Metabolic response of oligotrophic plankton communities to deep water nutrient enrichment

Patricia M. McAndrew*, Karin M. Bjorkman, Matthew J. Church, Paul J. Morris, Nicholas Jachowski, Peter J. le B. Williams, David M. Karl

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

43 Citations (Scopus)

Abstract

Studies on upper ocean plankton production and respiration in oligotrophic ecosystems are taken to imply that these regions are net heterotrophic (i.e. gross primary production [GPP] <respiration [R]). In this study we examined the hypothesis that the regularly observed state of net heterotrophy in the oligotrophic North Pacific Ocean may be interrupted by periodic bursts of net autotrophy when GPP becomes decoupled from R. To examine this hypothesis, we conducted a series of nutrient addition experiments in the oligotrophic North Pacific Subtropical Gyre (NPSG) in which nutrient-replete deep seawater was mixed with nutrient-depleted mixed-layer water. We monitored time-dependent changes in rates of GPP and R as well as dynamics of chlorophyll and nutrient concentrations. Our results consistently demonstrated that following the addition of nutrients: (t) phytoplankton biomass (chl a) and primary production increase; (2) the photoautotrophic plankton assemblage shifts from small (<2 mu m diameter) to large (> 10 mu m diameter), chl c-containing and Si-utilizing cells; and (3) community metabolism shifts from near balance, or slightly net heterotrophic, to demonstrably net autotrophic metabolism. These results suggest that nutrient availability partly regulates plankton community structure and dynamics, and could serve as a mechanism to temporally and spatially decouple GPP and R in oligotrophic open ocean ecosystems.

Original languageEnglish
Pages (from-to)63-75
Number of pages13
JournalMarine Ecology Progress Series
Volume332
Publication statusPublished - 2007

Keywords

  • respiration
  • Stn ALOHA
  • SARGASSO SEA
  • net community production
  • North Pacific Ocean
  • SKELETONEMA-COSTATUM
  • CELLULAR CHEMICAL COMPOSITION
  • MARINE DIATOMS
  • RESPIRATION
  • SURFACE WATERS
  • PACIFIC SUBTROPICAL GYRE
  • ohgotrophic
  • metabolic balance
  • nutrient addition
  • STATION ALOHA
  • AMMONIUM LIMITATION
  • OPEN-OCEAN

Cite this