scholarly journals Silica cycling in the ultra-oligotrophic eastern Mediterranean Sea

2014 ◽  
Vol 11 (15) ◽  
pp. 4211-4223 ◽  
Author(s):  
M. D. Krom ◽  
N. Kress ◽  
K. Fanning
Keyword(s):  
Mediterranean Sea ◽  
Silicic Acid ◽  
Deep Water ◽  
Phytoplankton Bloom ◽  
Eastern Mediterranean ◽  
Water Concentration ◽  
Western Mediterranean ◽  
Eastern Mediterranean Sea ◽  
Western Mediterranean Sea

Abstract. Although silica is a key plant nutrient, there have been few studies aimed at understanding the Si cycle in the eastern Mediterranean Sea (EMS). Here we use a combination of new measurements and literature values to explain the silicic acid distribution across the basin and to calculate a silica budget to identify the key controlling processes. The surface water concentration of ∼1 μM, which is unchanging seasonally across the basin, was due to the inflow of western Mediterranean Sea (WMS) water at the Straits of Sicily. It does not change seasonally because there is only a sparse population of diatoms due to the low nutrient (N and P) supply to the photic zone in the EMS. The concentration of silicic acid in the deep water of the western Ionian Sea (6.3 μM) close to the S Adriatic are an of formation was due to the preformed silicic acid (3 μM) plus biogenic silica (BSi) from the dissolution of diatoms from the winter phytoplankton bloom (3.2 μM). The increase of 4.4 μM across the deep water of the EMS was due to silicic acid formed from in situ diagenetic weathering of aluminosilicate minerals fluxing out of the sediment. The major inputs to the EMS are silicic acid and BSi inflowing from the western Mediterranean (121 × 109 mol Si yr−1 silicic acid and 16 × 109 mol Si yr−1 BSi), silicic acid fluxing from the sediment (54 × 109 mol Si yr−1) and riverine (27 × 109 mol Si yr−1) and subterranean groundwater (9.7 × 109 mol Si yr−1) inputs, with only a minor direct input from dissolution of dust in the water column (1 × 109 mol Si yr−1). This budget shows the importance of rapidly dissolving BSi and in situ weathering of aluminosilicate minerals as sources of silica to balance the net export of silicic acid at the Straits of Sicily. Future measurements to improve the accuracy of this preliminary budget have been identified.

scholarly journals Silica cycling in the ultra-oligotrophic Eastern Mediterranean Sea

2014 ◽  
Vol 11 (3) ◽  
pp. 4301-4334
Author(s):  
M. D. Krom ◽  
N. Kress ◽  
K. Fanning
Keyword(s):  
Mediterranean Sea ◽  
Silicic Acid ◽  
Deep Water ◽  
Phytoplankton Bloom ◽  
Eastern Mediterranean ◽  
Water Concentration ◽  
Western Mediterranean ◽  
Eastern Mediterranean Sea ◽  
Silicate Minerals

Abstract. Although silica is a key plant nutrient there have been few studies aimed at understanding the Si cycle in the Eastern Mediterranean Sea (EMS). Here we use a combination of new measurements and literature values to explain the silicic acid distribution across the basin and to calculate a silica budget to identify the key controlling processes. The surface water concentration of ~ 1 μM, which is unchanging seasonally across the basin was due to the inflow of Western Mediterranean Sea (WMS) water at the Straits of Sicily. It does not change seasonally because there is only a sparse population of diatoms due to the low nutrient (N and P) supply to the photic zone in the EMS. The concentration of silicic acid in the deep water of the western Ionian Sea (6.3 μM) close to the S. Adriatic area of formation was due to the preformed silicic acid (3 μM) plus biogenic silica (BSi) from the dissolution of diatoms from the winter phytoplankton bloom (3.2 μM). The increase of 4.4 μM across the deep water of the EMS was due to silicic acid formed from in-situ diagenetic weathering of alumina-silicate minerals fluxing out of the sediment. The major inputs to the EMS are silicic acid and BSi inflowing from the western Mediterranean (121 × 109 mol Si year−1 silicic acid and 16 × 109 mol Si year−1 BSi), silicic acid fluxing from the sediment (54 × 109 mol Si year−1), riverine (27 × 109 mol Si year−1) and subterranean ground water (9.7 × 109 mol Si year−1) inputs, with only a minor direct input from dissolution of dust in the water column (1 × 109 mol Si year−1). This budget shows the importance of rapidly dissolving BSi and in-situ weathering of alumino-silicate minerals as sources of silica to balance the net export of silicic acid at the Straits of Sicily. Future measurements to improve the accuracy of this preliminary budget have been identified.

scholarly journals Comparison of Hydrocarbon-Degrading Consortia from Surface and Deep Waters of the Eastern Mediterranean Sea: Characterization and Degradation Potential

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2246
Author(s):  
Georgia Charalampous ◽  
Efsevia Fragkou ◽  
Konstantinos A. