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.
Highlights
Nazionale delle Ricerche-Istituto per lo studio degli impatti Antropici e Sostenibilità in ambiente marino (CNR IAS), Oristano, Italy. 8IMEDMAR-UCV, Institute of Environment and Marine Science Research, Universidad Católica de Valencia SVM, Calpe, Alicante, Spain. 9Department of Chemical, Biological, Pharmaceutical and Environmental Sciences (CHIBIOFARAM), University of Messina, Viale F
Pen shell’s population health in Spain has plummeted, causing concern and a status change from “Vulnerable” category to “Critically Endangered” with a serious extinction risk (Orden TEC/1078/2018). This is due to a Mass Mortality Event (MME24,25) that affected P. nobilis populations of the south-western Mediterranean Sea starting in early autumn 2016 with extremely high mortality levels
Assuming that the mass mortality events described in this study have been caused by the newly described parasite H. pinnae[27], model simulations of particle drift dictated by regional surface currents suggest that parasite dispersion by surface currents could play an important role at a regional scale, as has been suggested before for other Haplosporidian species[44]
Summary
It plays a key role in the trophic web, serving as prey of other species (e.g., Octopus vulgaris13,14) and host of symbionts like the crustaceans Pontonia pinnophylax and Nepinnotheres pinnotheres[15] Several anthropogenic pressures such as pollution[16,17], anchoring[18,19], harvesting[20], habitat degradation[21,22] and environmental threats like for example global warming, which induces a decrease in juveniles’ survival rate[23] have contributed to accelerate the decline of pen shell populations in the last century, making this emblematic species one of the most important bio-indicators of ecosystem status in the Mediterranean basin. The occurrence of healthy P. nobilis populations in specific areas (e.g., Alfacs Bay in the Ebro Delta, with low salinity caused by freshwater discharges) points towards a relation between environmental factors such as salinity and/or temperature on disease prevalence or survival of H. pinnae
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
