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| Titel |
The impact of thermal pollution on benthic foraminiferal assemblages in the SE Mediterranean shore (Israel) as an analog to global warming |
| VerfasserIn |
Ruthie Nina Arieli, Ahuva Almogi-Labin, Sigal Abramovich, Barak Herut |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037227
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| Zusammenfassung |
| Scientific and public awareness to global warming increased significantly lately. In the
Mediterranean Sea the current rate of warming stands at 0.028 °C/year in accordance with
the forecast of global warming of 0.2 °C per decade. The aim of this study is to
examine the effects of locally elevated vs. natural SST on benthic foraminifera,
which are known to be sensitive bioindicators of environmental change. The thermal
patch originating from the "Orot Rabin" power plant off the coast of Israel was
chosen as a sampling area for this research since it presents a unique small-scale
analog for expected future rise in SST. Ten monthly sampling campaigns were
performed during a period of one year in 4 stations located along a temperature gradient
of approximately 10 °C, from the discharge site of the heated seawater to a few
kilometers south. Benthic foraminifera were collected from a shoreface complex of
macroalgae and sediments trapped within. The SST varied between winter, 25/18 °C
and summer, 36/31 °C along the transect. During the summer, the addition of the
temperature anomaly to the already extreme summer temperatures becomes a biologically
threat.
The natural seasonal variability, depicted best by station 4 located beyond the thermal patch,
shows that foraminifera reach maximal abundance in winter and spring. A significant
negative correlation was found between SST in all stations and benthic foraminiferal
assemblage characteristics. The abundance, species richness and species diversity show
negative correlation with the SST anomaly throughout most of the sampling period, though
the species diversity was not as significant as the abundance. The total foraminiferal
abundance was significantly lower at the thermally polluted stations, especially during the
summer, but also throughout the entire year, indicating that the thermal pollution has a
detrimental effect on benthic foraminifera, irrelevant to the natural cyclic changes in SST.
The foraminiferal abundances decrease drastically as the SST rises, reaching minimal
abundances when the SST rises above 30 °C, indicating that this temperature may be a
critical threshold above which foraminiferal growth and reproduction are severely
retarded.
Species richness reached extremely low values at the thermally polluted stations during the
summer, with a minimum of 3 species compared to a maximum of 24 in the natural,
unaffected station 4. This indicates that some species have adapted to the elevated
temperatures better than others. The foraminiferal assemblage, composed mostly of epiphytic
species, contains a total of 42 species with six species dominating the assemblage. Out of the
six dominant species Rosalina globularis, Tretomphalus bulloides and Textularia agglutinans
show a clear preference to the winter months, while species belonging Lachlanella reach
maximum abundances in spring and Pararotalia spinigera in summer. The miliolids,
Lachlanella sp. 1 and sp. 2 seem to have high tolerance to the elevated SST and even survived
the most extreme summer temperatures at the thermally polluted stations. In this research
we show that even a rise, as small as 2 °C, in SST can have serious ramifications
on the benthic community characteristics living in the near shore environment. If
foraminifera are affected to such an extent it is not unlikely that other more developed
marine creatures will be negatively affected as well, either directly by the rise in
SST or via the decrease in organisms lower down the marine food chain, such as
foraminifera. |
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