 |
| Titel |
Pigments, elemental composition (C, N, P, and Si), and stoichiometry of particulate matter in the naturally iron fertilized region of Kerguelen in the Southern Ocean |
| VerfasserIn |
M. Lasbleiz, K. Leblanc, S. Blain, J. Ras, V. Cornet-Barthaux, S. Hélias Nunige, B. Quéguiner |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 20 ; Nr. 11, no. 20 (2014-10-30), S.5931-5955 |
| Datensatznummer |
250117658
|
| Publikation (Nr.) |
 copernicus.org/bg-11-5931-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
The particulate matter distribution and phytoplankton community structure of
the iron-fertilized Kerguelen region were investigated in early austral
spring (October–November 2011) during the KEOPS2 cruise. The iron-fertilized
region was characterized by a complex mesoscale circulation resulting in a
patchy distribution of particulate matter. Integrated concentrations over
200 m ranged from 72.2 to 317.7 mg m−2 for chlorophyll a 314 to
744 mmol m−2 for biogenic silica (BSi), 1106 to 2268 mmol m−2
for particulate organic carbon, 215 to 436 mmol m−2 for particulate
organic nitrogen, and 29.3 to 39.0 mmol m−2 for particulate organic
phosphorus. Three distinct high biomass areas were identified: the coastal
waters of Kerguelen Islands, the easternmost part of the study area in the
polar front zone, and the southeastern Kerguelen Plateau. As expected from
previous artificial and natural iron-fertilization experiments, the
iron-fertilized areas were characterized by the development of large diatoms
revealed by BSi size–fractionation and high performance liquid
chromatography (HPLC) pigment signatures, whereas the iron-limited reference
area was associated with a low biomass dominated by a mixed (nanoflagellates
and diatoms) phytoplankton assemblage. A major difference from most previous
artificial iron fertilization studies was the observation of much higher
Si : C, Si : N, and Si : P ratios (0.31 ± 0.16, 1.6 ± 0.7
and 20.5 ± 7.9, respectively) in the iron-fertilized areas compared to
the iron-limited reference station (0.13, 1.1, and 5.8, respectively). A
second difference is the patchy response of the elemental composition of
phytoplankton communities to large scale natural iron fertilization.
Comparison to the previous KEOPS1 cruise also allowed to address the seasonal
dynamics of phytoplankton bloom over the southeastern plateau. From
particulate organic carbon (POC), particulate organic nitrogen (PON), and BSi
evolutions, we showed that the elemental composition of the particulate
matter also varies at the seasonal scale. This temporal evolution followed
changes of the phytoplankton community structure as well as major changes in
the nutrient stocks progressively leading to silicic acid exhaustion at the
end of the productive season.
Our observations suggest that the specific response of phytoplankton
communities under natural iron fertilization is much more diverse than what
has been regularly observed in artificial iron fertilization experiments and
that the elemental composition of the bulk particulate matter reflects
phytoplankton taxonomic structure rather than being a direct consequence of
iron availability. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|