Southwestern Mediterranean Sea Research Articles

Expansion history of the blue crab (Callinectes sapidus Rathbun, 1896) in the Eastern Iberian Peninsula (Western Mediterranean Sea).

Expansion history of the blue crab (Callinectes sapidus Rathbun, 1896) in the Eastern Iberian Peninsula (Western Mediterranean Sea).

Directional bilateral asymmetry in otolith morphology may affect fish stock discrimination based on otolith shape analysis

AbstractOtolith shape analysis is an efficient fish stock identification tool. However, most applications used left and right otoliths or only one of them arbitrarily chosen without testing for biases resulting from potential directional bilateral asymmetry (DA) in otolith shape, i.e. a unimodal population-level deviation form bilateral symmetry between right and left otolith shapes. In this study, 560 bogues (Boops boops) were sampled from 11 geographical locations from the Canary Islands to the Aegean Sea and elliptical Fourier descriptors were used to describe their otoliths’ shape. First, a significant otolith DA was observed at the global scale with an average amplitude of 2.77%. However, at the scale of sampling locations, DA was not always significant and varied in amplitude and direction. Second, population structure was investigated using the shape of either right otoliths or left otoliths or both together. Analyses based on right otoliths or both otoliths together, suggested three stock units: a North-Western Mediterranean Sea stock, an Eastern Mediterranean Sea stock, and a Central-Eastern Atlantic Ocean and South-Western Mediterranean Sea stock. In contrast, no coherent geographical pattern was found based on left otoliths. Our results highlight the importance of accounting for potential otolith DA in otolith shape-based stock identification.

Structural and functional responses of coastal marine phytoplankton communities to PAH mixtures

The toxicity of polycyclic aromatic hydrocarbons (PAHs) mixtures was evaluated on natural phytoplankton communities sampled from lagoons of Bizerte (South-western Mediterranean Sea) and Thau (North-western Mediterranean Sea). PAHs induced short-term dose and ecosystem-dependant decreases in photosynthetic potential. Chlorophyll a was negatively affected by increasing PAHs concentrations, together with dramatic changes in phytoplankton community composition. Size classes were strongly affected in the Bizerte compare to the Thau lagoon, with a decrease in nano- and microphytoplankton densities compare to picophytoplankton. In both locations, the diatom Entomoneis paludosa appeared favoured under PAH exposure as evidenced by increase in cell density, whereas autotrophic flagellates and dinophytes were strongly reduced. Smaller cells were more tolerant to exposure to highest PAHs concentrations, with persistent picophytoplankton carbon biomass at the end of the incubations. Apparent recovery of photosynthetic potential, accompanied with a regrowth of chlorophyll a under the lowest PAH doses, coincided with a significantly altered community composition in both lagoons. Furthermore, sensitivity to PAHs was not related to the phytoplankton cell size, and toxicity-induced modification of top-down control by grazers during the experiment cannot be excluded.

Selected organic pollutants (PAHs, PCBs) in water and sediments of Annaba Bay, Algeria

Annaba Bay is a coastal area (southwestern Mediterranean Sea) that receives large diffuse inputs from the Seybouse and Bouhamra wadis, which are influenced by anthropogenic activities. Surface waters and sediments from these wadis were analyzed for polycyclic aromatic hydrocarbons (16 PAHs) and polychlorinated biphenyls (seven PCBs) by using gas chromatography-mass spectrometry (GC–MS). Total PAHs ranged from 0.183 to 0.503 µg l− 1, in water, and from 250.16 to 509.58 µg.kg− 1 dw in sediments. Total PCB levels ranged from 0 to 0.003 µg l− 1 in water, and from 2.15 to 6.37 µg.kg− 1 dw in sediments. In order to identify pollution emission sources of PAHs, different diagnostic ratios were used, including low molecular weight/high molecular weight indexes. The results show that the pollution origin was mainly due to pyrolytic inputs in waters and sediments.

Interannual and seasonal effects of environmental factors on the zooplankton distribution in the solar saltern of Sfax (south-western Mediterranean sea)

Understanding interannual variation of zooplankton communities is a mean for assessment and monitoring of aquatic ecosystems. For this reason, we monitored the zooplankton community of the Sfax saltern (Tunisia) during four years (2000–2003). A multivariate method, the “STATICO analysis” was used to investigate the effect of environmental parameters on the abundance, distribution and composition of the zooplankton community according to time, in three ponds with different salinity values. The results revealed some seasonal and interannual variations of the zooplankton community. Copepods, which were the most abundant zooplankton species, were clearly influenced by the nutrient content variation (higher in spring and autumn) and the anthropogenic pollution level in each pond but their distribution was mainly related to salinity changes. In autumn, Oithona nana (Cyclopoida) proliferated in the least salty pond, Microsetella sp. (Harpacticoida) was abundant at intermediate salinity; and Harpacticus littoralis and Bryocamptus sp. (Harpacticoida) proliferated in the saltiest pond.

