Manipulating the hydroperiod affects plant and invertebrate communities in freshwater mesocosms, La Marque TX USA, 2019-2021

We used a mesocosm experiment with six flooding depths and seven drought durations, followed by seven months of recovery, to explore how freshwater wetlands typical of the Houston, Texas area would respond to different hydrological regimes that might occur if wetlands were drained in anticipation of a heavy rain that did not materialize, leading to a temporary period of little or no standing water. The experiment was conducted in 2019-2021. How quickly mesocosms dried out was a function of initial water depth, with mesocosms initially set with greater water depths (30 cm) taking on average 38 days to dry out. Individual plant species (14 were planted; 8 were common at the end of the recovery period) were affected drought length, flooding depth, or their interaction, with results varying among species. The composition of the plant community at the end of the drought period was strongly affected by drought length, and this effect persisted through seven months of recovery, with the 80- and 160-day drought treatments diverging most strongly from shorter drought treatments. Densities of mosquito larvae, snails and tadpoles were temporally variable, and affected more during the treatment period than after seven months of recovery. Our results indicate that managed wetlands in southeast Texas would be quite resilient to dry periods of up to 40 days in duration, especially if water was not completely drained at the beginning of the drought. In addition, some wetland species would persist in managed wetlands even if they experienced droughts of up to 160 days.