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Marine Biodiversity of the Mediterranean Sea: Situation, Problems and Prospects for Future Research
Abstract
Mediterranean marine biodiversity has received only a fraction of the attention accorded to its terrestrial counterpart, despite the great cultural and economic importance that the sea has been having for the Mediterranean countries. A rough estimate of more than 8500 species of macroscopic marine organisms should live in the Mediterranean Sea, corresponding to somewhat between 4% and 18% of the world marine species. This is a conspicuous figure if one considers that the Mediterranean Sea is only 0.82% in surface area and 0.32% in volume as compared to the world ocean. The high biodiversity of the Mediterranean Sea may be explained by historical (its tradition of study dates older than for almost any other sea), paleogeographic (its tormented geological history through the last 5 my has been determining the occurrence of distinct biogeographic categories), and ecological (its variety of climatic and hydrologic situations within a single basin has probably no equals in the world) reasons. Present-day Mediterranean biodiversity is undergoing rapid alteration under the combined pressure of climate change and human impact, but protection measures, either for species or ecosystems, are still scarce. To understand the role and patterns of Mediterranean marine biodiversity, marine ecological research should: first, re-value those scientific areas currently unfashionable with funding agencies (systematics, biogeography and taxonomy); second, start monitoring biodiversity with a long-term approach at a whole Mediterranean scale, possibly through an internationally co-ordinated network of marine protected areas.
... The Mediterranean Sea is recognized as a marine biodiversity hotspot, harboring between 4% and 18% of the world's marine species richness (Bianchi & Morri, 2000;Arvanitidis et al., 2002;Coll et al., 2010). Despite extensive studies conducted since ancient times, our understanding of the region's biodiversity remains incomplete, with new species still being discovered (Sturaro & Guerra-García, 2012;Beli et al., 2018;Gómez et al., 2024). ...
... Given the Mediterranean's importance as biodiversity hotspot (Bianchi & Morri, 2000;Coll et al., 2010Coll et al., , 2012Myers et al., 2000) and the ongoing challenges posed by human activities and environmental changes, one of the objectives of the 'WATER-MINING' project within the framework of Horizon 2020 aimed to enhance our understanding of the impacts of seawater desalination plants on marine biodiversity, by studying the condition of Posidonia oceanica seagrass meadows near the hypersaline outfalls of two major desalination plants in Cyprus, Larnaca and Dhekelia (Xevgenos et al., 2021). During the investigation, specimens of the genus Apseudopsis Norman, 1899 were collected. ...
... To a lesser degree the Levantine Sea has been influenced by warm-temperate Atlantic-Mediterranean fauna (Por, 1989;Bianchi et al., 2012). Currently the basin is influenced by significant influxes from the Red Sea (Bianchi & Morri, 2000;Coll et al., 2010;Galil et al., 2017). It remains uncertain whether the diversity of Apseudopsis in the Levantine Sea is affected by this invasion, due to the limited information available about benthic peracarids in the Red Sea. ...
The Mediterranean Sea is recognized as one of the most threatened marine
environments due to pollution, the unintentional spread of invasive species, and
habitat destruction. Understanding the biodiversity patterns within this sea is crucial
for effective resource management and conservation planning. During a research
cruise aimed at assessing biodiversity near desalination plants in the vicinity of
Larnaca, Cyprus, conducted as part of the WATER-MINING project (Horizon
2020), specimens of the tanaidacean genus Apseudopsis were collected. These were
classified into two species, identified as new to science, and are described herein as
Apseudopsis larnacensis sp. nov and Apseudopsis salinus sp. nov. Apseudopsis
larnacensis sp. nov is distinguished from its congeners by the presence of a lateral
apophysis on pleonite 5, which is longer than those on pleonites 1–4, hyposphenia on
pereonites 2–6, and six ventral spines on the propodus of pereopod 1. Apseudopsis
salinus sp. nov. is characterized by a rounded posterolateral margin on pereonite 6,
hyposphenia on pereonites 1–6, and four ventral spines on the propodus of pereopod
1. An updated key to the Atlantic and Mediterranean Apseudopsis species is provided.
This study provides an overview of the distribution, bathymetric, and habitat
preference of all known Apseudopsis species. Data extracted from the literature and
two popular online databases were analyzed to identify diversity patterns across seas
and ecoregions. Our analysis reveals that the Mediterranean is the most diverse
region for Apseudopsis, with the Levantine Sea hosting ten species and the South
European Atlantic Shelf seven species. Shallow waters and muddy and sandy habitats
are conducive for Apseudopsis occurrence.
... Marine biodiversity provides value in many aspects of the Mediterranean population, both culturally and socio-economically [1]. It affects food security, and the tourism and fisheries industries, while also being of high importance for the cultural heritage of the various population groups residing in Mediterranean countries [1][2][3]. ...
... Marine biodiversity provides value in many aspects of the Mediterranean population, both culturally and socio-economically [1]. It affects food security, and the tourism and fisheries industries, while also being of high importance for the cultural heritage of the various population groups residing in Mediterranean countries [1][2][3]. Biodiversity's importance is as of now widely recognized by many stakeholders apart from academics, like mass media, decision makers, and, most importantly, public opinion [1,[4][5][6][7]. Preserving the diversity of marine ecosystems is crucial as it sustains their functionality and prevents them from shifting into unfavorable conditions, thereby safeguarding the myriad direct and indirect advantages they offer. ...
... It affects food security, and the tourism and fisheries industries, while also being of high importance for the cultural heritage of the various population groups residing in Mediterranean countries [1][2][3]. Biodiversity's importance is as of now widely recognized by many stakeholders apart from academics, like mass media, decision makers, and, most importantly, public opinion [1,[4][5][6][7]. Preserving the diversity of marine ecosystems is crucial as it sustains their functionality and prevents them from shifting into unfavorable conditions, thereby safeguarding the myriad direct and indirect advantages they offer. ...
The Mediterranean Sea is the second largest biodiversity hotspot on earth, with over 700 identified fish species is facing numerous threats. Of more than 6000 taxa assessed for the IUCN Red List, a minimum of 20% are threatened with extinction. A total of eight key factors that affect vulnerability of marine fish species in the Mediterranean Sea were identified using the scientific literature and expert-reviewed validated databases. A database of 157 teleost fish species with threat status ranging from least concern to critically endangered was compiled. Nominal logistic curves identified the factor thresholds on species vulnerability, namely, age at maturity, longevity, and asymptotic length at 8.45 years, 36 years, and 221 cm, respectively. A second-degree stepwise regression model identified four significant factors affecting the threat category of Mediterranean fish species, namely, overfishing, by-catch, pollution, and age at maturity according to their significance. Predictive analysis using supervised machine learning algorithms was further employed to predict the vulnerability of Mediterranean marine fish species, resulting in the development of a framework with classification accuracy of 87.3% and 86.6% for Support Vector Machine (SVM) and Gradient Boosting machine learning algorithms, respectively, with the ability to assess the degree of variability using limited information.
... The Alboran Sea is considered to be one of the most significant hotspots of biodiversity within the Mediterranean Sea (Bianchi and Morri 2000;Templado 2011;Templado et al. 2021;Mateo-Ramírez et al. 2021;Rueda et al. 2021). Its unique location at the southernmost part of the European continent, in close proximity to the Strait of Gibraltar results in some exceptional characteristics, including distinct hydrodynamic features resulting from the mixing of Atlantic and Mediterranean waters, as well as productive coastal waters enriched by nutrient-rich upwellings (Parrilla and Kinder 1987;Sarhan et al. 2000). ...
... The specific geomorphological characteristics and diversification of bottoms of the northern Alboran Sea promote different sedimentary habitats (from mud to gravel bottoms and mixed ones), contributing to the enrichment of the local biodiversity , as detected in other specific areas of the world (Snelgrove and Butman 1994;Snelgrove 1998;Gray 2002;Levin et al. 2010). Furthermore, the Alboran Sea is categorized as a biogeographic sector and an independent ecoregion (Bianchi and Morri 2000;Spalding et al. 2007). ...
The composition and structure of circalittoral and bathyal soft bottom echinoderm assemblages along the northern Alboran Sea, including the Alboran Ridge, have been studied in relation to sediment and near-bottom water masses characteristics. Samples were taken using a beam-trawl (50 sampling stations from 40 to 774 m depth) during 2014, 2015 and 2016 MEDITS surveys (30 to 800 m depth range). A total of 99,390 individuals were collected and 53 taxa of the five classes of echinoderms were found, with ophiuroids and holothuroids being the most diverse and abundant taxa. A high abundance of Ophiocten abyssicolum was detected in some samples, probably related to the high productivity of the Alboran Sea. Multivariate analyses using echinoderm abundance data indicated the presence of six assemblages in relation to depth, salinity and sediment type. The geographic location of the Alboran Sea, its singular oceanographic and hydrological conditions and diverse sediment types promoting habitat heterogeneity, as well as the wide depth range may promote the high echinoderm biodiversity reported in the present study. The information provided for this important benthic component improves the current knowledge on the biodiversity of circalittoral and bathyal soft bottoms of the northern Alboran Sea, and could be used as a baseline for further monitoring programs under the framework of different directives such as the Marine Strategy Framework Directive.
... F. enigmaticus (Fauvel 1923), also known as the Australian tubeworm, is an alien serpulid polychaete that forms and inhabits calcareous tubes in brackish waters [17,104]. F. enigmaticus is a fouling species that affects ships, buoys, and harbor structures (most major ports are located on estuaries), and it is inadvertently spread by shipping (over hulls of ships) and shellfish movements [105,106]. ...
... High population densities, around 150,000 ind. m −2 , were reported from Tuscany, Italy (Mediterranean Sea) by Bianchi and Morri [17,104]. Additionally, its high fecundity (this species can spawn for several months during summer [6,108]) facilitates this rapid build-up in numbers [105]. ...
