NE Mediterranean Sea Research Articles

Analysing Spatiotemporal Variability of Chlorophyll-a Concentration and Water Surface Temperature in Coastal Lagoons of the Ebro Delta (NW Mediterranean Sea, Spain)

Coastal lagoons are highly productive transitional water bodies threatened by human factors and vulnerable to global climate change effects. Monitoring biophysical parameters in these ecosystems is crucial for their preservation. In this work, we used Sentinel-2 and Landsat imagery combined with in situ data to (1) develop preliminary algorithms for retrieving the Chl-a concentration and water surface temperature of six lagoons located in the Ebro Delta (NE Mediterranean Sea, Spain), and to (2) compute maps and trend lines for analysing their spatiotemporal evolution from 2015 to 2022. Our findings showed that the algorithms’ accuracy ranged from 72% to 78% and had limited potential under high Chl-a concentration regimes. Even so, they revealed the lagoons’ trophic status, usual fluctuations, and deviations of both parameters attributed to seasonal (i.e., light and temperature) and short-term physical (i.e., winds) forcing, as well as valuable spatial patterns potentially useful for conservation efforts and land use planning. Future work will focus on the acquisition of a larger in situ data sample under a range of environmental conditions to improve the algorithms’ robustness, which in turn will allow the investigation of natural and human factors controlling the dynamics of the two investigated parameters.

Complete mitochondrial genomes of the black corals Alternatipathesmirabilis Opresko & Molodtsova, 2021 and Parantipatheslarix (Esper, 1788) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae).

We describe the complete mitogenomes of the black corals Alternatipathesmirabilis Opresko & Molodtsova, 2021 and Parantipatheslarix (Esper, 1790) (Cnidaria, Anthozoa, Hexacorallia, Antipatharia, Schizopathidae). The analysed specimens include the holotype of Alternatipathesmirabilis, collected from Derickson Seamount (North Pacific Ocean; Gulf of Alaska) at 4,685 m depth and a potential topotype of Parantipatheslarix, collected from Secca dei Candelieri (Mediterranean Sea; Tyrrhenian Sea; Salerno Gulf; Italy) at 131 m depth. We also assemble, annotate and make available nine additional black coral mitogenomes that were included in a recent phylogeny (Quattrini et al. 2023b), but not made easily accessible on GenBank. This is the first study to present and compare two mitogenomes from the same species of black coral (Stauropathesarctica (Lütken, 1871)) and, thus, place minimum boundaries on the expected level of intraspecific variation at the mitogenome level. We also compare interspecific variation at the mitogenome-level across five different specimens of Parantipathes Brook, 1889 (representing at least two different species) from the NE Atlantic and Mediterranean Sea.

Deep learning-based forecasting of sea surface temperature in the interim future: application over the Aegean, Ionian, and Cretan Seas (NE Mediterranean Sea)

Deep learning-based forecasting of sea surface temperature in the interim future: application over the Aegean, Ionian, and Cretan Seas (NE Mediterranean Sea)

Phylogenetic analysis of invasive genus Lophocladia (Rhodomelaceae, Rhodophyta) reveals synonymy of L. lallemandii with L. trichoclados and first record of L. kuetzingii in the NE Atlantic

ABSTRACT Species identification in red algae poses significant challenges when relying solely on morphological characteristics. Consequently, the absence of molecular information often conceals misidentifications, cryptic diversity and introduced cryptic species. Within the genus Lophocladia, species have traditionally been delineated based on subtle morphological traits. Lophocladia trichoclados and Lophocladia lallemandii have been extensively documented in warm and temperate coastal regions, with the latter recognized as an invasive species in the Mediterranean. However, the molecular relationship between these species remains unexplored. To address this gap, a comprehensive taxonomic reevaluation of Lophocladia was conducted in the NE Atlantic, Mediterranean Sea and Red Sea. Through combined molecular and morphological analyses of 75 specimens, two distinct taxa of Lophocladia were identified within the study area. Sequences of the rbcL plastid gene unequivocally demonstrated that L. lallemandii and L. trichoclados are conspecific. Consequently, we propose the synonymization of L. lallemandii with L. trichoclados, which has nomenclatural priority. We report L. kuetzingii, a potentially introduced species from Australia, for the first time in the Macaronesian region of the North Atlantic. This finding underscores the importance of expanding red algal DNA datasets, as such efforts significantly enhance our ability to detect and discern introduced species. Additionally, this research highlights the existence of taxonomic uncertainties surrounding introduced species, even among those already classified as invasive.