Use of otolith-shape analysis for stock discrimination of Boops boops along the Algerian coast (southwestern Mediterranean Sea)

Otolith-shape analysis was examined to determine its utility for biological stock identification of the bogue Boops boops along the Algerian coast of the Mediterranean Sea. The outlines of 179 sagittal otolith pairs from fish collected at three locations (Oran, Bejaia and Annaba) between 2013 and 2016 were digitised and analysed for shape variation by elliptical Fourier analysis. Potential confounding sources of variation (fish length, age and sex, and left or right otolith position) were examined and accounted for in the analyses before interpretation of spatial differences in distribution of the stock. Redundancy analysis showed a significant difference between the left and right otoliths. No difference was correlated with sex and age, but fish length and sampling location had a significant effect on otolith shape. Differences in otolith shape between fish from the three locations (a span of approximately 1 000 km) were not large enough to support the concept of separate biological stocks of B. boops along the Algerian coast, as illustrated by the scatterplot of discriminant scores. This study emphasises the need to carefully evaluate the confounding effects of the otolith side (left or right) on the Fourier descriptors of otoliths before drawing conclusions about stock structure of the bogue on the basis of otolith-shape differences among samples of fish from different stocks or areas.

Seasonal variability of picophytoplankton under contrasting environments in northern Tunisian coasts, southwestern Mediterranean Sea

We investigated at the single cell level during 16months (June 2012 to September 2013) the temporal distribution of picophytoplankton (picoeukaryotes, Synechococcus and Prochlorococcus) communities in two contrasted ecosystems: the Bay of Bizerte characterised by an oligotrophic regime typical of the Mediterranean Sea and the Bizerte Lagoon that exhibits a mesotrophic/eutrophic state. We aimed at depicting seasonal variations and quantifying the relationships between the environmental factors and the structure and abundance of picophytoplankton communities. Results showed that picophytoplankton groups were able to grow under a wide range of environmental conditions varying seasonally, although their abundances and contributions to the total chlorophyll biomass significantly varied and showed importance in the Bay of Bizerte. Synechococcus was the most abundant group reaching 225∗103cells·cm−3 in the Bay and 278∗103cells·cm−3 in the lagoon. This group was present all over the year in both ecosystems. Structural equation model results pointed out a different configuration regarding the picophytoplankton environmental drivers. The complexity of the configuration, i.e. number of significant links within the system, decreased under enhanced eutrophication conditions. The less exposure to anthropogenic stress, i.e. in the Bay of Bizerte, highlight a larger role of nutrient and hydrological conditions on the seasonal variations of picophytoplankton, whereas a negative effect of eutrophication on picophytoplankton communities was unveiled in the Bizerte Lagoon. We stress that such influence may be exacerbated under expected scenarios of Mediterranean warming conditions and nutrient release in coastal ecosystems.

Intra- and interspecific niche partitioning in striped and common dolphins inhabiting the southwestern Mediterranean Sea

Intra- and interspecific niche partitioning in striped and common dolphins inhabiting the southwestern Mediterranean Sea

Saharan dust inputs and high UVR levels jointly alter the metabolic balance of marine oligotrophic ecosystems.

The metabolic balance of the most extensive bioma on the Earth is a controversial topic of the global-change research. High ultraviolet radiation (UVR) levels by the shoaling of upper mixed layers and increasing atmospheric dust deposition from arid regions may unpredictably alter the metabolic state of marine oligotrophic ecosystems. We performed an observational study across the south-western (SW) Mediterranean Sea to assess the planktonic metabolic balance and a microcosm experiment in two contrasting areas, heterotrophic nearshore and autotrophic open sea, to test whether a combined UVR × dust impact could alter their metabolic balance at mid-term scales. We show that the metabolic state of oligotrophic areas geographically varies and that the joint impact of UVR and dust inputs prompted a strong change towards autotrophic metabolism. We propose that this metabolic response could be accentuated with the global change as remote-sensing evidence shows increasing intensities, frequencies and number of dust events together with variations in the surface UVR fluxes on SW Mediterranean Sea. Overall, these findings suggest that the enhancement of the net carbon budget under a combined UVR and dust inputs impact could contribute to boost the biological pump, reinforcing the role of the oligotrophic marine ecosystems as CO2 sinks.

