK. Established seller since 2000.

  • Idioma: Inglés

    Editorial: IWA Publishing, London, 2004

    1843397072 / 9781843397076

    • Tapa blanda
    • Primera edición

    Librería: Grand Eagle Retail, Bensenville, IL, Estados Unidos de AmericaGrand Eagle Retail

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 154,17

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 1 disponible

    Paperback. Condición: new. Paperback. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives of the study are to develop a flexible and scientifically defensible conceptual model of the environmental effects of multiple stressors on river and stream ecosystems; develop a study design to test the conceptual model of multiple stressor effects; and, document the process used to arrive at the conceptual model. The multiple stressor conceptual model includes two main components: (1) a diagram that portrays the main features of the study team's understanding of how multiple stressors would interact and the nature of the effects; and (2) a series of three testable risk hypotheses. These two components follow the guidance provided by the U.S. EPA for ecological risk assessment. The proposed conceptual model encompasses the following key assumptions: interactions between the stressor and the ecosystem are dependant upon the existing baseline conditions; for each stressor/baseline combination there will theoretically be a functional and a structural response; effects on habitat are caused by structural or functional responses to stressors; and effects on habitat can cause structural or functional responses. A model for ecosystem response, this book combines the subsidy/toxicant dichotomy into a single relationship, addresses a long-standing controversy about whether functional or structural changes are expected first for any given situation, and leads to interesting hypotheses. Shipping may be from multiple locations in the US or from the UK, depending on stock availability. …

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: PBShop.store US, Wood Dale, IL, Estados Unidos de AmericaPBShop.store US

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 154,18

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 10 disponibles

    PAP. Condición: New. New Book. Shipped from UK. Established seller since 2000.

  • Idioma: Inglés

    Editorial: WERF, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Brook Bookstore On Demand, Napoli, NA, ItaliaBrook Bookstore On Demand

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 152,86

    Envío por EUR 5,50 
    Se envía de Italia a Estados Unidos de America

    Cantidad disponible: 9 disponibles

    Condición: new.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: GreatBookPricesUK, Woodford Green, Reino UnidoGreatBookPricesUK

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 148,34

    Envío por EUR 17,60 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 10 disponibles

    Condición: New.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: GreatBookPrices, Columbia, MD, Estados Unidos de AmericaGreatBookPrices

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Usado - Como Nuevo

    EUR 166,96

    Envío por EUR 2,35 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 10 disponibles

    Condición: As New. Unread book in perfect condition.

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Majestic Books, Hounslow, Reino UnidoMajestic Books

    Vendedor de 4 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 167,14

    Envío por EUR 7,63 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 3 disponibles

    Condición: New. pp. 148 Illus.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: Ria Christie Collections, Uxbridge, Reino UnidoRia Christie Collections

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 166,88

    Envío por EUR 10,99 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 7 disponibles

    Condición: New. In English.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Ria Christie Collections, Uxbridge, Reino UnidoRia Christie Collections

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 166,88

    Envío por EUR 10,99 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 9 disponibles

    Condición: New. In English.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Speedyhen, Hertfordshire, Reino UnidoSpeedyhen

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 131,35

    Envío por EUR 48,11 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 9 disponibles

    Condición: NEW.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: Speedyhen, Hertfordshire, Reino UnidoSpeedyhen

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 131,35

    Envío por EUR 48,11 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 7 disponibles

    Condición: NEW.

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Books Puddle, Woodside, NY, Estados Unidos de AmericaBooks Puddle

    Vendedor de 4 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 178,91

    Envío por EUR 3,55 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 3 disponibles

    Condición: New. pp. 148.

  • Idioma: Inglés

    Editorial: Iwa Pub, 2005

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: GreatBookPricesUK, Woodford Green, Reino UnidoGreatBookPricesUK

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Usado - Como Nuevo

    EUR 167,82

    Envío por EUR 17,60 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 10 disponibles

    Condición: As New. Unread book in perfect condition.

