Coral reefs of the Late Jurassic (Oxfordian) in northern Germany and France have a style of bioerosion that is closer to that of Late Triassic reefs than of modem ones. Boring sponges played minor roles here but gradually became more important in more southerly regions during the Tithonian. This is likely to be linked to a falling sea-level whose increased nutrient input triggered microbial growth in shallow water. With sponges feeding on microbes, the Late Jurassic was the time ofa change to modem borer associations in reefs.