Lakes, ponds, rivers and streams are prominent features of the Arctic landscape and are also common in many parts of Antarctica. These waters encompass a remarkable variety of conditions for aquatic life, and are proving to be attractive model systems for exploring general ecological themes. Some of these ecosystems have direct global implications, and are also sentinels of global climate change. This book brings together many of the world's leading researchers in polar limnology to describe these diverse aquatic environments and their ecology. It introduces each major ecosystem type including extreme ice shelf and glacial meltwaters; subglacial lakes and rivers; perennially ice-capped lakes; meromictic and epishelf lake systems; tundra lakes and ponds; seasonal streams; and the large Arctic rivers with their associated floodplain lakes. Separate chapters review the geomorphology of polar lake basins, high latitude paleolimnology; biogeochemistry; physical limnology; microbial processes; microbial biodiversity and biogeography; benthic photosynthetic communities including microbial mats and mosses; phytoplankton and primary production; zooplankton and benthic invertebrates; the ecology of high Arctic fish; food web structure and dynamics; and new and emerging themes in high latitude limnology. The book incorporates the overriding theme of climate change impacts as well as direct impacts resulting from human activity.