Recolonization and recovery dynamics of the macrozoobenthos after sand extraction in relict sand bottoms of the Northern Adriatic Sea

The long-term effects of sand extraction on macrozoobenthic communities were investigated in an offshore area in theNorthern Adriatic Sea characterised by relict sands formed during the last Adriatic post-glacial transgression. Surveyswere carried out before, during and 1, 6, 12, 18, 24 and 30 months after extraction at three impacted and seven referencestations. The operations did not influence the physical characteristics of the sediment, but they caused almost completedefaunation at dredged sites. Univariate and multivariate analyses highlighted that the macrozoobenthic communityresponses to the dredging operations were (1) a rapid initial recolonisation phase by the dominant taxa present beforedredging, which took place 6–12 months after sand extraction; (2) a slower recovery phase, that ended 30 months afterthe operations, when the composition and structure of the communities were similar in the dredged and reference areas.This pattern of recolonisation–recovery fits well with the commonly encountered scenario where the substratum merelyremains unchanged after marine aggregate extraction.