Monitoring Carbonate Production and Degradation (Azores, Portugal)
Final Report Abstract
The summits and flanks of the non-tropical Azores seamounts and volcanic islands provide a frame for intense biogenic carbonate-production and accumulation, classifying them as important ‘carbonate factory’ of the C factory type (cool water + controlled precipitate). The so-called heterozoan assemblage supports a pronounced biodiversity including carbonate-secreting benthic organisms (serpulids, molluscs, brachiopods, bryozoans, crinoids, scleractinians, stylasterids, etc.). In order to characterise this C factory a 2-year experiment was carried out in the southern Faial Channel with the support of the manned submersible ‘Lula’ to study the biodiversity of hardground communities and for budgeting carbonate production and degradation along a bathymetric and hydrographic transect covering all photic zones from the intertidal down to aphotic upper bathyal 500 m of water depth. Thereby we characterised the carbonate production centre with respect to (1) general habitat characteristics in the southern Faial Channel, (2) environmental data recorded in situ via high-resolution loggers, (3) the photic zonation pattern, (4) water properties such as nutrient and stable isotope signatures, (5) carbonate system parameters, and (6) carbonate accretion and bioerosion rates for different substrate types and orientations. These data allowed us to budget the carbonate cycling in this warm-temperate carbonate factory in the context of a latitudinal and environmental gradient roughly following the course of the Gulf Stream and the results may serve as an important integral for future carbonate and carbon cycle modelling. In addition, (7) a detailed assessment of the biodiversity of the calcareous epibenthos, respectively (8) the ichnodiversity of bioeroding biota, was undertaken. Complementing to the experimental work, the project undertook a quest for long-lived geochemical archives in the deep sea, since very stable environmental conditions in terms of salinity and temperature are encountered below 150 m water depth, providing an ideal frame for testing various candidates for ‘vital effects’ during the implementation of geochemical signals. Target species in this respect were (1) the cold-water corals Caryophyllia cyathus and Desmophyllum cristagalli, (2) the stylasterid Errina dabneyi, and (3) the newly described giant deep-sea oyster species Neopycnodonte zibrowii, that thrive protected under overhangs or along steep cliff faces in close to 500 m depth. Investigations included their microstructure, growth rate, stable isotope signature (d18O and d13C), and elemental composition (Mg, Sr, S, etc.). As it turned out, all of these target species exhibit certain ‘vital effects’ that can, however, partly be overcome by suitable evaluation methods. Particularly surprising was the finding that radiocarbon dating of N. zibrowii, revealed an impressive lifespan of up to more than 5 centuries, placing these giant oysters among the longest-lived non-colonial animals known to date. This longevity and a distinct incremental growth identify N. zibrowii as promising environmental archive, a fact that catalysed further research on these “Methusalah of the deep” accompanied by various reports in the print, internet and TV media.
Publications
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(2009) Reply to the Comment on "The ‘living-fossil community’ of the cyrtocrinoid Cyathidium foresti and the deep-sea oyster Neopycnodonte zibrowii (Azores Archipelago). [Palaeontology, Palaeoclimatology, Palaeoecology 271:77-83]". Palaeontology, Palaeoclimatology, Palaeoecology 279:235-236
Wisshak M, Neumann C, Jakobsen J & Freiwald A
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(2009) Shell architecture, element composition, and stable isotope signature of the giant deep-sea oyster Neopycnodonte zibrowii sp. n. from the NE Atlantic. Deep-Sea Research I 56:374-404
Wisshak M, López Correa M, Gofas S, Salas C, Taviani M, Jakobsen J & Freiwald A
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(2009) Skeletal reorganisation affects geochemical signals, exemplified in the stylasterid hydrocoral Errina dabneyi (Azores Archipelago). Marine Ecology Progress Series 397:197-208
Wisshak M, López Correa M, Zibrowius H, Jakobsen J & Freiwald, A
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(2009) The ‘living-fossil community’ of the cyrtocrinoid Cyathidium foresti and the deep-sea oyster Neopycnodonte zibrowii (Azores Archipelago). Palaeontology, Palaeoclimatology, Palaeoecology 271:77-83
Wisshak M, Neumann C, Jakobsen J & Freiwald A