Oxygen and carbon isotope variations in Chamelea gallina shells: Environmental influences and vital effects.

Stable isotopes in mollusc shells, together with variable growth rates and other geochemical properties, can register different environmental clues, including seawater temperature, salinity and primary productivity. However, the strict biological control over the construction of biominerals exerted by many calcifying organisms can constrain the use of these organisms for paleoenvironmental reconstructions. Biologically controlled calcification is responsible for the so called vital effects that cause a departure from isotopic equilibrium during shell formation, resulting in lower shell oxygen and carbon compared to the equilibrium value. We investigated shell oxygen and carbon isotopic composition of the bivalve Chamelea gallina in six sites along with a latitudinal gradient on the Adriatic Sea (NE Mediterranean Sea). Seawater δ18 O and δ13 CDIC varied from North to South, reflecting variations in seawater temperature, salinity, and chlorophyll concentration among sites. Shell δ18 O and δ13 C differed among sites and exhibited a wide range of values along with the ~400 km latitudinal gradient, away from isotopic equilibrium for both isotopes. These results hampered the utilization of this bivalve as a proxy for environmental reconstructions, in spite of C.gallina showing promise as a warm temperature proxy. Rigorous calibration studies with a precise insight of environment and shell growth are crucial prior to considering this bivalve as a reliable paleoclimatic archive.

Kuzeydoğu Akdeniz’den (Türkiye) Fistularia commersonii Rüppell 1835'nin Boy-Ağırlık İlişkileri

In this study, the length-weight data for bluespotted cornetfish, Fistularia commersonii in the Iskenderun Bay (NE Mediterranean Sea, Türkiye) was reported. F. commersonii specimens were caught from Iskenderun Bay between September 2018 and March 2019. The total length and total weight of both sexes varied from 23.0-108.1 cm and 4.0-599.58 g. The length-weight relationship was determined as W= 0.0005xL2.963 (R2= 0.969) with negative allometric growth for both sexes. The values of the exponent b of the length-weight relationships (LWRs) were 2.993 for females and 2.925 for males. This present study provides the first comprehensive gender-based description of the length-weight relationships of F. commersonii from the northeastern Mediterranean Sea, Türkiye

A new octocoral species of Swiftia (Holaxonia, Plexauridae) from the upper bathyal off Mauritania (NE Atlantic).

Three species of the genus Swiftia are known for the NE Atlantic Ocean and Mediterranean Sea. Remotely-operated vehicle (ROV) surveys and sampling on board RV Maria S. Merian during cruise MSM 16/3 'PHAETON' in 2010 provided footage and specimens of octocorals off Mauritania. Micro-computed tomography (micro-CT) reveals, for the first time in taxonomy of octocorals, the three-dimensional arrangement of the sclerites in a polyp. Swiftiaphaeton sp. nov. is described for the continental slope off Mauritania. This azooxanthellate octocoral is distinctive from NE Atlantic and Mediterranean congenerics by the dark red colour of the colonies (including the polyps), the presence of a layer of rod sclerites on top of the polyp mounds, and different sizes of polyps and sclerites. Using micro-CT has allowed the observation and imaging of a layer of sclerites that is distinct from other species of the same genus. ROV images revealed live records of S.phaeton sp. nov. in submarine canyons and on cold-water coral mounds in the upper-bathyal off Mauritania (396-639 m depth), mainly attached to dead coral, coral rubble, or rocks. The new species represents an extension of the genus distribution to the tropical latitudes (17°07'N and 20°14'N) of the NE Atlantic Ocean.

Grain size distributions in airborne dust, river-suspended loads, and marine sediments from southeastern Turkey (NE Mediterranean Sea)

Grain size distributions in airborne dust, river-suspended loads, and marine sediments from southeastern Turkey (NE Mediterranean Sea)

Reproductive biology of Charybdis (Goniohellenus) longicollis Leene, 1938 (Brachyura: Portunidae), in the north-eastern Mediterranean Sea, Turkey

