scholarly journals Seasonal and diel changes in the structure of a crustacean decapod assemblage associated to a shallow Cymodocea nodosa meadow in northern Tunisia (Mediterranean Sea). An overview of the Mediterranean decapod taxocoenoses.

2013 ◽  
Vol 15 (1) ◽  
pp. 59 ◽  
Author(s):  
A. DAOULATI ◽  
M. ANTIT ◽  
A. AZZOUNA ◽  
J. E. GARCIA RASO
Keyword(s):  
Mediterranean Sea ◽  
Reproductive Strategies ◽  
Time Lag ◽  
Early Summer ◽  
Cymodocea Nodosa ◽  
Total Abundance ◽  
Northern Tunisia ◽  
Significant Relationships ◽  
The Mediterranean ◽  
Summer Minimum

A study on the decapod assemblage inhabiting a shallow meadow of Cymodocea nodosa from the bay of La Goulette (Tunisia) was carried from February 2009 to February 2010. Monthly samples (with replicates) were taken in the morning and at night, with a small Agassiz trawl. In total 11699 specimens belonging to 41 species were caught. Significant day-night and seasonal changes are mainly related to movements (feeding) and recruitments. Higher abundance and richness were reported at night. Analyses rendered no significant relationships between the plant phenology and abundances and richness; neither between the total abundance and temperature, but significant correlations with a time lag of 3 - 4 months between these factors exist, which could be related with hatching and larval development period. The nocturnal and diurnal values in the diversity and equitability indexes are quite similar along the year (peaks in spring - early summer, minimum in autumn - early winter). This pattern is mainly due to the strong dominance of a few species, with maximum abundances during their recruitment events, whose seasonal and day-night changes have been determined. Besides, an overview of the decapods assemblage associated to this seagrass for the Mediterranean Sea has been carried out. The species can be divided into two groups (linked to the leaves and to the sediment). The differences in species composition between areas must be related to different sampling methodologies, feeding and reproductive strategies, but also to the layout and influence of the surrounding habitats.

scholarly journals Relationships between cytometric characteristics of high and low nucleic-acid bacterioplankton cells, bacterial production and environmental parameters along a longitudinal gradient across the Mediterranean Sea

2010 ◽  
Vol 7 (6) ◽  
pp. 8245-8279 ◽  
Author(s):  
F. Van Wambeke ◽  
P. Catala ◽  
P. Lebaron
Keyword(s):  
Nucleic Acid ◽  
Mediterranean Sea ◽  
Bacterial Production ◽  
Environmental Parameters ◽  
Early Summer ◽  
Bacterial Cells ◽  
Green Fluorescence ◽  
Flow Cytometric ◽  
Chlorophyll Distribution ◽  
The Mediterranean

Abstract. Heterotrophic bacterioplankton abundance and production were determined along vertical (down to bathypelagic layers) and latitudinal (from 4.9° E to 32.7° E) gradients across the Mediterranean Sea in early summer 2008. Abundance and flow cytometric characteristics (green fluorescence and side scatter signals) of high nucleic acid (HNA) and low nucleic acid (LNA) bacterial cells were investigated using flow cytometry. Contrarily to what is generally observed, the percentage of total bacteria represented by HNA cells (%HNA, range 30–69%) decreased with increased bacterial production (range 0.15–44 ng C l−1 h−1) although this negative relation was poorly explained (log-log regression r2=0.19). The %HNA as well as the mean side scatter of this group increased significantly with depth in the meso and bathypelagic layers. Our results demonstrated that vertical stratification with regard to chlorophyll distribution above, within or below the deep chlorophyll maximum plays an important role in influencing the distribution of cells, and in the relationships between the flow cytometric parameters and environmental variables such as chlorophyll a or bacterial production. Relationships between green fluorescence and side scatter of both HNA and LNA cells depended largely on chlorophyll distribution over the water column, suggesting that the dynamic link between HNA and LNA cells differs vertically.

scholarly journals Patterns in planktonic metabolism in the Mediterranean Sea

2009 ◽  
Vol 6 (12) ◽  
pp. 3081-3089 ◽  
Author(s):  
A. Regaudie-de-Gioux ◽  
R. Vaquer-Sunyer ◽  
C. M. Duarte
Keyword(s):  
Mediterranean Sea ◽  
Gross Primary Production ◽  
Western Mediterranean ◽  
Early Summer ◽  
Late Spring ◽  
Community Respiration ◽  
Net Community Production ◽  
R Ratio ◽  
The Mediterranean ◽  
Community Production

