Dissolved N:P ratio changes in the eastern tropical North Atlantic: effect on phytoplankton growth and community structure.

Czerny, Jasmin M. S., Hauss, Helena , Löscher, Carolin and Riebesell, Ulf (2016) Dissolved N:P ratio changes in the eastern tropical North Atlantic: effect on phytoplankton growth and community structure. Open Access Marine Ecology Progress Series, 545 . pp. 49-62. DOI 10.3354/meps11600.

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Abstract

Previous bioassays conducted in the oligotrophic Atlantic Ocean identified availability of inorganic nitrogen (N) as the proximate limiting nutrient control of primary production, but additionally displayed a synergistic growth effect of combined N and phosphorus (P) addition. To classify conditions of nutrient limitation of coastal phytoplankton in the tropical ocean, we performed an 11 d nutrient-enrichment experiment with a natural phytoplankton community from shelf waters off northwest Africa in shipboard mesocosms. We used pigment and gene fingerprinting in combination with flow cytometry for classification and quantification of the taxon-specific photoautotrophic response to differences in nutrient supply. The developing primary bloom was dominated by diatoms and was significantly higher in the treatments receiving initial N addition. The combined supply of N and P did not induce a further increase in phytoplankton abundance compared to high N addition alone. A secondary bloom during the course of the experiment again displayed higher primary producer standing stock in the N-fertilized treatments. Bacterial abundance correlated positively with phytoplankton biomass. Dominance of the photoautotrophic assemblage by N-limited diatoms in conjunction with a probable absence of any P-limited phytoplankton species prevented an additive effect of combined N and P addition on total phytoplankton biomass. Furthermore, after nutrient exhaustion, dinitrogen (N-2)-fixing cyanobacteria succeeded the bloom-forming diatoms. Shelf waters in the tropical eastern Atlantic may thus support growth of diazotrophic cyanobacteria such as Trichodesmium sp. subsequent to upwelling pulses.

Document Type: Article
Additional Information: WOS:000372571700005
Keywords: Phytoplankton; Nutrient limitation; Nitrogen and phosphorus stoichiometry; Diatoms; Diazotrophic cyanobacteria; Trichodesmium; Upwelling
Research affiliation: OceanRep > SFB 754 > B2
OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > SFB 754 > B8
Kiel University
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-N Experimental Ecology - Food Webs
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.3354/meps11600
ISSN: 0171-8630
Expeditions/Models/Experiments:
Date Deposited: 19 Apr 2016 07:56
Last Modified: 23 Sep 2019 20:40
URI: http://oceanrep.geomar.de/id/eprint/32098

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