Molecular biomarkers are valuable tools universally used for early warning monitoring due to their ability to detect stress at subcellular scales, even before visible or lethal changes occur in organisms. Their use is considered a priority, especially for those organisms that will be most affected by the global changes underway, such as sessile benthic organisms in shallow waters. Among them, reef-forming species play a vital role in maintaining biodiversity in temperate aquatic ecosystems. Little information is available on these organisms in the Mediterranean on the use of health status indicators at the level of biochemical responses. This review aims to highlight the need for a more in-depth analysis of the conditions of bioconstructors in a climate change scenario by using stress biomarkers. To achieve this goal, about 140 articles were selected based on a keyword search for a graphical visualization of the state of the art of the literature. Based on this overview, a literature review of selected works in the Mediterranean area was conducted to select both model organisms and molecular biomarkers for future analyses in this field. From the literature review, a gap analysis was produced, focusing on the main stressors related to global change and their effects on bioconstructors. Furthermore, an attempt was made to quantify and clarify the use of the various molecular biomarkers in different contexts. These findings should be considered in an updated protocol for monitoring programs and efforts at the European level, as outlined by the Marine Strategy Framework Directive (MSFD 2008/56/EC).
... With a surface area of 2,500,000 km 2 , the Mediterranean Sea represents less than 1% of the world's ocean area [1]. Despite this, the Mediterranean Sea is one of the richest reservoirs in the world in terms of marine and coastal biodiversity [2]. The Mediterranean Sea hosts more than 17,000 marine species, 20-30% of which are endemic, making it the sea with the highest rate of endemism [1][2][3][4][5]. ...
... Despite this, the Mediterranean Sea is one of the richest reservoirs in the world in terms of marine and coastal biodiversity [2]. The Mediterranean Sea hosts more than 17,000 marine species, 20-30% of which are endemic, making it the sea with the highest rate of endemism [1][2][3][4][5]. ...
Non-indigenous species (NIS) introduction notoriously threatens the Mediterranean Sea. In addition, Mediterranean coastal lagoons play a crucial role as nurseries for marine species, which new NIS arrivals can threaten. Therefore, monitoring and early warning of NIS presence is essential in preserving biodiversity. An innovative technique for rapid and accurate species identification and biodiversity screening is the application of environmental DNA (eDNA) metabarcoding. In this research, different Penaeidae (Arthropoda, Crustacea, Decapoda) NIS specimens were collected from a Mediterranean coastal lagoon after an early warning about a potentially invasive NIS arising from next-generation sequencing data. DNA barcoding of the DNA extracted from tissue samples and amplified with specifically designed primer pairs led to the recognition of Penaeus aztecus in this NATURA 2000 protected ecosystem for the first time. DNA barcoding from DNA isolated from the water where the living specimens were stored further validated the possibility of identifying P. aztecus starting from eDNA. This approach demonstrated the validity of environmental DNA analysis in the early screening of potentially invasive NIS presence in Mediterranean protected areas and ecosystems. This work describes an applicative example of the efficacy in improving the biomonitoring of lagoon ecosystems using molecular tools and it represents a guideline for the validation of eDNA metabarcoding data for the presence of potentially invasive species.
... The Mediterranean Sea is the largest and deepest enclosed sea on Earth. Located between Africa, Europe, and Asia, it is a hotspot of terrestrial and marine biodiversity [1][2][3]. Currently, it is known to host more than 17,000 described marine species [3], and although it occupies only 0.82% of the ocean's surface, it is home to about 10% of the world's marine species [1]. Even though the Mediterranean basin is one of the most studied seas in the world, there are still important gaps in knowledge on taxonomy, distribution, abundance, and temporal trends of occurrence for many taxa [3,4]. ...
... Located between Africa, Europe, and Asia, it is a hotspot of terrestrial and marine biodiversity [1][2][3]. Currently, it is known to host more than 17,000 described marine species [3], and although it occupies only 0.82% of the ocean's surface, it is home to about 10% of the world's marine species [1]. Even though the Mediterranean basin is one of the most studied seas in the world, there are still important gaps in knowledge on taxonomy, distribution, abundance, and temporal trends of occurrence for many taxa [3,4]. ...
The Salento peninsula in southern Italy (Mediterranean Sea) is a strip of land between the Adriatic and the Ionian Seas, both characterized by local regimes of currents, different geological and physical backgrounds, and quite diversified fauna. In this area, specimens of the sea cucumber Holothuria tubulosa (Brünnich, 1768) (Echinodermata) were collected at four stations in the spring and autumn of 2020 to investigate a possible symbiotic association with the inquiline fish Carapus acus (Brünnich, 1768). Among the collected holothurians, five pearlfish specimens were found in the body cavity of four H. tubulosa collected at 10 m of depth, in autumn, at “Grotta Verde” in Marina di Andrano, Lecce (Ionian Sea). More than half of the sea cucumbers from the latter station hosted the symbiont, suggesting the presence of a shallow population of C. acus inhabiting this coastal area. Furthermore, morphometric analysis carried out on the collected fish helped to shed light on the population dynamics characterizing this neglected species. This is the first report of C. acus from Apulian waters, allowing us to unite previously disjoined areas and providing essential baseline knowledge for planning future in-depth analysis of this difficult-to-study fish in a geographical area that is strategic in terms of the conservation of Mediterranean biodiversity. Furthermore, the range of preferred host species is extended, as C. acus was previously known to prefer other sea cucumber species such as Parastichopus regalis (Cuvier, 1817) instead of H. tubulosa. Finally, the finding of C. acus in a single station and in only one season is not trivial and delivers baseline useful information for future conservation purposes.
... In this context, the European Union has implemented a governance framework specifically aiming at assessing, monitoring, and preserving the status of the marine benthic natural heritage (Marine Strategy Framework Directive MSFD, 2014/89/EU) but also at promoting the sustainable exploitation of marine and coastal resources (European MSP Directive, 2008/56/EC). Among the European seas, the Mediterranean Sea is a hotspot of biodiversity, hosting more than 7.5 % of global biodiversity (Bianchi and Morri, 2000), with a high percentage of endemic species (Myers et al., 2000) and unique ecosystems. However, the basin is recognised to be "under siege" due to the historical and still ongoing impacts from multiple stressors such as littering and dumping, trawling, ghost fishing, seaborne traffic, and modification of the seafloor (Coll et al., 2012;Puig et al., 2012;Madricardo et al., 2017Madricardo et al., , 2019Canals et al., 2021;Budillon et al., 2022;Pellegrini et al., 2023;Trincardi et al., 2023). ...
High-resolution bathymetry provides critical information to marine geoscientists. Bathymetric big data help characterise the seafloor and its benthic habitats, understand sedimentary records, and support the development of offshore engineering infrastructures. From 27 September to 20 October 2022, the new CNR research vessel Gaia Blu explored the seafloor of the Naples and Pozzuoli gulfs and the Amalfi coastal area (Tyrrhenian Sea, Italy) from 50 to more than 2000 m water depth, acquiring about 5000 km² of multi-beam echo sounder data. This area is particularly vulnerable to abrupt changes driven by the dynamics of several volcanic complexes, active in the area, and by human-induced impacts reflecting the proximity to the highly populated and touristic coastal area of Naples and nearby famous islands. For these reasons, the seafloor of the area needs to be known and constantly monitored. The digital bathymetric data previously available are restricted to the shallow highly dynamic area of the Gulf of Naples and appear fragmented as they were acquired in successive years, with different goals thereby using a variety of devices, with markedly different spatial resolutions. In this paper, we present bathymetric maps of the Gulf of Naples and adjacent slope basins at unprecedented resolution using three state-of-the-art multi-beam echo sounders. These high-resolution data highlight the technological advances of geophysical surveys achieved over the last 20 years and contribute to assessing the most dynamic areas where changes in the seafloor over time can be quantified. The new digital multi-resolution bathymetric products are openly accessible via Marine Geosciences Data System MGDS (refer to “Data availability” section, Table 8, for datasets and product DOIs), perfectly matching the FAIR (findable, accessible, interoperable, and reusable) and open science principles.
... Fishing has been deeply connected with the cultures and economies of Mediterranean coastal communities for centuries [51]. The sea's rich biodiversity has traditionally supported livelihoods and provided sustenance. ...
This chapter explores the growing threats faced by top predators in the Mediterranean Sea. Climate change, overfishing, and plastic pollution may affect their migration patterns and lead them to abandon established reproduction areas. For instance, tuna might not find its spawning grounds due to warmer water, sea turtles might fight against plastic debris to lay their eggs, or dolphins might be tangled by a ghost net. These disruptions threaten entire predator populations, posing at risk the entire species with the death of young specimens and the reduction of offspring. The entire marine ecosystem suffers as these top predators play a vital role in maintaining a healthy balance. By examining the impact of different threats on biological and ecological aspects of movement and reproduction, this chapter shows the vulnerabilities of these important creatures, highlighting the urgent need for conservation efforts. Only with immediate actions can we ensure their survival and a healthy Mediterranean Sea for generations to come.
... Such anomaly is implicitly reported in Bianchi (2004), regarding the position of the boundary between the western and eastern Mediterranean. According to both Pérès & Picard (1964) and Bianchi & Morri (2000), the SoM (as well as the entire island of 3 Sicily) is considered to be part of the western Mediterranean. However, Giaccone & Sortino (1974) positioned the western-eastern boundary at the level of the Sicilian-Tunisian threshold. ...
... Biological invasions are considered as seriously threatening the global biodiversity thus constituting a crucial pervasive factor of its change (Galil 2007;Molnar et al., 2008;Occhipinti-Ambrogi & Galil, 2010). The Mediterranean Sea is a hotspot of biodiversity and endemism (Bianchi & Morri 2000;Coll et al., 2010) and is affected by the so-called "Lessepsian invasion" or "Erythrean invasion" a major biological marine invasion that followed the opening of the Suez Canal in 1869, especially after its recent widening. The Canal is an artificial waterway and also the most significant vector for introductions of non-indigenous species (NIS) to the Mediterranean basin, followed by shipping Galil et al., 2016;. ...
The Hellenic marine malacofauna is affected by current
environmental changes, ongoing research, and the introduction
of alien species. Out of the species in this work: Alveinus
miliaceus (Issel, 1869) and Pyrgulina maiae Hornung &
Mermod, 1924 are first records for Greece of those Lessepsian
migrants, Parthenina dantarti (Peñas & Rolán, 2008) is second
record, Finella pupoides A. Adams, 1860 is third record while
Turbonilla lactea (Linnaeus, 1758) is first image documented
record. Taxonomy is followed by discussion.
