After the Pinna nobilis l. mass mortality event in Bosnia and Herzegovina – A proposal for remediation of biofiltration services in marine ecosystem

Abstract

The Mass Mortality Event (MME) of endemic bivalve Pinna nobilis occurred in the Mediterranean Sea and brought this species to the brink of extinction. So far, the etiology of the disease was determined to be multifactorial. Apart from a wide spectrum of pathogenic microorganisms as a key factor, the indirect role is played by climate changes, ie. the increase in sea water temperature, which rises sensitivity of P. nobilis toward pathogens. In terms of conservation measures, the IUCN guidelines are species- oriented and recommend in situ and ex situ conservation. In this study, we examined 10,920 m2 of seabed in the territorial waters of Bosnia and Herzegovina (B&H) and confirmed the occurrence of MME with 100% mortality rate. Based on estimated Total Number of Individuals (TNI), the filtration capacity as an ecosystem service for the turbidity control in the Bay was assessed. Herein, we present a potential method for the assessment of ecosystem damages caused by the loss of fan shells and their biofiltration service. Our results showed that 58583 ± 27879 individuals were lost, which corresponds to the biomass of 11.47 t ± 6.41 t (± 55.87%). Hourly filtration potential (PRF) of P. nobilis is 68722.11 ± 38396.86 (± 55.87%) 95% CI, meaning that all populations could filter the entire sea water in the Neum Bay (0.2 km3) in a period of 78-275 days. We also determined the Compensation Ratio (CR) for bivalve shell Ostrea edulis, i.e. how many individuals of O. edulis are required to replace the function of one P. nobilis in terms of filtration capacity, which is CR = 2.72 ± 0.30 (11.03%). This paper provides a new approach to the MME of P. nobilis indicating urgent need for the marine ecosystem remediation and replacement of the lost ecosystem service by cultivation of compensatory species.