A modification of the leaf-nets method for sampling benthic invertebrates in spring habitats

The full ecological potential of spring habitats remains relatively unexplored mostly because of the lack of standardized sampling procedures and difficulties to collect representative biological samples, especially in small-sized springs. Recent studies on sampling methodologies in spring habitats indicated that a modified Surber net with a reduced frame area, reliably describes the structure and composition of spring communities. This method, however, is very invasive and may severely impact the spring, especially when a large number of samples is required. The paper presents a new quantitative method (leaf-nets) for sampling crenic invertebrates which combines a rather high efficiency with negligible impacts on spring habitat structure and biota. The effectiveness of the new methodology was tested in a medium-size rheocrene spring in Central Apennine, where spring assemblages were sampled in parallel with a modified Surber net and with the new method. Taxa richness and density were higher in the Surber net, while no between-method differences were recorded for the number of insect taxa and Simpson diversity. Furthermore, the overall functional organization of Surber net and leaf-nets assemblages was very similar. The new method sampled only 25% of the individuals cumulatively collected, but 75% of the total richness, with a good representation of the structure and the functional organization of spring assemblages. In comparison with the Surber net, the negligible loss of information of the new method is highly compensated by its minor invasivity, lower impacts on spring microhabitats and invertebrate populations and by its higher versatility. Leaf-nets could also be used to assess leaf-detritus breakdown in springs, thus allowing a better ecological characterization of these ecosystems. </p

Assessment of river quality within the context of the EU's water framework directive (2000/60/EC): the RiverNet Experiences

EnThe purpose of the EU's Water Framework Directive (WFD)is the achievement of ecological good status for all its superficial water bodies and courses.However,the most controversial and difficult aspect is the choice of an appropriate method to define a “reference condition ”,the expected value upon which comparisons are to be made and quantitatively expressed as EQR metric (ecological quality ratio).A major burden is the adjustment of national standards to assess the quality of aquatic habitats according to the technical specifications explicitly stated in the WFD.This aspect is also one of the major objectives within the RiverNet project.We compared standard methods used in Italy (not compliant with WFD requirements)with those currently under study by the pan-European intercalibration panel.Data spanning one year (2002)from the Abruzzo monitoring programwere used.Data from 229 samples (78 sites and 38 water courses)were reanalyzed using both Italian (LIM,IBE,SECA)and other metrics (family richness,BMWP,ASPT,EPT,EPT%).Resulting ecological status assessments were compared quantitatively and expressed as EQR.Indices based on benthic invertebrates were closely interrelated ($R2==0.71 –0.88 for pairwise correlations),and performed better than the abiotic LIM index.The BMWP index seems better suited than the non-WFD-compliant IBE index to describe ecological status.Though the dataset was relatively limited,we were able to identify 13 class-1 (least impacted)sites that can be used as reference sites for Abruzzo.Additionally,EQR-based range and threshold values for each tested metric were quantified for the high, good and moderate quality lasses.Utilization of historical data may be a cost-and time-effective approach potentially leading to a regional and nationwide establishment of reference conditions and range quality-class values for riverine systems

Corrigendum to: Structure, functional organization and biological traits of macroinvertebrate assemblages from leaf-bags and benthic samples in a third-order stream of Central Apennines (Italy) [Ecological Indicators 46 (2014) 84–91]

n/

Assessment of river quality within the context of the EU's water framework directive (2000/60/EC): the RiverNet Experiences