Abstract. Planktonic gross community production (GPP), net community production (NCP) and community respiration (CR) across the Mediterranean Sea was examined in two cruises, Thresholds 2006 and 2007, each crossing the Mediterranean from West to East to test for consistent variation along this longitudinal gradient in late spring to early summer. GPP averaged 2.4±0.4 mmol O2 m−3 d−1, CR averaged 3.8±0.5 mmol O2 m−3 d−1, and NCP averaged – 0.8±0.6 mmol O2 m−3 d−1 across the studied sections, indicative of a tendency for a net heterotrophic metabolism in late spring to early summer, prevalent across studied sections of the Mediterranean Sea as reflected in 70% of negative NCP estimates. The median P/R ratio was 0.6, also indicating a strong prevalence of heterotrophic communities (P/R<1) along the studied sections of the Mediterranean Sea. The communities tended to be net heterotrophic (i.e. P/R<1) at GPP less than 2.8 mmol O2 m−3 d−1. The Western Mediterranean tended to support a higher gross primary production and community respiration than the Eastern basin did, but these differences were not statistically significant (t-test, p>0.05). The net heterotrophy of the studied sections of the Mediterranean Sea indicates that allochthonous carbon should be important to subsidise planktonic metabolism during the late spring.

scholarly journals Mediterranean basin-wide correlations between Saharan dust deposition and ocean chlorophyll concentration

2012 ◽  
Vol 9 (7) ◽  
pp. 8611-8639 ◽  
Author(s):  
R. Gallisai ◽  
F. Peters ◽  
S. Basart ◽  
J. M. Baldasano
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Chlorophyll Concentration ◽  
Time Lag ◽  
Saharan Dust ◽  
Phytoplankton Production ◽  
Dust Deposition ◽  
Central Mediterranean ◽  
Concentration Data ◽  
The Mediterranean

Abstract. The fertilizing potential of atmospheric deposition on ocean production in the Mediterranean is a matter of debate. In this study, eight years (from 2000 to 2007) of weekly chlorophyll concentration data derived from SeaWiFS satellite observations and dust deposition data provided by the BSC-DREAM8b model are investigated in a basin-wide scale in the Mediterranean Sea to describe the geographical distribution and dynamics of both variables and to find potential relationships between them. In all analyses the largest positive cross correlation values are found with a time lag of 0 8-d periods. The coupling between annual cycles of chlorophyll and dust deposition may on average explain an 11.5% in chlorophyll variation in a large part of the Mediterranean. The Eastern Mediterranean shows the largest annual correlations, while the responsiveness to large events is small. The contrary is true for the Western and Northwestern Mediterranean where, if anything, only large events may add to the chlorophyll variability. The Central Mediterranean shows the highest responsiveness of chlorophyll to mineral dust deposition with annual contributions from seasonal variability as well as stimulations owing to large events. These results highlight the importance of dust deposition from African and Middle East origin in the potential stimulation of phytoplankton production in the nutrient depleted surface layers of the Mediterranean Sea.

scholarly journals Impact of ocean–atmosphere coupling on future projectionof Medicanes in the Mediterranean sea

2021 ◽  
Author(s):  
Jesús Gutiérrez-Fernández ◽  
Juan Jesús González-Alemán ◽  
Alba de la Vara ◽  
William Cabos ◽  
Dmitry V. Sein ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Atmospheric Stability ◽  
Coupled Model ◽  
Extratropical Cyclones ◽  
Climate Projections ◽  
Adaptation To Climate Change ◽  
Coupled Models ◽  
Climate Simulations ◽  
The Mediterranean ◽  
Summer Minimum

&lt;p&gt;The Mediterranean basin is one of the main cyclogenetic regions in the world. This is likely due to the orographic conditions, as well as the thermodynamic&lt;br&gt;characteristics found over the Mediterranean. Among the large amount of cyclones that develop in this area, cyclones with tropical characteristics&amp;#160;called medicanes (&amp;#8220;Mediterranean Hurricanes&amp;#8221;) eventually develop in the Mediterranean Sea. They have large harmful potential and a correct simulation of their evolution in climate projections is important for an adequate adaptation to climate change. Different studies suggest that ocean&amp;#8211;atmosphere coupled models provide a better representation of medicanes, especially in terms of intensity and frequency. In this work, we use the regionally coupled model ROM and its stand-alone atmospheric component (REMO) that in this work is used as uncoupled model to study how air-sea interactions affect the evolution of medicanes in future climate projections. We find that under the RCP8.5 scenario our climate simulations show an overall frequency decrease which is more pronounced in the coupled than in the uncoupled configuration, whereas the intensity displays a different behaviour depending on the coupling. These changes could be explained due to the decrease in the number of extratropical cyclones and the increase of atmospheric stability conditions. In the coupled run, the relative frequency of higher-intensity medicanes increases, but this is not found in the uncoupled simulation. Also, this study indicates that the coupled model simulates better the summer minimum in the occurrence of medicanes, avoiding the reproduction of unrealistically intense events that can be found in summer in the uncoupled model.&lt;/p&gt;

scholarly journals Time lags in reporting of biological invasions: the case of Mediterranean Sea

