Spatiotemporal bioerosion patterns in deep-water scleractinians from off Santa Maria di Leuca (Apulia, Ionian Sea)

This study focuses on the carbonate biodegradation processes of deep-water scleractinians from off Apulia at Santa Maria di Leuca (SML) in the Ionian Sea, including living colonies of Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus. The corallites were grouped into three zones: the live zone, edge zone and dead zone. In total, 13 trace types were encountered and are attributed to borings of sponges (3), fungi (6), foraminifers (2), bacteria (1) and annelids (1). Their relative spatial appearance within the host skeletons led to the distinction between six succession stages of bioerosion. The first endobiontic traces are exclusively produced by bacteria and fungi and are already present in the edge zone, which could be attributed to their fast growth rates and/or temporal exposure of the bare skeleton to the water column. In D. dianthus the entire ichnospecies assemblage has been documented within the first 1.9 cm below the live zone and represents the most condensed bioerosion succession amongst the coral species studied. The strongest degradation of corallites at SML is made by boring sponges, which can excavate 70% or more of the skeleton. The finding of a unilateral condensed succession of bioerosion stages may be linked to prevailing unidirectional strong currents. A comparison of the present ichnocoenosis with bioerosion studies from the Eastern Atlantic evidences a reduced ichnodiversity in Ionian Sea bathyal corals.