Quéguiner¹, Bernard, Richard T. Barber², Stéphane Blain³, Phillip W. Boyd⁴, Mark A. Brzezinski⁵, Hein De Baar⁶, Valerie M. Franck⁷, David A. Hutchins⁸, Karine Leblanc⁸, David M. Nelson⁹, Peter N. Sedwick¹⁰, Klaas R. Timmermans⁶ and Paul Tréguer³

¹LOB-UMR CNRS 6535, COM, Universite de la Mediterranee, Marseille 13288, France, Tel. (+33) 4 91 82 92 05, Fax. (+33) 4 91 82 19 91, E-mail : queguiner@com.univ-mrs.fr, ²Duke Univ. Marine Lab., Duke Marine Lab. Rd, Beaufort, ³LEMAR-UMR CNRS 6539, Pl. Copernic, Plouzané, France, ⁴NIWA, Univ. Otago, Dunedin, New Zealand, ⁵M.S.I., University of California, Santa Barbara, ⁶NIOZ, Den Burg, Texel, Netherlands, ⁷SOEST, University of Hawaii, ⁸Coll. Ocean. Atmosph. Sci., Oregon State University, Corvallis, ⁹Coll. Marine Studies, University of Delaware and ¹⁰Bermuda Biological Station for Research, St George’s, Bermuda

What did we learn about the limitation of the first trophic level during S.O. JGOFS? New concepts of phytoplankton limitation and their relation to particulate matter properties

Numerous process studies performed during S.O. JGOFS cruises have provided insights into how resources control phytoplankton growth, biochemical composition and elemental stoichiometry. The HNLC status of the open waters of the Southern Ocean can be explained by the low availability of iron, often acting in conjunction with limitation by low levels of silicic acid and irradiance (i.e., vertical mixing). That has led to a new concept of co-limitation of primary producers, whereby nutrient and light utilization are related to iron availability, as distinct from von Liebig’s “classical” idea of nutrient limitation.