Relationships between macroinvertebrates and detritus in freshwater wetlands

Abstract

Freshwater wetlands can produce a large volume of detritus annually, including hydrophyte litter in herbaceous habitats and tree-leaf litter and dead wood in forested habitats. It has been assumed that detritus provides many ecological benefits to resident macroinvertebrates and, in turn, that these macroinvertebrates contribute substantially to the breakdown of wetland detritus. However, research conducted to date provides ambiguous conclusions, with reciprocal macroinvertebrate–detritus relationships apparently changing in importance across different global freshwater wetlands. We reviewed the body of research and assessed 96 empirical studies on detritus and macroinvertebrates in freshwater wetlands. Based on this review, we conclude that detritus provides many benefits to macroinvertebrates, both as a nutritional source (hydrophyte and tree-leaf litter) and as habitat (dead wood). Shredder macroinvertebrates, which are adapted to consume detritus, were commonly reported in some freshwater wetlands but were rare or absent in most. Where shredders were common, they contributed substantially to detritus breakdown. Where shredders were rare, macroinvertebrates played minor roles in detritus breakdown, which was instead processed by the microbial community. When assessing ecosystem functions in freshwater wetlands, it will be important to know the specific nature of the resident macroinvertebrate assemblages and the different ways that these organisms may or may not influence C flows.