The continued development of the aquaculture industry is contributing to the proliferation of artificial structures in the marine environment. Observations of seaweed farms (infrastructure and biomass) suggest they act as a habitat for associated species. Seaweed farms differ from other forms of artificial infrastructure as the material deployed already has marine organisms (i.e. culture species) growing on it. This ‘priming’ of ropes with juvenile sporophytes may affect future development of communities by facilitating colonizing species or suppressing competitors. We call this process ‘ecological priming’: the provision of a biological platform that influences the successional development of specific communities. The communities that developed on ropes primed with Alaria esculenta individuals were compared with unprimed ropes to assess the ecological priming effect, at a commercial kelp farm in south-west Ireland. Species richness increased over two cultivation seasons and species composition was consistent between years, with distinct communities developing on primed and unprimed treatments. Timing of species occurrence on primed ropes was predictable with no predictable pattern occurring on unprimed ropes. Multivariate tests indicated distinct communities between treatments, with suppression of other algal species and potential facilitation of some species that have a particular association with A. esculenta on primed ropes. Communities from primed holdfasts contained a lower diversity of algal species compared with unprimed communities. Cultivated kelp holdfasts represent a habitat for distinct assemblages that reflect ecological priming of the substratum.

The fan mussel Pinna nobilis is a long lived species endemic to the Mediterranean Sea and is considered one of the biggest bivalve molluscs of the Mediterranean. A multitude of threats has provoked a great reduction in P. nobilis populations. To increase the knowledge about the recruitment period and number of Pinna nobilis recruits, two types of recruitment devices were deployed in July 2007 on a Marine Protected Area of Palma Bay, Mallorca (western Mediterranean). A total of 614 juveniles of P. nobilis, with a mean length and width of 2.76±0.04 and 1.10±0.01 cm respectively, were collected inside the artificial microhabitat generated by the knots of ‘device Type I’. Similarly, 691 P. nobilis were recruited with a mean length and width of 5.38±0.08 and 2.10±0.04 cm respectively from ‘device Type II’. Moreover, in the year 2007, the present study determined that P. nobilis recruitment takes place between the last week of August and the first week of September. This study produces some crucial information for effective protection and conservation of the fan mussel. Moreover, a Pinna nobilis artificial recruitment with seed collectors would permit an alternative tool for field studies without compromising the concentration of the vulnerable populations of this mollusc.