Skip Navigation



JPR Advance Access published online on June 2, 2007
Journal of Plankton Research, doi:10.1093/plankt/fbm047
This Article
Right arrow Advance Access manuscript (PDF)
Right arrow All Versions of this Article:
29/8/655    most recent
fbm047v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Delizo, L.
Right arrow Articles by Hall, J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Delizo, L.
Right arrow Articles by Hall, J.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2007. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org

Taxonomic Composition and Growth Rates of Phytoplankton Assemblages at the Subtropical Convergence East of New Zealand

Liza Delizo1,2, Walker O. Smith, Jr2,* and Julie Hall3

1 Virginia Institute of Marine Sciences, College of William and Mary, Gloucester Pt., VA 23062; 3 NIWA, P.O. Box 11-115, Hamilton, New Zealand

* Corresponding author: email wos{at}vims.edu

Received on November 2, 2005; revised on February 22, 2006; accepted on May 24, 2007


  Abstract

Off the eastern coast of New Zealand, warm, saline, nutrient-poor Subtropical Waters (STW) are separated from cool, fresher, relatively nutrient-rich Sub-Antarctic Waters (SAW) by the Subtropical Convergence (STC). The Chatham Rise, a submarine rise, restricts the latitudinal movement of the STC as well as mixing of STW and SAW. Due to this restriction, this sector of the STC is characterized by sharp gradients in temperature, macro- (nitrate, silicate, and phosphate) and micro- (iron) nutrient concentrations. Shipboard incubations were conducted during austral spring 2000 and 2001 to test the hypothesis that these gradients affect the taxonomic composition and/or growth rates of phytoplankton on either side of and at the STC. Maximum chlorophyll a concentrations during 2000 were 0.39 µg L–1, but were an order of magnitude higher in 2001. During both years STC phytoplankton were dominated by diatoms (77% of the total chlorophyll a during austral spring 2000 and 70% during spring 2001), whereas cryptophytes and prasinophytes dominated STW assemblages (27 and 36% during 2000, and 63 and 17% during 2001). Chlorophyll in the SAW was dominated by procaryotes and photosynthetic nanoflagellates during 2000 (17% procaryotes, 68% nanoflagellates), and by diatoms during the austral spring 2001 cruise (53%). Growth rates of the phytoplankton assemblage were determined by 14C-labeling of chlorophyll a and photosynthetic pigments. During 2000 temperature-normalized growth rates were near maximal at the STC, and decreased on average to less than half of the maximum north and south of that front, whereas in 2001 both absolute and relative growth rates were low at all stations. Growth rates did not closely parallel biomass of the various taxa, suggesting that nutrient limitation and/or grazing were significantly impacting standing stocks. It appeared that growth was strongly influenced by nutrients and light, but that biomass was more strongly influenced by grazing. The Subtropical Convergence is a globally important region of enhanced biomass and productivity; however, the phytoplankton assemblage reflects control by both top-down and bottom-up processes that makes a predictive understanding of the area's biogeochemical cycles extremely difficult.

Key Words: Phytoplankton • Chlorophyll • Growth Rate • Pigments • Subtropical Convergence

2 Present address: Florida Atlantic University, Boca Raton, FL 33431


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.