TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 57 (No. 3), pp. 377-384, 2001

Monothalamous Soft-Shelled Foraminifera at an Abyssal Site in the North Pacific: A Preliminary Report

Andrew J. Gooday1, Hiroshi Kitazato2*, Saori Hori2 and Takashi Toyofuku2

1Southampton Oceanography Centre, Empress Dock, European Way, Southampton, SO14 3ZH, U.K.
2Department of Life and Earth Sciences, Shizuoka University, Oya 836, Shizuoka 422-8529, Japan

(Received 10 May 2000; in revised form 30 October 2000; accepted 8 November 2000)

Abstract: Soft-shelled monothalamous foraminifera, including species belonging to the suborders Allogromiida and Astrorhizida (families Saccamminidae and Psammosphaeridae), are an abundant and diverse component of the meiofauna in the deep NE Atlantic but have never been systematically documented in the Pacific Ocean. We examined the 32-63 mm and >63 mm fractions of a sample (0-1 cm layer, surface area 52.8 cm2) from an abyssal plain in the subarctic North Pacific, close to the Aleutian Trench (48°05.43´ N, 176°55.06´ E; 5289 m water depth). The residues yielded an estimated 2876 stained foraminifera (=545 per 10 cm2) of which >75% occurred in the upper 0.5 cm layer and almost half in the 32-63 mm fraction. Rather less than a third (30.5%) of individuals, and about half of the morphospecies (56 out of 121), were soft-shelled monothalamous forms. Many of these, particularly the saccamminids, were tiny, <120 mm in maximum dimension. Based on our analysis of this sample, and previous results in the North Atlantic and NW Indian Oceans, we suggest that these poorly known taxa are a consistently important component of the abyssal meiofauna in well-oxygenated areas.

*Corresponding author E-mail: sehkita@ipc.shizuoka.ac.jp

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