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Best detection function (model m 13 ) of P. nobilis for the three habitat types in which individuals were detected (Posidonia oceanica meadows, mixed bottoms, and sandy bottoms). For each habitat type, two curves are depicted, corresponding to the minimum and maximum observed visibility at each habitat type.
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An important population of the endemic Mediterranean fan mussel Pinna nobilis thrives in the marine protected area of the Gera Gulf (Lesvos island, northeastern Aegean Sea, Greece), and was assessed for the first time. To estimate the abundance, spatial distribution and habitat use of fan mussels in the Gera Gulf, a distance sampling underwater sur...
Contexts in source publication
Context 1
... the distance from the line, y, is in cm, 'visibili- ty' in m, and the two variables 'mixed' and 'Posidonia' are 1 (one), if the habitat is mixed or Posidonia oceanica meadow respectively, and zero otherwise (Fig. ...
Context 2
... the detectability of fan mussels in Po- sidonia oceanica meadows was better than the detectabil- ity in mixed or sandy sediments (Fig. 5). This was largely because of the within-transect variation of visibility. The estimated index of visibility was an estimated average for the wider area on the specific date. However, at different habitats within each transect, visibility varied substantial- ly. In Posidonia oceanica meadows, visibility was better than in sandy areas ...
Citations
... Benthic communities have been described by Zenetos and Papathanasiou [27], whereas Tsatiris et al. [28] depicted among others the habitat distribution. Manoutsoglou et al. [25] and Lioupa et al. [29] described in detail the low but complex morphology of the gulf deeper than 11 m water depth, built by thousands of small reefs, and also presented initial information of buried structures. ...
Gera Gulf, a relatively small embayment on the island of Lesvos, serves as a representative example of a semi-enclosed, shallow marine system in Greece. Previous studies revealed that the gulf seafloor is occupied by numerous small reefs that are evenly distributed. Recently, seismic surveys together with gravity coring have shown numerous relict reefs within a fine-grained matrix, hosted at different stratigraphic levels above the inferred Holocene/Pleistocene boundary and locally extending up to the present seabed. The reefs are primarily engineered by the bivalve Ostrea edulis, with additional colonization by other marine organisms such as the coral Cladocora caespitosa. Key features identified in the seismic profiles include the widespread distribution of buried reef structures, erosional surfaces and unconformities also related to a paleolake, extensive fluid concentrations, and a major fault system paralleling the northeastern coast. Seismic record analysis and sediment dating suggest that the flooding of Gera Gulf began approximately 7500 BP, with O. edulis colonizing the seabed shortly thereafter. Buried reef structures were identified within the transgressive and highstand system tracts, characterized by varying sedimentation rates. These variations reflect changing environmental conditions, probably linked to specific climatic events during the Holocene epoch, which contributed to the evolution and shaping of the oyster reef terrain. Given the limited studies on recent or buried oyster reefs in similar environments, this study provides critical insights into the Holocene evolution of oyster reef terrains and their response to climate changes.
... Fan mussels were counted using the strip transect method in this study. This method gives more precise results since the boundaries are determined with precise strips and is frequently used in the estimation of fan mussel studies (García-March et al. 2002;Vafidis et al. 2014;Tsatiris et al. 2018;Karadurmuş and Sarı 2022a). Lead rope with a diameter of 3 mm and a length of 150 m, marked at intervals of five meters, was used as the transect material. ...
... Such depth (Šiletić and Peharda 2003;García-March et al. 2007a;Karadurmuş and Sarı 2022a) and habitat (Katsanevakis and Thessalou-Legaki 2009;Hendriks et al. 2011;Deudero et al. 2015;Acarlı et al. 2022;Karadurmuş and Sarı 2022a) related diversities have an important impact on fan mussels' survival and recruitment. Key environmental factors such as hydrodynamics, light intensity, temperature, and productivity in shallow waters strongly support the existence of the species (Prado et al. 2014;Russo 2017;Tsatiris et al. 2018). Results indicating that sandy grounds and seagrass beds are the primary habitats where the species thrives. ...
... Results indicating that sandy grounds and seagrass beds are the primary habitats where the species thrives. Muddy substrates seem to be unsuitable for attachment and may not provide the necessary conditions for the survival and growth of the species (Katsanevakis 2006;Tsatiris et al. 2018). ...
