 |
| Titel |
Drilling predation on molluscs in the northern Adriatic Sea: Spatial variability and temporal trends over the last millennia |
| VerfasserIn |
Markus Dengg, Sandra Wurzer, Ivo Gallmetzer, Alexandra Haselmair, Martin Zuschin |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127484
|
| Publikation (Nr.) |
 EGU/EGU2016-7366.pdf |
|
|
|
|
|
| Zusammenfassung |
| Competition and predation are essential ecological factors influencing biodiversity. In a
palaeontological context, the rate of predatory interactions between animal species is difficult
to reconstruct because traces of predation are rarely incorporated into the fossil record. In the
marine environment, the calcareous shells of molluscs, however, have good, long-time
preservation potential, and predation in this group is often exerted by carnivorous gastropods
that drill holes into mollusc shells. The prey’s perforated shells remain in the sediment and
can be used to study rates and intensities of predatory interactions in past marine molluscan
communities. Differences in drilling frequencies along a sediment core not only reflect
changes in local species richness and predation pressure, but may also mirror ecosystem
changes through space and time. This makes the analysis of drilling predation an
important tool when investigating the historical ecology of marine habitats. We
used 1.5-m-long sediment cores from seven shelf locations spread throughout the
northern Adriatic Sea basin to investigate regional and down-core variations in
drilling frequencies. In total, about 54,000 bivalve and 40,000 gastropod shells were
analysed to determine the following parameters: 1) overall drill frequency (DF), the
proportion of shells drilled by predators; 2) edge drill frequency (EDF, only in bivalve
shells), the proportion of shells with drilling traces at the shell edge; 3) multiple drill
frequency (MDF), the percentage of individuals with more than one drill hole, 4)
incomplete drill frequency (IDF), the percentage of shells unsuccessfully drilled; 5) prey
effectiveness (PE), the proportion of individuals resisting the predator’s attacks. Total drill
frequency across all cores is 18% for bivalves and 13% for gastropods, but there are
marked regional differences, with minima in the Po Delta (5%) and maxima in
Panzano Bay (24%). Edge-drilled shells and multiple drill holes on single shells
are very rare and occur on less than 1% of the investigated specimens. Also very
low (< 1%) is the percentage of incomplete drill holes, except for the sampling
location at the Brijuni Islands, Croatia (4%). Drilling frequencies show stronger
differences between localities than along individual cores. Significant correlations
exist between drilling intensities and prey species ecotype (especially for bivalves):
commensals, parasitic and suspension-feeding species are more frequently drilled than
other feeding types, as are infaunal species compared to species with epifaunal life
habits. Despite the strong spatial variation in drilling intensities, the DF values
of our samples are comparable to those typical for Cenozoic shelf environments. |
|
|
|
|
|
|