Beetles do better in wetlands with subsurface flow

Posted on March 4, 2011

The affinities of macroinvertebrates for different types of constructed wetland are not well understood.  Design alternatives for wetlands include the type of flooding system (surface or subsurface) and the presence or absence of planted vegetation.  A Hungarian study compared the abundance and species richness of aquatic beetles in three categories of constructed wetlands, namely: (1) surface flow, planted with 24 species of aquatic vegetation; (2) surface flow, unplanted; and (3) sub-surface flow.  The surface flow wetlands were relatively large (430 ha in total) with water depths up to 80 cm.  Surface flooding increased the water table around the neighboring lowlands, generating four subsurface flow wetlands. These were small (30 ha total), temporary and shallow (< 40 cm).  Beetles were sampled because they are considered to be good bioindicators of habitat quality.  Sampling was carried out three years after the plantings, and a total of 66 beetle taxa were recorded.   Species richness was significantly higher in the temporary sub-surface flow systems than the permanent surface-flow wetlands.  Species diversity profiles for the three types of wetlands were distinct, with diversity being higher in sub-surface flow systems and slightly higher in planted than in unplanted surface-flow wetlands.  The results suggest that subsurface flooding is a useful restoration technique because it provides favourable breeding conditions for aquatic beetles by excluding fish predators.  By increasing habitat diversity and providing food and refuge for young beetles, the presence of vegetation is also beneficial. 

Reference:  Molnár, A., Csabai, Z. & Tóthmérész, B.  2009.   Influence of flooding and vegetation patterns on aquatic beetle diversity in a constructed wetland complex.  Wetlands 29(4), 1214-1223.