ALBERT

Description: Oxygen and carbon stable-isotope compositions of modern benthic foraminifera in the Kara and Pechora estuarine regions of the Arctic continental shelf were compared with water d18O, d13CDIC, temperature, and salinity. The foraminiferal d18O distribution is mostly similar to that of equilibrium calcite, primarily controlled by mixing of runoff and seawater in near-estuarine areas (depth 〈 15-20 m), with additional temperature control seaward. The d13C composition is controlled by remineralization of organic matter, mostly imported by rivers, and by water mixing. Most analyses used the common Arctic foraminifer Elphidium excavatum forma clavata, which yields depleted d13C, as expected for an infaunal species. Isotope records for sediment cores off the Pechora and Yenisey rivers show a decelerating rise in isotope values, of up to 10 per mil in d18O, over the last 10 kyr in a pattern similar to that of rising sea level and concomitant retreat of river mouths, with local complexities probably resulting from glacio-isostatic rebound and changes in sedimentation.

Description: Foraminifera were examined in recent (〈100 years) fine-grained glaciomarine muds from surface sediments and cores from Nordensheld Bay, Novaja Zemlja, and Hornsund and Bellsund, Spitsbergen. This study presents the first data on modern foraminifera distribution for fjord environments in Novaja Zemlja, Russia. The data are interpreted with reference to the distribution of foraminiferal near Svalbard and the Barents Sea. In Nordensheld Bay, live and dead Nonionellina labradorica and Islandiella norcrossi are most abundant in the outer fjord. Cassidulina reniforme and Allogromiina spp. dominate in the middle and inner fjord. The dominant species are dissimilar to species occurring in other areas of the Barents Sea region, with the exception of Svalbard fjords. The number of live foraminifera (24 to 122 tests/10 cm1) in outer and middle Nordensheld Bay corresponds with values known from the open Barents Sea. However, the biomass (0.03 mg/10 cm**3) is two orders of magnitude less due to smaller foraminiferal test size, which in glaciomarine sediments reflects the absence of larger species, paucity of large specimens, and high occurrence of juvenile foraminifera. The smaller size indicates an opportunistic response to environmental stress due to glacier proximity. The presence of Quinqueloculina stalkeri is diagnostic of glaciomarine environments in fjords of Novaja Zemlja and Svalbard.