... However, many approaches follow qualitative methodologies that do not differentiate the results among the Mediterranean subregions. Defining a clear picture of the significant stressors and their highest-intensity locations would be a significant step forward in assessing Mediterranean risks and improving the sustainable development of coastal zones (Bianchi and Morri, 2000;Stelzenmüller et al., 2010;Tsikliras et al., 2015;Satta et al., 2017;Malvarez et al., 2021;Piroddi et al., 2022). ...
... Such anomaly is implicitly reported in Bianchi (2004), regarding the position of the boundary between the western and eastern Mediterranean. According to both Pérès & Picard (1964) and Bianchi & Morri (2000), the SoM (as well as the entire island of 3 Sicily) is considered to be part of the western Mediterranean. However, Giaccone & Sortino (1974) positioned the western-eastern boundary at the level of the Sicilian-Tunisian threshold. ...
The status of a distinct biogeographical sector for the area of the Strait of Messina has been widely acknowledged in the last two decades. However, clear-cut limits of this sectors have never been formalised. With the understanding that in nature the limits of biogeographical sectors are usually not clear-cut, and for the sake of unequivocally placing occurrences in this sector we have here: (1) summarized the history of the classification of the Strait of Messina as a biogeographical sector, and (2) provided the conventional limits of Sector 4, as far as possible reflecting main ecological traits and recognizable discontinuities with the neighbour sectors
... The focus on this kind of 'deluxe diversity' comes at the expense of the 'obscure diversity,' with species that play a more important role in enabling the ecosystem functioning and providing ecosystem services and goods [16][17][18][19][20][21]. This trend has also been called 'Walt Disney effect' by Bianchi and Morri [22]. As a result, there is a substantial bias with regard to the choice of taxa for which research funding is made available, a bias that is excessive when it comes to funding conservation, with an overwhelming dominance of birds and mammals [23,24]. ...
... This sub-basin receives the surficial Atlantic water flowing through the Strait, while Mediterranean waters flow close to the bottom into the Atlantic Ocean. This phenomenon promotes singular oceanographic and hydrological conditions that support an exceptional marine biodiversity and a privileged transitional ecosystem between these two big basins [1][2][3][4], resulting in the confluence of organisms from different biogeographical areas (Lusitanian, Mauritanian and Mediterranean) in the Alboran Sea which has been frequently considered a biodiversity hotspot, a biogeographical sector and a self-standing ecoregion [5,6]. ...
The Alboran Sea is the westernmost sub-basin of the Mediterranean Sea, and it is connected to the Atlantic Ocean through the Strait of Gibraltar. The Alboran Ridge is located in the middle of the Alboran Sea and represents a hotspot of biodiversity in the Mediterranean Sea. Besides their critical importance, there are few studies on the communities and changes in biodiversity, and they mostly concentrate on infralittoral and circalittoral bottoms. In this work, the composition, structure and bathymetric and temporal changes of megafauna of the Alboran Ridge were examined. Samples were collected from MEDITS surveys carried out between 2012 and 2022 at depths ranging from 100 to 800 m. Analyses were performed separately for each of the taxonomic groups: osteichthyes, chondrichthyes, crustaceans, molluscs, echinoderms and “other groups”. There was no common spatial organization for each of the faunistic groups studied, although most of them displayed differences between the shelf and the slope. The continental shelf was characterized by the highest values of community metrics such as abundance, biomass, species richness and mean weight of species for all groups except for chondrichthyes and crustaceans. Decreasing trends of some community metrics were detected in some of the faunistic groups throughout the study period.
... The Mediterranean Sea is the largest enclosed sea on Earth (0.82% in surface area and 0.32% in volume of the world ocean), hosting around 17,000 species, equivalent to around 10% of the world's marine biodiversity, and has been exploited by mankind since the dawn of civilizations (Bianchi and Morri 2000;Coll et al. 2010). Nowadays, with a human density of approximately 480 million inhabitants along its 46,000 km of coastline, to which is added a third of world's tourism (500 million expected in 2030), the Mediterranean Sea experiences one of the highest cumulated human pressures across the world's oceans (Drius et al. 2019;Laviola et al. 2022). ...
Aim
The Mediterranean Sea is one of the most anthropized seas in the world but also a marine biodiversity hotspot with many fish species under threat. The main goal of the study is to test whether on the heavily fished and anthropized Mediterranean coast, the less impacted Corsica and Balearic Islands, can be considered as refugia for threatened and elasmobranch fishes independently of protection by marine reserves.
Location
The French Mediterranean coast and three north‐western Mediterranean islands: Corsica and also Mallorca and Minorca from the Balearic archipelago.
Methods
We performed 187 fish surveys using environmental DNA metabarcoding on three islands and 109 along the continental coast. Of the 78 surveys on islands 22 correspond to no‐take marine reserves and of the 109 continental surveys 26 were carried out within reserves. After eDNA filtration, extraction, amplification, and sequencing we estimated the number of fish species but also the number commercial, threatened and elasmobranch fish species on each sample. We then performed an ANOVA by permutation to test the effect of insularity and protection on these four biodiversity metrics. We also modelled these four biodiversity metrics as a function of protection and human pressure but also environmental, habitat and sampling conditions. We also built species accumulation curves to obtain asymptotes representing the potential regional pools for each species category on both island and continental coasts.
Results
We obtained a total of 175,982,610 reads over the 187 eDNA samples that were assigned to 153 fish species including 17 elasmobranch species among which 7 were only detected on islands. We observed a higher total fish richness on continental than island surveys regardless of protection but a higher threatened and elasmobranch fish richness on the island than on continental surveys. We obtained a significant, negative and predominant human gravity impact on the diversity of elasmobranch species. The modelled asymptote reached 148 teleostean fish species on islands and 196 on the continental coastline with a very similar rate of diversity increase with sampling effort but the shape of the species accumulation curves differed markedly for elasmobranchs with a stronger increase in diversity with sampling effort on islands.
Main Conclusions
Our findings highlight that Mediterranean islands can be refugia for sharks and rays but also threatened fishes in this overexploited region. Our results also suggest that reducing or banning trawling activities may play a key role for conserving vulnerable fishes, beyond the benefits of no‐take marine reserves, which appear limited on these large home‐range species.
... The Mediterranean Sea is both a biodiversity hotspot (Bianchi and Morri, 2000) and one of the most exploited areas in the world (Coll et al., 2012;Hilborn et al., 2022). Unmanaged fishing, climate change, and invasive species make this ecosystem less resilient, increasing the risk of fish populations collapse (Halpern et al., 2008;Micheli et al., 2013;Colloca et al., 2017). ...
... The Mediterranean Sea is a global biodiversity hotspot, harbouring about 10% of the marine species acknowledged in the world ocean (Bianchi & Morri, 2000;Coll et al., 2010). Among the remarkable ecosystems distributed across this miniature ocean, underwater caves represent genuine reservoirs of biodiversity, displaying poorly resilient communities with more than 2300 taxa reported thus far (Gerovasileiou & Bianchi, 2021) and a considerable number of putative taxa remaining to be described. ...
Underwater caves are remarkable habitats of the Mediterranean Sea. In the present study, we compare the geomorphology of four underwater caves of the Marseille area and the associated sessile assemblages across two contrasted communities (Semi- Dark and Dark-cave communities). Using a non-destructive method of sampling, photoquadrats of the walls of the caves were performed in 2020 to assess the biodiversity and the structure of these communities. In addition, taking advantage of available reference data from 2015, we evaluate the changes in sponge assemblages for the period 2015-2020, focusing on observations of the Semi-Dark cave community. Our results illustrate how the diversity of environmental settings and cave morphologies shape the benthic community composition of the four caves. In all four caves, the Semi-Dark community is the more diverse and harbours the higher number of species when compared to the Dark community. Each cave presents a different species assemblage with in most cases, distinct dominant species which highlight the singularity of each cave. Moreover, our temporal change assessment demonstrates a critical decrease in sponge species richness for all caves, possibly related to the increasing frequency of marine heatwaves that have occurred in the last decade. Although some species (mostly in the Keratosa subclass) seem to be particularly affected, other species such as Chondrosia reniformis appear to have benefitted from the situation. Our findings underline the importance of biodiversity monitoring in a context of a rapidly changing environment, in particular in poorly resilient marine ecosystems such as underwater caves.
... Our study is a preliminary survey of the end-to-end (from microbes to fish) biodiversity inhabiting a Mediterranean deep sea environment, the Dohrn Canyon, with the use of eDNA metabarcoding. Despite its relatively small dimensions (0.82% of the ocean surface), the Mediterranean Sea is a hotspot of biodiversity hosting more than 7.5% of the global biodiversity (Bianchi and Morri, 2000). However, most of this biodiversity was reported more in coastal and shallow areas than in deep environments (Danovaro et al., 2010). ...
The deep sea represents the largest ecosystem on Earth, and the mesopelagic zone, particularly submarine canyons, provides fundamental ecosystem services. Despite their importance, deep sea habitats remain one of the least explored ecosystems due to their remoteness, inaccessibility, and high costs for exploration. In this study, we used environmental DNA (eDNA) metabarcoding to investigate the biodiversity of the Dohrn Canyon in the Gulf of Naples (ca. 800 m; Mediterranean Sea), using two gene markers (V9-18S rRNA Euk1391F and EukBr and 12S rRNA MiFish_U primers) to detect eukaryotes, both protozoans and metazoans, including fish. We report on the biodiversity of this deep environment, including 41 planktonic phyla and 5 mesopelagic fish. The copepod genus Clausocalanus was dominant among planktonic metazoa, while Radiolaria and the parasitic dinoflagellate Syndiniales were the most representative protist taxa. Most fishes detected belong to mesopelagic fauna. Our study reports a snapshot of the biodiversity of a poorly explored deep ecosystem and provides the base for future ecological investigations, highlighting the need to expand knowledge of the deep sea in the Gulf of Naples by integrating eDNA data and visual surveys.
