Bryozoan and serpuloidean distribution pattern on a deep-water slab (Bari Canyon, Adriatic Sea).

The distribution of bryozoans and serpulids colonising a large carbonate slab from the Bari Canyon (280 m) has been investigated. The two relatively platy opposite larger faces of the slab are remarkably different: one is mud-covered, whereas the other one is mud-free and colonised by encrusting organisms. Bryozoans and serpulids are present on both surfaces with a comparable number of species but the number of specimens is relatively higher on the mud-free surface than on the opposite one. Interestingly, a few species are selectively present on one face only and, even species shared by both surfaces, show a polarity for their abundance. In particular, flexible erect bryozoans are restricted to the mud-covered surface. Sediment smothering is suggested as the main cause for this polarity.