The use of palaeoecological and contemporary macroinvertebrate community data to characterize riverine reference conditions

Defining reference conditions is a crucial element in quantifying the extent of anthropogenic modification and for identifying restoration targets in riverine ecosystems. Despite palaeoecological approaches being widely applied in lakes to establish reference conditions, their use in lotic ecosystems remains limited. In this study, we examine contemporary, historical (1930 and 1972), and palaeoecological macroinvertebrate biodiversity and biomonitoring scores in Eastburn Beck, a headwater tributary of the River Hull (UK) to determine if palaeoecological approaches can be used to characterize lotic system reference conditions. Palaeoecological samples comprised a greater gamma diversity (18 taxa) than contemporary samples (8 taxa), samples taken in 1972 (11 taxa) and 1930 (8 taxa). Palaeoecological samples supported taxonomically different Gastropoda, Trichoptera, and Coleoptera (GTC) communities compared with contemporary and historical samples (1930 and 1972). Results from biomonitoring indices using the GTC community indicated that the palaeochannel had (a) similar invertebrate biological quality, (b) a less energetic flow regime, and (c) increased fine sediment deposits compared with the contemporary channel. The results clearly illustrate that palaeoecological data can provide a suitable method to characterize reference conditions for lotic habitats. However, it is important to recognize that faunal data from palaeochannel deposits provide a short-term “snapshot” of the conditions within the river immediately prior to its hydrological isolation. River restoration activities should therefore draw on multiple lines of evidence, including palaeoecological information where possible, to characterize a range of reference conditions to reflect the highly dynamic nature of lotic ecosystems

Regional and local environmental correlates of native Iberian fish fauna

Knowledge of fishes’ habitat requirements is an essential tool for species conservation. We examined the habitat requirements of nine native freshwater fish species using 165 undisturbed or minimally disturbed sites from eight river basins in western Iberia (northern and central Portugal). Six environmental descriptors were considered at the regional level, and six descriptors at a local scale. Statistical associations between local assemblage structure and environmental variables were quantified by canonical correspondence analyses. Logistic regression was performed for each species to identify regional and local factors related to its distribution at the sample sites. The results suggested a reasonable degree of specialisation in the use of local variables and dependence on regional variables. Logistic regression models showed a good adjustment (0.75 < AUC < 0.93). Results of habitat modelling using minimally disturbed sites helped to clarify species preferences for specific abiotic drivers

L'Occupation du Sol à Très Haute Résolution Spatiale améliore la compréhension des liens de causalités avec l'état écologique des cours d'eau

International audienceRecent progress in very high spatial resolution imagery (VHSRI) has increased the availability of fine-scale land cover data over extensive areas. This new spatial information might improve our understanding of how land cover affects stream ecosystems.Land cover information was investigated in whole catchments and riparian areas in Normandy (France) and related to stream macroinvertebrates at 155 sites. The first model was based on the land cover data obtained via moderate spatial resolution imagery (MSRI) at the catchment scale. The second and the third models were additionally based on riparian land cover data both locally (at the site) and upstream. The riparian land cover data were derived from the MSRI for the second and from the VHSRI for the third model.Riparian vegetation (at a distance from the channel of 5–100 m) was poorly detected by MSRI when compared to VHSRI. The model based on higher resolution data at the riparian scale (i) ensured that relationships identified at the riparian corridor scale were independent from those at whole catchment scale, (ii) identified the influence of riparian vegetation on the aquatic environment as being most pronounced when using data from a 20-m wide strip (i.e. 20 m on each bank for a total of 40 m) and (iii) disentangled the effects of roads from other urban infrastructure.This study confirms the advantages of using very high resolution data in landscape approaches to the study of aquatic ecosystems. It provides accurate spatial information at the riparian scale that improves interpretation of the influence of land cover on the ecological condition of streams and allows identification of relevant features for management