... Pelagic dinoflagellates show a lower percentage of endemic species compared to macroscopic or benthic species, and studies have concluded that pelagic dinoflagellates cannot be considered endemic (Bianchi and Morri, 2000;Gόmez and Boicenco, 2004;Gόmez, 2006). In this study, the number of species detected in a single sea constitutes approximately 34.5% of the total species given in the literature. ...
Using the evaluations of 77 literature studies conducted along the Turkish coasts of the Black Sea, Marmara Sea, Aegean Sea, and the Mediterranean Sea, a checklist has been compiled. It has been observed that the dinoflagellate flora is represented by a total of 330 species belonging to 75 different genera. This literature study has determined that the number of dinoflagellate species reaches up to 181 in the Black Sea, 158 in the Marmara Sea, 206 in the Aegean Sea, and 192 in the Mediterranean Sea. This study has revealed that particularly in the case of new species records, the characteristic structural features, distributions, and photographs of the species are not provided. It has also been observed that many geographical points have not been investigated yet, and some species reported as new records have previously been reported in earlier studies. In future studies, updating the checklist becomes crucial in terms of forming a dataset.
... Although the Mediterranean Sea is one of the major biodiversity hotspots hosting ≈7.5% of marine biodiversity at the global level [18,19], the fishing industry has represented a key economic sector since ancient times in this area. Abandoned, lost, or discarded fishing gears constitute a significant portion of marine litter in this region, accounting for as much as 98% of the total [20][21][22][23]. ...
This study presents novel information on sponge (Porifera) colonization of artificial substrates in the framework of the LIFE EU Strong Sea Life Project, focusing on the northwestern Sardinian Sea (Western Mediterranean Sea). Five abandoned, lost, or discarded fishing gears (ALDFGs) of the local artisanal fishery from circum-seas of the Asinara Island Marine Protected Area (MPA) were focused. The composition, taxonomic richness, relative abundance, and lifestyle of sponge assemblages are reported. Taxonomic richness is notably high with 2 classes and 13 orders comprising 26 families, 36 genera, and 47 species of Porifera displaying miniaturized body size and dominant encrusting to massive/erect growth forms. New records at species level are reported for the MPA, the Sardinian Sea, and the Western Mediterranean Sea. The successful colonization of the recovered ghost fishing gears by sponges highlights that adaptive strategies of these basal metazoans support their ability to settle and persist on synthetic materials. This dataset contributes to the inventory of (i) recovered ALDFGs in MPAs, (ii) exogenous substrata as suitable substrata for sponge settlement, and (iii) species richness of an MPA and (iv) promotes the biodiversity assessment of the plastisphere in a global context of ocean pollution.
... Despite its relatively small extent, the Mediterranean Sea is a hotspot of biodiversity, hosting a high number of species (more than 4% of all known marine species), with high rates of endemism (estimated at near 25%), and high rates of new species discovery (eg Bianchi and Morri 2000;Borsa 2002;Calvo et al. 2009;Coll et al. 2010;Claremont et al. 2011;Mouillot et al. 2011;Barco et al. 2013;Costello et al. 2017). Among the rich diversity of Mediterranean marine invertebrates, the molluscan Nudibranchia stands out in number of species and as a taxonomically challenging group, with over 180 described taxa (Trainito and Doneddu 2014). ...
... The Atlantic Ocean is connected to the Mediterranean in the very far west by the strait of Gibraltar, and the Suez Canal in the southeast connects the Mediterranean to the red sea and Indian ocean (Coll et al. 2010). As an incredibly diverse marine ecosystem, estimated to host between 4 and 18% of global marine biodiversity, the Mediterranean is one of the 25 hotspots for biodiversity in the world despite its small dimensions representing less than 0.8% of the world's ocean area (Bianchi and Morri, 2000;Cuttelod et al. 2009;Coll et al. 2010). Additionally, this sea hosts a uniquely high percentage of endemic species, thought to be almost 30% (Myers et al. 2000). ...
The spread of the Indo-Pacific lionfish Pterois miles into the Atlantic Ocean represents a well-known example of a successful invasion. Lionfish have successfully invaded the Atlantic, aided by biological traits such as high thermal tolerance, adaptability to various salinities, high fecundity, conspicuous defenses, and generalist feeding habits. The Mediterranean Sea is now experiencing an early-stage lionfish invasion, spreading westward from the eastern Mediterranean, likely through the Suez Canal. Using ecological niche modelling under various climate scenarios, we predict the potential spread of lionfish, identifying regions from low to high habitat suitability. Predictions indicate significant expansion, especially in the eastern and central Mediterranean, under greater warming scenarios. This expansion could lead to substantial declines in native species, decimation of commercially important fish stocks, and trophic cascades, severely impacting local economies and marine biodiversity. Urgent understanding and management of lionfish impacts in the Mediterranean are essential, given their established presence in the western Atlantic and documented ecological consequences.
... The establishment of anthropogenic forcing factors with a negative effect is what happened along the Ligurian coast, where urban expansion began in the 1850s through the construction of the main roads and railways (Burgos et al., 2017), but also through the construction of many tourist infrastructures that caused serious changes of the coastline during the XX century (Ferrari et al., 2005). The strong proliferation of urban and industrial structures along coastal regions inevitably impacted and destroyed natural habitats (Bianchi and Morri, 2000;Buonocore et al., 2021;Coll et al., 2010;Montefalcone et al., 2010; UNEP/MAP RAC/SPA, 2010), resulting in a change in the amount of natural capital stored by the habitats themselves. The Ligurian Sea hosts several pressures which may threaten the conservation status of marine coastal habitats, as for instance shipping, fishing, marine litter derived from densely populated areas (Bo et al., 2014;Relini, 1972aRelini, , 1972bRelini, , 1989 and commercial maritime traffic (Cattaneo-Vietti et al., 2010). ...
... Environmental change and vicariance events are the most important factors behind the large Mediterranean biodiversity 34 . The onset of glacial-interglacial cyclicity caused sea level fluctuations and implied the penetration into the Mediterranean Sea of species with either tropical or boreo-arctic affinities (Senegalese or Celtic biota, respectively) 14 . ...
Environmental gradients in the sea may coincide with phenotypic or genetic gradients resulting from an evolutionary balance between selection and dispersal. The population differentiation of the swimming crab, Liocarcinus depurator, an important by-catch species in the Mediterranean Sea and North-East Atlantic, was assessed using both genetic and morphometric approaches. A total of 472 specimens were collected along its distribution area, and 17 morphometric landmarks, one mitochondrial gene (COI) and 11 polymorphic microsatellite markers were scored in 350, 287 and 280 individuals, respectively. Morphometric data lacked significant differences, but genetic analyses showed significant genetic differentiation between Atlantic and Mediterranean populations, with a steeper gradient in COI compared to microsatellite markers. Interestingly, nuclear differentiation was due to an outlier locus with a gradient in the Atlantic-Mediterranean transition area overlapping with the mtDNA gradient. Such overlapping clines are likely to be maintained by natural selection. Our results suggest a scenario of past isolation with local adaptation and secondary contact between the two basins. Local adaptation during the process of vicariance may reinforce genetic differentiation at loci maintained by environmental selection even after secondary contact.
... In this context, the aim of this study is to assess patterns of coastal fish diversity in multiple habitats. To do so, we focused on the Mediterranean Sea, which represents a very heterogeneous system (Harmelin and Pergent 2006;Giakoumi and Kokkoris 2013), where a multitude of habitats can be found at a relatively small spatial scale, supporting high marine biodiversity (Bianchi and Morri 2000;Coll et al. 2010). In particular, we used as a case study the coastal waters of the Calabria Region, Southern Italy, covering three distinct habitats (rocky bottoms, sandy bottoms, and Posidonia oceanica meadows) to assess whether: 1) the three habitats sampled hold differences in the associated coastal fish assemblages (in terms of α-diversity, density, and biomass); 2) different habitats have similar contribution to the overall fish diversity of the coastal system investigated; and 3) fish diversity in the considered habitats can be influenced by the environmental and anthropogenic drivers considered. ...
... This unique location exposes the region to different oceanographic phenomena, such as the influx of Atlantic waters into the Mediterranean through the Strait of Gibraltar, upwelling systems along the Atlantic coastline and the oligotrophic nature of the Mediterranean Sea (García-Lafuente et al., 2021;Peliz et al., 2002). Collectively, these factors give rise to the rich biodiversity and productivity of the Andalusian marine ecosystems (Bianchi & Morri, 2000;Perret et al., 2023;Rueda et al., 2021). ...
Jellyfish blooms along coastal areas can pose significant challenges for beach users and local authorities. Understanding the factors influencing jellyfish presence is crucial for effective management and mitigation strategies.
In this study, citizen science data from the Andalusian coast (232 beaches, in 40 different localities) and machine learning techniques are used to investigate if the presence and absence of jellyfish along coastal areas can be predicted. A multi‐layer perceptron (MLP) neural network was employed to classify user comments regarding jellyfish presence or absence, achieving an accuracy of approximately 96%.
The MLP model demonstrated robustness in handling non‐linear classification problems and noise, although it showed lower precision for predicting jellyfish presence, likely due to an imbalance in the dataset. Environmental data were also incorporated to characterise the influence of sea surface temperature, wind direction and wind speed on jellyfish distribution. The results align with previous studies, suggesting these environmental factors significantly impact jellyfish presence.
Synthesis and applications. This research provides actionable recommendations for beach management. The implementation of continuous monitoring of sea surface temperature and wind conditions will enable more accurate predictions of jellyfish distribution. Adaptive management strategies that respond dynamically to environmental data will help mitigate the impact of jellyfish blooms on coastal tourism and public health.
... During the Quaternary, the alternation of glacial periods with warm interglacial periods allowed the influx into the Mediterranean of Atlantic species of boreal or subtropical origin (Bianchi et al. 2000). On the other side, the Mediterranean Sea is experiencing an important influx of Red Sea species after the artificial opening of the Suez Canal in 1869. ...
