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| Titel |
Down-core changes in molluscan death assemblages at Panzano Bay, an impacted area in the northern Adriatic Sea |
| VerfasserIn |
Alexandra Haselmair, Ivo Gallmetzer, Michael Stachowitsch, Adam Tomašových, Martin Zuschin |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127352
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| Publikation (Nr.) |
 EGU/EGU2016-7218.pdf |
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| Zusammenfassung |
| We use a historical ecology approach to shed light on the environmental history of the
northern Adriatic Sea over the last hundreds to thousands of years. We focus on down-core
changes in molluscan death assemblages, which serve as proxies for ecological shifts over
time. The northern Adriatic Sea is particularly suited to study ecosystem modification under
human pressure because it is among the most degraded marine ecosystems worldwide. We
chose a sampling station in Panzano Bay, close the Isonzo River mouth and not far from the
major industrial harbours of Trieste (Italy) and Koper (Slovenia), and traced down-core
changes in molluscan community structure in correlation to major anthropogenic
impacts that occurred here during the last centuries. Five sediment cores (1.5 m in
length and diameters of 90 and 160 mm) were taken at a water depth of 12 m. We
analysed grain size composition, the concentration of heavy metals and organic
pollutants, and radiometrically dated the sediment using 210Pb. Furthermore, we
dated shells of the abundant bivalve species Corbula gibba using 14C calibrated
amino acid-racemisation (AAR). The whole molluscan community in the cores was
analysed for species composition, abundance, taxonomic similarity, evidence for
ecological interactions (i.e., frequencies of drilling predation) and taphonomic conditions
of shells. The granulometric analysis shows that silt and clay dominate equally
throughout the cores. Radiometric sediment dating revealed an average sedimentation
rate of 2.5 mm/yr during the last 120 years. Shell dating points to a comparable
overall core age, with only a few shell specimens being older than 500 years in the
deepest core layer. In total, 10,452 mollusc individuals were analysed and 104 species
identified. The most abundant bivalve species are Kurtiella bidentata, Corbula gibba and
Abra nitida. Turritella communis and Nassarius pygmaeus are the most frequent
gastropod species. Down-core changes in species composition and molluscan abundance
are conspicuous, with a high peak in abundance between 20 and 50 cm depth and
another peak in the lower part of the core. These trends in community composition
correlate with the concentration curves of several heavy metals (Pb, Zn, Hg) and
polycyclic aromatic hydrocarbons. In the deeper core horizons, a high mercury peak
signals a massive and century-long contamination caused be the Idrija mercury
mine located up the Isonzo River. In the uppermost 20 cm of sediment, Pb, Zn and
PAHs display high concentrations and are accompanied by a decrease of formerly
abundant species (e.g. Kurtiella bidentata) and an increase of a few opportunists.
Our study shows how pollution, among other factors, affects individual mollusc
species and leads to marked and long-lasting changes on the community level. |
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