Humic substances occur in all kinds of aquatic systems, but are particularly important in northern, coniferous areas. They strongly modify the aquatic ecosystems and also constitute a major problem in the drinking water supply.
This volume covers all aspects of aquatic humic substances, from their origin and chemical properties, their effects on light and nutrient regimes and biogeochemical cycling, to their role regarding organisms, productivity and food web organization from bacteria to fish. Special emphasis is paid to carbon cycling and food web organization in humic lakes, but aspects of marine carbon cycling related to humus are treated as well.

Humic Substances as Ecosystem Modifiers - Introduction.- I BIOGEOCHEMICAL ASPECTS.- 1 Sources and Age of Aquatic Humus.- 2 Chemical Composition, Structure, and Metal Binding Properties.- 3 Humus and Acidification.- 4 Climate and Hydrologica Control of DOM Concentration and Quality in Lakes.- II HUMUS, LIGHT REGIMES AND PRIMARY PRODUCTION.- 5 Attenuation of Solar Radiation in Humic Waters.- 6 Effects of UV Radiation: Photochemöical Principles and Expermental Considerations.- 7 Phytoplankton, Primary Production and Nutrient Cycling.- 8 Nutrient Limitation and Bacteria-Phytoplankton Interactions in Humic Lakes.- III HUMUS AND SECONDARY PRODUCTION.- 9 The Role of Microbial Extracellular Enzymes in the Transformation of Dissolved Organic Matter in Humic Lakes.- 10 Degradation of Dissolved Organic Matter in Humic Waters by Bacteria.- 11 Food Webs and Carbon Cycling in Humic Lakes.- 12 Cycling of Dissolved Organic Matter in the Ocean.- Aquatic Humic Matter: from Molecular Structure to Ecosystem Stability