The objective of the present study was to update and consolidate the marine fish (bony and elasmobranch) checklist of Turkey based on supporting evidence. The species that came with natural and/or unnatural distribution routes into Turkish marine waters are included in the list. The current number of alien fish species was 100 belonging to 57 families recorded in the Turkish Seas. The highest number of species were found in the Tetradontidae and Gobiidae families. The Mediterranean coast of Türkiye consisted of the highest number of species (89 species), followed by the Aegean Sea with 55 species, the Marmara Sea with 12 species, and the Black Sea with 3 species. Considering the abundance status, 16.0% of the total alien fish species were considered very common, 34.0% common, 24.0% rare, 15.0% very rare, and 11.0% only one specimen of a species has been so far recorded. Only 17 species (17%) of the 100 alien fish species have economic value in terms of fishing in Turkey. Moreover, 22 species (22%) are poisonous, venomous, or sting. According to their origins, 87% of the alien fish species are of Indo-Pacific origin, 12% Tropical Atlantic origin, and 1% Northwest Pacific origin. The entry routes of alien fish species found in the Turkish seas are generally via the Suez Canal with a rate of 81%, followed by species passing through the Strait of Gibraltar with a rate of 11%. The species that come through the other entry routes are at a rate of 5% by ship transportation, 2% by Aquarium activities, and 1% by Aquaculture activities. Considering the habitat preference of these alien species, 43% are pelagic species, 14% are benthic species, 14% are rocky area species, 13% are shallow water and reef species, 11% are demersal species and 5% are other habitats, which are mainly distributed in the 0-100 m depth range.
... The Mediterranean Sea is amongst the most impacted ecoregions globally, for its geographic characteristics as a semi-enclosed basin, and the high population density along its coasts (Amoroso et al. 2018). This is of particular importance as the Mediterranean Sea constitutes a global biodiversity hotspot (Myers et al. 2000); the Basin hosts ~ 18% of known marine species, a quarter of which are endemic (Bianchi and Morri 2000;Mouillot et al. 2011). Nowadays, Mediterranean ecosystems are undergoing significant transformations, and many species are experiencing population decline or even local extinction due to, among others, overfishing (Yan et al. 2021). ...
Marine biodiversity monitoring in the Mediterranean’s increasingly threatened ecosystems is crucial for effective ecosystem conservation and management. Here, we leveraged the Mediterranean International Trawl Survey program (MEDITS) to implement eDNA sampling through the recently tested ‘metaprobe’ procedure and characterize fish assemblages in three separate areas off the Italian coasts: Northern Adriatic Sea (NoAS), Ligurian and Northern Tyrrhenian Sea (LNTS), and Sardinian Sea (SaS). By combining the information from two homologous mitochondrial 12S metabarcodes––i.e., Elas02 and Tele02 targeting elasmobranchs and teleosts, respectively––we identified 108 species, over 60% of which overlapped with those caught by the trawl net. We produced an accurate reconstruction of fish community composition of the examined sites, reflecting differences in species assemblages linked with both geographic area and depth range. Metaprobe eDNA data consistently returned a biodiversity ‘bonus’ mostly consisting of pelagic taxa not captured through bottom trawl surveys, including rare and endangered taxa (e.g., elasmobranchs). Overall, the spatial characterisation of the assemblages across the surveyed areas was better delineated and more robust using eDNA metabarcoding than trawl data. Our results support the operationalisation of the metaprobe as a simple, inexpensive, versatile sampling tool, in association with pre-existing ship surveys, to overcome many of the limitations of marine data collection and strengthen marine management.
... The Mediterranean Sea is a biodiversity hot spot because of its biogeographical conditions (Bianchi & Morri 2000), but its biodiversity is still underestimated. Molluscs are no exception and nudibranchs, which are a group of marine gastropod molluscs characterized by their soft body and the lack of external shells, are especially underestimated (Garzia et al. 2021). ...
In the present study, a revision of the phylogeny and taxonomy of the family Dorididae is carried out focusing on the genus Doris Linnaeus, 1758. The type species D. verrucosa Linnaeus, 1758 and a blueish and yellow morphotype of D. ocelligera collected in different localities in the Mediterranean Sea and the NorthEast Atlantic were sequenced, as well as D. bertheloti and the elusive D. marmorata for the first time. The genetic markers include the cytochrome c oxidase subunit I, 16S rRNA, and histone 3. The phylogenetic results suggest that the genus Doris is paraphyletic, and D. ocelligera morphotypes separate into two species, as confirmed with species delimitation tests. To complement the phylogenetic evidence with morphoanatomical data, the dissection of two specimens of each morphotype is conducted. Significant differences in morphological traits such as body shape, colouration patterns, and mantle tubercles come to light, together with anatomical differences in the relative shape and size of the radular teeth and reproductive structures. Considering the modern and old descriptions of D. ocelligera, it is finally concluded that the blueish morphotype belongs to D. ocelligera. In contrast, the yellow morphotype responds to the actual synonym Aldisa berghi (Vayssière, 1901), which is resurrected here as Doris berghi comb. rest. Considering the broad phylogeny of the family, some systematic notes at the genus level are here provided.
... In this context, we focused on different populations of S. prolifera in the Mediterranean Sea, a world region recognised to harbour one of the highest levels of diversity in macroscopic marine organisms (Bianchi and Morri 2000) and a biodiversity hotspot for polychaetes. We tested the true status of S. prolifera in this area, using additional evidence from molecular and ecological data, with coalescencebased species delimitation methods in addition to traditional morphology. ...
Syllis prolifera (Syllidae, Syllinae) is an abundant species of marine annelids commonly found in warm to temperate waters worldwide. Although morphological variability occurs among populations , S. prolifera has long been considered a cosmopolitan species, widely distributed in coastal environments, including acidified and polluted areas. However, the increasing number of cases of cryptic and pseudocryptic speciation in several polychaete families in recent years has led us to question whether S. prolifera represents a single globally distributed taxon or is a species complex. To address this question, we conducted an integrative study, combining morphological, ecological and molecular data of 52 S. prolifera specimens collected in different localities across the western Mediterranean Sea and the Gulf of Cadiz. Our phylogenetic and species delimitation analyses that included two mitochondrial DNA markers (COI and 16S rRNA) were congruent in not considering S. prolifera a unique entity. Five distinct lineages that can also be recognised by certain morphological and ecological traits were identified from these analyses instead. Overall, our study does not support the homogeneity of S. prolifera across the Mediterranean Sea, providing a new example of pseudocrypticism in marine invertebrates.
... The Mediterranean Sea only covers 0.82% of the global oceanic surface, but it shows a high biodiversity, since more than 4% of all known marine species live in this basin [1][2][3]. ...
The Mediterranean Sea is known to be a hot spot for marine biodiversity, especially if considering the highly specialized Heterobranchia mollusks. In recent years, there has been increasing effort to fill some knowledge gaps existing on Mediterranean heterobranch diversity, but, to date, several potentially interesting habitats remain unexplored. In fact, most studies have been focused on sea slugs inhabiting coastal areas and lakes, but those living in extremely variable areas like Mediterranean rocky tide pools remain almost completely ignored even if it is reported worldwide that they can host a high sea slug diversity. In this context, the rocky tide pool system near the 'Passetto' urban beach (Ancona, Italy) in the North Adriatic Sea (Mediterranean Sea) represents a biodiversity hot spot, highlighting the importance of the conservation of this peculiar habitat. A preliminary quantitative survey on the associated Heterobranchia unveiled a thriving community residing in this limited and fragile habitat, and it inspired a more detailed investigation as performed in the present study. In order to reveal the presence of species that have gone unnoticed, an in-depth study was carried out between 2018 and 2022, which aimed to amplify the knowledge on this vulnerable environment and the fauna associated with this as yet poorly known habitat. Tide pooling activities corroborated by photographic analyses allowed the recording of 45 taxa in total and the addition of 25 species to the previously known list. Within those, (i) two species were potentially new to science, (ii) one was recorded in the Mediterranean Sea for the first time, (iii) two species were added to the Italian fauna, and (iv) one species constituted a new record for Sector 9 of the Italian Seas.
... As a result of the peculiar geomorphologic and oceanographic characteristics, the Strait of Sicily is one of the most important biodiversity hotspots in the Mediterranean Sea (Vega Fernańdez et al., 2012;Deidun et al., 2015;Di Lorenzo et al., 2018). Furthermore, the rocky bottoms of the Strait represent an important crossroad for the distribution of benthic species between the two Mediterranean basins (Bianchi and Morri, 2000). These features make the area highly sensitive to anthropogenic pressures, including exploitation of the geological resources, laying of submarine pipelines and cables, dumping of waste into the sea, and especially fishing activities. ...
Introduction
The black coral Leiopathes glaberrima is a key component of deep-sea animal forests of the Western Mediterranean and North-Atlantic hard bottoms. Due to its ecological role, biological characteristics and sensitivity to fishing activities, it has been included in the Annex II of the Barcelona Convention, listed as an endangered species in IUCN Red Lists, and recognized as an indicator of Vulnerable Marine Ecosystems by the FAO.
Methods
During a survey conducted in the Strait of Sicily, 140 ROV transects were carried out allowing the characterization of environmental preferences, associated fauna and population structure of L. glaberrima in the study area.
Results and discussion
1020 colonies were distributed between 165 and 672 meters and arranged in 17 patches and isolated colonies. The average height was determined to be 40.9 ± 1.0 cm, with the range spanning from a minimum of 5 cm up to nearby 200 cm. Pristine colonies accounted for 62.9%, mainly constituted by small-sized individuals densely aggregated (up to 14.5/m2 in a single frame) in the eastern part of the area. 24.5% of the specimens were dead and localized in the western margin where we reported a rare case of mass mortality in the deep-sea environment and the first ever described for black corals, opening new scenarios regarding the possibility that these events can occur in environments previously considered safe from danger. The triggering causes of these events in inaccessible environments are actually only hypothesized, but it is not to be excluded that, sooner or later, a similar effect could potentially result from anthropogenic climate changes.
... The study area is located along the northern margin of the Alboran Sea (Western Mediterranean). This small basin represents the Atlantic-Mediterranean marine transition area, connecting both oceanic domains, as well as the confluence point of three biogeographical units (Lusitanian, Mauritanian and Mediterranean), coexisting organisms from those areas together with some endemic species restricted to this zone (Bianchi and Morri, 2000;Ekman, 1953;Rueda et al., 2021;Templado, 2011). These characteristics make the Alboran Sea to be considered a self-standing ecoregion. ...
