Abstract

The distribution of living (rose Bengal stained) foraminiferal species along three U.S. East Coast submarine canyons was investigated to determine if any populations were restricted to narrow ranges of water depth or specific canyon subenvironments. Thirty samples were collected from eleven sites (ranging from 1438 to 2500 m water depth) along Wilmington, South Wilmington, North and South Heyes canyons during dives of the DSRV Alvin. Percent abundance data of foraminiferal species in each sample were analyzed using Q-mode cluster analysis. The species composition of each cluster group was examined by calculating occurrence (O), constancy (C), and biofacies fidelity (BF). Species diversity measures H(S) and E were also determined. These analyses show that live benthic foraminifera have broad, depth-related distribution patterns. Three main groups were identified. The abyssal realm is discriminated from the lower bathyal realm by variations in ubiquitous species proportions and by the presence of several rarely occurring species in abyssal samples. The shallower and deeper portions of the lower bathyal realm can be separated but only by varying proportions of species. No canyon subenvironments that we sampled have distinctive living faunas. The three-fold depth-related subdivision of the study area closely matches a previously published subdivision based on dead foraminifera in this area. The lower bathyal and abyssal regions of the study area show no sign of significant downslope sediment transportation.

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