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Impacts from a changing climate, in particular sea-level rise, will be most acutely felt on small oceanic islands. A common configuration of mid-latitude islands is the sandy barrier island. Sable Island, Nova Scotia, Canada is a vegetated sand island near the shelf edge, 160 km from the nearest point of land, that is morphologically similar to a barrier island. This study uses 60 years of airphoto records to analyse changes in coastline position through digitized shore and vegetation (foredune proxy) lines. Rates of coastal movement are analysed to model the future (2039) coastal configuration. The analyses suggest that the majority of the coastline on Sable Island is in retreat, with net retreat on the south side of the island only partially offset by modest net advance on the north side. The different morphologies of the beach-dune systems of South Beach and North Beach, driven by incident wind and waves, yield these different coastline responses. Projected loss of 10 ha by 2039 of the climax heath vegetative community to shoreline retreat suggests a trend toward island instability due to coastline migration. Island-wide data set trends show support for two different but complementary hypotheses about whole-island evolution: (1) the island is mobile via bank migration driving southern coastline changes and experiencing sediment transport toward the east, or (2) the island is generally immobile and losing subaerial sediments (and thus shrinking) likely due to ongoing (and accelerating) sea-level rise. Key words: coastal change, coastal erosion, small island geomorphology, Sable Island, sea-level rise. C'est dans les petites îles océaniques que les impacts d'un climat changeant, en particulier la hausse du niveau de la mer, se feront le plus fortement sentir. Les îles de moyennes latitudes se présentent souvent sous forme d'îles-barrières constituées de sable. L'île de Sable (Nouvelle-Ecosse, Canada) est une île de sable végétalisée située près de la marge du plateau continental, à 160 km de la terre la plus proche et s'apparente, du point de vue morphologique, à une île-barrière. Nous utilisons 60 années de photographies aériennes pour analyser les changements de l'emplacement du trait de côte reflété par les lignes numérisées du rivage et de la végétation (variable substitutive de l'avant-dune). Les vitesses de déplacement du trait de côte sont analysées afin de modéliser la configuration future (2039) de la côte. Les analyses portent à croire que la majeure partie de la ligne de côte de l'île de Sable est en recul, un recul net étant observé du côté sud de l'île qui n'est que partiellement compensé par une modeste avancée nette du côté nord. Les différentes formes adoptées par les systèmes plage-dune des plages Sud et Nord, modelées par le vent et les vagues incidents, produisent différentes réactions de la ligne de côte. La disparition projetée, d'ici 2039, de 10 ha de la communauté végétale climacique d'éricacées en raison du recul du rivage laisse présager une tendance à l'instabilité de l'île causée par la migration de la ligne de côte. Les tendances émanant des ensembles de données pour l'ensemble de l'île appuient deux hypothèses différentes, mais complémentaires concernant l'évolution globale de l'île, à savoir : (1) l'île est mobile, la migration des rives entraînant des modifications de la ligne de côte sud et le transport de sédiments vers l'est ou (2) l'île est généralement immobile et perd des sédiments subaériens (de sorte qu'elle rapetisse), probablement en raison de la hausse en cours (et s'accélérant) du niveau de la mer. [Traduit par la Rédaction] Mots-clés : changement des côtes, érosion côtière, géomorphologie des petites îles, île de Sable, hausse du niveau de la mer., Introduction Small oceanic islands are important scaled-down indicators of coastal change driven by changing ocean dynamics. In particular, sea-level rise (SLR), projected globally to be between 0.26 and 0.77 m [...]

Recent advances in the ability to quantify longitudinal connectivity of riverine systems is enabling a better understanding of how connectivity affects fish assemblages. However, the role of connectivity relative to other factors, such as land use, in structuring biological assemblages is just emerging. We assessed the relevance of a structural connectivity index to stream fish communities at a relatively large scale (across five watersheds of Lake Ontario) while controlling for confounding habitat variables, such as land use, elevation, and stream topology. The results were assessed to determine whether species' sensitivities to connectivity are in accordance with expectations of life history. Our results indicated that at large scales, structural connectivity explains significant amounts of variation in community structure (1% to 5.4% as measured by Bray-Curtis similarity), but remains secondary to other habitat components. Connectivity also was significantly related to abundance in three of the seven species assessed. The lower explanatory power of our models compared with studies done at smaller scales suggests that the relevance of connectivity to fish communities is scale-dependent and diminishes relative to other environmental factors at larger spatial extents. Des avancees recentes permettant de mieux quantifier la connectivite longitudinale de systemes fluviaux permettent une meilleure comprehension de l'incidence de la connectivite sur les assemblages de poissons. Toutefois, la comprehension du role de la connectivite dans la structuration des assemblages biologiques comparativement a celui d'autres facteurs comme l'utilisation du sol demeure limitee. Nous avons evalue la pertinence d'un indice de connectivite structurale pour les communautes de poissons de cours d'eau a une echelle relativement grande (couvrant cinq bassins versants du lac Ontario), en tenant compte de variables de confusion associees a l'habitat telles que l'utilisation du sol, l'altitude et la topologie du cours d'eau. Les resultats ont ete evalues afin de determiner si la sensibilite des especes a la connectivite concorde avec les previsions relativement au cycle biologique. Nos resultats indiquent que, a grande echelle, la connectivite structurale explique une portion significative des variations de la structure de la communaute (de 1% a 5,4%, mesuree avec l'indice de similarite de Bray-Curtis), mais que son influence demeure secondaire comparativement a celle d'autres composantes de l'habitat. La connectivite etait aussi significativement reliee a l'abondance pour trois des sept especes evaluees. La puissance explicative plus faible de nos modeles comparativement a des etudes realisees a plus petite echelle donne a penser que l'importance de la connectivite pour les communautes de poissons depend de l'echelle et que, a des echelles plus grandes, elle diminue relativement a celle d'autres facteurs du milieu. [Traduit par la Redaction], Introduction The increased awareness of the effects of anthropogenic structures that may act as barriers on aquatic ecosystems has prompted new research to understand, quantify, and mitigate fragmentation impacts (Fullerton [...]

