‘Ten Years After’—a long‐term settlement and bioerosion experiment in an Arctic rhodolith bed (Mosselbukta, Svalbard)

• Published in: Geobiology
• Main Authors: Wisshak, Max, Meyer, Neele, Kuklinski, Piotr, Rüggeberg, Andres, Freiwald, André
• Other Authors: Deutsche Forschungsgemeinschaft
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2021
• Subjects: Foraminifera*; Svalbard
• Online Access: http://dx.doi.org/10.1111/gbi.12469; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gbi.12469; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gbi.12469

Abstract Rhodolith beds and bioherms formed by ecosystem engineering crustose coralline algae support the northernmost centres of carbonate production, referred to as polar cold‐water carbonate factories. Yet, little is known about biodiversity and recruitment of these hard‐bottom communities or the bioeroders degrading them, and there is a demand for carbonate budgets to include respective rates of polar carbonate build‐up and bioerosion. To address these issues, a 10‐year settlement and bioerosion experiment was carried out at the Arctic Svalbard archipelago in and downslope of a rhodolith bed. The calcifiers recorded on experimental settlement tiles (56 taxa) were dominated by bryozoans, serpulids and foraminiferans. The majority of the bioerosion traces (30 ichnotaxa) were microborings, followed by attachment etchings and grazing traces. Biodiversity metrics show that calcifier diversity and bioerosion ichnodiversity are both elevated in the rhodolith bed, if compared to adjacent aphotic waters, but these differences are statistically insignificant. Accordingly, there were only low to moderate dissimilarities in the calcifier community structure and bioerosion trace assemblages between the two depth stations (46 and 127 m), substrate orientations (up‐ and down‐facing) and substrate types (PVC and limestone), in that order of relevance. In contrast, surface coverage as well as the carbonate accretion and bioerosion rates were all significantly elevated in the rhodolith bed, reflecting higher abundance or size of calcifiers and bioerosion traces. All three measures were highest for up‐facing substrates at 46 m, with a mean coverage of 78.2% (on PVC substrates), a mean accretion rate of 24.6 g m −2 year −1 (PVC), and a mean bioerosion rate of −35.1 g m −2 year −1 (limestone). Differences in these metrics depend on the same order of factors than the community structure. Considering all limestone substrates of the two platforms, carbonate accretion and bioerosion were nearly in balance at a net rate of −2.5 g m ...