Updated November 5th, 2002Acidification in the Canadian Aquatic Environment: Scientific Criteria For Assessing the Effects of Acidic Depostion on Aquatic Ecosystems
Author: Associte Committee on Scientific Criteria for Environmental Quality
Source: Nation Research Council of Canada - NRCC Associate Committe on Scientific Criteria for Environmental Quality - Subcommittee on Water
Date: 1981Effects of Acidification on Aquatic Biota
Microorganisms: Very little information is available on the role of microorganisms in ecosystems affected by acidic deposition. Sulfur cycle bacteria have been shown in certain circumstances to contribute significantly to the acid neutralizing capacity of surface waters via sulfate reduction. Studies have indicated that microbial decomposition of organic matter is markedly reduced at pH levels encountered in acidic lakes.
Phytoplankton: The phytoplankton biomass of acidic lakes is not significantly different from that of non-acidic lakes with comparable totla phosphorus concentrations.
Zooplankton: Acidification of lakes is accompanied by chagnes in the occurrence and abundance of species of zooplankton and in the diversity and biomass of zooplankton communities. In lakes having pH's below 5.0, the occurrence and relative abundance of several crustacean species were markedly reudced. Although little information is available, it appears that the acidification of lakes is accompnied by a reduction in the biomass of zooplankton. One result of such a reduction is that zooplankton exert less control over phytoplankton community structure than in non-acidic lakes.
Fishes: After acidification, numberous lakes are known to be devoid of fish. In addition, a number of rivers have lost specific fish populations. For example, in Norway and Sweden, thousands of fishless lkaes have been identified. The number of fish species has been positively correlated with pH. Stress due to acidification is commonly associated with a drastic reduction in population size and biomass, often leaving a small number of large fish prior to extinction. The exact mechanism responsible for recruitment failure is not known; however, it may involve the impariment of ionic regulation or failure of alrval emergence
