Late Holocene benthic formainifera beneath perennial sea ice on an Arctic continental shelf

The Canadian Ice Island Project allows geological, biological and oceanographic studies of regions on the Arctic margin that are beneath the perennial pack ice. High-resolution seismic profiles, grab sampling and bottom photography resulted in the discovery of siliceous sponge reefs on the Axel Heiberg Shelf. Sponge colonies interspersed with mudflats form a variety of biotopes for a rich benthic life. The formainifera assemblage is characterized by large numbers of specimens, high species diversity, predominance of calcareous specimens, and a nearly complete lack of living fauna. The perennial sea ice cover is the main controlling factor of the environment. Low regional runoff and rapid freezing of leads in the ice may explain periodic high bottom salinity, reduced detrital deposition, and low organic matter production. The surface foraminifera assemblage is of a subfossiliferous nature which represents an accumulation of dead tests over approximately 1000 years. Small-scale biotope differences and the resulting patchy distribution of species evolved from the environmental stability of the area. The species composition is unique when compared with other known shallow-water Arctic regions and shows a slight affinity with the Pacific fauna, suggesting a migration through the Bering Strait

Exceptionally preserved Late Albian (Cretaceous) Arcellaceans (Thecamoebians) from the Dakota Formation near Lincoln, Nebraska, USA

Thousands of exceptionally well-preserved Arcellaceans (Thecamoebians) have been recovered from a Late Albian (Cretaceous) deposit. Sedimentary samples were obtained from a clayey-silt leaf bed in the Dakota Formation, outcropping in a clay pit excavated by the Yankee Hill Brick Company, located near Lincoln, Nebraska. Based on recovered freshwater macrophyte spore and fossil remains, the leaf bed is a lagerstätten of paleobotanical remains in which the paleoenvironment has been interpreted as a quiescent freshwater setting. The large number of recovered thecamoebians revealed a high intraspecific variability in test morphology that is comparable to Holocene thecamoebian populations. Consequently, we employ the thecamoebian strain taxonomic framework, a first for ancient thecamoebians. Extant species contained in this collection include Difflugia oblonga, Difflugia protaeiformis, Difflugia urens, Pontigulasia compressa, Lagenodifflugia vas, Cucurbitella tricuspis, Lesquereusia spiralis and the cysts of environmentally stressed protozoans—with only one new species reported, Difflugia baukalabastron. The well-preserved nature of the taxa, suggesting little taphonomic bias, and the lack of significant new species supports the current hypothesis of minimal evolution in thecamoebian lineages through geologic time

Fragile abyssal foraminifera (including new Komokiacea) from the Nares Abyssal Plain

The study of eight samples from the Nares Abyssal Plain has shown that the rhizopodan surface population of the area is dominated by forms with fragile, flexible tests. In this rarely reported component of the abyssal population we have identified 20 new species for which holotypes have been designated and figured. We have also designated five lectotypes for species previously described and introduced new terms essential for the concise description of komoki and few other abyssal foraminifera. For the rapid identification of the more complex and less known genera we have provided an identification key. -from Author

Can smaller benthic foraminifera be ignored in paleoenvironmental analyses?

Investigations of the distribution patterns have been carried out on various size fractions of faunal assemblages (eg, >63 mu m, >125 mu m, >150 mu m, >250 mu m and >300 mu m). In our study, information obtained from examination of the 63-125-mu m and the >125-mu m fractions is compared with published data based solely on the larger size fractions. We found that sieves with large openings (125 mu m, 150 mu m, 250 mu m, 300 mu m) allow a significant loss of specimens, including environmental index species, and may have created artificial 'barren zones' in sequences dominated by small-sized species. This suggests that inclusion of the 63-125-mu m fraction in foraminiferal studies may be well worth the additional time and effort required. Data from different sources certainly could be more readily compared or integrated if this procedure was more widely adopted in paleoceanographic studies. -Author

Recent Arctic shelf Foraminifera: seasonally ice covered vs. perennially ice covered areas

Benthic Foraminifera are abundant, highly diverse, and predominantly calcareous on siliceous sponge reefs of the W Axel Heiberg shelf. A total of 110 species, including 38 agglutinated taxa, were identified in 47 surface samples. Living specimens usually constitute <3%, indicating a residual fauna. An important environmental parameter is the perennial ice cover, which causes high salinity, a low sedimentation rate, and a limited food supply. The availability of niches with sufficient nutrient supply and the diverse nature of