... The high levels of marine biodiversity in Mediterranean biota derive primarly from the Atlantic Ocean but, anyway, the special variability of climate conditions and the long phylogenetic history of the basin have caused in time the evolution, the diffusion and the establishment of many temperate and endemic species [20][21][22][23]. In particular, as regards endemics, their percentages reach a total value of 20.2% distributed in the following divisions: Porifera (48%), Mysidacea (36%), Ascidacea (35%), Cumacea (32%), Echinodermata (24%), Bryozoa (23%), Seaweeds and Seagrasses (22%), Aves (20%), Polychaeta (19%), Pisces (12%), Cephalopoda (10%) and Decapoda (10%) [19] (Figure 2). ...
The Mediterranean Sea is one of the most important biodiversity hotspots worldwide. The high biodiversity level of the basin is confirmed by the presence of about 17,000 marine species of which 20.2% are endemics. Amongst them, Posidonia oceanica (Linnaeus) Delile can form, in pristine coastal waters, large and extensive meadows, performing a pivotal role in endemic processes. However, the richness of marine biota is, actually, affected by some threats such as habitat loss, marine pollution, climate changes, eutrophication and the establishment of invasive alien species coming from the Indo-Pacific region through the pathway of Suez Canal. This trend could lead to a new kind of marine biodiversity influenced by the introduction of termophilic species altering the pattern of Mediterranean biota. Anyway, it is necessary a global approach, ensuring the better ecological conditions so to protect marine biodiversity in meditrranean seawaters.
... The Mediterranean Sea is often considered a marine biodiversity hot spot (Bianchi and Morri 2000, Lejeusne et al. 2010, Selig et al. 2014. It is currently undergoing a dramatic shift in faunal composition (Evans et al. 2015, Zenetos et al. 2022), yet, here we demonstrate that some of the species of this well-studied marginal land-locked sea are still unknown to science, hampering studies on biodiversity change. ...
Background
The marine isopod family Acanthaspidiidae Menzies, 1962 (Asellota, Janiroidea) has global distribution from shelf to hadal depth. The majority of species has been recorded from relatively deep waters and the Southern Hemisphere. To date, 36 species have been described in the family belonging to three genera: Ianthopsis Beddard, 1886; Iolanthe Beddard, 1886; and Mexicope Hooker, 1985.
New information
Here, a new species of Mexicope is described from Maltese waters, adding a fourth species to the genus. It is the first member of the family reported from the Mediterranean Sea. The new species can be recognised by the unique combination of the following characters: cephalothorax with pre-ocular spine large and pointed anterolaterally, rostral projection blunt, eyes reduced; pereonal sternites each with one ventral spine; pereonite two lateral margins with single projection; pleotelson posterior apex long, projecting to approximately half of the length of the uropod protopod; pleopods I distolateral lobes projecting beyond distomedial lobes, apices curved and pointed laterally; uropod exopod length approximately 0.5 endopod length. An identification key to the species of Mexicope is presented and the generic diagnoses of Ianthopsis and Mexicope are compared, discussed and revised.
... The critical situation of commercial stocks is aggravated by other several factors such as the invasion of new species, pollution or marine litter, eutrophication and climate change, that alone or in combination with fisheries contribute to worsening the Mediterranean species populations [17]. The Mediterranean Sea is a biodiversity hotspot [9,55] that has experienced climate-driven reductions in precipitation, increased salinity, stratification and overall seawater warming [1]. In the future, Mediterranean fisheries are predicted to suffer from climate-driven alterations because (i) sea surface temperature is projected to increase between +1.73 • C and +2.97 • C by the end of the century, (ii) further stratification will modify the mesoscale structures dynamic [1] that are of high importance for fisheries with commercial interest, and (iii) primary production is predicted to decrease in the north-western Mediterranean [3,15,44]. ...
... Number of species per taxon in this phylum refers to 1673 species of Gastropoda (Manousis et al., 2018), 430 Bivalvia, 14 Scaphopoda, and 64 Cephalopoda (Coll et al., 2010;Bruno and Marco, 2014) in the eastern Mediterranean. A few studies about mollusks were done (Bianchi and Morri, 2000), especially in the infralittoral, to the circalittoral zone, and generally restricted to particular region (Galil and Lewinsohn, 1981;Karakassis and Eleft heriou, 1997;Conides et al., 1999;Koutsoubas et al., 2000;Koulouri et al., 2006;Çinar et al., 2008;Çinar et al., 2012a). In addition, new molluscan species in the Levantine Sea have been recorded in recent years (Ozturk, 2015;Steger et al., 2018;Marco-Herrero et al., 2022). ...
This study aimed to describe the distribution and diversity of soft bottom mollusk community in the Syrian transitional region and to assess the state of alien species in the northern part of the Syrian coast north of Latakia (Ibn Hani site) since 2010, at depths ranging between 110-160 m. Sixty benthic samples were collected monthly using a Van-Veen grab 1/40 m 2. Water temperature, salinity, pH, and dissolved oxygen of the subsurface water were measured. Molluscan specimens were isolated and identified at the species level. The abundance and biomass for each species in the samples and per square meter were considered to assess spatial and temporal variation of Molluscan assemblages between depths within the months. A total of 167 mollusk species belonging to 3 classes were identified, 57 newly recorded in Syria, and 18 (10.7%) non-indigenous species were found. Among these, three new aliens of Retusa truncatula, Styloptygma beatrix, and Afrocardium richardi were recorded for Syria. The presence of these mollusks was associated with the soft sediments (mud), which did not differ by time or depths. The results revealed that the Molluscan community was dominant by Bittium arenarium, B. tarentinum, Odostomia lorioli, Turritella turbona, Varicorbula gibba, Nucula nucleus, and Lembulus pella. A significant decrease in biomass is expected due to overfishing and severe nutrient deficiency. Our study adds a large number of mollusks to the list of previously recorded species and confirms the increase in the number of aliens and the expansion of their spread in the medium depths. Greater efforts are required to detect more aliens and evaluate their progress, spread, and their relationship with natives, especially in harbors and port environments.
Marine heatwaves (MHWs) are periods of abnormally warm ocean temperatures that exert significant impacts on marine ecosystems. MHWs are commonly identified as periods when temperature conditions surpass predetermined thermal thresholds. Although they can propagate beneath the ocean’s surface, MHWs are typically assessed using sea surface temperatures. In this study, we investigate the future progression and depth penetration of MHWs across the Mediterranean Sea and the existing network of Marine Protected Areas (MPAs). We utilize daily three-dimensional seawater temperature projections from the POLCOMS-ERSEM model for the period 2006–2100 from surface to 2000 m depth under the RCP8.5 forcing scenario, to explore the future spatio-temporal properties of MHWs. We employ two different baseline climatological periods for establishing thresholds based on which MHWs are identified: one remains constant, while the other is adjusted in time to reflect the evolving adaptive capacities of ecosystems in response to long-term warming trends. Our analysis reveals that, regardless of the threshold applied, the Mediterranean MPAs will experience long-lasting and intense MHWs in the future across the ocean’s depths. While the utilization of a shifting baseline period results in shorter and milder shallow MHWs within the Mediterranean MPAs (i.e. annual duration: 45 days per year and mean annual intensity: 1.63 °C) compared to the fixed baseline approach (i.e. annual duration: 195 days per year and mean annual intensity: 1.89 °C), deeper ocean zones exhibit a saturation of MHWs, with year-round events, particularly below 1000 m, under both baseline approaches. Our findings highlight the profound penetration of MHWs into the ocean's depths, posing a serious threat to the protected ecosystems of the Mediterranean, especially in marine subsurface environments. Notably, our findings suggest that MHWs are expected to demonstrate similar spatio-temporal patterns to those observed within the MPAs across the entire Mediterranean basin. MPAs are, thus, anticipated to face equivalent challenges from MHW impacts, affecting their protected ecosystems and biodiversity across various depths.
The spread of the Indo-Pacific lionfish Pterois miles into the Atlantic Ocean represents a well-known example of a successful invasion. Lionfish have successfully invaded the Atlantic, aided by biological traits such as high thermal tolerance, adaptability to various salinities, high fecundity, conspicuous defences and generalist feeding habits. The Mediterranean Sea is now experiencing an early-stage lionfish invasion, spreading westward from the eastern Mediterranean, likely through the Suez Canal. Using ecological niche modelling under various climate scenarios, we predict the potential spread of lionfish, identifying regions from low to high habitat suitability. Predictions indicate significant expansion, especially in the eastern and central Mediterranean, under greater warming scenarios. This expansion could lead to substantial declines in native species, decimation of commercially important fish stocks and trophic cascades, severely impacting local economies and marine biodiversity. Urgent understanding and management of lionfish impacts in the Mediterranean are essential, given their established presence in the western Atlantic and documented ecological consequences.
Microalgal diversity enables the possibility to employ them in technological applications, as widely shown by the modern literature. While there exists an extensive body of literature concerning the technological applications of microalgae, the scientific knowledge of microalgal species remains relatively limited. Therefore, there is still potential for unlocking new opportunities through the study of the microalgal biodiversity, particularly in the Mediterranean region, which is unique because of its sub regional diversity. While some studies have assessed
microalgae distribution in the Mediterranean area, and others have focused on specific aspects of their technical exploitation, this review seeks to offer a comprehensive overview of isolated microalgal species and their technological applications. Microalgae from the Mediterranean area share common characteristics, such as low half-saturation constants and acclimation to high light intensity, making them ideal for specific technological applications. While the search for new microalgae for technological purposes can help in biodiversity conservation,
numerous species still remain underexplored, offering potential for innovative applications. However, the key finding from the critical analysis of the literature is that the diversity of microalgae in the Mediterranean region is its true richness, allowing for their versatile applications across various processes. The work focuses on the Mediterranean area, i.e., having coastlines along the Mediterranean Sea and on aquatic microalgae, coming from water with different salinity levels. This review offers an intrinsic ecological and technological perspective and provides a fresh outlook on the microalgal sector, promoting its expansion in the Mediterranean area and the development of sustainable bio-industries.
