The influence of water quality and macroinvertebrate colonization on the breakdown process of native and exotic leaf types in sub-alpine stream

Abstract

Most of the energy input of low-order lotic food webs derives from non-living sources of terrestrial organic matter. For this reason, many studies have examined patterns of leaf breakdown; most recently, interest has focused on the importance of water quality or the nature (native versus exotic) of plant material. In this study, we combined both aspects by analyzing the breakdown process and macroinvertebrate colonization of leaf bags containing leaves of different plant types in two nearby sites with different levels of water quality. We exposed a total of 600 leaf bags made of five leaf types (three native: Alnus incana, Populus alba and Quercus robur; and two exotic: Reynoutria japonica and Robinia pseudoacacia) at two sites of the Pellice River (northwestern Italy). Leaf bags were retrieved after 10, 20, 30, 40, 50 and 60 days, leaf mass loss determined and the associated macroinvertebrates quantified. Significant differences were found in the mass loss and in the colonization of leaf bags between sites but not between native and exotic species. Dry mass loss was different among species but without any evident relation with exotic or native origin of plants. In our study sites, geographical origin of plant detritus is not per se central in shaping macroinvertebrate colonization and mass loss because the impact of wastewater treatment plant effluent seems to be much more important than plant origin in the breakdown process.

Environmental drivers of leaf breakdown in an urban watershed

“…All sites were high in nutrients and exhibited flashy hydrology. I used the standard 'litter bag' technique with two different mesh sizes to quantify the effect of macroinvertebrates on leaf breakdown (Bärlocher, 2005;Bo et al, 2014;Cheever and Webster, 2014). Including 5 sites in the field study allowed me to examine how physicochemical conditions, which varied among 8!…”

“…The goal of our study was to measure environmental drivers of leaf breakdown rate in an urban watershed. To measure the effect of shredding macroinvertebrates on leaf breakdown, we used the litter bag method with two mesh sizes at each site (Bärlocher, 2005;Bo et al, 2014;Cheever and Webster, 2014). We predicted that flooding and nutrient availability would be positively related to breakdown rate, but where abundant, facultative shredding macroinvertebrates could play a secondary role in enhancing leaf breakdown.…”

Exploring Macroinvertebrates Ecological Preferences and Trait-Based Indicators of Suspended Fine Sediment Effects in the Tsitsa River and Its Tributaries, Eastern Cape, South Africa

“…Similarly, [8] found invertebrate shredders to be the only feeding groups that demonstrated reduced abundance with increased fine sediments in two lowland UK streams. Further, the palatability of CPOM for shredders depend on the initial actions of microbes on leaf litter [52]. However, suspended sediments can inhibit the rate of microbial breakdown of litter, through reduced light energy and temperature [52], thereby affecting the nutritional quality of CPOM for macroinvertebrate shredders.…”

Leaf-Nets (LN): A New Quantitative Method for Sampling Macroinvertebrates in Non-Wadeable Streams and Rivers

“…Although not expressly investigated in this paper, the new method could also be employed for the assessment of functional characteristics of non-wadeable watercourses. The LN method may allow a concomitant evaluation of structural and functional characteristics of large-river ecosystems because, as for the leaf-bags assay, the mass loss of LN Praghmites leaves could be used as an indirect measure of detritus breakdown (Gessner and Chauvet, 2002;Bo et al, 2014). Finally, we should also emphasize that the new proposed sampling device is cost effective and relatively simple to build.…”