Of Rocks and Hard Places: Comparing Biotic Assemblages on Concrete Jetties versus Natural Rock along a Microtidal Mediterranean Shore

Abstract

ABSTRACT Bonnici, L.; Borg, J.A.; Evans, J.; Lanfranco, S., and Schembri, P.J., 2018. Of rocks and hard places: Comparing biotic assemblages on concrete jetties versus natural rock along a microtidal Mediterranean shore. The species composition and structure of littoral assemblages on concrete jetties were compared with those on natural rocky shores at two localities on the microtidal NE coast of Malta. Algal species richness and total algal biomass were significantly lower on jetties. Faunal species richness and faunal abundance were also lower on jetties, albeit not significantly so. Jetties and natural rocky shores differed in relative species composition. The algae Palisada perforata/Laurencia obtusa and several mobile animals, mostly crustaceans, molluscs, and polychaetes, were more abundant on rocky shores. In particular, the supralittoral gastropod Melarhaphe neritoides had a density ranging between 8 ind./m2 to 98 ind./m2 on rocky shores but was never recorded on jetties. Conversely, the algae Cla...