The Mediterranean Sea is a semi-enclosed oceanic basin that communicates with the Atlantic Ocean and can be subdivided into seven geographical regions. It is considered a hotspot of biodiversity and is characterised by high rates of endemism. Over the past decades, many studies showed the presence of potential geographical breaks both across the Atlanto-Mediterranean transition and within the Mediterranean Sea. These investigations led to the identification of three distinct types of population genetic structures: (1) populations characterized by panmixia; (2) Atlanto-Mediterranean geographical partitioning; and (3) possible further subdivision between East and West Mediterranean basins. In this review, mainly focused on Christoph Schubart’s works and interests, we summarize the different patterns of gene flows across the Atlanto-Mediterranean transition and within the Mediterranean Sea, recorded for decapod species living in littoral zones. Although some species share similar biological traits, larval dispersal mechanisms and habitat preferences, differences in their phylogeographic and population genetic structures do emerge. These findings confirm the complex nature of gene flows across the Atlanto-Mediterranean transition and within the Mediterranean basin and how difficult it is to achieve a generalised picture of the phylogeographical patterns of Atlantic-Mediterranean species.
The blue shark, Prionace glauca, is the most abundant pelagic shark in the open ocean but its vulnerability remains poorly understood while being one of the most fecund sharks. In the Mediterranean Sea, the blue shark is listed as Critically Endangered (CR) by the International Union for Conservation of Nature. The species is facing a strong decline due to fishing, and scientific data regarding its genetic structure and vulnerability are still lacking. Here, we investigated the genetic diversity, demographic history, and population structure of the blue shark within the Mediterranean Sea, from samples of the Gulf of Lion and Malta, using sequences of the mtDNA control region and 22 microsatellite markers. We also compared our mitochondrial data to previous studies to examine the Atlantic-Mediterranean population structure. We assessed the blue shark’s genetic vulnerability in the Mediterranean basin by modelling its effective population size. Our results showed a genetic differentiation between the Atlantic and the Mediterranean basins, with limited gene flow between the two areas, and distinct demographic histories making the Mediterranean population an independent management unit. Within the Mediterranean Sea, no sign of population structure was detected, suggesting a single population across the Western and Central parts of the sea. The estimated effective population size was low and highlighted the high vulnerability of the Mediterranean blue shark population, as the estimated size we calculated might not be sufficient to ensure the long-term persistence of the population. Our data also provide additional evidence that the Gulf of Lion area acts as a nursery for P. glauca, where protection is essential for the conservation strategy of the species in the Mediterranean.
The deep-water benthos (115-2100 m) was sampled in the Atlantic-Mediterranean exchange area. The species richness of the bryozoan fauna (146 spp.) showed a marked between-site variability. Peaks of species richness occurred on both sides and in the Strait of Gibraltar under various conditions of temperature and salinity. The common features of the corresponding sites were the abundance of suitable substrates and the presence of currents facilitating supply of food and propagules. In the Alboran Sea, the species richness decreased with depth more rapidly than in the Atlantic and the depth distribution of several deep-water species showed an upward shift. There is an eastward decrease in the stock of Atlantic species: 15% of them are not found beyond the Strait sill and only 79% of the remaining species extend to the whole Mediterranean. Several endemic Atlantic species or morphotypes can live in conditions of typical Mediterranean water (high temperature and salinity), but do not spread beyond the E limits of either the Gibraltar Strait or the Alboran Sea. These occurrences are hypothesized to be signatures of local increases of the trophic resources, which could mask the barrier effect of the Mediterranean oligotrophy. The organic sedimentation originating from the high-productivity area localized in the NW of the Alboran Sea appears to create this distribution pattern. -Authors
Posidonia oceanica is a slow-growing and long-lived Mediterranean seagrass, sensitive to reduction in water transparency that may damage or even kill the plant without possibility of recovery. Meadow decline has been evident especially in the northern Mediterranean Sea and is generally associated with human disturbance. In most cases the lack of infonnation on P. oceanica distribution before disturbance does not allow the quantification of damage suffered by the meadows. In this work we present an approach to quantify the decline of P. oceanica off liguria. Seagrass bed distribution maps were analysed to mesoscale, working on the hypothesis that natural (rivers) and human (town and terrestrial links) disturbances had a cumulative, negative and long-term effect on P. oceanica. Curves of Disturbance (CD) were calculated comparing P. oceanica cover of defined physiographic units to five types of disturbance: river annual mean flows (m 3 S·l), harbour surface (ha), coastal lengths (km) of towns and terrestrial links (roads and railways). The curves allowed quantification of the decline of cover connected to each type of disturbance for each physiographic unit.
This book contains the papers presented at a NATO Advanced Research Institute on "Mediterranean Marine Ecosystems", held at Heraklion-Crete, Greece, from September 23-27, 1983. A workshop rather than a conference, it was sponsored by the Eco-Sciences Special Programme Panel, in cooperation with the Marine Science Panel. The third of its kind, it was scheduled in the framework of a project on a multidisciplinary integrated approach to the study of the Mediterranean. This Sea and the surrounding land was not only the cradle of many civilizations but is, up to the present time, one of the major world areas of marine traffic, communication and exchanges, fisheries and aquacultures, inshore human activities and ••• pollu tion. To a certain degree it constitutes a gigantic natural labo ratory, where the fate of threatened aquatic and terrestrial eco systems including the human one, is tested. The Mediterranean Sea, with its geological history and present day geographic, hydrological and climatic conditions is believed to form an ecological entity. Important exchanges and mutual influences take place with the surrounding land area and the water masses, naturally (Atlantic, Black Sea) or artificially (Red Sea), connected to the Mediterranean. Therefore, a better and in-depth knowledge of the various ecosystems, benthic, planktonic and nektonic, neritic or pelagic, in the Western or the Eastern Basin seems to be a pre requisite to any action in preserving, upgrading and managing the natural resources of the area.
The desert theory of the Mediterranean surfaced in 1970 following the deep-sea drilling cruise aboard the Glomar Challenger. This envisaged the Mediterranean basin to have been separated from the Atlantic Ocean about 6 million years ago and to have dried up with the floor at about 3000 m depth resembling a gigantic Death Valley on which thick evaporite salts accumulated; at the beginning of the Pliocene, Atlantic water is though to have surged back into the basin as a giant waterfall at Gibraltar. The author argues, however, that the configuration of the Mediterranean was considerably different at the end of the Miocene than at present and that the seafloor remained almost continually covered by very saline waters, perhaps one hundred to several hundred metres deep. -J.G.Harvey
We compare the value of using habitat categories and species assemblages as surrogates for marine biological diversity in the context of choosing a set of representative areas for a marine reserve network. Habitat categories were based on interpretation of aerial photographs and maps, and on local knowledge. Species assemblages were created from comprehensive survey data on 977 taxa (mainly species), derived from an intensive three-year study of a temperate marine embayment, and classified into plant, fish, and invertebrate assemblages. Reserves were selected using a heuristic iterative algorithm to simulate a marine reserve network based on 10-80% representation of each surrogate. The effectiveness of each surrogate was evaluated by comparing the number of taxa that would be coincidentally included in each simulated reserve for the bay. Areas selected to represent 10% or 20% of the surrogates were best chosen using fish or invertebrate assemblages, because by spatial coincidence, they included 60-80% of all available taxa. However, areas selected to represent ≥40% of the surrogates were generally best derived from habitat categories, because they included ≥93% of all available taxa. Plant assemblages were generally poor surrogates for overall species richness. These findings suggest that habitat-level surrogates may be a highly cost-effective method for initial identification of high-priority areas to manage marine diversity of coastal ecosystems.
Outlines the significance of the Late Miocene salinity crisis, when the Mediterranean Sea became separated from the Atlantic, together with Pliocene, Pleistocene and Quaternary environmental changes to the biota of the Mediterranean. A few species have recently entered from the Atlantic. The origins of the present benthos are mooted (an Ibero-Moroccan gulf palaeofauna being favoured) and the problem of accounting for Mediterranean endemics is raised. Details are provided on the fauna of the circalittoral soft bottoms (coastal detritic, muddy-detritic, terrigenous mud-shelf and shelf-edge assemblages); offshore rocky-bottom assemblages; and bathyal assemblages (deep-sea coral and mud communities). -P.J.Jarvis
Recently, Grassle and Maciolek (1992) have reported results from a transect at 1500 m off the east coast of USA where they found 625 species from 60 000 individuals. In a transect taken along a similar gradient on the Norwegian continental shelf 627 species were found from 42 653 individuals. Difficulties in making such a comparison are discussed; yet the conclusion is that a coarse comparison at the level of number of species for a comparable number of individuals is valid. On this basis the Norwegian shelf shows comparable or higher diversity than the deep sea off the east coast of the USA.
Outlines the early evolution of the Tethys and Mediterranean seas, including comments on the evolution of the Atlantic Ocean and the relationships of the alpine belts to the genesis of the Mediterranean basin. Closer attention is paid to the evolution of the W Mediterranean Basin, examining the Balearic Basin, Alboran Sea and Tyrrhenian Sea, and noting the stratigraphic record of this region. Global events leading to the Messinian salinity crisis when, during the Late Miocene, the Mediterranean became separated from the Atlantic, and geological evidence for this crisis are reviewed, and a dynamic model of the crisis is essayed. Regional depositional patterns during the Pliocene and Quaternary are discussed, particularly in terms of likely primary factors influencing sedimentation, and an attempt is made at modelling these phenomena.-P.J.Jarvis
Biodiversity can be considered at various levels of biological organisation and over a range of spatial and temporal scales. Extrapolation between these scales is problematic. Data on macrobenthos suggest consistent patterns of species numbers in relation to body size, but whether these might result from sampling artifacts needs further investigation. Species richness measures are unsuitable for assessing comparative biodiversity on broad regional scales, and alternative measures based on taxonomic distinctness are suggested as being more appropriate.
