Comparison of Winter and Summer Growth Stages of the Diatom Eucampia antarctica from the Kerguelen Plateau and South of the Antarctic Convergence Zone

Abstract

On ODP Leg 119, specimens collected of Eucampia antarctica (Castracane) Mangin var. antarctica exhibited morphological and distribution patterns that contrasted with those of Eucampia antarctica var. recta (Mangin) G. Fryxell et Prasad. E. antarctica var. antarctica was found over the northern Kerguelen Plateau, north of the summer Antarctic Convergence Zone, in the subpolar plankton and in the sediments. E. antarctica var. recta was found close to the continent in Prydz Bay. It was also collected near and under the ice in the northern Weddell Sea on a National Science Foundation Division of Polar Programs project (1983)(1984)(1985)(1986)(1987)(1988).A key feature for distinguishing the two varieties in the field is the growth habit, with curvature in broad girdle view of the nominate, subpolar variety in both the winter stage and the more lightly silicified summer stage. A low ratio of terminal to intercalary valves results from the repeated division of the original doublets into chains of considerable length of the winter stage. Small spines around the elevations of one valve serve to clasp the sibling valve and maintain the chain formation. Cells of E. antarctica var. recta tend to be somewhat larger than E. antarctica var. antarctica, and they form chains that are straight in broad girdle view but slightly curved in narrow girdle view. There are no spines on an elevation of the valve, and a hyaline ring surrounds the pore field, forming a costate ocellus in the winter.This truly polar variety shows less growth in the winter stage, with a higher ratio of terminal to intercalary valves in Prydz Bay than that of the nominate variety from the subpolar regions over the Kerguelen Plateau.

High-resolution Holocene climate record from Maxwell Bay, South Shetland Islands, Antarctica

“…antarctica (S/A [symmetric versus asymmetric forms] ratio; Leventer et al, 2002;Shipboard Scientifi c Party, 2005). Variations in Eucampia antarctica morphology ratio of terminal to intercalary valves (T/I ratio; Fryxell, 1991) are also observed. Both ratios show similar trends.…”

Study of Entrained Antarctic Diatoms from the Southwest Indian Ocean

“…Dominant Antarctic dia toms were identified up to species and subspecies level; iden ti fication of less abundant diatoms was done up to the generic level. Taxonomic identification of diatoms was done following handbooks (Hustedt 1958, Hasle 1965, Fen ner et al 1976, Johansen & Fryxell 1985, Villareal & Fry xell 1983, Fryxell 1991, Zielinski 1993. The relative abun dance of each diatom species was calculated against the total diatom abundance to understand the origin of the do mi na ting forms of the diatom assemblage (Fig.…”

“…Eucampia antarctica produces mor pho logically different summer and winter stages, dif fe rent terminal and intercalary valves and also different warm and cold varieties. This ratio can be used to study seaice extent (Kaczmarska et al 1993, Fryxell 1991. Actinocyclus actinochilus (Ehrenberg) Simonsen has a re la tive abundance of about 2 %.…”

Morphological study of the genus Eucampia (Bacillariophyceae) in Korean coastal waters

“…Only species from the polar regions have resting spores, e.g., Eucampia antarctica (Fryxell andPrasad 1990, Hasle andSyvertsen 1996). The thickness of their cell wall changes with season (Fryxell 1991).…”

“…Only species from the polar regions have resting spores, e.g., Eucampia antarctica (Fryxell andPrasad 1990, Hasle andSyvertsen 1996). The thickness of their cell wall changes with season (Fryxell 1991). Currently, eight species of the genus Eucampia have been reported around the world (Van Landingham 1969, Fryxell and Prasad 1990, Rivera et al 2003.…”