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

Abstract

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.

Sustainable Management of High-Impact Non-Native Molluscs and Their Potential Commercial Importance in the Eastern Adriatic Sea

“…The impact on the biodiversity of listed species includes a negative impact on native species or entire communities through competition for resources (B. haraonic and native Mytilaster minimus, M. gigas, and native O. edulis), predation (R. venosa), hybridisation (R. philippinarum and native R. decussata), disease transmission (M. gigas), introduction of hitchhiker non-native species (M. gigas), and ecosystem engineering. A striking example of non-native mollusc species impact on keystone species or species of high conservation value is large numbers of A. transversa found on installed collectors for the endemic Mediterranean bivalve P. nobilis in Brijuni National Park [146]. Since P. nobilis is already at high risk of extinction due to mass mortality, even in MPAs such as Brijuni National Park, and it is an obligation to ensure its maximum possible protection and recovery, A. transversa should be closely monitored and a programme of active eradication should be considered as this serious competitor may pose an additional threat to Mediterranean endemic P. nobilis.…”

“…Ref. [146] found large numbers of A. transversa on installed collectors of Pinna nobilis (Linnaeus, 1758) in Brijuni National Park. This result indicates the negative impact of A. transversa on keystone species or species of high conservation value such as the endemic Mediterranean bivalve P. nobilis.…”