The swimming crab, Charybdis (Goniohellenus) longicollis Leene, 1938, is a Lessepsian migrant into the Mediterranean and little is known about its biology in Iskenderun Bay, north-eastern Mediterranean, Turkey. The size of crabs, sex-ratio and spawning period of this species was defined from 951 specimens in order to understand their reproduction and development in the NE Mediterranean Sea. The crabs were found to occur throughout the year. Carapace width (CW) ranged between 7.22 to 100.60 mm and total weight ranged from 1.34 to 164.09 g. Male-female sex ratio was 0.6:1. Highest gonado-somatic index (GSI) was seen in March and September for females and in May for males. Ovigerous females were present throughout the year, with peak spawning activity in July and September. The CW of the ovigerous female crabs ranged between 23.71 and 95.93 mm. In winter months, GSI of males and females decreased. However, spawning season of C. (G.) longicolis in Yumurtalık Cove was observed throughout the year.

“Crash landing” obligation for Mediterranean mixed fisheries: Evaluation of management strategies using bioeconomic modelling in the Aegean Sea

Minimizing unwanted catches is a major milestone for achieving sustainable fisheries. In the framework of the Common Fisheries Policy, a landing obligation is being established progressively in European waters (Article 15, EU Regulation 1380/2013). Supplementary management measures have been proposed to support and enhance the effectiveness of this new regime. In this context, the effect of the landing obligation on a demersal mixed fishery (coastal and trawl fleet) in the Aegean Sea (NE Mediterranean Sea) was assessed in terms of both biological and economic sustainability. Our results show that the landing obligation alone does not ensure sustainable fisheries. Management action should be directed to the introduction of additional measures. Evidence suggests that improving selectivity and protecting the nursery grounds are possible solutions to decrease discards and ensure sustainable fisheries in the long term. The landing obligation can have a role in incentivizing the adoption of these management measures that ensure lower fishing mortality on juvenile fish.

Paleo-ecologic and neotectonic evolution of a marine depositional environment in SE Rhodes (Greece) during the early Pleistocene

We have studied benthic foraminiferal assemblages in a marine sediment section (Pefka E section) from the Lindos Bay Formation deposited during the early Pleistocene to provide new insights into the paleo-ecologic and neotectonic evolution of the SE part of the island of Rhodes (NE Mediterranean Sea). Relatively high amounts of eutrophic/low oxygen tolerant species and a comparatively high foraminiferal diversity indicate generally mesotrophic conditions at the sea floor and the presence of well-oxygenated bottom waters. These conditions are attributed to generally elevated surface water productivity and related organic matter fluxes during the early Pleistocene, which is in contrast to the modern oligotrophic conditions in this region. The abundance of individual species shows orbital-driven variability in the obliquity (41 kyr) and precessional (∼23 kyr) bands. Obliquity-driven changes in food availability are indicated by increased percentages of Cassidulina carinata s.l. during marine isotope stages (MIS) 44 and 42, reflecting enhanced food fluxes under glacial conditions. Precession-driven changes are observed for Ca. carinata s.l., Cibicidoides pseudoungerianus s.l., Cibicidoides mundulus and Gyroidinoides altiformis. These changes likely reflect prolonged near-coastal phytoplankton blooms triggered by local fresh-water runoff at times of Northern-Hemisphere insolation maxima, coeval to the formation of sapropels in the adjacent deep-sea basins. The application of a benthic foraminiferal transfer function allowed for the identification of a number of short-term subsidence-uplift cycles, superimposed by overall long-term subsidence of the SE coast of Rhodes. Estimated average uplift and subsidence rates vary between ∼4.2 and ∼10.3 mm/yr. These rates of tectonic motions are distinctly higher compared to most other estimates from Rhodes and suggest a complex neotectonic history of the island during the early Pleistocene, involving both large-scale and local motions associated with alternating compressional and extensional regimes.

Long-term changes in abundance and diversity of tintinnids in the Gulf of Trieste (Northern Adriatic Sea)