Fan mussel (Pinna nobilis) is one of the largest bivalve species in the Mediterranean Sea. The situation of the species is critical as it faces widespread mass mortality attributed to pathogens in various parts of the Mediterranean Sea. The Sea of Marmara (SoM) offers a unique environment for fan mussel populations, with some areas hosting alive populations. This study aims to explore and describe new P. nobilis populations in the SoM that are known to be not affected by mortality. An area of 28,200 m² at 47 stations along the 105 km coastline in the southern part of the SoM was explored using underwater visual transects. A total of 544 alive fan mussels were recorded during the underwater surveys, ranging in total shell height from 11.8 to 31.4 cm. The mean density was estimated as 5.3 ind 100 m⁻² although maxima of 18.8 ind 100 m⁻² were recorded in some stations. These density hotspots were distributed from the shoreline to a 10 m depth range and 100 m distance from the shoreline in sandy and seagrass meadow habitats. The presence of juveniles provided evidence of successful recruitment. The distribution pattern and recorded mortalities were attributed to hydrodynamic factors and intense human activities. Potential environmental factors (low salinity and temperature) in the SoM may control or delay the possible spread of the lethal pathogens. Favorable conditions result in mussels’ resilience and survival mechanisms. The SoM offer a promising larval reservoir for the recolonization of affected areas, such as those found in the Aegean Sea, through larval exportation.
... Despite its ecological significance, P. nobilis larval phase and dispersal potential remain poorly understood (Kersting & Garcia-March, 2017;Trigos et al., 2018;Kersting et al., 2020). The species primarily inhabits soft-bottom areas within seagrass meadows (Prado et al., 2014;Kersting & García-March, 2017), but it can also be found in other substrates, such as unvegetated sandy areas, boulders, detritus beds, and marl beds (Katsanevakis, 2006;Basso et al., 2015;Kersting & Garcia-March, 2017;Tsatiris et al., 2018). Pinna nobilis plays a pivotal ecological role, actively filtering large amounts of detritus from the water and contributing to water clarity (Trigos et al., 2014). ...
Since the first confirmed records of mass mortality events (MME) in the Aegean Sea in 2018, Pinna nobilis populations in Greek seas have been decimated. To bolster recovery efforts, this study aimed to assess the status of fan mussel populations in the Aegean and Ionian seas and investigate potential recolonization through natural recruitment. From May 2022 to May 2023, 163 independent underwater visual surveys were conducted across various locations and depths along the Greek coastline. A total of 4348 P. nobilis individuals was recorded, of which 87.3% were found dead and 12.7% were alive. The sole surviving fan mussel populations were located in the semi-enclosed gulfs of Amvrakikos in the Ionian Sea and of Kalloni in the Aegean Sea, with estimated recent mortality rates (excluding potential poaching) of 7.7% and 6.3%, respectively. To track potential new recruitment, a network of larvae collectors was deployed in multiple locations. Additionally, an ocean circulation model (OCM) was developed to predict the export and fate of larvae from the surviving populations in the Marmara Sea towards the Aegean Sea. Beyond the MME, this study identified several other threats, which significantly endanger fan mussel survival. The findings of this study underscore the urgent need to implement protection measures and restoration actions to enhance the chances of P. nobilis survival and recovery in the Greek seas.
... This is particularly evident along the northern Adriatic coast of the region, where extended seagrass meadows are absent and, no trace of P. nobilis was encountered, except in the Tremiti archipelago where both P. oceanica meadows and pen shells were found. By contrast, present data reporting P. nobilis as associated with various seagrass species, such as P. oceanica, C. nodosa, and Zostera sp., are consistent with the macroscale and mesoscale association between P. nobilis and seagrass meadows sensu lato and most literature reporting ubiquitous distribution of P. nobilis both in lagoon-estuarine 21,22,[24][25][26]31 and in marine ecosystems 4,7,9,14,16,24 . ...
The dramatic Mass Mortality Event, MME, of Pinna nobilis populations initially detected in the western Mediterranean basin, has also spread rapidly to the central and eastern basin. Unfortunately, there is still a significant lack of information on the status and health of P. nobilis, since only a fragmentary picture of the mortality rate affecting these populations is available. Regarding the Italian coast, several surveys have given only localized or point-like views on the distribution of species and the effect of the MME. Therefore, for the first time, this study investigated P. nobilis density of individuals, distribution and mortality throughout 161 surveys along 800 km of coastline in the Apulia region (South-east of Italy). The geographical scale of this investigation made it the largest ever conducted in Italy, and this was achieved through a rapid and standardized protocol. During this monitoring campaign, 90 km of linear underwater transects were surveyed, along which no live individuals were observed. This result allowed to estimate that the P. nobilis populations had totally collapsed, with a mortality rate of 100% in Apulia. The distributional pattern of the species showed a strong overlap with seagrass meadows on meso-and macro-geographical scale, however this was not the case on a micro-scale. This result evidenced that relationships between P. nobilis and seagrass meadows are not limited to the habitat patch, but cross the boundaries of seagrass leading us to suggest that the distribution of P. nobilis hold a trophic link through the cross-boundary subsidy occurring from seagrass meadows to the nearby habitat, by means of the refractory detrital pathway. npj Biodiversity (2022) 1:3 ; https://doi.