Organochlorines in the surface sediments of the Bahiret el Bibane lagoon (Tunisia, Southwestern Mediterranean Sea)

ABSTRACTOrganochlorines (including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs)) were analysed in 10 surface sediment samples collected from the Bahiret el Bibane lagoon, which is one of the most productive lagoons and one of the most important active commercial fish traps in the southern Tunisia. The aim was to obtain information concerning the recent deposition of these compounds in this area, together with the levels, the distribution and any potential biological risk. Total concentrations of OCPs and PCBs in the sediments ranged from below the limit of detection (<lod) to 20.3 ng g−1 and from 29.5 to 88.2 ng g−1 dw, respectively. The spatial distribution of PCBs suggested that the sources of these contaminants are probably located outside the lagoon and are transported by water currents and atmospheric deposition. Compared with some other regions of the world, the Bahiret el Bibane lagoon exhibited low to moderate levels of PCBs and OCPs. According to established sediment quality guidelines, PCBs and Lindane at most of the study sites would be more concerned for the ecotoxicological risk in the Bahiret el Bibane lagoon. The results of this study could provide a useful aid for the sustainable marine management of the region.

First record of the Atlantic blue crab Callinectes sapidus (Crustacea: Brachyura: Portunidae) in the Segura River mouth (Spain, southwestern Mediterranean Sea)

A single male individual of Callinectes sapidus (Crustacea, Decapoda, Portunidae) was collected on 6 December 2014 in the Segura River mouth in southeastern Spain. Information on collection site, DNA barcoding, and its present distribution and dispersal strategies are provided.

Significance of bottom currents in deep-sea morphodynamics: An example from the Alboran Sea

We present an interdisciplinary study of the geomorphology, sedimentology and physical oceanography of the Alboran Sea (south-western Mediterranean Sea) to evaluate the potential role of bottom currents in shaping the Spanish and Moroccan continental margins and adjacent basins. Bathymetric and seismic data have allowed the recognition of the contourite deposits, including depositional (plastered, sheeted, channel-related, mounded confined, elongated and separated drifts), erosive (moats, channels and furrows) and mixed (terraces and scarps) features. Hydrographic data offer new insights into the distribution of the Mediterranean water masses, and reveal that bottom circulation of the Western Intermediate Water (WIW) and the Levantine Intermediate Water (LIW) interact with the Spanish slope, and the Western Mediterranean Deep Water (WMDW) on the Moroccan slope, Spanish base-of-slope and deep basins. The integration of distinct datasets and approaches allows a proposal of a new sedimentary model for the Alboran Sea that details the significance of bottom current processes in shaping deep-sea morphology. This model considers the bottom circulation of water masses governs physiography, that interface positions of water-masses with contrasting densities sculpt terraces on a regional scale, and that the morphologic obstacles play an essential role in the local control of processes and water-mass distributions. Our findings demonstrate the pivotal role of bottom water circulation in seafloor shaping and sedimentary stacking patterns for continental margins, establishing a new outlook for future studies of deep marine sedimentation.

Effects of increasing levels of pharmaceutical penicillin G contamination on structure of free living nematode communities in experimental microcosms

A microcosm experiment was conducted to examine the effects of the pharmaceutical (penicillin G) on free living nematode communities of a Tunisian coastal zone (South-Western Mediterranean Sea). Sediments were contaminated with five penicillin G dose [D1 (3mgL−1), D2 (30mgL−1), D3 (300mgL−1), D4 (600mgL−1), D5 (700mgL−1)], and effects were examined after 30 days. Results showed significant differences between nematode assemblages from undisturbed controls and those from penicillin G treatments. Most univariate measures, including diversity (H′), species richness (d), equitability (J) and number of species (S) decreased significantly with increasing level of the antibiotic contamination. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the penicillin treatments were varied: Kraspedonema octogoniata and Paracomesoma dubium were eliminated at all the antibiotic doses tested and seemed to be intolerant species to penicillin G contamination; Oncholaimus campylocercoides although survived even the highest dose D5, showed definite reduction in its abundance and may be classified as “opportunistic” species at this dose, whereas, Nannolaimoides decoratus which showed a positive response with an increase in density even at highest concentration of contaminant, seems to be “penicillin G resistant” species.

