World Congress of Malacology Antwerp ... - Unitas Malacologica

Distribution and ecology of Thyasiridae (Mollusca: Bivalvia) in coastal waters of Hordaland,
Norway
Keuning, Rozemarijn 1 ; Schander, Christoffer 1,2 ; Kongsrud, Jon 3 ; Willassen, Endre 3
1. Department of Biology, University in Bergen, P.O. box 7800, N-5020, Bergen, Norway,
Email: rozemarijn.keuning@student.uib.no
2. Centre of Geobiology, Allegaten 41, 5007 Bergen, Norway,
Email: christoffer.schander@bio.uib.no
3. Bergen Museum, University in Bergen, P.O. box 7800, N-5020, Bergen, Norway,
Email: jon.kongsrud@zmb.uib.no, endre.willassen@zmb.uib.no
As pollution of marine environments is getting more of an issue and the oil industry, among others,
has become more interested in monitoring marine environments, the search for species able to
respond to environmental changes related to oil spills or other forms of pollution, is more focussed.
Several marine species have been recognized as environmental indicators, and bivalves seem to be
important. Their filter-feeding behaviour renders them sensitive to environmental change and
responses to pollution may both be positive and negative.
The Thyasiridae is a group of burrowing bivalves occurring in both shallow and deep waters. Sixteen
species are currently recognized from the North-east Atlantic, of which 12 have been reported from
the British shelf. A similar number of species is expected to be found in Norwegian coastal waters.
Several species live in symbiosis with sulphide oxidizing bacteria. With their extensive burrowing
behaviour they contribute to oxidizing the sediments, and in their deep burrows they mine the
reducing sediments for sulphides. This behaviour is interesting since it means that the species can reoxidize
reducing and polluted sediments, making the sediments more attractive to sulphide-intolerant
benthos.
It has previously been difficult to study the Thyasiridae due to lack of sufficient literature, therefore,
not much is known about the genus in Norwegian coastal waters. By revising extensive museum
material and re-sampling several stations we want to (1) provide an overview of the populations of
the different species along the coast of Hordaland, accompanied by geographic and bathymetric
information, and (2) collect data from sediment analyses in order to investigate the potential of the
Thyasiridae as environmental indicators. The material will be documented using SEM images.
Thyasira succisa, not previously described from coastal waters in Norway, has been identified from
samples taken in 2003, deposited at the Natural History Museum in Bergen.
The evolutionary adaptation of mollusks to deep-sea vents: insights from their fossil history
Kiel, Steffen
Earth Sciences, University of Leeds, Leeds LS2 9JT, UK,
Email: steffen.kiel@gmx.de
Deep-sea hydrothermal vents and methane seeps are inhabited by numerous molluscan clades. It has
been proposed that mollusks used sunken whales and wood (coined whale- and wood-falls) as
‘stepping stones’ during their adaptation to these extreme environments. This ‘stepping stone
hypothesis’ is here explored using fossil evidence. Numerous whale- and wood-fall communities
have been found in Late Eocene to Early (35-20 Ma) Miocene deep-water strata in Washington State,
USA, including the oldest whale-fall community known to date. The Eo-Oligocene (35-23 Ma)
whale-fall communities lack typical vent- and seep-type taxa but are very similar in their taxonomic
composition to contemporary wood-falls. The lack of typical vent/seep taxa at the early whales shows
that the early whales where not used as stepping stones by these taxa, contrary to the prediction of the
‘stepping stone hypothesis’. It was apparently not before the middle Miocene (16 Ma) that decaying
whale carcasses were sulfide-rich enough to support vent- or seep-like communities.
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