Interannual variation of the vagile benthic community in Port de Sagunt (Valencia, Spain)

Harbours have always been considered to have high anthropogenic pressure, due to various sources of stress affecting the environment. One of these is the construction of artificial structures to defend or build the harbour itself. This study aims to investigate the impact that two types of these structures can have on the benthic vagile assemblages. In the harbour of Sagunto (Valencia, Spain), a breakwater, made of rock blocks, and a pier, built of concrete, were studied with different samplings on both substrates over the course of a whole year. The results showed that species richness, heterogeneity and evenness indices on average did not differ between the two substrates, but rather between different sampling dates, indicating that both types of substrates are able of accommodating assemblages with similar diversity, despite the differences between the two substrates in term of materials and conformation. Analysing the assemblage structure instead, it was observed that only three species of polychaetes, Platynereis dumerilii, and species in the families Polynoidae and Eunicidae, have significant different abundances between the two substrates, indicating a possible relationship between these polychaetes and the substrates on which they live. For two other species, the crab Pilumnus hirtellus and a worm in the family Syllidae (Polychaeta), differences in abundance were found when considering the interaction between the two factors in the study, sampling date and substrate. In four species, Cyathura carinata, Monocorophium sextonae, Liljeborgia dellavallei and Hiatella arctica, differences in abundance were found only when considering different sampling dates, probably due population dynamics related to their life cycles.