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Challenging paradigms in estuarine ecology

Challenging paradigms in estuarine ecology. Mike Elliott a & Alan Whitfield b a Institute of Estuarine and Coastal Studies (IECS), University of Hull, Hull HU6 7RX, UK b South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown 6140, South Africa. Contents:.

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Challenging paradigms in estuarine ecology

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  1. Challenging paradigms in estuarine ecology Mike Elliott a & Alan Whitfield b a Institute of Estuarine and Coastal Studies (IECS), University of Hull, Hull HU6 7RX, UK b South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown 6140, South Africa

  2. Contents: • Introduction - what, why, how • Paradigms 1-8 • Final points - ‘so what?’, ‘what if?’ Acknowledgements: The authors gratefully acknowledge the ideas of many unwitting and unknowing colleagues, friends, students, authors and referees!

  3. Paradigms - what, why, how? Here we are using the term paradigm to mean a set of concepts or accepted philosophies that define a science, which have been developed over the history of a field but which are amenable to testing via the scientific method using hypothesis generation. Kuhn (1970) considers that a scientific paradigm can cover concepts and observations, questions and hypotheses and the interpretation of field, laboratory and modelling observations, measurements and outcomes. Hence there must be the ability to prove or disprove the paradigms or to test for deviations from what is accepted. Here we take the view that (a) paradigms do not have to be mutually exclusive; (b) they are a set of unifying concepts central to the science and management of estuaries.

  4. Definitions, Scales, Ecotones and Linkages • Paradigm 1: An estuary is an ecosystem in its own right but cannot function indefinitely on its own in isolation and that it depends largely on other ecosystems, possibly more so than do other ecosystems. • Paradigm 2: As ecosystems, estuaries are more influenced by scale than any other aquatic system; their essence is in the connectivity across the various scales and within the water body they are charact-erised by one or more ecotones ( ).

  5. Hydromorphological and Organic Functioning • Paradigm 3: Hydromorphology is the key to understanding estuarine functioning but these systems are always influenced by salinity (and the resulting density/buoyancy currents) as a primary environmental driver. • Paradigm 4: Although estuaries behave as sources and sinks for nutrients and organic matter, in most systems allochthonous organic inputs dominate over autochthonous organic production.

  6. Variability, Resilience and Redundancy • Paradigm 5: Estuaries are physico-chemically more variable than other aquatic systems but estuarine communities are less diverse taxonomically and the individuals are more physiologically adapted to environmental variability than equivalent organisms in other aquatic systems.

  7. Diversity, Tolerances, Stress, Productivity • Paradigm 6: Estuaries are systems with low diversity/high biomass/high abundance and their ecological components show a diversity minimum in the oligohaline region which can be explained by the stress-subsidy concept where tolerant organisms thrive but non-tolerant organisms are absent (cf. Estuarine Quality Paradox)

  8. Pressures, Valuing, Valuation and Management • Paradigm 7: Estuaries have more human-induced pressures than other systems and these include both exogenic unmanaged pressures and endogenic managed pressures. Consequently their management has to not only accommodate the causes and consequences of pressures within the system but, more than other ecosystems, they need to respond to the consequences of external natural and anthropogenic influences.

  9. DPSIR modelling framework

  10. ExUP EnMP ExUP ExUP EnMP

  11. Delivery and Protection of Ecosystem Services & Societal Benefits • Paradigm 8: Estuaries provide a wider variety of ecosystem services and an increased delivery of societal benefits than many other ecosystems. Hence estuaries are one of the most valuable aquatic ecosystems serving human needs but for this to occur they require functional links with the adjoining terrestrial, freshwater and marine systems.

  12. The Way Ahead - So what?, What if? • Is it valuable to define, refine and challenge paradigms? • Can they be a unifying tool in assessing and managing estuaries worldwide? • Will they provide focus on the major issues requiring research attention worldwide? • Will they allow us to know the limitations of our science and management? • Does the research community agree with the paradigms proposed? • Can they be derived for other TraC habitats (lagoons, fjords, open coasts, etc.)? • Feedback: Mike.Elliott@hull.ac.uk; a.whitfield@saiab.ac.za

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