A guide to managing and restoring wetlands in Western Australia Conditions in wetland waters In Chapter 2: Understanding wetlands Version 1 A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands Introduction to the guide Western Australia’s unique and diverse wetlands are rich in ecological and cultural values and form an integral part of the natural environment of the state. A guide to managing and restoring wetlands in Western Australia (the guide) provides information about the nature of WA’s wetlands, and practical guidance on how to manage and restore them for nature conservation. The focus of the guide is natural ‘standing’ wetlands that retain conservation value. Wetlands not addressed in this guide include waterways, estuaries, tidal and artifi cial wetlands. The guide consists of multiple topics within fi ve chapters. These topics are available in PDF format free of charge from the Western Australian Department of Environment and Conservation (DEC) website at www.dec.wa.gov.au/wetlandsguide. The guide is a DEC initiative. Topics of the guide have predominantly been prepared by the department’s Wetlands Section with input from reviewers and contributors from a wide range of fi elds and sectors. Through the guide and other initiatives, DEC seeks to assist individuals, groups and organisations to manage the state’s wetlands for nature conservation. The development of the guide has received funding from the Australian Government, the Government of Western Australia, DEC and the Department of Planning. It has received the support of the Western Australian Wetlands Coordinating Committee, the state’s peak wetland conservation policy coordinating body. For more information about the guide, including scope, purpose and target audience, please refer to the topic ‘Introduction to the guide’. DEC welcomes your feedback and suggestions on the guide. A publication feedback form is available from the DEC website at www.dec.wa.gov.au/wetlandsguide. i Conditions in wetland waters A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands Contents of the guide Introduction Introduction to the guide Chapter 1: Planning for wetland management Wetland management planning Funding, training and resources Chapter 2: Understanding wetlands Wetland hydrology Conditions in wetland waters Wetland ecology Wetland vegetation and fl ora Chapter 3: Managing wetlands Managing hydrology Wetland weeds Water quality Secondary salinity Phytophthora dieback Managing wetland vegetation Nuisance midges and mosquitoes Introduced and nuisance animals Livestock Chapter 4: Monitoring wetlands Monitoring wetlands Chapter 5: Protecting wetlands Roles and responsibilities Legislation and policy These topics are available in PDF format free of charge from the DEC website at www.dec.wa.gov.au/wetlandsguide. ii Conditions in wetland waters A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands ‘Conditions in wetland waters’ topic Acknowledgments Primary author: Dr Lien Sim, DEC Additional text by Christina Mykytiuk, Justine Lawn and Joanne O’Connor, DEC Reviewers and/contributors The following people have been consulted in the development of this topic: Emma Van Looij, Department of Water Jennifer Higbid, DEC Dr Ken Atkins, DEC The valuable contribution of each of these people, and people who have contributed their photos, is gratefully acknowledged. Project manager: Justine Lawn, DEC Publications management: Joanna Moore, DEC Graphic design: Stuart Ridgway, Stuart Ridgway Design Cover photo: courtesy of Professor Jenny Davis (Manning Lake, Cockburn) Symbols used in diagrams are courtesy of the Integration and Application Network (http://ian.umces.edu/symbols/), University of Maryland Center for Environmental Science. Recommended reference When referring to the guide in its entirety, the recommended reference is: Department of Environment and Conservation (2012). A guide to managing and restoring wetlands in Western Australia. Department of Environment and Conservation, Perth, Western Australia. When specific reference is made to this topic, the recommended reference is: Department of Environment and Conservation (2012). ‘Conditions in wetland waters’, in A guide to managing and restoring wetlands in Western Australia, Prepared by L Sim, Department of Environment and Conservation, Perth, Western Australia. Disclaimer While every effort has been made to ensure that the information contained in this publication is correct, the information is only provided as a guide to management and restoration activities. DEC does not guarantee, and accepts no liability whatsoever arising from, or connected to, the accuracy, reliability, currency or completeness of any material contained in this guide. Much of the material in this topic was compiled prior to 2009. New information on this subject between the compilation date and publication date has not been captured in this topic. iii Conditions in wetland waters A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands Contents Introduction ............................................................................................................ 1 Light availability (including shade, turbidity and colour) ................................... 5 Water temperature ............................................................................................... 17 Dissolved oxygen ................................................................................................. 22 Salinity, conductivity and ionic composition ...................................................... 30 Stratification ......................................................................................................... 40 Acidity/alkalinity ................................................................................................... 47 Redox potential .................................................................................................... 63 Carbon ................................................................................................................... 67 Nitrogen and phosphorus .................................................................................... 81 Sulfur ................................................................................................................... 103 iv Conditions in wetland waters A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands Ecological character: the sum of a wetland’s biotic and abiotic components, functions, drivers Before you begin and processes, as well as the h threatening processes occurring Before embarking on management and restoration investigations and in the wetland, catchment and activities, you must consider and address the legal requirements, safety region considerations, cultural issues and the complexity of the ecological processes Physico-chemical: relating which occur in wetlands to ensure that any proposed actions are legal, safe to physical chemistry. In this and appropriate. For more guidance, see the topic ‘Introduction to the guide’. guide, used in reference to the physical and chemical characteristics of wetland waters. INTRODUCTION The natural physical and chemical conditions in wetland waters significantly influence the characteristics of wetlands, including the living conditions for plants, animals and microbes that live in or visit them. These conditions determine the ability of these organisms to produce or seek out energy sources, and to get, or be exposed to, suitable amounts of light, oxygen, salts, heavy metals and other important substances from water and sediment. Important physical and chemical conditions in wetland waters include: • light availability (including shade, turbidity and colour) • water temperature • dissolved oxygen • salinity, conductivity and ionic composition • stratification • acidity/alkalinity • redox potential • carbon • nitrogen • phosphorus • sulfur These conditions are an important determinant of a wetland’s ecological character. The natural variety in these conditions amongst wetlands contributes to the diversity of WA wetlands and their biodiversity. In order to manage a wetland, whether it is relatively natural or altered, it is important to understand these physical and chemical conditions and the processes driving them. ➤ Managers of wetlands with altered wetland conditions will find this topic a useful foundation for management techniques outlined in the topics ‘Water quality’ and ‘Secondary salinity’ in Chapter 3. The physical and chemical characteristics of a wetland are often referred to as its ‘physico-chemical environment’. The way in which the physico-chemical environment interacts with other aspects of a wetland is illustrated in Figure 1. 1 Conditions in wetland waters A guide to managing and restoring wetlands in Western Australia Chapter 2: Understanding wetlands Climate Geomorphology Hydrology Water regime Water budget - timing - frequency - duration - extent & depth - variability Water level Inputs and outputs Time Physico-chemical environment Biotic components Temperature Sediment Salinity Deposition concentration Figure 1. The physico-chemical environment has an important effect on the living conditions of a wetland (adapted from Mitsch and Gosselink 2007).1 The plants, animals and microbes of a particular wetland are adapted to specific Microbe: an organism that chemical and physical conditions,