ECOLOGICAL EFFECTS OF RIVER ICE BREAK-UP - A REVIEW AND PERSPECTIVE

1. Abiotic disturbances strongly modify spatial and temporal patterns of lotic ecosystem community structure and function. Such effects are produced because disturbances alter organic matter, nutrient and conta minant dynamics and the distribution and abundance of bacterial, algal , macroinvertebrate and fish communities. 2. River ice break-up is a s easonal disturbance in rivers at high altitudes and latitudes world-wi de and is characterized, in part, by large increases in current veloci ty, stage, water temperature, concentrations of suspended materials an d substrate scouring. 3. These abiotic factors are likely to have impo rtant effects on primary producers, consumers, and food-web dynamics o f river biota. Despite the potential importance of river ice break-up on community structure and function, detailed information describing t he magnitude of their effects and underlying causal mechanisms is scar ce. 4. The objective of this paper is to provide a hydrological and ec ological review and perspective on the potential effects of ice break- up on lotic ecosystems. Specifically, the potential importance of brea k-up on water temperature, river sediments and geomorphology, riverine energy sources, contaminants, and its effects on river biota and food -web dynamics are evaluated.