Leaf litter and invertebrate colonization : the role of macroconsumers in a subtropical wetland (Corrientes, Argentina)

Abstract

We studied the breakdown rates and the invertebrate abundance and biomass for the litter of five native aquatic plants (Eichhornia crassipes, Eichhornia azurea, Thalia multiflora, Oxycaryum cubense and Hydrocotyle ranunculoides) in a shallow rain-fed lake using litter bags. The diets of the prawn Pseudopalaemon bouvieri and the amphipod Hyalella curvispina were determined and classified into five food items. Litter breakdown was fast (>0.010 day−1) for all species studied, although the breakdown rates were significantly affected by the litter species. The abundance of invertebrates colonizing the litter was significantly different among the species, but the biomass did not differ. The invertebrate taxa that colonized the litter of the different species were broadly similar, consisting primarily of oligochaetes, amphipods, prawns, ostracods, gastropods, water mites and several types of insect larvae (chironomids and mayflies). In terms of the number of individuals, naidid oligochaetes dominated the assemblages. In terms of biomass, P. bouvieri and H. curvispina reached 67.6 and 18.2 % of the total, respectively. Our results indicate that macroconsumers are involved in the breakdown process, since these species consume plant remains and detritus and highlight the importance of leaf litter composition on the abundance of invertebrates that colonize the litter.