... comm.). Although some high values around 10−15 ind. 100 m −2 have been re corded (Venice lagoon, Italy, Russo 2012;Mar Menor, Spain, Giménez-Casalduero et al. 2020;around the Balearic Islands, Spain, Vázquez-Luis et al. 2014), the most common values in most areas range around 1−2 ind. 100 m −2 (Rabaoui et al. 2010, Basso et al. 2015b, Trigos & Vicente 2018, Tsatiris et al. 2018. Fan mussel populations have also been found in other marine lagoons of the Mediterranean Sea, for example, in the Diana saltwater pond in Corsica (de Gaulejac et al. 2005, Simide et al. 2019, Lake Vouliagmeni, Greece (Katsanevakis 2009), Aquatina lagoon, Italy (Marrocco et al. 2018), Ghar el Melh lagoon, Tunisia (Zakhama-Sraieb et al. 2011), and Mar Menor and Alfacs Bay, Spain (Prado et al. 2014, Giménez-Casalduero et al. 2020, and were previously reported in Thau lagoon (Foulquié et al. 2020). ...
... Both Salses-Leucate and Thau re ceive freshwater inflows from sources which decrease the surrounding salinity: 2 western karstic springs (Font Estramar and Font Dame in Salses-Leucate) and the Vène and Pallas rivers, as well as the submarine spring of the Vise which emerges under water, near Balaruc, in Thau (Fleury et al. 2007), which could explain the absence or low density of fan mussels in these areas. Similar results were found in the Gera Gulf (Lesvos Island, Greece), where higher densities of fan mussels were found near the connection to the sea (Tsatiris et al. 2018), and in Alfacs Bay, where individuals settled in the southern part of the bay and were absent from the northern part which receives irrigation channels from rice fields (Prado et al. 2014). The proximity to freshwater inflows can lead to high salinity fluctuations, which is a structuring factor that may limit the survival of fan mussels. ...
In 2019, the status of the Mediterranean fan mussel Pinna nobilis was elevated to ‘Critically Endangered’ on the IUCN Red List, in response to the pandemic caused by the parasite Haplosporidium pinnae . Identifying refuge habitats, free from parasites, is critical to the survival of the mussel. The distribution of P. nobilis was investigated along the Occitan coast (Northwest Mediterranean Sea) because of the presence of a unique lagoonal system that may provide potential refuges. Interviews with users and managers were conducted to identify target zones where the species was sighted. In situ surveys were carried out to define the main aggregations of fan mussels and characterize the habitat. Line transects were deployed to count and measure individuals to estimate density, abundance, and size distribution. Population densities were variable, ranging from 0.6 ± 0.2 (SE) to 70.8 ± 7.6 ind. 100 m ⁻² , representing one of the highest densities reported in the Mediterranean Sea. The total abundance of individuals across the coast was extrapolated to 163000, with 87% located in Thau and Salses-Leucate, highlighting these lagoons as essential for the survival of the species. This study also revealed the diversity of habitats colonized by P. nobilis . In the context of the pandemic, only the lagoon populations remain unaffected and provide natural refuges that have disappeared from all open-water coastal areas. However, the conditions in these lagoons could become unfavorable, leading to the collapse of the last P. nobilis populations. We therefore propose that Thau and Salses-Leucate lagoons, which harbor the largest remaining populations of P. nobilis, should be declared as conservation priorities.
... There is compelling evidence that depth significantly affects species density (Zavodnik, 1967;Šiletić & Peharda, 2003;Coppa et al., 2013). Tsatiris et al. (2018) argued that different densities are primarily due to the relationship of depth with several essential environmental parameters such as temperature, light intensity, hydrodynamics, bottom substratum, and primary and secondary productivity. Stagnant waters in protected areas where there is no human activity provide unexposed conditions for P. nobilis, and populations were determined to peak at less than a meter deep (Prado et al., 2014;Russo, 2017). ...
