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Copyright of Ecoscience (Ecoscience) is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Deglaciation of the James Bay region was highly dynamic, with the occurrence of ice (Cochrane) readvances into glacial Lake Ojibway around final deglaciation time, which culminated with the drainage of Ojibway waters into Hudson Bay and subsequent incursion of the Tyrrell Sea at ∼8 ka. Renewed interest on these events comes from the possible link between the drainage of the ice-dammed Lake Agassiz-Ojibway and a major climate deterioration known as the 8.2-ka cooling event. Recent glaciological modeling suggests that this drainage may have occurred subglacially, a mechanism that can accommodate more than one lake discharge, as suggested by marine records. The exact number and timing of drainage events, as well as location of the lake discharge pathway(s) remain, however, largely unconstrained. Here we focus on the events that led to the drainage of Lake Ojibway by documenting late-glacial sedimentary sequences located east of James Bay. Our investigations indicate that the deglacial sequence consists of a readvance till, extensive Ojibway rhythmites, and thick marine sediments. The glaciolacustrine and marine units are separated by a 60 cm-thick horizon composed of laminated silt beds containing rounded clay balls and disseminated clasts resulting from the abrupt drainage of the lake. Radiocarbon dating of marine fossils lying above the drainage horizon indicates that the glaciolacustrine episode ended around 8128–8282 cal yr BP. Micropaleontological analyses reveal that freshwater ostracods (Candona sp.) and marine microfossils (foraminifers, dinocysts) occur together in the upper part of the Ojibway sediments. Analysis of oxygen isotopes (δ18O) of ostracods and foraminifers originating from the same stratigraphic position show highly contrasting values that suggest possible subglacial exchanges between Lake Ojibway and Tyrrell Sea waters prior to the final drainage event. The complexity of the deglacial events is further indicated by radiocarbon dating of marine shells retrieved from a Cochrane till that suggests that the last ice readvance occurred almost simultaneously with the final lake discharge. These results bring additional constraints on the drainage mechanism of the coalesced Lake Agassiz-Ojibway and indicate that the James Bay region formed an important drainage pathway for meltwaters at the end of the last deglaciation. [Copyright &y& Elsevier]

The seaweed flora from James Bay, Canada is compared with three contiguous northeastern Canadian Arctic areas (Hudson Bay, Hudson Strait, and the Ellesmere-Baffin Islands area extending northward to the Arctic Ocean). A conspicuous reduction pattern was evident with 131 taxa recorded for the Ellesmere-Baffin Islands area, 106 for Hudson Strait, 81 from Hudson Bay, and 44 in James Bay. The Ellesmere-Baffin Islands area has a more rocky open coastal environment and higher salinities than James Bay, which is more highly sedimented and impacted by hydroelectric development and freshwater discharge. The Ellesmere-Baffin Islands area (∼32-30.5%) has a higher mean number of shared taxa (90.0 ± 18.4 SE) than James Bay (37.6 ± 2.7 SE), while Hudson Strait and Hudson Bay have intermediate values of 78 ± 14.1 SE and 64 ± 9.2 SE, respectively. The combined flora from the four areas consists of 164 taxa, including 49 red, 65 brown, 1 chrysophyte, and 49 green algae. Fifty of these total taxa (31%) were only found in one area, with 25 occurring between Ellesmere Island and Baffin Island, 13 within the Strait proper, and 6 in both Hudson and James Bays. Strong habitat and salinity gradients, as well as the great distances between collection sites and the haphazard nature of collections may have contributed to these restrictive patterns. Cheney's (1977) floristic ratio documents that all four geographies (including their composite flora) have cold water floras. Four new distributional records are documented from James Bay: Chaetomorpha minima, Elachista fucicola, Phyllophora pseudoceranoides, and Spyridia filamentosa. The cryptogenic taxon Spyridia, which has unclear origins, is a warm-water disjunct in the northwestern Atlantic previously known only from one site in Nova Scotia and a few locations in southern Maine/New Hampshire but mostly south of Cape Cod, Massachusetts. A single introduced species (Dumontia contorta from Europe) is recorded from James Bay and the Ellesmere-Baffin Islands area, while none are documented from the other areas. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Field-Naturalist is the property of Ottawa Field Naturalists' Club and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)