Currently, there is little comparative data on ‘efficiency’ of different engineering species, i.e. species richness, density and biomass of the associated organisms that have been supported by engineering species. The use of fouling communities makes it possible to compare the efficiency of different engineering species under the same conditions, which is necessary to obtain correct estimates and difficult to do when studying natural bottom communities. In this study, we have analysed the fouling communities in four different mussel culture farms in the White Sea to test the following hypotheses. (1) Different engineering species (mussel Mytilus edulis, solitary ascidian Styela rustica, sponge Halichondria panicea) have different assemblages of the associated vagile fauna. (2) Mytilus edulis is the most efficient engineering species, i.e. species richness, species diversity, density and biomass of the associated vagile fauna is higher in the mussel communities than in those dominated by Styela rustica or Halichondria panicea. The first hypothesis was confirmed, while the second was rejected. In all the culture farms studied, all parameters of the mussel-associated vagile fauna were not higher and in most cases were even lower than those of the fauna associated with ascidians or sponges. The reason for this seems to be the very dense packing of mussels in patches. Therefore, Mytilus edulis is not the most efficient engineering species among fouling organisms, at least in the conditions of the subarctic White Sea. The data obtained are particularly important in view of the ever-increasing volume of anthropogenic substrate and fouling communities in coastal marine ecosystems.

Submerged artificial surface imitates newly available habitat for settlement of marine fauna. It also enables study of the timing of benthic larval settlement. Such knowledge is important if the model of possible recovery after disturbance in protected areas is to be assessed. During this study recruitment of sessile benthic invertebrate fauna at spatial and temporal scales was investigated using artificial panels submerged in the Skomer Marine Nature Reserve (Wales, UK). Panels were exchanged monthly between May 2009 and September 2011 (with the exclusion of winter time). Recruitment was highly variable with regard to time and distribution; abundance and number of recruiting species varied significantly between sites (about 2 km apart from each other), depths (6 and 12 m), position on panels (top or underside) and years without any obvious trends. The highest number of individuals and highest values of species richness were at Bernies Rocks, at the greater depth and on the underside surface of panels. Bryozoans were the dominant taxon on panels in each studied year and month. Most macrofaunal species noted on panels exhibit a colonial life strategy with short-lived, non-feeding larval stage. Although many species settle all year round, levels of settlement usually peak in summer months, showing a seasonal recruitment pattern (Bugula fulva, Spirobranchus triqueter, Chorizopora brongniarti and Escharoides coccinea). Some species had a pronounced settlement peak in spring (e.g. Electra pilosa and Balanus crenatus).

The diversity and distribution of polychaete species under the families Nereididae, Syllidae and Eunicidae in sub-tidal fouling assemblage was studied by submerging wood as test substratum. Wooden panels were fitted onto a raft and submerged in Kudankulam coastal waters (south east coast of India) in pre-monsoon, monsoon and post-monsoon seasons from May 2003 to July 2005. Panels (in replicate) were retrieved from the raft at 15-day intervals. A total of 24 polychaete species belonging to the three families were identified from the test panels. Perinereis cultrifera, Platynereis dumerilii, Syllis variegata, Syllis truncata, and Eunice australis were the dominant species observed on the test panels. The abundance of major polychaete group was varied considerably between the panel series submerged in May 2003 (post-monsoon), November 2003 (monsoon) and July 2004 (pre-monsoon). The major difference in the polychaete community structure was the low abundance of both nereidids on pre-monsoon season panels and the eunicids on monsoon and post-monsoon season panels.

In summer 2010, a systematic survey was carried out in the harbours of La Spezia (Ligurian Sea) and Olbia (western Tyrrhenian Sea) with the aim of studying alien species in Italian commercial harbours. Biological samples were collected by replicate scraping on the concrete walls of docks at the beginning and at the end of the summer season. Identification to species level revealed the presence of Tricellaria inopinata, an invasive alien cheilostome bryozoan of Pacific origin, first introduced to Europe in the Lagoon of Venice (Italy) in 1982. Thereafter it has been reported in other ports in Britain, Belgium, The Netherlands, France, Spain, Portugal, Tunisia, Ireland, Scotland, Germany and Massachusetts (USA). Its finding in the harbours of La Spezia and Olbia represents the first record of the species in the Ligurian Sea and in the western-central Tyrrhenian Sea, respectively. Commercial harbours are common sites of biotic invasions due to the presence of the most important vectors of alien species introduction, namely aquaculture, and shipping. The occurrence of T. inopinata in the harbours of La Spezia and Olbia is discussed, taking into consideration possible pathways of introduction into the western Mediterranean Sea, which very likely is the transfer of molluscs from the northern Adriatic (namely the Lagoon of Venice).

Settlement of the fouling community is generally influenced by the physical, chemical and biological properties of the settling surface. The colour of the substratum may also exert an influence on larval settlement. In the present study, the influence of surface colour on the recruitment of fouling communities was investigated by suspending acrylic panels (red, green, blue, white and yellow) in coastal waters. Results showed that the colour of the substratum plays an important role in the recruitment of sessile species. Recruitment was comparatively high on red and blue coloured surfaces. Barnacle and tubeworm recruitment showed significant variation (Tukey test, P < 0.05) between different coloured surfaces. The significant conclusion of this study is that the colour of the artificial substrata should be taken into consideration when interpreting results from short-term biofouling studies.

In order to investigate the intensity and variability of fouling recruitment on artificial hard substrates, three sites were chosen in the First Inlet of the Mar Piccolo of Taranto (Southern Italy, Ionian Sea). Taxa richness and percentage coverage were examined in three different sampling times within each site. Differences were tested both by univariate and multivariate statistical analysis (ANOVA, SIMPER and MDS). The results show that each site seems to be characterized by its own structural make-up over the whole period of observation, underlying the presence of large-scale variability. By contrast, variability on a smaller scale within each site (replicates) appeared less marked, both in space and time. A set of a quite stable group of species characterized each site. Differences between sites were maintained over time with a difference in community evolution although with a tendency towards a higher similarity in species composition along the time.

The vertical distribution of fouling communities in Kudankulam coastal waters was studied for a period of one year (January to December 2005) by suspending wooden test panels at 1 m, 4 m and 7 m depths. Panels were submerged on short-term duration (15 days) and long-term basis (cumulative). The fouling organisms observed were barnacles, mussels, ascidians, polychaetes, amphipods and seaweeds. Recruitment was observed on the panels throughout the year with a considerable variation in relation to time and depth. On the short-term series, the fouling biomass varied from 0.218 to 1.23 g.dm−2 (dry wt) at 1 m, 0.23 to 4.72 g.dm−2 (dry wt) at 4 m and 0.241 to 5.66 g.dm−2 (dry wt) at 7 m depths. The biomass of the fouling community that colonized on the long-term panels ranged between 0.79 and 35 g.dm−2 (dry wt) at 1 m, 3.72 and 58.2 g.dm−2 (dry wt) at 4 m and 0.241 and 55.9 g.dm−2 (dry wt) at 7 m depths. At 1 m depth, macro-algae, ascidians (Botryllus tuberatus and Diplosoma sp.) and amphipods were the dominant species. Barnacles, tube worms and ascidians (Didemnum spp.) were abundant on the 4 m and 7 m depth panels. In general, the fouling community recruitment was higher at 4 m than 1 m and 7 m depths.