Biogeographic classification of the Caspian Sea
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...
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doaj-9defb3c1f0dd4b00be0da576180fe0642020-11-24T21:07:21ZengCopernicus PublicationsBiogeosciences1726-41701726-41892014-11-0111226451647010.5194/bg-11-6451-2014Biogeographic classification of the Caspian SeaF. Fendereski0M. Vogt1M. R. Payne2Z. Lachkar3N. Gruber4A. Salmanmahiny5S. A. Hosseini6Gorgan University of Agricultural Sciences and Natural Resources, Faculty of Fisheries and Environmental Sciences, Gorgan, IranEnvironmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, SwitzerlandEnvironmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, SwitzerlandEnvironmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, SwitzerlandEnvironmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, SwitzerlandGorgan University of Agricultural Sciences and Natural Resources, Faculty of Fisheries and Environmental Sciences, Gorgan, IranGorgan University of Agricultural Sciences and Natural Resources, Faculty of Fisheries and Environmental Sciences, Gorgan, IranLike 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 <i>a</i> concentrations between the different ecoregions shows significant differences (one-way ANOVA, <i>P</i> < 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.http://www.biogeosciences.net/11/6451/2014/bg-11-6451-2014.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
F. Fendereski M. Vogt M. R. Payne Z. Lachkar N. Gruber A. Salmanmahiny S. A. Hosseini |
spellingShingle |
F. Fendereski M. Vogt M. R. Payne Z. Lachkar N. Gruber A. Salmanmahiny S. A. Hosseini Biogeographic classification of the Caspian Sea Biogeosciences |
author_facet |
F. Fendereski M. Vogt M. R. Payne Z. Lachkar N. Gruber A. Salmanmahiny S. A. Hosseini |
author_sort |
F. Fendereski |
title |
Biogeographic classification of the Caspian Sea |
title_short |
Biogeographic classification of the Caspian Sea |
title_full |
Biogeographic classification of the Caspian Sea |
title_fullStr |
Biogeographic classification of the Caspian Sea |
title_full_unstemmed |
Biogeographic classification of the Caspian Sea |
title_sort |
biogeographic classification of the caspian sea |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2014-11-01 |
description |
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 <i>a</i> concentrations between the different ecoregions shows
significant differences (one-way ANOVA, <i>P</i> < 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. |
url |
http://www.biogeosciences.net/11/6451/2014/bg-11-6451-2014.pdf |
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