Ecological niches of open ocean phytoplankton taxa
Résumé
We characterize the realized ecological niches of 133 phytoplankton taxa in the open ocean based on observations from the MAREDAT initiative and a statistical species distribution model (MaxEnt). The models find that the physical conditions (mixed layer depth, temperature, light) govern large-scale patterns in phyto-plankton biogeography over nutrient availability. Strongest differences in the realized niche centers were found between diatoms and coccolithophores. Diatoms (87 species) occur in habitats with significantly lower temperatures, light intensity and salinity, with deeper mixed layers, and with higher nitrate and silicate concentrations than coccolithophores (40 species). However, we could not statistically separate the realized niches of coccolithophores from those of diazotrophs (two genera) and picophytoplankton (two genera). Phaeocystis (two species) niches only clearly differed from diatom niches for temperature. While the realized niches of diatoms cover the majority of niche space, the niches of picophytoplankton and coccolithophores spread across an intermediate fraction and diazotroph and colonial Phaeocystis niches only occur within a relatively confined range of environmental conditions in the open ocean. Our estimates of the realized niches roughly match the predictions of Reynolds' C-S-R model for the global ocean, namely that taxa classified as nutrient stress tolerant have niches at lower nutrient and higher irradiance conditions than light stress tolerant taxa. Yet, there is considerable within-class variability in niche centers, and many taxa occupy broad niches, suggesting that more complex approaches may be necessary to capture all aspects of phytoplankton ecology.
Mots clés
Angers CEDEX 01
France}
Université d'Angers
UPRES EA 2644
[15]{Laboratoire des Bio-Indicateurs Actuels et Fossiles (BIAF)
[11]{Department of Biological Sciences
Old Dominion University
Norfolk
VA
USA}
[12]{InstfBiogeochemie uSchadstoffdynamik
Universitätstrasse 16
8092 Zürich
Switzerland}
[13]{Department of Marine Sciences
Sultan Qaboos University
California 90095
Poland}
141 Warszawa
02-
Polish Academy of Sciences
Department of Antarctic Biology
[10]{Institute of Biochemistry and Biophysics
Sultanate of Oman}
[14]{National Oceanography Centre
SO14 3ZH
Southampton
Waterfront Campus
Tasmania
Hobart
Private Bag 129
University of Tasmania
}
[8]{Institute for Marine and Antarctic Studies
PO Box 11103
The Ferry Landing
[9]{The Freshwater Biological Association
Australia}
7001
Ambleside
Far Sawrey
UK}
[17]{University of Groningen
Centre for Life Sciences Ecophysiology of Plants
LA22 0LP
Los Angeles
[16]{UCLA
49045