INFAUNAL BENTHIC FORAMINIFERA IN DISENCHANTMENT AND YAKUTAT BAYS, ALASKA

Short (40-cm) sediment multicores were collected aboard the R/V Alpha Helix in Disenchantment Bay and Yakutat Bay during June 2004 as part of a program to understand fjord processes. Sediment samples from four cores were stained with Rose Bengal and fixed with a 4% buffered formalin solution to determine downcore distribution of living foraminifera. Core tops contained 65-90% stained foraminifers, dominated by Elphidium excavatum with some Buccella frigida and Cassidulina spp. These stained faunas represent foraminifers living at the time of collection. Living specimens of Spiroplectammina earlandi, B. frigida, and E. excavatum were noted at depths down to 20 cm. In multicore AHY04MC2#6, living specimens of S. earlandi were abundant between depths of 11 and 18 cm. Common living S. earlandi were found at depths of 6 to 10 cm and 16 to 20 cm in AHY04MC1#2, suggesting an infaunal habitat for this species. Both of these multicores occur in the basinal portion of Disenchantment Bay. Very few S. earlandi (living or dead) were found in multicore AHY04MC6#4 on the slope of Disenchantment Bay or multicore AHY04MC8#6 in Yakutat Bay. Living E. excavatum are common from 6 to 8 cm in AHY04MC2#6, but are rare in the other multicores below 2 cm. Low numbers of living B. frigida (<10 specimens per sample) were present throughout the multicores. Statistical analyses show that the living (stained) assemblages are significantly different from the dead (unstained) assemblages in both Disenchantment Bay and Yakutat Bay. When S. earlandi is eliminated from the analyses, living assemblages are not significantly different than dead assemblages for the two multicores in Disenchantment Bay. This may support the idea that S. earlandi is infaunal and its distribution is unrelated to taphonomic processes. In addition to foraminifera, diatoms are abundant in the multicores down to 6 cm. Abundant diatoms may indicate annual blooms associated with increased seasonal melting of tidewater glaciers at the head of Disenchantment Bay.