The macrofouling on offshore platforms at Ravenna

Abstract

The fouling which settles on gas platform piles was studied using samples taken in 1993 from the PCWA and ANTARES platforms positioned, at 7 and 10.5 km from the shore respectively and on bottoms at 12 m and 14 m in the Adriatic Sea. For each platform a pile was chosen as representative of the macrofouling found on the whole platform. In March and September 1993 samples were obtained by scraping an area of 600 cm2 from three or four different aspects (North, East, South, West), at the same depth. Samples were taken at depths of 0.5, 5.5 and 12 m on PCWA and 0.5, 7 and 12 m on ANTARES. Photographs and video recordings taken over the whole length of the chosen pile were used for an additional description of the settlement. On both platforms the macrofouling was characterized by a dominance of mussels from sea surface to a depth of about 10 m. Near the bottom the bivalve Crassostrea gigas, barnacles, hydroids and serpulids were more important. The presence of the bryozoan Schizoporella errata (present only at ANTARES) and the zoanthid Epizoanthus arenaceus (present only at PCWA) were the main differences at this depth. The fouling, or mussel weights, of the two platforms were similar for the two seasons, even though the highest values were registered in September on PCWA (1 m) with 1561.3 g/dm2, of which 1553 g/dm2 comprised mussels. A comparison is drawn with a previous fouling experiment (which used one-year panels) carried out in 1975-76.