The influence of substrate type on macroinvertebrate assemblages within agricultural drainage ditches

Artificial drainage ditches are common features in lowland agricultural catchments that support a wide range of ecosystem services at the landscape scale. Current paradigms in river management suggest activities that increase habitat heterogeneity and complexity resulting in more diverse floral and faunal assemblages; however, it is not known if the same principles apply to artificial drainage ditch systems. We examined the effects of four artificial substrates, representing increasing habitat complexity and heterogeneity (bricks, gravel, netting and vegetation), on macroinvertebrate community structure within artificial drainage ditches. Each substrate type supported a distinct macroinvertebrate community highlighting the importance of habitat heterogeneity in maintaining macroinvertebrate assemblages. Each substrate type also displayed differing degrees of community heterogeneity, with gravel communities being most variable and artificial vegetation being the least. In addition, several macroinvertebrate diversity metrics increased along the gradient of artificial substrate complexity, although these differences were not statistically significant. We conclude that habitat management practices that increase habitat complexity are likely to enhance macroinvertebrate community heterogeneity within artificial drainage channels regardless of previous management activities.