Effects of drought on the colonization speed and pattern of benthic macroinvertebrate communities in experimental mesocosm wetlands

We studied benthic macroinvertebrate colonizers in the early successional phases in wetland ecosystems. Field experiments were conducted in newly created mesocosm wetlands in the experimental station of Korea University in the central Korean Peninsula from June 2011 to June 2013. We selected experimental periods of one year for initial colonization (pre-drought) and subsequent one year for recolonization (post-drought) with a drought period of 50 days between them. The colonization speed was evaluated using the newly adopted colonization index (CI) and the colonization pattern using multivariate analysis (NMS) and similarity percentages test (SIMPER). Furthermore, we categorized the benthic macroinvertebrate communities according to their biological traits in relation to drought. Our results showed that the species diversity increased and colonization index decreased over time during the pre-drought and post-drought; especially, the colonization speed was 2.5-fold higher post-drought than pre-drought. The results of community analysis revealed that the benthic macroinvertebrate communities differed significantly between the pre-drought and post-drought periods in terms of a number of taxa abundance. Drought-resistant benthic macroinvertebrates colonized rapidly in post-drought and the aquatic vegetation accelerates the colonization of benthic macroinvertebrate communities. Therefore, we classified the benthic macroinvertebrate taxa into three groups for drought disturbance: (1) a resistant group which generally emerge after the initial colonization period; (2) a sensitive group, with diverse life history strategies and biological traits such as active migration or population decline after drought disturbance; and (3) a seasonal group, which emerge only during certain periods and were not markedly influenced by drought.