Macroinvertebrates in woodland pools and ditches and their response to artificial drainage in Estonia

Since the twentieth century, freshwater ecosystems have been extensively drained. Despite the magnitude of artificial drainage, its impact on freshwater biodiversity, especially on small forest waterbodies, is still poorly known. We examined macroinvertebrate taxon richness and assemblages in forest landscapes, comparing natural temporary waterbodies situated in drained and undrained areas, ditches, and wheel rut pools. We aimed to determine macroinvertebrates that are characteristic to these waterbodies, the impact of forest drainage on them, and the functioning of ditches as an alternative habitat for aquatic macroinvertebrates. Altogether 181 waterbodies within six landscape regions were surveyed, identifying 171 macroinvertebrate taxa. Taxa accumulation curves pooling all the regions indicated that natural waterbodies situated in drained areas harbored less invertebrate taxa than other waterbody types. Thus drainage has effect at supraregional scale. At the waterbody scale, however, we did not detect substantial forest drainage effect on taxon richness or assemblages. Ordering of the waterbody types by richness differed between landscape regions, suggesting that macroinvertebrates are largely dependent on landscape characteristics. Since neither total and mean richness nor assemblages did not differ significantly between natural temporary waterbodies and drainage ditches, the latter could be considered as an alternative habitat for invertebrates at least in semi-naturally managed forests.