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| Titel |
Large clean mesocosms and simulated dust deposition: a new methodology to investigate responses of marine oligotrophic ecosystems to atmospheric inputs |
| VerfasserIn |
C. Guieu, F. Dulac, K. Desboeufs, T. Wagener, E. Pulido-Villena, J.-M. Grisoni, F. Louis, C. Ridame, S. Blain, C. Brunet, E. Bon Nguyen, S. Tran, M. Labiadh, J.-M. Dominici |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 9 ; Nr. 7, no. 9 (2010-09-20), S.2765-2784 |
| Datensatznummer |
250004970
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| Publikation (Nr.) |
 copernicus.org/bg-7-2765-2010.pdf |
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| Zusammenfassung |
Intense Saharan dust deposition occurs over large oligotrophic areas in the
Mediterranean Sea and in the Tropical Atlantic, and its impact on the
biogeochemical functioning of such oligotrophic ecosystems needs to be
understood. However, due to the logistical difficulties of investigating
in situ natural dust events, and due to the inherent limitations of microcosm
laboratory experiments, new experimental approaches need to be developed. In
this paper, we present a new experimental setup based on large, clean
mesocoms deployed in the frame of the DUNE (a DUst experiment in a
low-Nutrient, low-chlorophyll Ecosystem) project. We demonstrate that these
tools are highly relevant and provide a powerful new strategy to in situ studies of
the response of an oligotrophic ecosystem to chemical forcing by atmospheric
deposition of African dust. First, we describe how to cope with the large
amount of dust aerosol needed to conduct the seeding experiments by
producing an analogue from soil collected in a source area and by performing
subsequent appropriate physico-chemical treatments in the laboratory,
including an eventual processing by simulated cloud water. The comparison of
the physico-chemical characteristics of produced dust analogues with the
literature confirms that our experimental simulations are representative of
dust, aging during atmospheric transport, and subsequent deposition to the
Mediterranean. Second, we demonstrate the feasibility in coastal areas to
installing, in situ, a series of large (6 × 52 m3) mesocosms without
perturbing the local ecosystem. The setup, containing no metallic parts and
with the least possible induced perturbation during the sampling sequence,
provides an approach for working with the required conditions for
biogeochemical studies in oligotrophic environments, where nutrient and
micronutrients are at nano- or subnano-molar levels. Two, distinct "seeding
experiments" were conducted by deploying three mesocosms serving as
controls (CONTROLS-Meso = no addition) and three mesocosms seeded with the
same amount of Saharan dust (DUST-Meso = 10 g m−2 of sprayed dust).
A large panel of biogeochemical parameters was measured at 0.1 m, at 5 m and
10 m in all of the mesocosms and at a selected site outside the mesocosms
before seeding and at regular intervals afterward. Statistical analyses of
the results show that data from three mesocosms that received the same
treatment are highly reproducible (variability < 30%) and that there is
no significant difference between data obtained from CONTROLS-Meso and data
obtained outside the mesocosms.
This paper demonstrates that the methodology developed in the DUNE project
is suitable to quantifying and parameterizing the impact of atmospheric
chemical forcing in a low-nutrient, low-chlorophyll (LNLC) ecosystem. Such
large mesocosms can be considered as 1-D ecosystems so that the
parameterization obtained from these experiments can be integrated into
ecosystem models. |
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