Physical, chemical, and biological consequences of episodic aluminum additions to a stream1

AlCl 3 was added to a second‐orderroborated field results, added Al producing a 20% reduction in surface tension. We suggest that added Al may have associated with organic functional groups, rendering DOC more hydrophobic and less soluble. Some of these alumino‐organic substances subsequently may have accumulated at the air‐water interface. Terrestrial and aquatic invertebrate drift was also altered with elevated Al; we attribute drift to responses to chemical changes in the stream such as Al and H + toxicity or to a physical change in surface film. stream to simulate episodic increases in Al concentration during acidic snowmelt. Significant decreases in pH and DOC and accumulation of foam at the surface (visible evidence of reduced surface tension) accompanied a stepwise increase in Al in the water. Laboratory experiments cor