Effects of Acidification and Alkalinization on a Periphytic Algal Community in an Alaskan Wetland

Experimental research examining how algal communities respond to changes in pH is sparse in the wetland literature. In this study, we used a mesocosm experiment to examine the response of a periphytic algal community to a wide range of pH levels, both decreased to pH 5 (acid treatment) and increased to pH 9 (alkaline treatment) from ambient conditions (pH 7) in an Alaskan marsh. We examined algal communities growing on stems of Equisetum fluviatile (L.) after 24 days of colonization at experimental pH levels. Alkalinization resulted in a two-fold increase in concentrations of inorganic nutrients (dissolved inorganic N, soluble reactive P, SiO2) and a significant increase in algal accrual relative to the control. There were distinct shifts in euglenoid taxa in the alkaline treatment, including a significant increase of Trachelomonas and a significant decrease of Euglena relative to the control. Acidification resulted in an increase of Mougeotia (Chlorophyta, Zygnemataceae) and a decrease in overall taxa richness, which coincided with a significant reduction in concentrations of dissolved inorganic carbon. Trends observed in our study indicate that alkalization may significantly alter algal community structure and loosen nutrient restraints on algal productivity, while acidification may reduce algal diversity in boreal wetlands.