Material and methods -- The Kosterfjord study site -- Bioerosion patterns -- Carbonate accretion patterns -- Quantitative bioerosion and carbonate accretion -- Ecological and palaeoenvironmental implications -- Summary and conclusions -- Outlook. Bioerosion is the major force driving the degradation of marine skeletal carbonates and limestone coasts. A wide spectrum of mechanical and/or chemical boring, scraping or crushing organisms break down calcereous substrates, comprising various grazers, macroborers and especially microborers. Their traces on and within hard substrates are known from fossil carbonates as old as the Precambrian and serve as valuable palaeoenvironmental indicators. Bioerosion processes have been extensively studied in tropical seas, while corrsponding investigations from cold-temperate to polar settings remain sparse. For the first time, an experimental study yields insight into the pace of carbonate degradation and the chronology of boring community development along a bathymetric gradient in a high-latitude setting.