The effects on benthic macroinvertebrate communities of simulated degradation of streams enabled evaluation of the effects of starting condition, type of degradation, and biota descriptor on the type 1 and type 2 error rates of bioassessment. Benthic macroinvertebrate communities from five reference streams in the Fraser River basin (British Columbia, Canada) were used as the starting conditions of replicated simulations of the effects of suspended sediments in three temporal patterns (none, one-time severe, constant moderate). The dynamics of the simulated stream communities and the type 1 and type 2 errors associated with bioassessments, as described by (i) taxon richness, (ii) EPT (Ephemeroptera, Plecoptera, Trichoptera) richness, (iii) proportion of EPT individuals in the community, (iv) difference in composition from the median reference community (MCDist), (v) Simpson's diversity, and (vi) Simpson's equitability, depended on the combination of starting condition, simpact treatment, and the biota descriptor. To reduce type 1 and type 2 errors in bioassessments using the reference condition approach, bioassessment programs should include (i) matching of test and expected reference communities and refinement of the definition of reference condition and (ii) several biota descriptors that include measures of richness, tolerance, and community composition. Les consequences de degradations simulees de cours d'eau sur les communautes de macroinvertebres benthiques nous ont permis d'evaluer les effets des conditions de depart, du type de degradation et du descripteur de la faune sur les taux d'erreurs de types 1 et 2 dans les evaluations biologiques. Nous avons utilise les communautes benthiques de macroinvertebres de cinq cours d' eau temoins dans le bassin versant du Fraser (Colombie-Britannique, Canada) comme situations de depart dans des simulations (faites en double) des effets des sediments en suspension selon trois patrons temporels (aucun deversement, un seul deversement severe, deversement modere continu). La dynamique des communautes d'eau courante simulees et les erreurs de types 1 et 2 associees aux evaluations biologiques dependent de la combinaison des conditions de depart, du traitement d'impact et du descripteur faunique; les communautes sont decrites par (i) la richesse taxonomique, (ii) la richesse en EPT (Ephemeropteres, Plecopteres, Trichopteres), (iii) la proportion des EPT dans la communaute, (iv) la difference entre la communaute et la communaute mediane de reference (MCDist), (v) la diversite de Simpson et (vi)l'equitabilite de Simpson. Afin de reduire les erreurs de types 1 et 2 dans les evaluations biologiques qui utilisent la methodologie des conditions de reference, les programmes d' evaluation biologique devraient comprendre (i) un accord entre les tests et les communautes de reference attendues et un raffinement de la definition de conditions de reference et (ii) plusieurs descripteurs fauniques qui incluent des mesures de la richesse, de la tolerance et de la composition de la communaute. [Traduit par la Redaction], Introduction The reference condition approach (RCA) to bioassessment (Bailey et al. 2004) has become a common method of evaluating ecosystem health, particularly in the context of streams. The specifics of [...]

Anthropogenic barriers to fish passage, such as culverts and dams, are major factors impeding the persistence and recovery of aquatic species. Considerable work has focused on mitigating these impacts; however, activities associated with measuring and restoring connectivity of aquatic ecosystems often face challenges in determining the passability of barriers by aquatic species. Hydrological modeling software that incorporates biological aspects of a focal species is often used as a relatively inexpensive method for assessing barrier passability for restoration decisions. However, the biological relevance of these approaches remains to be rigorously tested. We assessed passage rates of PIT-tagged Brook TroutSalvelinus fontinalisthrough four road culverts and adjacent reference sites (unaltered areas of the streams) on the island of Newfoundland to determine whether upstream passage through road culverts was more restrictive than unaltered reference areas of the stream. Next, we examined the usefulness of barrier passability predictions derived from FishXing software by comparing them with in situ movement data for this species. Brook Trout passage for three of the four reference sites had a significantly higher range of passable stream flows compared with that for culverts, indicating the presence of velocity barriers in culverts. However, FishXing predictions of suitable fish passage discharges were conservative, and tagged fish successfully navigated partial barriers that were at least 2–3 times the upper limits of stream flow predicted to allow successful passage. The results of our study show a clear need for an improved understanding of fish movement through these structures so that barrier assessment techniques can be refined. The implications of not doing so may lead to restoration actions that result in limited biological benefit. Received February 6, 2013; accepted July 2, 2013 [ABSTRACT FROM AUTHOR]