Which of the following would be the strongest evidence in support of a scientist's contention that a local area was experiencing acid deposition? 1. An increase in the rate of photosynthesis of aquatic plants in a local lake 2. A sudden die-off of all the fish in a local stream 3. A gradual increase in temp. of local lake 4. Increase in concentration of soluable heavy metals in local pond For some reason, I think the answer is 4. If the acid deposition is serious enough, organisms can die quite rapidly as a result of Al,Hg, or other metal ions from leaching in the bedrock, which can be acidic or neutral. Is this wrong? Thanks.