Seasonal and bathymetric effects on macrofouling invertebrates’ primary succession in a mediterraenan non-indigenous species hotspot area

Abstract

The present study investigates macrofouling development in the Mar Grande of Taranto (Central Mediterranean Sea), a wide confined area that has attracted considerable attention in recent years due to the establishment of numerous non-indigenous species (NIS). Different starting times of a yearly primary succession on artificial substrates were tracked so as to investigate the matching of the development pattern with contingency and/or convergence models, identifying NIS's structural role in the community endpoint. Our results show that during the experiment all assemblages tended to converge towards multiple contingent communities according to starting times and depths. The differences are due to propagule availability which influence further species interactions. Thus the endpoint patterns are defined by a contingent community development determined by the seasonal species pool, their phenologies, pre-and post-settlement events, and species interactions. The most important structuring species was Mytilus galloprovincialis, which was present in almost all the endpoint assemblages, in particular when it recruits at early stages of the community development. Another abundant species at the endpoint was the alien Branchiomma boholense; which was a persistent structural component contributing to an alternative state in which Mytilus galloprovincialis loses its structural importance and where B. boholense becomes dominant, leading to an increase in fouling biodiversity of the endpoint assemblage.

An Innovative IMTA System: Polychaetes, Sponges and Macroalgae Co-Cultured in a Southern Italian In-Shore Mariculture Plant (Ionian Sea)

“…The pattern of community development observed on the bare vertical collectors utilized, containing, at the base, individuals of Sabella, agrees with previous studies on the fouling community obtained with the use of panels [75]. The macrofouling colonization investigated in the bare collector was followed until a "stable point" was reached after almost nine months; at this point, all the structures were characterized by a shallow assemblage (0-3 m), dominated by M. galloprovincialis, and a deeper assemblage (3-10 m), dominated almost exclusively by sabellid worms.…”

“…The temperature shows seasonal variations typical of the coastal Ionian regions with an average annual value of about 18 • C, while the salinity is about 38% and is almost uniform over the year. The area is affected by intense Mytilus galloprovincialis farming, a species that finds, in the area, optimal conditions to dominate the final stage of the shallow local fouling communities, sometimes competing with solitary ascidians as well as with sabellid polychaetes [73][74][75].…”

“…For this purpose, adult worms of the species Sabella spallanzanii collected around the area were inserted in the last meter of their length, acting as spawners and enhancing self-settlement on the collectors ( Figure 3A). This species was chosen because it represents a natural and abundant element of the fouling communities all around in the area [73][74][75]77]. Of the 196 collectors, only 184 were followed until the end of the year cycle because some of them were utilized for a previous experimentation on S. spallanzanii biomass [78].…”

“…The method presently utilized, focused on obtaining recruitment directly on bare collectors, is very simple and does not require any management cost after the immersion of collectors. The method is based on strong local knowledge on the fouling community settlement dynamic coupled with the knowledge of sabellid life cycles and their recruitment dynamics [43,44,75,86,87], and is linked to the massive presence in the environment of this species.…”

The Mediterranean in check: Biological invasions in a changing sea

“…A study conducted by means of artificial panels in this biotope showed a higher fouling diversity linked to the abundance of AS. In particular, two congener polychaete sabellids, Branchiomma luctuosum and B. boholensis , together with the colonial ascidian Polyandrocarpa zorritensis , hamper the dominance of M. galloprovincialis at the surface of the system, so fostering a more diverse benthic assemblage (Lezzi & Giangrande, 2018). Our monitoring studies in the area have been going on for 30 years (Giangrande, Licciano, et al, 2014).…”