Abstract
Abstract Mussels, belonging to the species Mytilus galloprovincialis Lamark, 1819, represent the most important species for the Italian shellfish production. In EU, Italy is the second largest producer of this species (coming only after Spain), and the first one in the Mediterranean Region. The production comes mostly from aquaculture in lagoons and open-sea and to a smaller extent, from wild populations in the central and northern Adriatic Sea (77% of Italian production). However, in the last few years, both farmed and wild mussels have shown issues in terms of meat reduction and increased shell fragility, which negatively affect their quality, and hence their market value. Since farming technics have not been substantially modified with time, and changes also affect the wild populations, these impacts are inevitably caused by environmental phenomena that have occurred in recent years. Seen as scientific data regarding how these changes impact product quality are lacking, the current information comes solely from producers. In this contest, the ENDRIMUS Project wants to pose attention on this phenomenon happening in the Adriatic Sea, identifying which environmental drivers can mainly affect the growth of mussels in this area. It has been established in literature that river discharges are the main source of nutrients and other inorganic elements, which are at the base of the trophic web in the Adriatic Sea. By employing an interdisciplinary team of experts in marine ecology and biology, environmental and analytical chemistry, and oceanography, ENDRIMUS will evaluate which environmental drivers mainly affect the growth and quality of farmed and wild mussel populations along a latitudinal gradient from North to South of the Italian Adriatic coast. For this purpose, physical and biochemical features, as well as biological variables of the water column will be investigated, along with phytoplankton community abundance and composition, which represent an important source of food for these filter feeding animals. Biological analysis on mussel content and an in-depth study on the shell features at the macro, micro and nanoscale level will be carried out on samples from farmed and wild mussels collected at different sites, to evaluate how this bivalve species is sensitive to variations in environmental conditions. ENDRIMUS points out the importance of considering multiple environmental parameters to investigate bivalve growth and allow for a proper management of bivalve aquaculture. Indeed, given the great socio-economic relevance of Mytilus galloprovincialis along the Italian Adriatic coasts, projects like this one are crucial to guarantee a knowledge-based management of this important resource. The results produced will be disseminated to international, national, and regional stakeholders and the scientific community, in order to provide useful information for future development in mussel farming.
Results achieved
A clear spatial gradient emerged across the study area. Northern sites (Rimini and Senigallia) were characterised by lower salinity, higher nutrient concentrations, elevated chlorophyll-a levels, and greater phytoplankton abundance, reflecting the influence of riverine inputs and the southward-flowing Western Adriatic Current. The southern site (Giulianova) displayed more oligotrophic conditions, with reduced phytoplankton biomass and lower trophic richness. Seasonal variability was equally pronounced: summer stratification suppressed nutrient resupply and phytoplankton growth despite high irradiance, while winter mixing promoted diatom blooms and enhanced food availability for filter feeders. The summer 2024 season was particularly extreme, with marine heatwaves driving sea surface temperatures above 30 °C for over 30 consecutive days in parts of the Adriatic, coinciding with a severe mucilage event and causing extensive mussel mortalities at several central-southern sites. A molecular qPCR approach was used to quantify seven phytoplankton taxa directly from mussel tissue, providing direct evidence of trophic exposure at each site and season. The diatom Chaetoceros socialis was the most abundant taxon detected in mussel tissues, with peak values during winter at Rimini, reflecting the alignment between bloom dynamics in the water column and mussel feeding activity. Notably, the toxic dinoflagellate Dinophysis spp. was detected in mussel tissues even at very low water-column concentrations, highlighting the capacity of mussels to accumulate potentially harmful species and signaling implications for the safety monitoring of Adriatic aquaculture production. The Condition Index (CI) showed significant spatial and seasonal variability. Higher CI values were recorded at northern sites, particularly at mussel farm installations, and during the winter-spring period, coinciding with phases of enhanced phytoplankton availability and favourable metabolic conditions. Random Forest modelling identified trophic variables, dinoflagellate abundance, small phytoplankton cells (<5 µm), Dinophysis spp., and particulate inorganic matter (PIM), as the primary predictors of CI, suggesting that food quality and nutritional diversity are the key determinants of physiological condition in this species. Shell structural properties responded to a different and partially independent set of environmental drivers. Bulk density and apparent porosity varied significantly across seasons and between farming and wild contexts, while micro-density remained stable around 2.6 g/cm³, consistent with biologically precipitated aragonite and calcite. A clear seasonal pattern was observed: shells were more porous and less dense during winter, coinciding with rapid growth and high food availability, and became denser and more compact in summer, when higher carbonate saturation states and elevated temperatures promoted more controlled shell deposition. Farmed mussels exhibited higher CI but more porous shells compared to wild conspecifics, reflecting the contrasting ecological pressures of longline farming environments, stable food supply, reduced predation, lower hydrodynamic forcing, versus natural or artificial reef habitats where physical and ecological constraints favour structurally denser shells. Random Forest analysis confirmed that shell porosity and bulk density were primarily driven by carbonate chemistry (pCO₂), salinity, PIM, and small phytoplankton, highlighting the cumulative and integrative nature of calcification responses compared to the more rapid trophic sensitivity of CI. Shell mechanical resistance (maximum load to fracture) showed weaker and less consistent correlations with environmental variables, and no clear spatial or seasonal pattern was detected, suggesting that organic matrix reinforcement may partially buffer the effects of structural variability on overall mechanical integrity. Taken together, these results demonstrate that physiological condition and shell structural performance are governed by distinct and partially independent pathways of energy allocation. CI responded primarily to short-term trophic conditions and food quality, while shell properties reflected cumulative environmental and ecological pressures acting on calcification over seasonal timescales. From an applied perspective, this decoupling has direct relevance for Adriatic mussel aquaculture: assessments based solely on CI or meat yield may overlook critical differences in shell robustness, with consequences for handling efficiency and overall product quality. The ENDRIMUS project demonstrates that integrating shell structural traits with conventional biometric and condition-based metrics provides a more comprehensive and operationally relevant framework for evaluating mussel quality, informing site selection, and supporting the sustainable management of both farmed and wild populations in an environmentally variable and climatically sensitive coastal system.Dettagli del progetto
Responsabile scientifico: Stefano Goffredo
Strutture Unibo coinvolte:
Dipartimento di Scienze Biologiche, Geologiche e Ambientali
Coordinatore:
ALMA MATER STUDIORUM - Università di Bologna(Italy)
Contributo totale di progetto: Euro (EUR) 237.249,00
Contributo totale Unibo: Euro (EUR) 88.324,00
Durata del progetto in mesi: 24
Data di inizio
30/11/2023
Data di fine:
28/02/2026