First record and potential trophic impact of Phyllorhiza punctata (Cnidaria: Scyphozoa) along the north Tunisian coast (South Western Mediterranean Sea)

The Australian spotted scyphomedusa Phyllorhiza punctata was recorded for the first time in Tunisian waters in August 2012, in the lagoon of Bizerte (Tunisia). Metaephyrae and juveniles occurred simultaneously in August 2012. The occurrence of adult medusae was detected from September to November 2012, and from August to October 2013. This is the second record of a reproducing population of P. punctata in the Mediterranean Sea. The low abundance of mesozooplankton in summer and autumn 2012 coincides temporally with the highest density of P. punctata recorded in the lagoon, suggesting that predation by this alien jellyfish may have been a limiting factor for the mesozooplankton abundance on site.

What can otolith shape analysis tell us about population structure of the European sardine, Sardina pilchardus, from Atlantic and Mediterranean waters?

The European sardine, Sardina pilchardus, exhibits a complex population structure, which has produced conflicting results in previous genetic studies. Despite its importance in the fisheries industry, stock delineation for management and conservation purposes is still a matter of debate throughout the distribution range of the species. This study examines whether otolith shapes are more efficient than genetic markers to detect population structure in pelagic species with large population sizes. Sardines were analyzed from 15 sampling localities in the Northeast Atlantic and Mediterranean Sea covering almost the whole distribution range of the species. A combination of otolith shape indices and elliptic Fourier descriptors was investigated by multivariate statistical procedures. Within the studied area, three distinct groups were identified with an overall correct classification of 77%. Group A: northern Mediterranean Sea and Gulf of Gabès; group B: Atlantic Morocco–south Alboran–Algero-provençal coasts; and group C: European Atlantic coast. The Almeria–Oran front and the Gibraltar strait are not an efficient barrier for sardine population separation as there seems to be exchanges between populations of the south-western Mediterranean Sea and those of the Moroccan Atlantic Ocean coast or Gulf of Cadiz. The results are discussed in relation to environmental conditions, oceanographic features, and physical barriers to dispersal in the study area, and compared with those obtained by previous genetic, morphometric, and meristic data. For pelagic species with high gene flow, present results highlighted the need to take into account the identification of phenotypic stocks to ensure sustainable fishery benefits and efficient conservation as they may have unique demographic properties and responses to exploitation.

Comparison of diet and otolith growth of juvenile wild fish communities at fish farms and natural habitats

AbstractJuvenile fish of &amp;gt;20 different species use offshore floating sea cages as settlement habitats in the Mediterranean Sea. In the present work, surveys were conducted to identify differences between species composition and abundance of new settlers among farms and control rocky-shore environments and to test for variation in their diets. Along with this, otolith growth and morphology analyses were also applied to better understand the consequences for the ecology and growth performance of several fish species that use coastal farms as recruitment habitats in the southwestern Mediterranean Sea. Results showed that fish farms are acting as a new habitat for the settlement of juvenile fish and that detected abundance could be compared with that found at natural habitats such as shallow rocky environments. However, a consistent pattern for all the studied species was a significant variation in otolith-shape descriptors, principally identified through the Aspect Ratio index, which was lower for the farm-associated species Atherina boyeri, Oblada melanura, and Sarpa salpa. Otolith modifications were effectively detected by elliptic Fourier descriptors since multivariate analysis correctly identified farm or control origin at 78.8, 85.1, and 86.1% for A. boyeri, O. melanura, and S. salpa individuals, respectively. According to these results, fish farms may offer new settlement habitat for several fish species on open coastal areas and provide resources equivalent to rocky habitats, but at the same time causing some effect on fish growth as a potential consequence of the availability of particulate organic matter derived from feed pellets.

Dynamic energy budget model: a monitoring tool for growth and reproduction performance of Mytilus galloprovincialis in Bizerte Lagoon (Southwestern Mediterranean Sea).

Mussel farming is the main economic activity in Bizerte Lagoon, with a production that fluctuates depending on environmental factors. In the present study, we apply a bioenergetic growth model to the mussel Mytilus galloprovincialis, based on dynamic energy budget (DEB) theory which describes energy flux variation through the different compartments of the mussel body. Thus, the present model simulates both mussel growth and sexual cycle steps according to food availability and water temperature and also the effect of climate change on mussel behavior and reproduction. The results point to good concordance between simulations and growth parameters (metric length and weight) for mussels in the lagoon. A heat wave scenario was also simulated using the DEB model, which highlighted mussel mortality periods during a period of high temperature.