The biogeographical research of today is mainly concerned with the explaining of the pattern of species and ecosystem distribution from a causal point of view. Unfortunately this effort involves difficult questions to which the present development of biogeography does not give precise answers. Recently three hypotheses have been advanced concerning terrestrial and freshwater biogeography; they are known as the vicariance, the dispersal and the ecological models, according to the set of factors that is considered more important in determining the distribution of plants and animals (Endler, 1982). The vicariance and dispersal hypotheses tend to emphasize especially the historical factors, whereas the ecological hypothesis reflects the present ones. However it seems clear that a synthesis is needed which may incorporate these competing models and that in every case ecology plays a major role together with dispersal and vicariance (Davis, 1982). Consequently it appears very useful also for marine biogeographical research to adopt a plural approach which should take into consideration the different sets of factors and their interrelationships. As other branches of biology, biogeography is directly concerned with evolutionary problems. When we analyze the role of ecological factors we cannot consider only the present one, but also that which they played in geological time, influencing the immigration and extinction of species and the evolutionary rates of taxa and ecosystems.
The endemic part of a fauna deserves particular attention not only for discussions of biogeographical problems but also in connection with the ecosystems occurring in the area. As far as the Mediterranean is concerned, endemism has often been considered by authors dealing with different groups of animals. The ratio of endemic species, of course, is variable according to them but as a whole it is high, having been estimated at 15–16% (Menzies, 1973). An excellent report has been presented by Fredj (1974) who discussed several problems after having examined the situations observed in some groups of benthic invertebrates.
This book had its origin when, about five years ago, an ecologist (MacArthur) and a taxonomist and zoogeographer (Wilson) began a dialogue about common interests in biogeography. The ideas and the language of the two specialties seemed initially so different as to cast doubt on the usefulness of the endeavor. But we had faith in the ultimate unity of population biology, and this book is the result. Now we both call ourselves biogeographers and are unable to see any real distinction between biogeography and ecology.
The overall effect of anthropogenic and climatic pressures in a bay east of Marseilles, France, was a period of prolonged disequilibrium affecting all the macrobenthic assemblages and their facies. This was caused by changes in the deep current pattern and, in particular, an increase in silting of the infra- and circalittoral bottom throughout the bay, accompanied by inputs of organic matter and the regression of the Posidonia oceanica meadows from the lower limit upwards. -from Author
A few case studies from the Ligurian Sea provide examples of how climate change has influence on marine biodiversity. This influence may be either direct (bryozoan population dynamics, coral growth, sea-grass shoot density) or indirect, mediated by biotic interactions (bivalves in a sandy bottom community) or marine currents (fish and rocky bottom communities, entering of southern species. The difficulty of distinguishing between anthropogenic and climatic actions on the marine biota emphasises the need to study marine biodiversity in the context of the physical setting and the relevant space and time scales.
Changes in the abundance of macroinvertebrate species documented in a rocky intertidal community between surveys in 1931-1933 and 1993-1996 are consistent with the predicted effects of recent climate warming. We resampled 57 0.84-m2 plots of an intertidal transect first surveyed by W. G. Hewatt at Hopkins Marine Station (HMS), Pacific Grove, California, between 1931 and 1933. Replicating precisely the location of the plots and methodology used by Hewatt, we documented changes in the abundances of 46 invertebrate species, indicating that this intertidal community changed significantly during the 60 yr between surveys. Changes in abundance were related to geographic ranges of species. Most southern species (10 of 11) increased in abundance, whereas most northern species (5 of 7) decreased. Cosmopolitan species showed no clear trend, with 12 increasing and 16 decreasing. Although Hewatt did not record algal species as thoroughly as invertebrates, we were able to document a massive decline in cover of Pelvetia compressa, a cosmopolitan fucoid alga that is typically more common in the southern part of its range. Shoreline ocean temperature, taken daily at HMS, warmed by 0.79°C during this 60-yr period, with average summer temperatures up to 1.94°C warmer in the 13 yr preceding our study than in the 13 yr preceding Hewatt's. The hypothesis that climatic warming drove the observed range-related community shifts is supported further by historical records and data from other investigators: Several alternative hypotheses to explain changes in the invertebrate community at HMS, including habitat changes, anthropogenic effects, indirect biological interactions, El Nino-Southern Oscillation (ENSO) events, and upwelling are considered to be less important than climate change. Changes in species' abundances over a short period (3 yr) were relatively small compared to large species shifts over 60 yr and were unrelated to geographic range of the species, indicating that short-term population fluctuations play a relatively minor role in the long-term community changes that we observed.
Recent investigations in marine biodiversity have given cause to rethink some basic assumptions about marine biodiversity. Only c160 000 marine species have been described. This contrasts with the possibly one million described species of insects. Estimates for the total insect diversity range from about 5 × 106 up to 2 × 108. Compared with these figures marine biodiversity would appear trivial, <1.3% of the world's metazoans being marine. But such a comparison is hugely misleading as it makes no sense to compare the number of described marine species with the estimated total terrestrial diversity. When a methodology similar to that used for terrestrial global biodiversity estimates is used, a global macrofauna diversity of 1 × 107 species can be calculated. The biodiversity of the small marine metazoa, the meiofauna, may be an order of magnitude higher. Recent investigations into local diversity patterns have highlighted the importance of non-equilibrium patch dynamics in species diversity. A spatial-temporal mosaic of unique small-scale patches, operating against a low disturbance, low nutrient background prevents competitive exclusion and allows a high regional species pool in environments such as the deep sea and tropical rainforests. -from Author
This chapter examines the response of animals to climatic change on a world-wide scale. In terms of populations, the response to climatic change is the prime environmental agent. Individuals are affected by a gamut of environmental factors, but the populations have evolved to resist them insofar as they can. The evolution of migration has resulted in a larval drift between spawning ground and nursery ground, where, presumably, the opportunities for larval survival, in terms of food, have been maximized for very long periods. Thus, the match/mismatch mechanism is really part of the pattern of migration; it should be absent from populations that do not migrate and from those that may not experience lack of food. The chapter attempts to describe the principal climatic change makers that are at work and identifies some characteristic time and space scales of climatic variation. Some recent trends of climatic and hydrographic variation are also described. Set against this background of environmental change, the chapter reviews those changes in marine populations that are thought to be attributable to some variation in the physical environment. These various elements of change are brought together in an attempt to cast light on the processes involved.
A quick dip into the literature on diversity reveals a bewildering range of indices. Each of these indices seeks to characterize the diversity of a sample or community by a single number. To add yet more confusion an index may be known by more than one name and written in a variety of notations using a range of log bases. This diversity of diversity indices has arisen because, for a number of years, it was standard practice for an author to review existing indices, denounce them as useless, and promptly invent a new index. Southwood (1978) notes an interesting parallel in the proliferation of new designs of light traps and new permutations of diversity measures.
Recent surveys in the southern and central North Sea and the Dutch Wadden Sea revealed that the whelk Buccinum undatum L. can no longer be found in areas where whelks were abundant twenty or more years ago. The decline of whelk populations tends to coincide with areas of various, intense human activities, which may cause either pollution or physical damage. Potential causes for the decline of whelks from the southern North Sea and coastal areas are discussed and considered in view of North Sea ecology and protective policies for the North Sea.
The performance of three methods for the estimation of species richness are tested using computer simulations. Each method relies on different theoretical background: the method of Stout and Vandermeer is based on the species-area relation; Cohen's method assumes the log-normal distribution of species abundances, whereas the jackknife procedure is a non-parametric technique with no distributional assumptions. These methods were applied on a wide range of simulated community types. Factors considered in the generation of both communities and samples were: total species richness, community equitability, density and aggregation level of individuals on samples. Reliability of the estimators was measured as the ratio of estimated to actual richness. The results provide evidence for a consistent negative bias in all the estimators. Reliable estimations depend on the proportion of the whole community included in the sample, i.e. sample representativeness. Stout and Vandermeer's method shows the worst performance as it is strongly affected by aggregation and total species richness. Care is recommended when comparing different community types, but communities with similar attributes can be successfully compared using these methods.
Summary •The objectives of this paper are to test the performance of the taxonomic distinctness index, +, in a number of environmental impact scenarios, to examine its relationship with functional diversity and to examine the influence of habitat type and diversity on the index. •The index was applied to data on free-living marine nematodes from the coasts of Britain and Chile. •The taxonomic distinctness of nematodes from environmentally degraded locations was generally reduced in comparison with that of more pristine locations, often significantly so. •Some habitat types may have naturally lower values of taxonomic distinctness than others. However, unless the habitats are degraded in some way the + values do not generally fall below the lower 95% confidence limit of the simulated distribution under a null hypothesis that the assemblages behave as if they are a random selection from the regional species pool. This ameliorates the problem encountered with species richness measures of biodiversity, which are much more strongly affected by habitat type and complexity, thus making comparisons difficult between data sets from different habitats or where habitat type is uncontrolled. •Taxonomic distinctness in marine nematodes is shown to be related to trophic diversity: a reduction in trophic diversity will lead to a reduction in taxonomic distinctness, although not necessarily to a reduction in species richness. Trophic composition itself is clearly affected by pollution, but is also strongly responsive to the major influence of habitat type. •These features of the taxonomic distinctness index, coupled with its lack of dependence on sampling effort or differences in taxonomic rigour between workers and a statistical framework for the assessment of the significance of departure from expectation, suggest that it may prove to be a biologically and ecologically relevant measure of biodiversity. •This paper demonstrates that the taxonomic distinctness index has a number of theoretical and logistical advantages over measures of species richness for the purposes of environmental assessment.
Historical and in situ temperature and salinity data for the period 1950-2987 are examined to study the seasonal and interannual variability of the core properties of Modified Atlantic Water (MAW) and Levantine Intermediate Water (LIW) in the Western Mediterranean Sea. The seasonal cycle is well detected in the MAW core temperature but not in the salinity. The seasonal difference between MAW/LIW cores indicates that at basin scale, the maximum MAW/LIW mixing occurs in winter, when Garret et al. (1990) deduced a tendency to overmixing conditions in the Western Mediterranean. The data show a definite interannual increase in the LIW core temperature and salinity during the nearly 40 years of data. This may be due to regional or global climatic changes or decreses in river runoff in the eastern Mediterranean.