C3 and C4 plant leaf breakdown and assimilation by aquatic macroinvertebrates in streams of the Brazilian Atlantic Forest

Abstract

The breakdown of allochthonous plants is of great importance in providing energy and nutrients in streams. In this regard, shredder macroinvertebrates play an important role in decomposing organic matter. Changes in land use strongly influence the type of material entering a stream, which ultimately affects the food chain dependent on this material. This study compared the decay of C3 (Mollinedia schottiana) and C4 (Brachiaria brizantha) plants in the montane Atlantic Forest of Brazil using litterbag experiments in two streams draining watersheds of different land uses. Concomitantly, we investigated the colonisation and assimilation of these plant detritus by aquatic macroinvertebrates. The breakdown of C4 plants in the forest stream was faster than that of C3 plants; however, aquatic macroinvertebrates did not assimilate the C4 carbon. These results support other studies that have shown a greater abundance of shredders in montane tropical streams (lower temperature) than in lowland streams. Moreover, the findings of this study support the view that changes in land use alter the structure of the benthic community, and that these changes can alter the leaf breakdown process.