This study presents the results of the first broad-scale assessment of the spatial distribution of the fan mussel (Pinna nobilis Linnaeus, 1758) population in the Gulf of Erdek (Sea of Marmara, Turkey), based on underwater surveys. The population density and structure of mussels were estimated by diving along strip transects between the shoreline and a depth of 15.8 m, in a study area of 9080 km2. A total of 2164 mussels were counted, of which 78.8% were alive, and 21.2% were dead in 29 sites. The mean density was calculated as 18.3 ± 3.3 ind•100 m-2, and recorded densities reached 71.2 ind•100 m-2 among the studied sites. Although mussel density was very high (>15 ind•100 m-2) in nine regions, dead mussels were also recorded in the gulf. Benthic habitats, depth range, and exposure levels seem to play a crucial role in the spatial distribution and survival of fan mussels. The average height (± SE) was calculated as 19.5 ± 0.35 cm and 24.9 ± 0.37 cm for alive and dead mussels, respectively. The percentage of juveniles (≤20 cm) was 57% in the population, and they dominated in seagrass meadow beds and shallow waters. Despite many deaths due to uncertain causes, the results indicate a partially promising scenario for the fan mussel population in the Gulf of Erdek and highlight the existence of many alive juveniles that could play a primary role in the sustainability of the population. This situation is not static, as anthropogenic changes and human activities could affect population welfare in the future. These high-density sites need to be protected, and protection measures in these locations should include all effects that may cause incidental mortality.
... We did not notice the presence of a habitat type with the flowering plant Posidonia oceanica meadows. As factors potentially affecting detectability, namely, the size of fan mussel individuals, a habitat type and water visibility were all absent and given the good visibility, absence of juveniles and a habitat type inhabited by Posidonia oceanica meadows, we had no visual obstacles during our underwater surveys (as shown in Figure 7), and we did not specifically address the detection function (Tsatiris et al., 2018). ...
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 km 3) 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.
... This could explain the absence or low density of fan mussels in these areas. Similar results were found in Gera Gulf (Lesvos Island, Greece) where higher densities of fan mussels were found next to the connection to the sea (Tsatiris et al., 2018) and in Alfacs Bay, where individuals settled in the southern part of the bay and were absent from the northern part which receives irrigation channels from rice fields (Prado et al., 2014). The proximity to freshwater inflows can lead to high fluctuations of salinity, which could thus be a structuring factor that may limit the development of fan mussels. ...
... L'extinction d'une espèce n'est pas un processus immédiat et il est généralement précédé par le déclin progressif de ses populations, conduisant à la perte de diversité génétique (Ceballos et al., 2017). La Les lagunes et les ports concentrent un grand nombre d'activités anthropiques, générant ainsi beaucoup de pressions sur l'environnement (artificialisation, pollution, surexploitation, etc.) qui peuvent conduire à la dégradation de l'habitat (Kennish and Paerl, 2010 (Russo, 2012) mais les valeurs les plus communes sont généralement autour de 1 à 2 individus/100 m² (Basso et al., 2015b;Rabaoui et al., 2010;Tsatiris et al., 2018). Ce résultat est inattendu car la grande nacre est généralement considérée comme une espèce côtière. ...
... A similar value was found in the Gulf of Gabes, in Tunisia, where density reached 56 ind/100 m²(Rabaoui et al., 2010). The highest density ever reported was around 1 200 ind/100 m² in Venice lagoon(Russo, 2012) whereas the most common values in other areas are around 1 -2 ind/100 m²(Basso et al., 2015b;Rabaoui et al., 2010;Tsatiris et al., 2018). However, a comparison of aggregation densities among different studies is complicated as the sampling design and analyses vary significantly. ...
