COMPARISONS OF VERTICAL DISTRIBUTION PATTERNS OF LIVING (STAINED) BENTHIC FORAMINIFERA FROM THE ALEUTIAN MARGIN

Vertical distribution patterns of living (rose Bengal-stained) benthic foraminifera were analyzed within tube core sediments taken by the ROV JASON II from the Aleutian margin near Unimak Island. Results from three sites(3283m, 3310m, and 1988m) were compared to better understand the ecology of benthic foraminifera in this region. Habitats examined include those of methane seep and non-seep environments. At a non-seep site(1988m water depth) the agglutinated assemblage (>150µ) had a density maximum at the 0-1cm interval, while standing stocks of calcareous foraminifera had an infaunal maximum. Dominant infaunal taxa included: Globobulimina pacifica, Nonionella stella, Nonionella globosa, Elphidium sp., and Chilostomella oolina. At this site, the deep infaunal species, G. pacifica, reached unusually high densities (about 90/50cc) between 3 and 5cm. In contrast, the foraminiferal assemblage at a non-seep site at(3310m) was dominated by agglutinated taxa (over 90%), with high densities of Rhabdammina, Reophax, Trochammina sp., and Recurvoides. The methane seep site(3283m) was also dominated by agglutinated taxa, with calcareous taxa occurring only in the top 0-1cm surface interval. Elphidium sp. was common at the seep site, and most Cibicidoides wuellerstorfi were found attached to pogonophoran worm tubes elevated above the sediment-water interface. Results from this study reveal clues about the factors that control the distribution of foraminifera, and provide modern analog data for interpretations of the paleoceanographic record.