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Owing to the enormity and complexity of the Laurentian Great Lakes, an ecosystem classification is needed to better understand, protect, and manage this largest freshwater ecosystem in the world. Using a combination of statistical analyses, published knowledge, and expert opinion, we identified key driving variables and their ecologically relevant thresholds and delineated and mapped aquatic systems for the entire Great Lakes. We identified and mapped 77 aquatic ecological units (AEUs) that depict unique combinations of depth, thermal regime, hydraulic, and landscape classifiers. Those 77 AEU types were distributed across 1997 polygons (patches) ranging from 1 to >48 000 km 2 in area and were most diverse in the nearshore (35 types), followed by the coastal margin (26), and then the offshore (16). Our classification and mapping of ecological units captures gradients that characterize types of aquatic systems in the Great Lakes and provides a geospatial accounting framework for resource inventory, status and trend assessment; research for ecosystem questions; and management and policy-making. Résumé : En raison de l'énormité et de la complexité des Grands Lacs laurentiens, une classification des écosystèmes est nécessaire pour mieux comprendre, protéger et gérer ce plus grand écosystème d'eau douce du monde. En utilisant une combinaison d'analyses statistiques, de connaissances publiées et d'opinions de spécialistes, nous avons cerné des variables clés et leurs seuils importants sur le plan écologique, et délimité et cartographié les systèmes aquatiques pour l'entièreté des Grands Lacs. Nous avons cerné et cartographié 77 unités écologiques aquatiques (UEA) qui représentent les différentes combinaisons de profondeur, de régime thermique et de variables hydrauliques et du paysage importantes pour la classification. Ces 77 types d'UEA sont répartis sur 1997 polygones (parcelles) de superficies allant de 1 à >48 000 km 2 , la région sublittorale en présentant la plus grande diversité (35 types), suivie des bandes côtières (26), puis de la zone extracôtière (16). La classification et la cartographie des unités écologiques font ressortir les gradients qui caractérisent les types de systèmes aquatiques dans les Grands Lacs et fournissent un cadre géospatial de référence pour l'inventaire des ressources, l'évaluation des statuts et tendances, la recherche sur des questions touchant aux écosystèmes et la gestion et l'élaboration de politiques. [Traduit par la Rédaction]

Despite the importance of species-area relationships (SARs) to conservation, SARs in humanfragmented rivers have received little attention. Our aim was to test for the presence and strength of SARs for littoral fish assemblages of an extensively dammed river in south-central Ontario, Canada, and to examine long-running hypotheses for the drivers of SARs. Twenty-six navigational dams with locks built between 1837 and 1913 occur along the 160 km length of the Trent River examined in this study. We evaluated the relationship between richness and fragment area, and then used linear models to test whether the area per se, habitat diversity, or other hypotheses were best supported by the data. A power-function relationship with area explained 46% of the variation in fish species richness, and the slope (z = 0.4) was high compared with SARs reported from other ecosystems, indicating that species accumulated rapidly with an increase in fragment area. Multi-predictor models suggested that area was significantly related to richness, but that vegetation cover diversity had a stronger relative effect. The slope of our SAR may indicate that there is a high degree of isolation between populations in different fragments, even though the lock system reportedly allows some passage of organisms. Our findings also suggest that mitigating against local extinction due to small population sizes (i.e., area effects), and enhancing aquatic vegetation cover may be viable strategies for promoting species diversity in the study river. Studies of SARs in fragmented rivers may offer additional benefits to supporting restoration planning where efforts are being made to increase species diversity.