Litter Decomposition in Aquatic Ecosystems

This book provides a comprehensive overview of the methods used to examine the decomposition of plant litter, one of the most fundamental ecosystem processes. Special emphasis is placed on leaf litter in fresh waters, but most methods are equally applicable to plant litter in coastal marine and terrestrial ecosystems. Rather than presenting specific protocols, the book focuses on the principles and concepts underlying the various methods and their relative merits and limitations.--Specifically the multi-authored chapters deal with:-litter mass loss and the controlling factors-detritivores, fungi and bacteria associated with decomposing litter-bulk chemical litter properties-models describing the decomposition process-the use of litter decomposition in bioassessment and educationLitter Decomposition in Aquatic Ecosystems is part of the new Ecological Methods and Concepts series (formerly Methods in Ecology). The series provides graduate students and practicing research scientists with the latest information on experimental techniques and current thinking in ecology.

1. Litter decomposition in aquatic ecosystems: aims and achievements, concepts and challenges 1.1. History and terminology 1.2. Why study litter decomposition? 1.3. Aquatic ecosystems in which litter decomposition is likely to be important: streams, freshwater marshes, salt marshes, mangroves, seagrass beds, macroalgal beds, deep sea (wood) 1.4. Litter types subject to decomposition in aquatic ecosystems: leaves of terrestrial woody plants; wood; leaves and other tissues of submerged, floating-leaved and emergent macrophytes, including roots and rhizomes; carcasses of large animals such as fish 1.5 Overview of current concepts 1.6 Emerging principles and distinctions among litter decomposition systems 1.7 Challenges and prospects 1.8. Aims and structure of the book 2. Experimental approaches in aquatic litter decomposition studies 2.1. Basic field procedures 2.1.1. Litter pack and mesh bag method (leaf litter, wood, animal carcasses) 2.1.2. Tagging techniques (emergent and floating-leaved macrophyte tissues, branchwood, logs) 2.1.3. Release and retrieval of leaf litter 2.1.4. Inferences from input-output-storage measurements 2.1.5. Wood density as a measure of wood decay state 2.1.6. Dendrochronology 2.2. Manipulation of litter quality 2.2.1. Removal and addition of selected litter constituents 2.2.2. Manipulating nutrient contents 2.2.3. Isotopic labelling 2.2.4. Quality changes resulting from altered atmospheric gas composition (CO2, O3) 2.3. Microcosm studies 2.3.1. Assessing the importance of environmental controlling factors 2.3.2. Testing for effects of community composition and diversity 2.3.3. Microbial decomposition budgets 2.4. Ecosystem manipulations 2.4.1. Whole-ecosystem litter exclusions and additions 2.4.2. Manipulating litter retention capacities 2.4.3. Fertilization 2.4.4. Experimental warming (enclosures, plots, whole ecosystems) 2.4.5. Modification of hydrological regimes (standing-dead decomposition systems, temporarily aquatic systems) 2.4.6. Chemical pollution and its remediation (e.g. acidification and liming, metal and pesticide contamination) 2.5. Community manipulations 2.5.1. Manipulation of microbial decomposer communities 2.5.2. Manipulating litter-associated food webs 3. Physical and bulk chemical characterization of decomposing litter 3.1. Physical properties of leaf litter and wood (various sorts of "penetrometers") 3.2. Lignin and cellulose: wet chemical methods such as Van Soest and Klason procedures, enyzmatic methods for cellulose, near-infrared reflectance spectroscopy 3.3. Polyphenolics (bulk chemical methods such as Folin-Denis/Ciocalteau, protein-precipitation potential, proanthocyanidins; identification of constituent monomers) 3.4. Labile carbohydrates (low-molecular carbohydrates, starch, pectin, identification of constituent monomers) 3.5. Lipids (bulk) 3.6. Proteins (buffer-extractable, total) 3.7. Elemental contents (C, N, P, cations); wet chemical methods, possibly also near-infrared reflectance spectroscopy 4. Presence, production and activity of microbial decomposers 4.1. Microscopic detection (light microscopy, scanning and transmission electron microscopy, confocal laser microscopy) 4.2. Fungal biomass, growth, production and reproduction 4.2.1. Biomass (ergosterol, glucoseamine, hyphal length, immunological techniques, ATP) 4.2.2. Growth rate and production (acetate-ergosterol method and potential alternatives, approaches based on nucleic acid synthesis) 4.2.3. Reproduction of aquatic hyphomycetes in streams 4.2.4. Reproduction of marsh fungi on standing-dead emergent macrophytes 4.3. Bacterial abundance, biomass, growth and production 4.3.1. Abundance and biomass (epifluorescent direct counts with image analysis, muramic acid, lipid A, other markers) 4.3.2. Growth an