2019 ◽  
Vol 20 (2) ◽  
pp. 469 ◽  
Author(s):  
ARGYRO ZENETOS ◽  
EIRINI GRATSIA ◽  
ANA-CRISTINA CARDOSO ◽  
KONSTANTINOS TSIAMIS
Keyword(s):  
Biological Invasions ◽  
Mediterranean Sea ◽  
Time Lag ◽  
Taxonomic Group ◽  
Time Lags ◽  
Indigenous Species ◽  
Prevention Measures ◽  
The Mediterranean ◽  
Taxonomic Groups ◽  
Non Indigenous Species

Time lags in non-indigenous species (NIS) reporting can create uncertainty in the analysis of NIS introduction rates, which can lead to inadequate actions, prevention measures and their evaluation. The present study aims to highlight time lags in marine NIS reporting in the Mediterranean Sea, i.e.: the time that mediates from the detection of a new NIS in the Mediterranean Sea until its publication. Our results revealed that the time lag in NIS reporting in the Mediterranean Sea has been considerably decreased during the last decades. There is also a noticeable difference in the time lag of reporting NIS in association with the taxonomic group of the species. Fish have generally shorter time lags in their reporting when compared with other taxonomic groups (e.g. macrophytes, Annelida, Bryozoa). Considering the widespread concern on marine introductions, it is essential to recognize the importance of taking into account time lags of reporting NIS that skew introduction patterns of marine NIS, permitting thus more accurate management assessments.

scholarly journals Flow cytometric assessment of specific leucine incorporation in the open Mediterranean

2011 ◽  
Vol 8 (2) ◽  
pp. 253-265 ◽  
Author(s):  
A. Talarmin ◽  
F. Van Wambeke ◽  
P. Catala ◽  
C. Courties ◽  
P. Lebaron
Keyword(s):  
Nucleic Acid ◽  
Mediterranean Sea ◽  
Early Summer ◽  
Biogenic Elements ◽  
Leucine Incorporation ◽  
Surface Layers ◽  
Flow Cytometric ◽  
Dissolved Organic Compounds ◽  
Heterotrophic Prokaryotes ◽  
The Mediterranean

Abstract. The surface of the Mediterranean Sea is a low-phosphate-low-chlorophyll marine area where marine heterotrophic prokaryotes significantly contribute to the biogeochemical cycles of all biogenic elements such as carbon, notably through the mineralization of dissolved organic compounds. Cell-specific leucine incorporation rates were determined in early summer in the open stratified Mediterranean Sea. The bulk leucine incorporation rate was on average 5 ± 4 pmol leu l−1 h−1 (n=30). Cell-specific 3H-leucine incorporation rates were assayed using flow cytometry coupled to cell sorting. Heterotrophic prokaryotes (Hprok) were divided into cytometric groups according to their side scatter and green fluorescence properties: high nucleic acid containing cells (HNA) with high scatter (HNA-hs) and low scatter (HNA-ls) and low nucleic acid containing cells (LNA). Cell-specific leucine incorporation rates of these cytometric groups ranged from 2 to 54, 0.9 to 11, and 1 to 12 × 10-21 mol cell−1 h−1, respectively. LNA cells represented 45 to 63% of the Hprok abundance, and significantly contributed to the bulk leucine incorporation rates, from 12 to 43%. HNA/LNA ratios of cell-specific leucine incorporation were on average 2.0 ± 0.7 (n=30). In surface layers (from 0 m down to the deep chlorophyll depth, DCM), cell-specific rates of HNA-hs were elevated (7 and 13 times greater than LNA and HNA-ls, respectively). Nevertheless, on average HNA-hs (26%) and LNA (27%) equally contributed to the bulk leucine incorporation in these layers. Prochlorococcus cells were easily sorted near the DCM and displayed cell-specific leucine incorporation rates ranging from 3 to 55 × 10-21 mol leu cell−1 h−1, i.e. as high as HNA-hs'. These sorted groups could therefore be defined as key-players in the process of leucine incorporation into proteins. The mixotrophic features of certain photosynthetic prokaryotes and the high contribution of LNA cells to leucine incorporation within the microbial communities of the Mediterranean could be reinforced.

