Colonisation and bioerosion of experimental substrates by benthic foraminiferans from euphotic to aphotic depths (Kosterfjord, SW Sweden) |
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Authors: | Max Wisshak Andres Rüggeberg |
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Institution: | (1) Institute of Palaeontology, Loewenichstr. 28, 91054 Erlangen, Germany;(2) Leibniz-Institut für Meereswissenschaften, IFM-GEOMAR, Wischhofstr 1-3, 24148 Kiel, Germany |
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Abstract: | In the cold-temperate setting of the Swedish Kosterfjord area, experimental carbonate and PVC substrates were deployed for
a 6, 12 and 24-month duration along a transect from euphotic to aphotic depths in order to study bioerosion and carbonate
accretion patterns. Among the organisms that contribute to the latter by secreting calcareous skeletons, epibenthic foraminiferans
represent a major component, both in terms of diversity (a dozen species) as well as in the number of individuals (exceeding
50,000 individuals per m2 at certain depths). The by far dominating species were found to be Cibicides lobatulus and the agglutinating Lituotuba lituiformis, along with smaller numbers of Planorbulina mediterranensis, Tholosina vesicularis and Nubecularia lucifuga. The foraminiferal distribution exhibits a pronounced abundance maximum in shallow waters at 7 and especially 15 m and a
maximum in diversity at 15-50 m water depth. Some of the foraminiferans encountered, such as Cibicides lobatulus and the rare Gypsina vesicularis, were found to contribute also to the bioerosion of the calcareous substrates by etching shallow attachment scars. These
prominent traces witness the former presence of benthic foraminiferans on fossil to Recent hardgrounds, inferring a potential
applicability as an in situ proxy where tests are not preserved. Estimated minimum carbonate production rates for the dominant Cibicides lobatulus reach a maximum of 0.326 g/m2/year with the highest rates occurring at 7 to 30 m water depth. Carbonate production rates are up to two magnitudes higher
on the PVC (0-0.326 g/m2/year) than on the carbonate substrates (0-0.010 g/m2/year) and are considerably higher than estimates previously reported from the western Baltic. |
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Keywords: | Benthic foraminiferans Settlement experiment Carbonate accretion Bioerosion Kosterfjord Skagerrak |
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