Meiofauna assemblages associated with mussel beds along an urban harbor

Harbors are extreme examples of coastal urbanization. Artificial substrata in the Ravenna harbour are almost completely dominated by mussel beds. Mussel clumps provide substrata for small mobile fauna (meiofauna). The aim of the thesis is to study the meiofauna associated to the mussels attached to the harbour structures. Moreover, the thesis provides the basis for the construction of a local meiofaunal genetic database, with the final goal of time and cost reduction on meiofaunal assessment through a metabarcoding approach. Mussel beds and associated meiofauna were sampled in two locations of the port (North vs. South) in two types of artificial substrata (rock boulders vs. concrete seawalls) at two different times. Taxonomic assessment of the meiofauna was carried out. Mussel bed complexity was evaluated by means of different measures (e.g. weight, volume, length of valve). The main results are: 1) meiofauna assemblages are very different in the two substrata, but these differences were influenced by locations and by the sampling periods. The number of taxa and diversity index on the rock boulders, the more complex primary substratum, resulted higher than those on the seawalls. 2) Variables analysed altogether showed differences between substrata, locations and times. A weak correlation was found between the mussel bed descriptors and the associated meiofauna assemblages. The number of structural mussels and the mean size lengths resulted responsible for the relationship. These results suggest that other measures of mussel complexity are needed, and that meiofauna assemblages vary depending on different substrata and to abiotic conditions associated to the locations (e.g. marine currents, exposition-to-sun). The genetic research identified a lack of sequences of species from the Adriatic Sea, especially for the “permanent” meiofauna. Alignment of the available sequences identified in the V7 and V8 regions of the SSU_18S a good target for meiofaunal barcoding.