Habitat use and ontogenetic shifts of fish life stages at rocky reefs in South-western Mediterranean Sea

The present study aimed at exploring the habitat use by fish life stages and ontogenetic shifts in a South-western Mediterranean rocky reef. The relation with rocky reef habitat structure (complexity, heterogeneity, total cover and depth) was visually surveyed on a monthly basis, in four locations and during one year, for the abundance of young-of-the-year (YOY) and juvenile reef fish. Fish assemblage responded significantly to spatial and temporal variations of structural microhabitat, this response being species-specific. Abundance of fish life stages was directly related to temperature variation, with higher abundances occurring on warmer months. Also, habitat differences occurred between YOY and juveniles of a series of species from shallow steeper rocky habitats to deeper complex rocky bottoms with high total cover. Spatial differences in YOY and juvenile abundance across locations could be attributed to fine-scale habitat preference, from purely rocky, more complex sites, with greater slopes and depths, to sites harbouring more heterogeneous habitats. By characterising the microhabitat association of fish life stages (both YOY and juveniles), and identifying for what species this influence may interfere with spatial and temporal patterns, the present study can be used as a basis for pluriannual monitoring of fish recruitment success in the area in order to better understand their population dynamics.

First Record of Pampus argenteus (Euphrasen, 1788) (Osteichthyes: Stromateidae) in the Tunisian Coast (Mediterranean Sea)

First Record of Pampus argenteus (Euphrasen, 1788) (Osteichthyes: Stromateidae) in the Tunisian Coast (Mediterranean Sea) The second Mediterranean record of the silver pomfret, Pampus argenteus is reported, with the capture of four specimens in the Gulf of Hammamet (North-East Tunisia) on March 15th 2007. The species is a non-indigenous for the Mediterranean, being native to the Indo-West Pacific area. A short description of all these specimens is given and the presence of this species in the Mediterranean is critically discussed. This note describes the first record of the P. argenteus in the Tunisian waters (Southwestern Mediterranean Sea).

Mortality rates in by-caught loggerhead turtle Caretta caretta in the Mediterranean Sea and implications for the Atlantic populations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 489:225-234 (2013) - DOI: https://doi.org/10.3354/meps10411 Mortality rates in by-caught loggerhead turtle Caretta caretta in the Mediterranean Sea and implications for the Atlantic populations I. Álvarez de Quevedo1,*, M. San Félix2, L. Cardona1 1Department of Animal Biology and Institut de Recerca de la Biodivesitat (IRBio), Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain 2Vellmarí Formentera, 07870 Formentera, Spain *Email: alvarezdequevedo@ub.edu ABSTRACT: Reliable estimates of the post-release mortality probability of marine turtles after incidental by-catch are essential for assessing the impact of longline fishing on these species. Large numbers of loggerhead turtles Caretta caretta from rookeries in the northwestern Atlantic Ocean have been by-caught annually in the southwestern Mediterranean Sea since the 1980s, but nothing is known about their post-release mortality probability under natural conditions. Pop-up archival transmitting tags were attached to 26 loggerhead turtles following incidental capture by Spanish longliners. Hooks were not removed, and 40 cm of line was left in place. The post-release mortality probability during the 90 d following release ranged from 0.308 to 0.365, and was independent of hook location. When the post-release mortality probability was combined with previously reported estimates of the mortality probability before hauling, the aggregated by-catch mortality probability ranged from 0.321 to 0.378. Assuming a total annual by-catch of 10656 loggerhead turtles by the Spanish longline fleet operating in the southwestern Mediterranean, by-catch results in 3421 to 4028 turtle deaths annually. This range is equivalent to 8.5-10.1% of the approximately 40000 turtles inhabiting the fishing grounds used by Spanish longliners, most of them from rookeries in the northwestern Atlantic. As a consequence, the accumulated mortality during the oceanic stage is expected to be larger for those loggerhead turtles of Atlantic origin that spend several years in the Mediterranean Sea than for turtles of the same cohort that remain in the Atlantic. For this reason, the Mediterranean can be considered a dead end for loggerhead turtle populations nesting in the Atlantic, although the actual demographic relevance of by-catch mortality of loggerhead turtles in the Mediterranean remains unknown. KEY WORDS: Caretta caretta · By-catch · Mortality · Longlines · Mediterranean · Satellite tags Full text in pdf format See Comment and Reply Comment on this article PreviousNextCite this article as: Àlvarez de Quevedo I, San Félix M, Cardona L (2013) Mortality rates in by-caught loggerhead turtle Caretta caretta in the Mediterranean Sea and implications for the Atlantic populations. Mar Ecol Prog Ser 489:225-234. https://doi.org/10.3354/meps10411 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 489. Online publication date: August 28, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.