A flashing light may not be that flashy: A systematic review on critical fusion frequencies.

BACKGROUND: Light pollution could represent one of the main drivers behind the current biodiversity erosion. While the effects of many light components on biodiversity have already been studied, the influence of flicker remains poorly understood. The determination of the threshold frequency at which a flickering light is perceived as continuous by a species, usually called the Critical Fusion Frequency (CFF), could thus help further identify the impacts of artificial lighting on animals. OBJECTIVE: This review aimed at answering the following questions: what is the distribution of CFF between species? Are there differences in how flicker is perceived between taxonomic classes? Which species are more at risk of being impacted by artificial lighting flicker? METHODS: Citations were extracted from three literature databases and were then screened successively on their titles, abstracts and full-texts. Included studies were critically appraised to assess their validity. All relevant data were extracted and analysed to determine the distribution of CFF in the animal kingdom and the influence of experimental designs and species traits on CFF. RESULTS: At first, 4881 citations were found. Screening and critical appraisal provided 200 CFF values for 156 species. Reported values of CFF varied from a maximum of between 300 Hz and 500 Hz for the beetle Melanophila acuminata D. to a mean of 0.57 (± 0.08) Hz for the snail Lissachatina fulica B. Insects and birds had higher CFF than all other studied taxa. Irrespective of taxon, nocturnal species had lower CFF than diurnal and crepuscular ones. CONCLUSIONS: We identified nine crepuscular and nocturnal species that could be impacted by the potential adverse effects of anthropogenic light flicker. We emphasize that there remains a huge gap in our knowledge of flicker perception by animals, which could potentially be hampering our understanding of its impacts on biodiversity, especially in key taxa like bats, nocturnal birds and insects.

The nationwide 'ZNIEFF' inventory in France: an open dataset of more than one million species data in zones of high ecological value.

Background: In France, a 'natural zone of ecological, faunistic or floristic value' (Zone Naturelle d'Intérêt Écologique, Faunistique et Floristique - ZNIEFF) is a natural area, regionally known for its remarkable ecological characteristics. The ZNIEFF inventory is a naturalist and scientific survey programme launched in 1982 by the Ecology Ministry, with support from the French National Museum of Natural History (MNHN). New information: This paper describes the ZNIEFF national dataset, which comprises 1,013,725 data for various animal (38%), plant (59%) and fungal (2%) species in terrestrial and marine zones (May 2020). A total of 19,842 sites throughout continental France. as well as in the overseas Departments and territories (Guadeloupe, Martinique, Mayotte, La Réunion, French Guiana, Saint-Martin, Saint-Barthélemy and Saint-Pierre-et-Miquelon), are included in the ZNIEFF dataset (May 2020). This dataset is now available in open access.All data were collected by skilled naturalists using professional protocols over almost 40 years. They consist mainly of observations of rare, threatened or endemic species, all validated by regional experts. Data are updated twice a year after national validation in both national (INPN-OpenObs) and global (GBIF) biodiversity web platforms. Some of the observed species, the so-called 'trigger species' or 'determinant' species, are of central interest for a site to be designated a ZNIEFF (zone of high ecological value). This concerns more than 35,000 taxa, mainly angiosperms, insects, fungi, birds and fish.

Modeling diadromous fish loss from historical data: Identification of anthropogenic drivers and testing of mitigation scenarios.

Diadromous fishes have drastically declined over the last century, especially in Europe. Several authors have highlighted the role of large dams in this decline, but in fact, its causes are potentially multiple and cumulative, including degradation of local environmental conditions and widespread fragmentation of hydrographic networks associated with the pervasive establishment of smaller barriers. Consequently, there is a need to improve the identification and prioritization of the drivers of diadromous species loss in order to identify and apply the most appropriate conservation and restoration measures. In this study, we used both historical sources (from mid-18th to early 20th century) and current data to quantify the long-term loss of diadromous taxa over 555 sites throughout the French river network. Then, we modeled the effects of several anthropogenic pressures (e.g. barriers, water quality, hydrological and river morphological alterations) on diadromous taxon loss. Lastly, we assessed the potential consequences of four different scenarios of anthropogenic pressure reduction. Due to uncertainties in historical sources, some species were grouped into taxa leading to a potential underestimation of actual species extinctions. Despite this limitation, our results showed that the decline in diadromous assemblages is widespread but with contrasting magnitudes depending on site locations. The maximum height and density of barriers appeared as the major factors of taxon loss. Over the scenarios tested, we observed that exclusively improving local conditions have much more limited effects than restoring river continuity. Focusing actions on large dam removal did not show the strongest responses compared to removing medium and small-sized barriers. For effective and sustainable restoration of diadromous fish assemblage, (1) historical occurrences of diadromous fishes should be used as an indicator for assessing recovery, and (2) undertaken measures must be adapted to each basin to target and limit the number of barriers to remove while allowing diadromous fish recovery.

A diagnosis-based approach to assess specific risks of river degradation in a multiple pressure context: Insights from fish communities.