Les systèmes marins côtiers sont généralement discontinus et constitués d’une mosaïque de paysages sous-marins différents, créant ainsi des distributions parfois très fragmentées chez les espèces qui les colonisent. Les espèces marines côtières sont donc structurées en réseaux de populations connectées entre elles via la dispersion larvaire. Comprendre le fonctionnement et la connectivité entre les populations d’une espèce est indispensable pour adapter les stratégies de conservation. La grande nacre, Pinna nobilis, est une espèce endémique de la mer Méditerranée qui fait aujourd’hui face à une crise majeure qui menace sa survie. Depuis Octobre 2016, des mortalités de masse sont signalées sur ses populations, à travers toutes la mer Méditerranée, causées par un protozoaire parasite, Haplosporidium pinnae. Il s’agit d’un évènement sans précédent, que ce soit par le taux de mortalité (près de 100 %) ou la vitesse de propagation, et qui pourrait conduire à l’extinction de l’espèce. En se focalisant sur le littoral Occitan, cette thèse apporte des connaissances sur la biologie et l’écologie de l’espèce mais aussi sur son fonctionnement et les processus qui permettent le maintien de ses populations afin de proposer des priorités de conservation. Ainsi, nous avons mis en évidence la diversité d’habitats colonisés par l’espèce ainsi que l’importance des lagunes car elles abritent près de 90 % des grandes nacres, sur le littoral Occitan, et semblent servir d’habitat refuge à l’espèce en limitant l’infestation par le parasite. A l’aide de marqueurs microsatellites nouvellement développés, nous avons montré une structure génétique très homogène sur toute la côte, ce qui implique un certain niveau de connectivité et laisse penser qu’une grande partie de la diversité génétique de l’espèce reste préservée dans les lagunes. En se focalisant sur la population de la baie de Peyrefite, dans la Réserve Naturelle Marine de Cerbère-Banyuls, et grâce à une analyse de parenté, nous avons apporté des connaissances sur la dynamique démographique et les processus de repeuplement de l’espèce. L’ensemble de cette thèse permet de définir des recommandations qui seront utiles à la mise en place de mesures de conservation adaptées, indispensables pour la survie de l’espèce.
... Over the last few decades, its numbers have drastically declined [2], and the species is now protected under Annex IV of the Habitats Directive, Annex II of the Barcelona Convention, and national legislation in Croatia and most Mediterranean countries. The decline has been attributed to uncontrolled trawling [3], illegal collection for food or souvenirs by amateur divers, and devastation of their natural habitats due to anthropogenic inputs [1,4]. Some coastal waters in the Mediterranean basin that are known as natural habitats of this protected species have been designated as marine parks, such as the Mljet Island National Park in Croatia or the Parque Natural de Cabo de Gata-Nijar [5] and the Parque Nacional Marítimo-Terrestre del Archipiélago de Cabrera in Spain [6]. ...
Noble pen shells (Pinna nobilis) along the Eastern Adriatic coast were affected by mass mortalities similarly to the populations across the Mediterranean basin. Samples of live animals and organs originating from sites on Mljet Island on the south and the Istrian peninsula on the north of the Croatian Adriatic coast were analyzed using histology and molecular techniques to detect the presence of the previously described Haplosporidium pinnae and Mycobacterium spp. as possible causes of these mortalities. To obtain more information on the pattern of the spread of the mortalities, a study was undertaken in Mljet National Park, an area with a dense population of noble pen shells. The results of the diagnostic analysis and the velocity of the spread of the mortalities showed a significant correlation between increases in water temperature and the onset of mortality. Moderate to heavy lesions of the digestive glands were observed in specimens infected with H. pinnae. A phylogenetic analysis of the detected Haplosporidium pinnae showed an identity of 99.7 to 99.8% with isolates from other Mediterranean areas, while isolated Mycobacterium spp. showed a higher heterogeneity among isolates across the Mediterranean. The presence of Mycobacterium spp. in clinically healthy animals a few months before the onset of mortality imposes the need for further clarification of its role in mortality events.
... In the Greek coasts of the Aegean Sea, the density of the species locally exceeded 2 ind.10m -2 in Souda Gulf (Crete) (Katsanevakis & Thessalou-Legaki, 2009), 1 ind.10m -2 in Gera Gulf (Lesvos) (Tsatiris et al., 2018), and 0.7 ind.10m -2 (with a mean estimate of 0.3 ind.10m -2 ) in the southern Aegean Islands (Vafidis et al., 2014). In the other sub-regions of the Mediterranean Sea, the average population density of this species was estimated as 2 ind.10m -2 in the Adriatic Sea (Šiletić & Peharda, 2003), and 0.1 ind.10m -2 in the western Mediterranean Sea (Coppa et al., 2010). ...
A total of 12 Pinna nobilis beds were found and studied at depths between 2 and 6 m in the south Marmara Islands (Sea of Marmara). Fan mussel individuals in the beds were healthy with a few old dead specimens, indicating that the epidemic, which has devastated P. nobilis populations in the Mediterranean Sea, has not reached the Sea of Marmara, making the region a refuge area for the species. The average density of P. nobilis in the area varied between 0.6 ind.10 m-2 and 24 ind.10 m-2. The P. nobilis shells overall provided substrata or refuge for 14 species (10 sessile and 4 motile), from macroalgae to fish. Shells of juvenile and adult specimens had different species assemblages. Four distinct assemblages were detected on shells, primarily formed by the red alga Gracilaria bursa-postaris, egg cocoons of the invasive alien Rapana venosa, the gastropod Bittium reticulatum and the serpulid polychaete Spirobranchus polytrema.
