16 - Acidification Effects

Abstract

This chapter focuses on acidification effects on benthic-algal structures. Acid inputs to aquatic ecosystems can occur either through natural processes, such as volcanic emissions, thermal effluents, peat bog drainage inflow, and oxidation in geological areas with sulfur containing rocks, or through anthropogenic causes. More recent ecosystem-acidification studies have focused on anthropogenic activities such as mining and waste leachates, alteration in land use, and most importantly, the increase in atmospheric sulfur and nitrogen oxides originating from smelters and fossil fuel power plants. These oxides, precursors of strong acids, affect the pH of dry and wet precipitation, and contribute to the acidification of surface waters of large, poorly buffered regions of Europe and North America. As a large number of research over the past two decades in the Northern Hemisphere deals mainly with this anthropogenic acid deposition, it forms the core of this review. Studies relating to periphyton, considered the autotrophic component, the algae, but less frequently, the heterotrophic component, the bacteria, and fungi, which can be important elements in the response of algae to changes in the physical and chemical variables of the environment.