A modification of the leaf-bags method to assess spring ecosystem functioning: benthic invertebrates and leaf-litter breakdown in Vera Spring (Central Italy)

The evaluation of leaf detritus processing (decomposition and breakdown) is one of the most simple and cost-effective method to assess the functional characteristics of freshwater ecosystems. However, in comparison with other freshwater habitats, information on leaf litter breakdown in spring ecosystems is still scarce and fragmentary. In this paper, we present results of the first application of a variant of the leaf-bags method to assess structure of macroinvertebrate assemblages and leaf-litter breakdown in a Central Apennines (Italy) cold spring which was investigated from July 2016 to October 2016. Notwithstanding the stable conditions of almost all hydrological and physico-chemical parameters, we found significant temporal differences in (i) % of mass loss of poplar leaves (ii) number of Ephemeroptera, Plecoptera and Trichoptera taxa, (iii) shredder and predator densities. We demonstrate that detritus processing in cold springs may be faster than or as fast as in warmer streams/rivers. Shredders activity and biocoenotic interactions, rather than temperature and nutrients load, were the main drivers of the process. A routine application of the modified leaf-bags may contribute to expand our knowledge on detritus processing in cold springs and may help to predict impacts of climate warming on freshwater ecosystem functioning.

Transport and consumption of organic detritus in a neotropical limestone cave

Caves are permanently aphotic environments, a fact that precludes the occurrence of photosynthetic organisms. In these systems the resource is allochthonous, coming mainly from the surrounding epigean environment, being imported by physical and biological agents. Even knowing about the importance of the organic allochthonous resources in caves, little is known of their importation and processing. The present work had as an objective, the measuring the coarse particulate organic matter processing and import rates in the subterranean environment. The cave studied was Lapa da Fazenda Extrema I, limestone cave, located in Brazilian savanna biome. Through bimonthly collections, it was observed that the organic detritus penetrated into the cave in low amounts in dry season and high amounts in rainy season. The processing of the organic plant matter in the aquatic hypogean environment was moderate (K-day=0.025), in the epigean environment the processing was predominantly slow (K-day =0.0104). The detritus commonly brought to the interior of the cave were large woods (58.18 g/day), followed by leaves and fragmented material (12.76 g/day), fruits and seeds (0.0069 g/day), animal carcasses (0.002 g/day) and roots (0.001 g/day). The highest richness and abundances of invertebrates were found in the same periods in which there were the highest rates of organic matter import to the cave.Keywords: cave, detritus processing, energy flow.