Living benthic foraminifera of the Okhotsk Sea: faunal composition, standing stocks and microhabitats.

Bubenshchikova, Natalia, Nürnberg, Dirk , Lembke-Jene, Lester and Pavlova, Galina (2008) Living benthic foraminifera of the Okhotsk Sea: faunal composition, standing stocks and microhabitats. Marine Micropaleontology, 69 . pp. 314-333. DOI 10.1016/j.marmicro.2008.09.002.

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Abstract

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm2), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm2), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.

Document Type: Article
Keywords: Living benthic foraminifera, microhabitat, organic matter flux, oxygen minimum zone, Okhotsk Sea
Research affiliation: AWI
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.marmicro.2008.09.002
ISSN: 0377-8398
Projects: INTAS, KOMEX
Date Deposited: 03 Dec 2008 16:51
Last Modified: 21 Jun 2017 09:05
URI: http://oceanrep.geomar.de/id/eprint/3430

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