Fouling Community on Pinna nobilis Larval Collectors in the Adriatic-Impact of Invasive Species

In the last few years, the endemic Mediterranean bivalve Pinna nobilis has been exposed to dramatic mortality in its entire area, which could lead to the extinction of the species. Throughout the Mediterranean, a lot of effort is being put into finding ways of preserving it. One of the methods used to monitor recruitment and juveniles' survival is the installation of collectors for bivalve larvae. We installed collectors at two locations: in Brijuni National Park (North Adriatic) and Luka Cove (central Adriatic). Our aim was to compare the fouling community on the collectors in two consecutive years (2019 and 2020), especially because the installation of collectors in 2020 coincided with mass mortality events of P. nobilis in the area. The number and size of juvenile P. nobilis and the qualitative and quantitative composition of the fouling communities were determined. The results show a reduction in the number and size of juvenile P. nobilis and an explosion of the invasive bivalve Anadara transversa population on collectors in the second year. In Luka Cove, another invasive species-the ascidian Styela plicata-also seriously affected other organisms on the collectors to the point of preventing analysis of the fouling community.

Automated summary

In the last few years, the Mediterranean bivalve Pinna nobilis has experienced significant mortality, threatening its survival. Efforts have been made in the Mediterranean to preserve the species, including the use of bivalve larvae collectors to monitor recruitment and survival of juveniles. The installation of collectors in two locations allowed for comparison of fouling communities in consecutive years, revealing a decrease in the number and size of juvenile P. nobilis and an increase in the invasive bivalve Anadara transversa population in the second year.