Planktic foraminiferal populations and test flux in the eastern North Atlantic Ocean


Planktic foraminiferal assemblages vary in response to seasonal fluctuations of hydrographic properties, between water masses, and after periodical changes and episodic events (e.g. reproduction, storms). Distinct annual variability of the planktic foraminiferal flux is also known from sediment trap data. In this paper we discuss the short-term impacts on interannual flux rates based on data from opening-closing net hauls obtained between the ocean surface and 500 m water depth. Data were recorded during April, May, June, and August at around 47°N, 20°W (BIOTRANS) in 1988, 1989, 1990, 1992, 1993, and during May 1989 and 1992 at 57°N, 20-22°W. Species assemblages closely resemble each other when comparing the mixed layer fauna with the fauna of the upper 100 m and the upper 500 m of the water column. In addition, species assemblages >100 µm are almost indistinguishable from assemblages that are >125 µm in test size. The standing stock of planktic foraminifers at BIOTRANS can vary by more than one order of magnitude over different years; however, species assemblages may be similar when comparing corresponding seasons. Early summer assemblages (June) are distinctly different from late summer assemblages (August). Significant variations in the species composition during spring (April/May) are independent of the mixed layer depth. Spring assemblages are characterized by high numbers of Globigerinita glutinata. In particular, day-to-day variations of the number of specimens and in species composition may have the same order of magnitude as interannual variations. This appears to be independent of the reproduction cycle. Species assemblages at 47°N and 57°N are similar during spring, although surface water temperatures and salinities differ by up to 10°C and 0.7 (PSU). We suggest that the main factors controlling the planktic foraminiferal fauna are the trophic properties in the upper ocean productive layer.Planktic foraminiferal carbonate flux as calculated from assemblages reveals large seasonal variations, a quasi-annual periodicity in flux levels, and substantial differences in timing and magnitude of peak fluxes. At the BIOTRANS station, the average annual planktic foraminiferal CaCO3 fluxes at 100 and 500 m depth are estimated to be 22.4 and 10.0 g/m**2/yr, respectively.

Supplement to: Schiebel, Ralf; Hemleben, Christoph (2000): Interannual variability of planktic foraminiferal populations and test flux in the eastern North Atlantic Ocean (JGOFS). Deep Sea Research Part II: Topical Studies in Oceanography, 47(9-11), 1809-1852

Related Identifier IsSupplementTo
Metadata Access
Creator Schiebel, Ralf ORCID logo; Hemleben, Christoph
Publisher PANGAEA
Publication Year 2000
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 153 datasets
Discipline Geosciences; Natural Sciences
Spatial Coverage (-22.304W, 33.940S, -17.757E, 57.996N); Azores front; Northeast Atlantic; Biotrans; Madeira Basin; Rockall Plateau; Aegir Ridge; Lofoten Basin; Norwegian Sea; Bear Island; NE Atlantic; North Atlantic
Temporal Coverage Begin 1988-04-08T09:40:00Z
Temporal Coverage End 1993-06-16T08:56:00Z