scholarly journals Characterization of the bio-optical anomaly and diurnal variability of the particulate matter, as seen from the scattering and backscattering coefficients, in ultra-oligotrophic eddies of the Mediterranean Sea

2011 ◽  
Vol 8 (4) ◽  
pp. 7859-7919 ◽  
Author(s):  
H. Loisel ◽  
V. Vantrepotte ◽  
K. Norkvist ◽  
X. Mériaux ◽  
M. Kheireddine ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Mediterranean Sea ◽  
Early Summer ◽  
Global Ocean ◽  
Optical Parameters ◽  
Diel Variation ◽  
Backscattering Coefficient ◽  
Diurnal Variability ◽  
The Mean ◽  
The Mediterranean

Abstract. The variability of the inherent optical properties is investigated in the ultra-oligotrophic waters of the Mediterranean Sea sampled during the BOUM experiment performed during the early summer 2008. Bio-optical relationships found for the ultra-oligotrophic waters of the three anticyclonic gyres sampled significantly depart from the mean standard relationships provided for the global ocean, confirming the particular character of these Mediterranean waters. These optical anomalies are diversely related to the specific biological and environmental conditions occurring in the studied ecosystem. Specifically, the surface specific phytoplankton absorption coefficient exhibits values lower than those expected from the general relationships mainly in relation with a high contribution of relatively large sized phytoplankton. Conversely, the particulate backscattering coefficient, bbp, values are much higher than the mean standard values for a given chlorophyll-a concentration, TChl-a. This feature can presumably be related to the relevant influence of highly refractive submicrometer particles of Saharan origin in the surface layer of the water column. The present measurements also show that the Mediterranean Sea is greener than TChl-a alone indicates, as already stressed in previous studies. This color anomaly is partly explained by the estimated colored dissolved organic matter and submicrometer particles absorption coefficients, and to a greater extent by the high bbp/TChl-a values assuming that these particles backscatter light similarly in the green and blue parts of the visible spectrum. The diel variation of both the particulate matter attenuation and backscattering coefficients were also investigated specifically. Despite some differences in the timing and the magnitude of the daily oscillations found for these optical parameters, potential for the backscattering coefficient daily oscillation to be used, similarly to that for the attenuation coefficient, as a proxy for estimating carbon community production budget has been highlighted for the first time. This result is particularly relevant for present and future geostationary spatial ocean color missions.

scholarly journals Characterization of the bio-optical anomaly and diurnal variability of particulate matter, as seen from scattering and backscattering coefficients, in ultra-oligotrophic eddies of the Mediterranean Sea

2011 ◽  
Vol 8 (11) ◽  
pp. 3295-3317 ◽  
Author(s):  
H. Loisel ◽  
V. Vantrepotte ◽  
K. Norkvist ◽  
X. Mériaux ◽  
M. Kheireddine ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Mediterranean Sea ◽  
Early Summer ◽  
Global Ocean ◽  
Optical Parameters ◽  
Diel Variation ◽  
Backscattering Coefficient ◽  
Diurnal Variability ◽  
The Mean ◽  
The Mediterranean

Abstract. The variability of inherent optical properties is investigated in the ultra-oligotrophic waters of the Mediterranean Sea sampled during the BOUM experiment performed during early summer 2008. Bio-optical relationships found for ultra-oligotrophic waters of the three anticyclonic gyres sampled significantly depart from the mean standard relationships provided for the global ocean, confirming the peculiar character of these Mediterranean waters. These optical anomalies are diversely related to the specific biological and environmental conditions occurring in the studied ecosystem. Specifically, the surface specific phytoplankton absorption coefficient exhibits values lower than those expected from the general relationships mainly in relation with a high contribution of relatively large sized phytoplankton. Conversely, the particulate backscattering coefficient, bbp, values are much higher than the mean standard values for a given chlorophyll-a concentration, TChl-a. This feature can presumably be related to the relevant influence of highly refractive submicrometer particles of Saharan origin in the surface layer of the water column. The present measurements also show that the Mediterranean Sea is greener than TChl-a alone indicates, as already stressed in previous studies. This color anomaly is partly explained by the estimated colored dissolved organic matter and submicrometer particles absorption coefficients, and to a greater extent by the high bbp/TChl-a values assuming that these particles backscatter light similarly in the green and blue parts of the visible spectrum. The diel variation of both the particulate matter attenuation and backscattering coefficients were also investigated specifically. Despite some differences in the timing and the magnitude of the daily oscillations found for these optical parameters, potential for the backscattering coefficient daily oscillation to be used, similarly to that for the attenuation coefficient, as a proxy for estimating carbon community production budget has been highlighted for the first time. This result is particularly relevant for present and future geostationary spatial ocean color missions.

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