Assessing the role of dust deposition on phytoplankton ecophysiology and succession in a low-nutrient low-chlorophyll ecosystem: a mesocosm experiment in the Mediterranean Sea 1Stazione Zoologica Anton Dohrn, Villa Comunale, 80121, Naples, Italy
03 May 2013
2Université Pierre et Marie Curie-Paris 6, UMR7621, LOMIC, Observatoire Océanologique, 66650 Banyuls/Mer, France
3CNRS, UMR7621, LOMIC, Observatoire Océanologique, 66650 Banyuls/Mer, France
4Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN), CNRS-Université Paris VI, Campus Jussieu, Paris, France
5Laboratoire d'Océanographie de Villefranche/Mer, CNRS-INSU, UMR7093, Observatoire Océanologique, 06230, Villefranche/Mer, France
6Université Pierre et Marie Curie-Paris 6, UMR7093, LOV, Observatoire Océanologique, 06230, Villefranche/Mer, France
Received: 30 November 2012 – Published in Biogeosciences Discuss.: 21 December 2012 Abstract. In this study, we investigate the response of the phytoplankton community,
with emphasis on ecophysiology and succession, after two experimental
additions of Saharan dust in the surface water layer of a low-nutrient
low-chlorophyll ecosystem in the Mediterranean Sea. Three mesocosms were
amended with evapocondensed dust to simulate realistic Saharan dust events,
while three additional mesocosms were kept unamended and served as controls.
The experiment consisted in two consecutive dust additions and samples were
daily collected at different depths (−0.1, −5 and −10 m) during one
week, starting before each addition occurred. Data concerning HPLC pigment
analysis on two size classes (< 3 and > 3 μm), electron
transport rate (ETR) vs. irradiance curves, non-photochemical fluorescence
quenching (NPQ) and phytoplankton cell abundance (measured by flow
cytometry), are presented and discussed in this paper. Results show that
picophytoplankton mainly respond to the first dust addition, while the second
addition leads to an increase of both pico- and nano-/microphytoplankton.
Ecophysiological changes in the phytoplankton community occur, with NPQ and
pigment concentration per cell increasing after dust additions. While
biomass increases after pulses of new nutrients, ETR does not greatly vary
between dust-amended and control conditions, in relation with
ecophysiological changes within the phytoplankton community, such as the
increase in NPQ and pigment cellular concentration. A quantitative assessment
and parameterisation of the onset of a phytoplankton bloom in a
nutrient-limited ecosystem is attempted on the basis of the increase in
phytoplankton biomass observed during the experiment.
The results of this study are discussed focusing on the adaptation of
picophytoplankton to nutrient limitation in the surface water layer, as well
as on size-dependent competition ability in phytoplankton.
Revised: 19 March 2013 – Accepted: 12 April 2013 – Published: 03 May 2013
Citation: Giovagnetti, V., Brunet, C., Conversano, F., Tramontano, F., Obernosterer, I., Ridame, C., and Guieu, C.: Assessing the role of dust deposition on phytoplankton ecophysiology and succession in a low-nutrient low-chlorophyll ecosystem: a mesocosm experiment in the Mediterranean Sea, Biogeosciences, 10, 2973-2991, doi:10.5194/bg-10-2973-2013, 2013.