Abundance and composition of the planktonic tintinnid ciliates were studied in the Gulf of Trieste (Northern Adriatic Sea, NE Mediterranean Sea) from July 1998 to July 2016. Tintinnids were collected biweekly-monthly from the LTER station C1 (200 m offshore, 17.5 m depth) at four depths (surface, 5 m, 10 m and 15 m). The maximum tintinnid abundance reached 4476 ind. L-1 at surface in February 2016. The tintinnid community comprised a maximum of 35 species and was dominated by the genera Stenosemella, Tintinnopsis, Codonellopsis, Salpingella and Eutintinnus. The most abundant species were Stenosemellanivalis, Tintinnopsisnana, Codonellopsisschabi, Salpingellarotundata and Eutintinnusapertus. We found a species-specific correlation with the abiotic factors considered, i.e., temperature and salinity. Temperature was positively correlated with S.rotundata and E.apertus and negatively with S.nivalis. Salinity was negatively correlated with the majority of the detected species. Agglutinated species presented winter maxima while hyaline species showed higher abundance in summer-autumn. Some key species were present over the whole period studied. Significant differences within the water column were not seen in the species composition, but were seen in the relative abundances of the same species at different depths. Stenosemellanivalis, S.ventricosa and Tintinnopsisberoidea can be considered as keystone species in the area and their possible loss can be seen as a signal of changes in the structure of the entire planktonic system.

The family Apseudidae Leach, 1814 (Crustacea: Tanaidacea) in the Gulf of Gabès (Mediterranean Sea): taxonomic and biogeographic remarks and description of Apseudopsis gabesi Esquete sp. nov.

Species of Apseudidae Leach, 1814 are often found in high numbers in benthic samples and represent an important element of the infaunal assemblages of the coasts of the NE Atlantic and Mediterranean Sea. Precise knowledge of the species diversity, as well as accurate identification tools, is a need for obtaining reliable conclusions from benthic ecological studies and environmental assessment surveys. During a benthic survey carried out in the Gulf of Gabes (Tunisia), one Apseudes Leach, 1814 and four Apseudopsis Norman, 1899 species were identified, including one species new to science. Apseudopsis gabesi Esquete sp. nov. is distinguished from other species of the genus for having double ventral apophyses on pereonite 2, pereonites 2–6 with lateral indentations, ventral protuberances on antennule peduncle articles 2 and 3, three ventral spines on pereopod 1 propodus and no spine on merus. A ventral apophyse on cephalothorax is a newly recorded taxonomic character for Apseudopsis mediterraneus (Băcescu, 1961). Apseudopsis annabensis (Guţu, 2002) and Apseudopsis ostroumovi Băcescu and Cărăusu, 1947 are new records for Tunisian waters. Additionally, we comment on the taxonomic characters allowing the identification of the species and the diagnosis of the genus and propose the original name to Apseudes robustus Sars, 1882, and Apseudes israeliticus (Băcescu, 1961) comb. nov. is herein accepted and elevated to species rank. Additionally, the presence of abnormal numbers of spines on pereopod 1 propodus is discussed. The distribution of the Apseudopsis in the Mediterranean Sea is commented.

Stock structure of Trachurus picturatus from the NE Atlantic and Mediterranean Sea using microsatellite DNA markers

Stock structure of Trachurus picturatus from the NE Atlantic and Mediterranean Sea using microsatellite DNA markers

Comparative Determination of Phosphorus Fractions in Coastal Surface Sediment (NE Mediterranean Sea) by ICP-OES and UV/VIS Spectrometry

Comparative Determination of Phosphorus Fractions in Coastal Surface Sediment (NE Mediterranean Sea) by ICP-OES and UV/VIS Spectrometry

Occurrence of the Spotted Sea Hare Aplysia dactylomela (Rang 1828, Aplysiidae) in the Yeşilovacık Bay, Norteastern Mediterranean Coast of Turkey

The alien opisthobranch, Aplysia dactylomela, is recorded for the first time from the Yeşilovacık Bay in 2017. One specimen of A. dactylomela was photographed at the infralittoral zone of the Bay . The length of the specimen was 35 cm. The individual was photographed while feeding on rocks covered with algae. The first record of the A. dactylomela from the Mediterranean Sea was reported from the island of Lampedusa (Central Mediterranean Sea) was reported in 2002. In the following years, A. dactylomela was reported from the North-Eastern Sicily, from the coast of Hatay (NE Mediterranean Sea of the Turkey), from the island of Crete (Aegean Sea), from the coast of Kaş (NE Mediterranean Sea of the Turkey), from the Cirkewwa (Malta), from the Akhziv submarine canyon (Israel), from the island of Paros (Aegean Sea), from the island of Susac (Crotia), from the Montenegro (SE Adriatic Sea), from the Egadi Islands marine protected area (western Sicily), from the Capo San Donato harbour (Ligurian Sea).