In the context of increasing pressure on water bodies, many fish-based indices have been developed to evaluate the ecological status of rivers. However, most of these indices suffer from several limitations, which hamper the capacity of water managers to select the most appropriate measures of restoration. Those limitations include: (i) being dependent on reference conditions, (ii) not satisfactorily handling complex and non-linear biological responses to pressure gradients, and (iii) being unable to identify specific risks of stream degradation in a multi-pressure context. To tackle those issues, we developed a diagnosis-based approach using Random Forest models to predict the impairment probabilities of river fish communities by 28 pressure categories (chemical, hydromorphological and biological). In addition, the database includes the abundances of 72 fish species collected from 1527 sites in France, sampled between 2005 and 2015; and fish taxonomic and biological information. Twenty random forest models provided at least good performances when evaluating impairment probabilities of fish communities by those pressures. The best performing models indicated that fish communities were impacted, on average, by 7.34 ±â€¯0.03 abiotic pressure categories (mean ±â€¯SE), and that hydromorphological alterations (5.27 ±â€¯0.02) were more often detected than chemical ones (2.06 ±â€¯0.02). These models showed that alterations in longitudinal continuity, and contaminations by Polycyclic Aromatic Hydrocarbons were respectively the most frequent hydromorphological and chemical pressure categories in French rivers. This approach has also efficiently detected the functional impact of invasive alien species. Identifying and ranking the impacts of multiple anthropogenic pressures that trigger functional shifts in river biological communities is essential for managers to prioritize actions and to implement appropriate restoration programmes. Actually implemented in an R package, this approach has the capacity to detect a variety of impairments, resulting in an efficient assessment of ecological risks across various spatial and temporal scales.

Implementation options for DNA-based identification into ecological status assessment under the European Water Framework Directive.

Assessment of ecological status for the European Water Framework Directive (WFD) is based on "Biological Quality Elements" (BQEs), namely phytoplankton, benthic flora, benthic invertebrates and fish. Morphological identification of these organisms is a time-consuming and expensive procedure. Here, we assess the options for complementing and, perhaps, replacing morphological identification with procedures using eDNA, metabarcoding or similar approaches. We rate the applicability of DNA-based identification for the individual BQEs and water categories (rivers, lakes, transitional and coastal waters) against eleven criteria, summarised under the headlines representativeness (for example suitability of current sampling methods for DNA-based identification, errors from DNA-based species detection), sensitivity (for example capability to detect sensitive taxa, unassigned reads), precision of DNA-based identification (knowledge about uncertainty), comparability with conventional approaches (for example sensitivity of metrics to differences in DNA-based identification), cost effectiveness and environmental impact. Overall, suitability of DNA-based identification is particularly high for fish, as eDNA is a well-suited sampling approach which can replace expensive and potentially harmful methods such as gill-netting, trawling or electrofishing. Furthermore, there are attempts to replace absolute by relative abundance in metric calculations. For invertebrates and phytobenthos, the main challenges include the modification of indices and completing barcode libraries. For phytoplankton, the barcode libraries are even more problematic, due to the high taxonomic diversity in plankton samples. If current assessment concepts are kept, DNA-based identification is least appropriate for macrophytes (rivers, lakes) and angiosperms/macroalgae (transitional and coastal waters), which are surveyed rather than sampled. We discuss general implications of implementing DNA-based identification into standard ecological assessment, in particular considering any adaptations to the WFD that may be required to facilitate the transition to molecular data.

Assessing the ecological status in the context of the European Water Framework Directive: where do we go now?

The Water Framework Directive (WFD) is now well established as the key management imperative in river basins across Europe. However, there remain significant concerns with the way WFD is implemented and there is now a need for water managers and scientists to communicate better in order to find solutions to these concerns. To address this, a Science-Policy Interface (SPI) activity was launched in 2010 led by Directorate-General for Research and Innovation and Onema (the French national agency for water and aquatic ecosystems), which provided an interactive forum to connect scientists and WFD end-users. One major aim of the SPI activity was to establish a list of the most crucial research and development needs for enhancing WFD implementation. This paper synthesises the recommendations from this event highlighting 10 priority issues relating to ecological status. For lakes, temporary streams and transitional and coastal waters, WFD implementation still suffers from a lack of WFD-compliant bioassessment methods. For rivers, special attention is required to assess the ecological impacts of hydromorphological alterations on biological communities, notably those affecting river continuity and riparian covering. Spatial extrapolation tools are needed in order to evaluate ecological status for water bodies for which no data are available. The need for more functional bioassessment tools as complements to usual WFD-compliant tools, and to connect clearly good ecological state, biodiversity and ecosystem services when implementing WFD were also identified as crucial issues.

Effects of small weirs on fish parasite communities.

In this study, we examined the impacts of small weirs on the parasite community of gudgeon and toxostome in a medium-sized river. We tested changes on parasite species diversity using indices that capture both richness and abundance characteristics, and we examined parasite community structure with null models (co-occurrence index C score) and a multiple discriminant function analysis (MDFA). Our results showed that parasite community diversity of gudgeon is strongly influenced by weirs with a maximum diversity upstream of the weirs. Weirs also induce change in abundance of gudgeon parasite species particularly during summer. Nevertheless, we obtained that weirs had no effect on the parasite co-occurrence patterns. In addition, similarity indices indicate that the parasite faunas of newly established limnophilic species (roach and bleak) are host-specific and are rarely transmitted to other fish species. We conclude that fish parasite communities responded in different ways to the presence of impassable weirs, but, in a general tendency, changing environmental conditions induced by weirs may represent an ecological risk.

The effects of the ectoparasite Tracheliastes polycolpus (Copepoda: Lernaeopodidae) on the fins of rostrum dace (Leuciscus leuciscus burdigalensis).

Rostrum dace (Leuciscus leuciscus burdigalensis) from the River Viaur were found to be infested with the ectoparasite Tracheliastes polycolpus (Copepoda: Lernaeopodidae). Samples from five study sites along the river revealed different patterns of parasite infestation. Heavily infested fish were found at the upper study sites whereas much lower infestation levels were observed at the lower study sites. The copepods showed an aggregated dispersion pattern on host fins. The results showed significantly preferred microhabitats, with adult females being more abundant on the anal, pelvic and along the external part of the pectoral fins. The anal and pelvic fins were damaged by the parasite with a loss of their surface area. These fin alterations may reduce the fish's swimming ability and therefore affect the rostrum dace population. Our findings highlight the need to study the effects of parasites on stream fish populations.