EnThe purpose of the EU's Water Framework Directive (WFD)is the achievement of ecological good status for all its superficial water bodies and courses.However,the most controversial and difficult aspect is the choice of an appropriate method to define a “reference condition ”,the expected value upon which comparisons are to be made and quantitatively expressed as EQR metric (ecological quality ratio).A major burden is the adjustment of national standards to assess the quality of aquatic habitats according to the technical specifications explicitly stated in the WFD.This aspect is also one of the major objectives within the RiverNet project.We compared standard methods used in Italy (not compliant with WFD requirements)with those currently under study by the pan-European intercalibration panel.Data spanning one year (2002)from the Abruzzo monitoring programwere used.Data from 229 samples (78 sites and 38 water courses)were reanalyzed using both Italian (LIM,IBE,SECA)and other metrics (family richness,BMWP,ASPT,EPT,EPT%).Resulting ecological status assessments were compared quantitatively and expressed as EQR.Indices based on benthic invertebrates were closely interrelated ($R2==0.71 –0.88 for pairwise correlations),and performed better than the abiotic LIM index.The BMWP index seems better suited than the non-WFD-compliant IBE index to describe ecological status.Though the dataset was relatively limited,we were able to identify 13 class-1 (least impacted)sites that can be used as reference sites for Abruzzo.Additionally,EQR-based range and threshold values for each tested metric were quantified for the high, good and moderate quality lasses.Utilization of historical data may be a cost-and time-effective approach potentially leading to a regional and nationwide establishment of reference conditions and range quality-class values for riverine systems

A modification of the leaf-nets method for sampling benthic invertebrates in spring habitats

The full ecological potential of spring habitats remains relatively unexplored mostly because of the lack of standardized sampling procedures and difficulties to collect representative biological samples, especially in small-sized springs. Recent studies on sampling methodologies in spring habitats indicated that a modified Surber net with a reduced frame area, reliably describes the structure and composition of spring communities. This method, however, is very invasive and may severely impact the spring, especially when a large number of samples is required. The paper presents a new quantitative method (leaf-nets) for sampling crenic invertebrates which combines a rather high efficiency with negligible impacts on spring habitat structure and biota. The effectiveness of the new methodology was tested in a medium-size rheocrene spring in Central Apennine, where spring assemblages were sampled in parallel with a modified Surber net and with the new method. Taxa richness and density were higher in the Surber net, while no between-method differences were recorded for the number of insect taxa and Simpson diversity. Furthermore, the overall functional organization of Surber net and leaf-nets assemblages was very similar. The new method sampled only 25% of the individuals cumulatively collected, but 75% of the total richness, with a good representation of the structure and the functional organization of spring assemblages. In comparison with the Surber net, the negligible loss of information of the new method is highly compensated by its minor invasivity, lower impacts on spring microhabitats and invertebrate populations and by its higher versatility. Leaf-nets could also be used to assess leaf-detritus breakdown in springs, thus allowing a better ecological characterization of these ecosystems

Influence of aperiodic summer droughts on leaf litter breakdown and macroinvertebrate assemblages: testing the drying memory in a Central Apennines River (Aterno River, Italy)

Climate changes, geomorphologic modifications and the rise in water demand for human uses contribute to ‘‘aperiodic summer drought’’ (ASD) events in Mediterranean-type rivers. ASD results in a reach that flows in one summer, dries in next or more summers, and then flowing again. The ecological structure and function of streams affected by ASD are understudied, especially with respect to permanent and regular intermittent streams. We tested the drying memory in a reach of Aterno River (Italy) disturbed by ASD. Leaf litter breakdown of Phragmites australis and macroinvertebrate assemblages were studied. Discharge was monitored since 2006. The experiment was performed during summer 2010 using the litterbag technique, and was replicated four times. The disturbed site was affected by drought in the three previous summers while the control was always flowing. Taxonomic diversity indices, abundance and structure of macroinvertebrate assemblages varied significantly between sites. Instead, leaf litter breakdown wasn’t influenced by ASD. Therefore ASD events seem to affect the structure of macroinvertebrate assemblages, confirming the role of drying memory of the systems. The resilience of leaf litter breakdown in reach affected by ASD seems to be high, probably depending on the activity of selected microbial communities and macroinvertebrate features like metabolism and biomass

Influence of seasonal multiannual drought events on the resilience of ecosystem processes and macroinvertebrate assemblages in a Central Apennine stream (Aterno River, Italy)