Phytoplankton variability and community structure in relation to hydrographic features in the NE Aegean frontal area (NE Mediterranean Sea)

The structure of phytoplankton community in the salinity-stratified Northeastern Aegean frontal area adjacent to the Dardanelles Straits was investigated on a seasonal basis (autumn, spring and summer) and in relation to circulating water masses: the modified Black Sea Water (BSW) and the Levantine Water (LW). By employing High Performance Liquid Chromatography (HPLC) for the analysis of phytoplankton pigments in conjunction with conventional cell counting methodologies (i.e. inverted light microscopy, flow cytometry) and primary production measurements, a comprehensive qualitative and quantitative characterization of phytoplankton community composition and its activity was conducted. Chlorophyll-a normalized production and estimated growth rates presented the highest values within the ‘fresh’ BSW mass during summer, though generally growth rates were low (<0.4 d−1) at all seasons. The spatiotemporal variation of BSW outflow was found to greatly affect the relative contribution of pico-, nano- and micro-phytoplankton to total phytoplankton biomass and production. Large cell organisms, and in particular diatoms, were closely associated with the surface BSW masses outflowing from the Straits. Our results showed that all phytoplankton size components were significant over time and space suggesting a rather multivorous food web functioning of the system.

Coccolithophore combination coccospheres from the NE Mediterranean Sea: new evidence and taxonomic revisions

Numerous specimens of coccolithophore combination coccospheres in water samples collected from the North Aegean and Tyrrhenian (Mediterranean Sea) have been photographed using the scanning electron microscope.As a consequence a series of taxonomic revisions are proposed, in which the names of the heterococcolithophores and holococcolithophores involved in the same life-cycle are synonymized. This has resulted in synonymizing the genus Coronosphaera with Syracosphaera and establishing one new combination; Syracosphaera arethusae (Kamptner 1941) comb. nov.

Using a phylogeographic approach to investigate the diversity and determine the distributional range of an isopod (Crustacea: Peracarida), Stenosoma nadejda (Rezig, 1989) in the Atlantic-Mediterranean region

The genus Stenosoma comprises 13 species in the NE Atlantic, Mediterranean and Black Sea. Recent studies have improved knowledge on the distributional patterns of the genus, reducing species ranges and allowing the identification of cryptic species. Lacking a free-swimming life-stage, Stenosoma typically display small- to medium-sized ranges, with the exception of S. nadejda which occurs in the Atlantic-Mediterranean region. In this study, we build upon previous work and examine phylogeographic patterns of S. nadejda throughout its entire range to assess levels of genetic differentiation and evidence of cryptic species. While Elongation Factor 1α gene sequences revealed an almost absence of genetic and geographic structure across the entire distribution of S. nadejda, the Cytochrome c oxidase subunit I gene sequences revealed a phylogenetic split defining two Mediterranean clades. Our results confirm the wide distribution of S. nadejda in the Atlantic/Mediterranean region and show that the distribution of the two Mediterranean clades does not match the east–west break in genetic continuity typically displayed by many species. This pattern is probably a consequence of sporadic long-distance dispersal by rafting. Conversely, an almost absence of shared haplotypes at the local level, conforms to the recognized poor ability of peracarids for autonomous dispersal.

Spatial and temporal variability of small-sized copepod assemblages in a shallow semi-enclosed embayment (Kalloni Gulf, NE Mediterranean Sea)

The small-sized copepod community structure (&lt;1 mm) and its response to environmental variability was examined during an annual cycle in Kalloni Gulf, a semi-enclosed coastal system in the NE Aegean Sea. Α 90 µm net was used in order to adequately sample the smaller copepod fractions. In the copepod ecology the spatial patterns dominated over the seasonal. Total copepod abundance increased towards the inner gulf area while diversity indices followed the opposite trend. The inner gulf copepod assemblage area was affected by the increasing magnitude of eutrophication, characterized by high abundance values, low species richness and dominance of a single species (e.g.Oithona nana). A clear seasonal succession of species was observed, ordered by temperature, salinity, chlorophyll a, heterotrophic bacterial biomass, organic and inorganic nutrients. Freshwater inputs and the subsequent nutrient inflow was a dominant phenomenon enhancing copepod production and negatively affecting the biodiversity of the assemblage. The great contribution of copepod larval stages in the total community and their year-round presence indicate the continuous production of copepods during the annual cycle, highlight the importance of the smaller size fraction and encourage the use of finer mesh-size nets when assessing the structure and dynamics of copepod communities.