Leaf consumption by invertebrate aquatic shredders in the Amazon: effects of climate change and microbial conditioning

We grew leaves of Montrichardia arborescens in four microcosm chambers with different temperatures and CO2 concentrations simulating the scenarios of expected climate change. These leaves were used to feed shredders (Phylloicus) and to assess the effects of changes in leaf quality on their consumption. We also evaluated the effect of detritus conditioning by microorganisms on leaf consumption. We hypothesized that leaves of plants grown under different environmental conditions could offer substrata of different qualities to microorganisms colonizing them, and, consequently the shredder consumption rate would differ according to leaf conditioning. The microcosm chambers for plant growth simulated three different combined air temperature and CO2 scenarios, relative to the real-time (control) current conditions in Manaus-Brazil. The leaf consumption experiment was performed only in the control chamber. Specific leaf area was positively affected by predicted climate change, while tannins were detected only in leaves of plants grown in chambers simulating a changed climate. Other leaf detritus parameters were similar in all chambers. Shredders showed higher consumption rates in leaves developed under mild and intermediate conditions in relation to control. Shredder consumption was similar in conditioned and unconditioned treatments. Thus, shredder consumption was influenced more by the intrinsic quality of leaves than by microorganism conditioning, but we were not able to show effects of climate change on leaf quality that could explain differences in shredder consumption.