This research provides a rare field experiment on the resilience of ecosystem processes and macroinvertebrate assemblages by multiannual drought events, in a Mediterranean river. Here, we studied the influence of multiannual drought events on the decomposition process of leaf detritus and on the recovery of macroinvertebrate assemblages, both in the leaf-bag and in the bottom samples. Two sites, Acciano and Tione, located in a third order branch of a Central Apennines river (Abruzzo, Italy) were monitored form 2007 to 2009 with the aim to record the drought events during summer and bottom samples of macroinvertebrate assemblages were collected in the flowing period of the summer. In the monitored years, Acciano was exposed to drought events during the summer of each monitored year, while Tione was always flowing. In the 2010, we performed an experimental design to analyse the effect of progressive desiccation on leaf detritus decomposition process and on macroinvertebrate assemblages from the leaf-bags and bottom samples. Unexpected, during the 2010 year Acciano was always flowing and sampling was carried out from June to September. Since Tione was right, the unexpected event was a great fortune for us because we were able to analyze the recovery of both functional process and macroinvertebrate community structure and traits in Acciano site respect to Tione site, after multiannual seasonal drought disturbance. Decomposition process was analyzed in both sites and in 4 periods (from June to September, monthly) using the leaf-bag technique; 12 leaf-bag containing 3 g of dry Phragmites australis (Cav.) Steudel leaves were submerged at each site and period, and retrieved after 30 days. Macroinvertebrate assemblages were collected from both leaf-bag samples and bottom samples, and the main structural descriptors and traits were compared between sites and among sampling periods. Bottom samples were available also in the previous three years. The obtained results showed no difference between sites of the decomposition process of Phragmites australis leaves, while significant differences of the structural descriptors and traits of macroinvertebrate assemblages were rarely observed between sites, just in some month were significant and main linked to trophic traits. Finally, this study showed that also in correspondence of climate change drought disturbance become more unpredictable mainly in Mediterranean type rivers, moreover functional processes are not affected by dryining memory, while the descriptors of trophic traits seem to be more affected by dryining memory

Structure, functional organization and biological traits of macroinvertebrate assemblages from leaf-bags and benthic samplesin a third-order stream of Central Apennines (Italy)

Information on both structure and functions is essential to evaluate the ecological integrity of streamecosystems and their response to natural and anthropogenic disturbance. Leaf-bags have been widelyemployed to assess stream ecosystem processes and the degree of leaf mass consumption has been pro-posed as one of the most useful functional descriptor in aquatic environments. However, the breakdownrate of leaves has been compared with structural indicators of macroinvertebrate assemblages derivedfrom leaf-bags or from benthic samples, without any direct comparison on the characteristics of com-munities sampled with the two methods. The main objective of the paper is to conduct a comparativeanalysis of the structure, functional organization and biological traits of macroinvertebrate assemblagesfrom artificial leaf packs and from benthic samples of a third-order stream in the Central Apennines(Italy).Of the 43 macroinvertebrate taxa globally found in our survey, 9 showed low ability or scarce attitudeto colonize leaf-bags, while 6 rare taxa were exclusively sampled in artificial leaf packs. Both assemblageswere characterized by the dominance of Chironomidae, though they were more abundant in leaf-bags(71% of total individuals collected) than in benthic samples (44%). Conversely, the mayfly Baetis sp. com-prised more than 17% of total individuals collected with Surber nets and only 5% of leaf-bag assemblages.We found that compared to benthic assemblages, leaf-bag communities were less diversified with alower richness and a lower number of Ephemeroptera, Trichoptera and Plecoptera (EPT) taxa; significantdifferences also emerged in assemblage composition.Contrary to what expected, artificial leaf packs resulted not particularly attractive for shredder orga-nisms and were mainly colonized by collectors. Also the biological trait profiles of the leaf-bag communitywere significantly different from those shared by resident benthic taxa.Our findings could have profound implications in the assessment of the structural and functionalintegrity of stream ecosystems and in studies on freshwater biodiversity and ecosystem functioning.In these studies, the two methods (leaf-bags and Surber nets) should be regarded as complementary andnot alternative

Corrigendum to: Structure, functional organization and biological traits of macroinvertebrate assemblages from leaf-bags and benthic samples in a third-order stream of Central Apennines (Italy) [Ecological Indicators 46 (2014) 84–91]

Results of the PERMANOVA analysis on the differences in composition, functional organization and biological traits of macroinvertebrate assemblages in leaf-bags and Surber net samples of the River Aterno. p-values are based on 9999 permutations