Planktonic C:Fe ratios and carrying capacity in the southern Drake Passage

TitlePlanktonic C:Fe ratios and carrying capacity in the southern Drake Passage
Publication TypeJournal Article
Year of Publication2013
AuthorsHopkinson B.M, Seegers B., Hatta M., Measures C.I, Mitchell B.G, Barbeau K.A
JournalDeep-Sea Research Part Ii-Topical Studies in Oceanography
Volume90
Pagination102-111
Date Published2013/06
Type of ArticleArticle
ISBN Number0967-0645
Accession NumberWOS:000320142000010
Keywordsantarctic waters; biomass; coastal; electron-transport; Elemental ratios; growth; Iron; light; limitation; marine-phytoplankton; natural iron fertilization; ocean; Plankton; Southern Ocean
Abstract

The carbon to iron (C:Fe) ratio of planktonic biomass constrains net production in iron-limited regions of the ocean and is an important parameter for predicting biomass production from iron inputs. On a cruise to the southern Drake Passage in July-August 2006, we used two approaches to determine the C:Fe ratio of planktonic material: dual-radiotracer labeling and net biomass production in iron-limited grow-out experiments. There was variability in C:Fe ratios among experiments, but values from the two methods overlapped with average values of 1.4 x 10(5) (mol:mol) for the radiotracer method and 1.7 x 10(5) for the net biomass production method. This is notable since the net biomass production method is a new approach to determine C:Fe ratios. Although it has potential issues related to bottle effects and sensitivity to trace contamination, the method avoids some of the questions associated with iron speciation and bioavailability since ambient iron supports production. Because light intensity is known to affect C:Fe ratios in phytoplankton through photosynthetic iron demands, we tested the effect of light level on C:Fe in Antarctic assemblages. In contrast to what is seen in many phytoplankton cultures, C:Fe ratios increased at low-light, but we suspect that this is due to initial photoinhibition of the low-light adapted winter assemblages at higher light levels. (c) 2012 Elsevier Ltd. All rights reserved.

DOI10.1016/j.dsr2.2012.09.001