Characterization of macroinvertebrate communities in the hyporheic zone of river ecosystems reflects the pump-sampling technique used

The hyporheic zone of river ecosystems provides a habitat for a diverse macroinvertebrate community that makes a vital contribution to ecosystem functioning and biodiversity. However, effective methods for sampling this community have proved difficult to establish, due to the inaccessibility of subsurface sediments. The aim of this study was to compare the two most common semi-quantitative macroinvertebrate pump-sampling techniques: BouRouch and vacuum-pump sampling. We used both techniques to collect replicate samples in three contrasting temperate-zone streams, in each of two biogeographical regions (Atlantic region, central England, UK; Continental region, southeast France). Results were typically consistent across streams in both regions: Bou-Rouch samples provided significantly higher estimates of taxa richness, macroinvertebrate abundance, and the abundance of all UK and eight of 10 French common taxa. Seven and nine taxa which were rare in Bou-Rouch samples were absent from vacuum-pump samples in the UK and France, respectively; no taxon was repeatedly sampled exclusively by the vacuum pump. Rarefaction curves (rescaled to the number of incidences) and non-parametric richness estimators indicated no significant difference in richness between techniques, highlighting the capture of more individuals as crucial to Bou-Rouch sampling performance. Compared to assemblages in replicate vacuum-pump samples, multivariate analyses indicated greater distinction among Bou-Rouch assemblages from different streams, as well as significantly greater consistency in assemblage composition among replicate Bou-Rouch samples collected in one stream. We recommend Bou-Rouch sampling for most study types, including rapid biomonitoring surveys and studies requiring acquisition of comprehensive tax on lists that include rare taxa. Despite collecting fewer macroinvertebrates, vacuum-pump sampling remains an important option for inexpensive and rapid sample collection

Ecosistemi di acque interne e di transizione

In questo contributo la vulnerabilità degli ecosistemi acquatici ai cambiamenti climatici è analizzata in relazione ai meccanismi di organizzazione e mantenimento della biodiversità e dei processi ecosistemici. Dai processi degli ecosistemi derivano funzioni che forniscono una serie di benefici o servizi per il genere umano (Daily et al., 2009). Tali servizi sono in larga misura dipendenti dalle componenti biologiche degli ecosistemi86. Negli ecosistemi acquatici i processi biogeochimici (ad es. denitrificazione batterica e assimilazione da parte della vegetazione acquatica), garantiscono l’abbattimento dei nutrienti, una funzione ecosistemica che produce il servizio di depurazione dell’acqua. Altri servizi sono la laminazione delle piene, la ricarica degli acquiferi, la regolazione del microclima locale, la produzione di risorse alimentari quali pesci, crostacei, ecc. (Jones, 2013). Le alterazioni degli ecosistemi, in particolare la perdita di specie e la diminuzione della biodiversità danneggiano questi servizi, con ricadute anche di tipo economico(si pensi, ad esempio, ai costi della depurazione dell’acqua destinata al consumo umano)

Spatial Organisation of an Insect Ensemble in a Mediterranean Ecosystem: the Tenebrionid Beetles (Coleoptera: Tenebrionidae) Inhabiting an Adriatic Coastal Sand Dune Area

We studied the spatial organisation of an ensemble (phylogenetically bounded group of species that use a similar set of resources within a community) of tenebrionid beetles in a Mediterranean coastal sand dune ecosystem in Southern Italy (Molise region). Within a transect from the seashore to the inner dune, we identified four biotopes defined by different vegetation types. We found a community dominated by few sand specialised and r-selected tenebrionid species. Overall tenebrionid abundance was lowest on the upper beach, highest on the embryonic shifting dunes and then from there declined further inland. The embryonic shifting dunes biotope showed the highest diversity and the lowest dominance. This pattern suggests that tenebrionid beetels are able to cope with the challenging salty and xerothermic conditions of the seaward margin. Although some species were too rare to assess their biotope preference, our data support that, at least some, were distributed with different abundance over the four dune biotopes. These differences are likely related to different preferences for different characteristics of substratum and detritus

Effectiveness of Biomass/Abundance Comparison (ABC) Models in Assessing the Response of Hyporheic Assemblages to Ammonium Contamination

Abundance-Biomass Comparison (ABC) models, first described for marine benthic macrofauna, have been applied successfully to other marine and terrestrial/freshwater fauna but never to ecotonal communities. In particular, to our knowledge, ABC models have not been applied to hyporheic communities. This study represents the first application of ABC models to hyporheic assemblages. We aimed at testing the effectiveness of ABC models in describing the perturbation of hyporheic communities subjected to an existing/known disturbance. To this end, we applied the models to the hyporheic community of an Apennine creek, where the hyporheic waters of the upstream stretch were uncontaminated, whereas those of the downstream stretch were contaminated by ammonium. We also tested separated models for the summer and winter periods to account for potential variability due to season. ABC models provided a satisfactory description of the hyporheic community changes due to ammonium by showing the abundance dominance curve overlying that of the biomass in the downstream stretch contrarily to what was observed in the upstream stretch. However, ABC models did not highlight any significant seasonal effects. Our results showed that ABC models have the potential to be used as assessment tools for ecological quality of hyporheic zones in temperate regions

The Influence of the Recording Time in Modelling the Swimming Behaviour of the Freshwater Inbenthic Copepod Bryocamptus pygmaeus

The analysis of copepod behaviour gained an increasing impetus over the past decade thanks to the advent of computer-assisted video analysis tools. Since the automated tracking consists in detecting the animal's position frame by frame and improving signals corrupted by strong background noise, a crucial role is played by the length of the video recording. The aim of this study is to: (i) assess whether the recording time influences the analysis of a suite of movement descriptive parameters; (ii) understand if the recording time influences the outcome of the statistical analyses when hypotheses on the effect of toxicants/chemicals on the freshwater invertebrate behaviour are tested. We investigated trajectory parameters commonly used in behavioural studies-swimming speed, percentage of activity and trajectory convex hull-derived from the trajectories described by the inbenthic-interstitial freshwater copepod Bryocamptus pygmaeus exposed to a sub-lethal concentration of diclofenac. The analyses presented in this work indicate that the recording time did not influence the outcome of the results for the swimming speed and the percentage of activity. For the trajectory convex hull area, our results showed that a recording session lasting at least 3 min provided robust results. However, further investigations are needed to disentangle the role of concurrent factors, such as the behavioural analysis of multiple individuals simultaneously, whether they are of the same or opposite sex and the implications on sexual behaviour, competition for resources and predation