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| Titel |
Biogeographic classification of the Caspian Sea |
| VerfasserIn |
F. Fendereski, M. Vogt, M. R. Payne, Z. Lachkar, N. Gruber, A. Salmanmahiny, S. A. Hosseini |
| 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 ; 11, no. 22 ; Nr. 11, no. 22 (2014-11-27), S.6451-6470 |
| Datensatznummer |
250117695
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| Publikation (Nr.) |
 copernicus.org/bg-11-6451-2014.pdf |
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| Zusammenfassung |
| Like other inland seas, the Caspian Sea (CS) has been influenced by climate
change and anthropogenic disturbance during recent decades, yet the
scientific understanding of this water body remains poor. In this study, an
eco-geographical classification of the CS based on physical information
derived from space and in situ data is developed and tested against a set of
biological observations. We used a two-step classification procedure,
consisting of (i) a data reduction with self-organizing maps (SOMs) and (ii) a
synthesis of the most relevant features into a reduced number of marine
ecoregions using the hierarchical agglomerative clustering (HAC) method. From
an initial set of 12 potential physical variables, 6 independent variables
were selected for the classification algorithm, i.e., sea surface temperature
(SST), bathymetry, sea ice, seasonal variation of sea surface salinity
(DSSS), total suspended matter (TSM) and its seasonal variation (DTSM). The
classification results reveal a robust separation between the northern and
the middle/southern basins as well as a separation of the shallow nearshore
waters from those offshore. The observed patterns in ecoregions can be
attributed to differences in climate and geochemical factors such as distance
from river, water depth and currents. A comparison of the annual and monthly
mean Chl a concentrations between the different ecoregions shows
significant differences (one-way ANOVA, P < 0.05). In particular, we
found differences in phytoplankton phenology, with differences in the date of
bloom initiation, its duration and amplitude between ecoregions. A first
qualitative evaluation of differences in community composition based on
recorded presence–absence patterns of 25 different species of plankton, fish
and benthic invertebrate also confirms the relevance of the ecoregions as
proxies for habitats with common biological characteristics. |
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