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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2006.01.006 Byline: B.H. Corliss (a), X. Sun (a), C.W. Brown (b), W.J. Showers (c) Keywords: Benthic; Foraminifera; Deep-sea; Paleoceanography; North Atlantic Abstract: The stable isotopic composition of benthic foraminifera has been widely used to reconstruct deep-ocean circulation, but questions have been raised about the influence of organic carbon flux on the carbon isotopic composition of deep-sea taxa. We show that annual and seasonality of primary productivity in the North Atlantic do not affect [delta].sup.13C of Planulina wuellerstorfi, but that the intermittency or seasonality of primary production has a significant effect (0.9a[degrees] change over 60[degrees] latitude) on [delta].sup.13C of Epistominella exigua, reflecting the influence of pelagic-benthic coupling and microhabitat preferences on test geochemistry. These results support the use of [delta].sup.13C of P. wuellerstorfi in paleocirculation studies and suggest that the [delta].sup.13C of E. exigua can be used to reconstruct seasonality of productivity. Author Affiliation: (a) Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Box 90227, Durham, NC 27708, USA (b) Office of Research and Applications, National Oceanic and Atmospheric Administration, College Park, MD 20742, USA (c) Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27607, USA Article History: Received 1 July 2005; Revised 21 January 2006; Accepted 27 January 2006

Fourteen algae clones belonging to four different classes, including clones of Pseudo-nitzschia (Bacillariophyceae), some of which are capable of producing the toxin domoic acid, have been studied by means of resonance Raman spectra excited at 457.9 and 488 nm. Spectra taken at both excitation wavelengths are of high quality and are sufficiently distinct to differentiate clones at the algal class level. All spectra contain major features near 1000, 1153, and 1523 [cm.sup.-1], which are strongly resonance enhanced due to carotenoid pigments. Weaker features between 920-980 and 1170-1230 [cm.sup.-1], also due to carotenoid pigments, are more characteristic of the algae clones and more directly reflect different carotenoid composition. Similarities and differences among spectra have been analyzed by the method of principal component analysis (PCA). A distinct clustering of spectral data according to algal class has been shown by PCA score plots. All Pseudo-nitzschia clones can be separated from other classes of algae on the basis of spectra, but it is not possible to distinguish toxic Pseudo-nitzschia from nontoxic clones on the basis of these spectra, which reflect only differences in carotenoid composition.

The stable isotopic composition of benthic foraminifera is widely employed to reconstruct deep-ocean circulation, but questions are raised about the influence of organic carbon flux on the carbon isotopic composition of deep-sea taxa. The studies suggest that the [delta][.sup.13C] of Epistominella exigua can be used to reconstruct seasonality of productivity.