Ted E. Delaca

FEEDING ADAPTATIONS OF THE FORAMINIFERAN CIBICIDES REFULGENS LIVING EPIZOICALLY AND PARASITICALLY ON THE ANTARCTIC SCALLOP ADAMUSSIUM COLBECKI

The calcareous foraminifer Cibicides refulgens is a conspicuous and abundant component of the epifaunal community living on the valves of the free-swimming Antarctic scallop, Adamussium colbecki. Examination of this association using light microscopy, scanning electron microscopy, radiotracer, and resin-casting/sectioning techniques, demonstrates that the foraminifer possesses a combination of morphological and physiological adaptations, unique among benthic calcareous foraminifera, which enhance its ability to acquire nutrients in an otherwise oligotrophic and seasonal environment. Three distinct modes of nutrition are employed: (1) grazing the algae and bacteria living upon the scallop shell surface, (2) suspension feeding through the use of a pseudopodial net deployed from a unique superstructure of agglutinated tubes which form an extension to the calcareous test, and (3) parasitism by eroding through the scallops shell, and using free amino acids from the highly concentrated pool in the extrapallial cavity.

NOTODENDRODES HYALINOSPHAIRA (SP. NOV.): STRUCTURE AND AUTECOLOGY OF AN ALLOGROMIID-LIKE AGGLUTINATED FORAMINIFER

We describe Notodendrodes hyalinosphaira, a large (up to 2.7 cm long), facultatively arborescent, agglutinated foraminifer. The species occurs abundantly, and apparently exclusively, in Explorers Cove, an embayment of western McMurdo Sound, Antarctica. The primary agglutinated test is an infaunal, unilocular sphere comprised of a single layer of principally quartz sand grains. Two secondary test features may be associated with the quartz sphere: (1) a thick cover of fine detrital material and/or (2) one, or rarely two, daisy-shaped appendages extending into the water column. These secondary test features in Notodendrodes hyalinosphaira apparently reflect trophic plasticity, ranging from infaunal uptake of dissolved nutrients to suspension feeding. Particle analysis reveals distinct size-class distributions for each test component, indicating a high degree of particle selection. The cell body (sarcode), which occupies approximately half of the quartz-sphere volume, is encased by a theca possessing a single aperture. Notodendrodes hyalinosphaira belongs to unilocular agglutinated foraminifera possessing certain structural similarities with allogromiids.

Assessment of the impact of nuclear wastes in the Russian Arctic

Abstract Concern for nuclear contamination in the Arctic stems from many sources: atmospheric (from global fallout from nuclear testing, or Chernobyl type accidents, marine or ocean current transport, riverine or groundwater transport, biological (migratory species), and ocean dumped wastes. Some of the sources are from quite a distance, such as the radionuclide contamination which enters the Arctic Ocean from the direct discharge of radioactive waste into the waters of the Irish and North seas from western European fuel reprocessing facilities at Sellefield and la Hague. These facilities are maintained by the United Kingdom and France and operate in compliance with international standards. Despite this compliance, and a significant reduction in recent years in the discharge activity levels, these facilities have together discharged over 3 million Curies (Commission of the European Community, 1989). A portion of this discharge is carried into the Arctic Ocean. Concentrations of Cs137 in the Kara Sea appear to have decreased significantly over time in concert with decreases in the European discharge rates. Most of the direct nuclear contamination in the Arctic are from Russian sources over a period of 40+ years associated with the cold war activities, military and weapons productions facilities, decommissioning facilities, operation of the nuclear icebreaker fleet, and wastes from nuclear power plants