Invertebrate grazers are a crucial factor for grass litter mass loss and nutrient mobilization during aquatic decomposition

Abstract

The decomposition process of plant litter is very important for carbon turnover. Much is known about the impact of invertebrate shredders on this process, but the effect of invertebrate grazers (e.g. detritivore freshwater snails) on litter processing has received little attention. These grazers are quite prevalent in some aquatic ecosys- tems. Therefore, a laboratory batch experiment was conducted to assess the effect of invertebrate grazers (aquatic snails) on aquatic litter decomposition and nutrient mobilization. Litter containing different amounts of silicon was used because silicon content is known to affect grazers. Invertebrate grazers had a significant effect on litter de- composition, increasing leaf mass loss by 100 % and reducing the cellulose content by 25 %. The leaf litter silicon content had no effect on these grazers. Furthermore, litter silicon content showed strong negative effects on nutrient remobilization, whereas the mobilization of calcium, nitrogen and DOC was affected by the invertebrates. It could be concluded that invertebrate grazer may have an important role in aquatic litter decomposition by decreasing litter cellulose content and enhancing mobilization of nutrients.