Tracking a mass mortality outbreak of pen shell Pinna nobilis populations: A collaborative effort of scientists and citizens

Abstract

A mass mortality event is devastating the populations of the endemic bivalve Pinna nobilis in the Mediterranean Sea from early autumn 2016. A newly described Haplosporidian endoparasite (Haplosporidium pinnae) is the most probable cause of this ecological catastrophe placing one of the largest bivalves of the world on the brink of extinction. As a pivotal step towards Pinna nobilis conservation, this contribution combines scientists and citizens’ data to address the fast- and vast-dispersion and prevalence outbreaks of the pathogen. Therefore, the potential role of currents on parasite expansion was addressed by means of drift simulations of virtual particles in a high-resolution regional currents model. A generalized additive model was implemented to test if environmental factors could modulate the infection of Pinna nobilis populations. The results strongly suggest that the parasite has probably dispersed regionally by surface currents, and that the disease expression seems to be closely related to temperatures above 13.5 °C and to a salinity range between 36.5–39.7 psu. The most likely spread of the disease along the Mediterranean basin associated with scattered survival spots and very few survivors (potentially resistant individuals), point to a challenging scenario for conservation of the emblematic Pinna nobilis, which will require fast and strategic management measures and should make use of the essential role citizen science projects can play.

Epidemiology of Noble Pen Shell (Pinna nobilis L. 1758) Mass Mortality Events in Adriatic Sea Is Characterised with Rapid Spreading and Acute Disease Progression

“…It has been previously indicated that corresponding sea currents could be involved in transporting pathogens and/or their still unknown vectors or fomites to promote disease dispersion [ 27 ]. Recent studies applied modelling of the sea currents directions and movement to P. nobilis MMEs [ 4 ]. The surveillance program designed to monitor MMEs in naïve areas of the Croatian coast took into account the major direction and speed of prevailing surface sea currents.…”

Multiple Non-Species-Specific Pathogens Possibly Triggered the Mass Mortality in Pinna nobilis

“…Protozoans are typically the first putative pathogens investigated in cases of mass mortality involving bivalves. In particular, haplosporidian endoparasites have been the cause of mortality events for many bivalve populations [ 45 ], and they have been extensively studied, especially in mollusks of high commercial interest [ 46 , 47 , 48 , 49 , 50 , 51 ]. Indeed, H. pinnae was initially considered as the potential promoter of the mass mortality of P. nobilis [ 7 , 8 ] because it was the first pathogen found in large quantities on dead and moribund fan mussel individuals [ 12 , 13 , 14 , 15 ] and because it has been considered to be a specific-species protozoan of P. nobilis .…”

Impacts of Marine and Lagoon Aquaculture on Macrophytes in Mediterranean Benthic Ecosystems

“…A wasting disease (90% to near 100% mortality) occurred in Spain in 2016 (Darriba, 2017;Vázquez-Luis et al, 2017). Subsequently, this mortality spread to the whole of the Mediterranean (González-Wangüemert et al, 2018;Pergent, 2018;Bianchi et al, 2019;Cabanellas-Reboredo et al, 2019). Mortality is caused by a unicellular parasite, Haplosporidium pinnae, a species previously undescribed (Catanese et al, 2018).…”

“…The latter hypothesis is by far the most probable: the new parasite presents many of the features that characterize an introduced species (see Ribera and Boudouresque, 1995;Boudouresque, 1999a), e.g., the weak genetic diversity and the pattern of expansion. Many haplosporidans are parasites of bivalves in the north-western Pacific; some of them were introduced to Europe via shellfish transfers, with dire consequences (Sindermann, 1992;Cabanellas-Reboredo et al, 2019). The possible primary vector species of H. pinnae (Magalana gigas?…”

“…is still unidentified. Currents and ballast waters seem to have been involved in its spread within the Mediterranean (Cabanellas-Reboredo et al, 2019); in addition, a putative reservoir species (Mytilus galloprovincialis?) could account for long-distance dispersal.…”