  • Idioma: Inglés

    Editorial: IWA Publishing, GB, 2004

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: Rarewaves.com USA, London, LONDO, Reino UnidoRarewaves.com USA

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 189,24

     Gastos de envío gratis 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 4 disponibles

    Paperback. Condición: New. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study, which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives addressed in this report are: (1) review and critique the existing body of knowledge for multiple stressors; (2) develop a searchable, annotated bibliography of multiple stressor research; and, (3) identify gaps in the body of knowledge.  A rigorous, theoretical basis for the prediction of multiple stressor effects could not be developed from the literature on experimental studies of multiple stressor effects in aquatic ecosystems. Despite the wealth of observational data, the existence of several useful tools for interpretation of cause/effect relationships (including formal Stressor Identification methods), and the studies reviewed in this report, there are no tools that allow a confident, a priori, prediction of ecosystem response to multiple stressors. The current literature provides, at best, a series of site-specific glimpses of the response of ecological communities and ecosystems to multiple stressors. There is seldom, if ever, any reference to a more generalized model of multiple stressor effects apart from the discussion of the expectations regarding additivity versus synergism. Many articles that purport to be multiple stressor studies do not go beyond an inventory of the various stresses and upsets affecting the ecosystem, without attempting to assess the interactions among them.…

  • Idioma: Inglés

    Editorial: IWA Publishing, GB, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Rarewaves.com USA, London, LONDO, Reino UnidoRarewaves.com USA

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 189,42

     Gastos de envío gratis 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 5 disponibles

    Paperback. Condición: New. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives of the study are to develop a flexible and scientifically defensible conceptual model of the environmental effects of multiple stressors on river and stream ecosystems; develop a study design to test the conceptual model of multiple stressor effects; and, document the process used to arrive at the conceptual model. The multiple stressor conceptual model includes two main components: (1) a diagram that portrays the main features of the study team's understanding of how multiple stressors would interact and the nature of the effects; and (2) a series of three testable risk hypotheses. These two components follow the guidance provided by the U.S. EPA for ecological risk assessment. The proposed conceptual model encompasses the following key assumptions: interactions between the stressor and the ecosystem are dependant upon the existing baseline conditions; for each stressor/baseline combination there will theoretically be a functional and a structural response; effects on habitat are caused by structural or functional responses to stressors; and effects on habitat can cause structural or functional responses.…

  • Idioma: Inglés

    Editorial: IWA Publishing, GB, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Rarewaves USA, HEBRON, KY, Estados Unidos de AmericaRarewaves USA

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 189,86

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 5 disponibles

    Paperback. Condición: New. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives of the study are to develop a flexible and scientifically defensible conceptual model of the environmental effects of multiple stressors on river and stream ecosystems; develop a study design to test the conceptual model of multiple stressor effects; and, document the process used to arrive at the conceptual model. The multiple stressor conceptual model includes two main components: (1) a diagram that portrays the main features of the study team's understanding of how multiple stressors would interact and the nature of the effects; and (2) a series of three testable risk hypotheses. These two components follow the guidance provided by the U.S. EPA for ecological risk assessment. The proposed conceptual model encompasses the following key assumptions: interactions between the stressor and the ecosystem are dependant upon the existing baseline conditions; for each stressor/baseline combination there will theoretically be a functional and a structural response; effects on habitat are caused by structural or functional responses to stressors; and effects on habitat can cause structural or functional responses.…

  • Idioma: Inglés

    Editorial: Intl Water Assn, 2005

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Revaluation Books, Exeter, Reino UnidoRevaluation Books

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 178,91

    Envío por EUR 11,73 
    Se envía de Reino Unido a Estados Unidos de America

    Cantidad disponible: 2 disponibles

    Paperback. Condición: Brand New. 1st edition. 148 pages. 10.80x8.10x0.40 inches. In Stock.

  • Idioma: Inglés

    Editorial: IWA Publishing, GB, 2004

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: Rarewaves USA, HEBRON, KY, Estados Unidos de AmericaRarewaves USA

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 193,30

     Gastos de envío gratis 
    Se envía dentro de Estados Unidos de America

    Cantidad disponible: 4 disponibles

    Paperback. Condición: New. There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study, which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives addressed in this report are: (1) review and critique the existing body of knowledge for multiple stressors; (2) develop a searchable, annotated bibliography of multiple stressor research; and, (3) identify gaps in the body of knowledge.  A rigorous, theoretical basis for the prediction of multiple stressor effects could not be developed from the literature on experimental studies of multiple stressor effects in aquatic ecosystems. Despite the wealth of observational data, the existence of several useful tools for interpretation of cause/effect relationships (including formal Stressor Identification methods), and the studies reviewed in this report, there are no tools that allow a confident, a priori, prediction of ecosystem response to multiple stressors. The current literature provides, at best, a series of site-specific glimpses of the response of ecological communities and ecosystems to multiple stressors. There is seldom, if ever, any reference to a more generalized model of multiple stressor effects apart from the discussion of the expectations regarding additivity versus synergism. Many articles that purport to be multiple stressor studies do not go beyond an inventory of the various stresses and upsets affecting the ecosystem, without attempting to assess the interactions among them.…

  • Idioma: Inglés

    Editorial: WERF, 2004

    1843397196 / 9781843397199

    • Tapa blanda

    Librería: Kennys Bookshop and Art Galleries Ltd., Galway, GY, IrlandaKennys Bookshop and Art Galleries Ltd.

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 178,14

    Envío por EUR 9,50 
    Se envía de Irlanda a Estados Unidos de America

    Cantidad disponible: 7 disponibles

    Condición: New. 2004. Annotated. paperback. . . . . .

  • Idioma: Inglés

    Editorial: IWA Publishing, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: Biblios, frankfurt am main, HESSE, AlemaniaBiblios

    Vendedor de 4 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 183,25

    Envío por EUR 9,95 
    Se envía de Alemania a Estados Unidos de America

    Cantidad disponible: 3 disponibles

    Condición: New. pp. 148.

  • Idioma: Inglés

    Editorial: IWA PUB, 2005

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: moluna, Greven, Alemaniamoluna

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 167,10

    Envío por EUR 48,99 
    Se envía de Alemania a Estados Unidos de America

    Cantidad disponible: 5 disponibles

    Condición: New. KlappentextrnrnThere is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water.

  • Idioma: Inglés

    Editorial: IWA Publishing Jul 2004, 2004

    1843397072 / 9781843397076

    • Tapa blanda

    Librería: AHA-BUCH GmbH, Einbeck, AlemaniaAHA-BUCH GmbH

    Vendedor de 5 estrellas
    Contactar con el vendedor

    Condición: Nuevo

    EUR 183,42

    Envío por EUR 35,00 
    Se envía de Alemania a Estados Unidos de America

    Cantidad disponible: 2 disponibles

    Taschenbuch. Condición: Neu. Neuware - There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives of the study are to develop a flexible and scientifically defensible conceptual model of the environmental effects of multiple stressors on river and stream ecosystems; develop a study design to test the conceptual model of multiple stressor effects; and, document the process used to arrive at the conceptual model. The multiple stressor conceptual model includes two main components: (1) a diagram that portrays the main features of the study team's understanding of how multiple stressors would interact and the nature of the effects; and (2) a series of three testable risk hypotheses. These two components follow the guidance provided by the U.S. EPA for ecological risk assessment. The proposed conceptual model encompasses the following key assumptions: ¿ interactions between the stressor and the ecosystem are dependant upon the existing baseline conditions; ¿ for each stressor/baseline combination there will theoretically be a functional and a structural response; ¿ effects on habitat are caused by structural or functional responses to stressors; and ¿ effects on habitat can cause structural or functional responses. Risk hypotheses were required to complete the conceptual understanding of multiple stressor effects. The study team developed an overall theory of ecosystem response to multiple stressors based upon the central notion that almost every stressor is potentially either a subsidy (producing stimulatory effects) or a toxicant (producing inhibitory effects) in an ecosystem, depending upon its concentration. Furthermore, the study team proposes that the subsidy/toxicant response curves for different kinds of stressors are all of the same general shape; the difference lying where on the curve the new input places the ecosystem in question. This is a new model for ecosystem response (although grounded in earlier theories). It combines the subsidy/toxicant dichotomy into a single relationship, addresses a long-standing controversy about whether functional or structural changes are expected first for any given situation, and leads to interesting new hypotheses. Most importantly, this model is testable and can be used to predict ecosystem responses to multiple stressors of different kinds in different baseline conditions. …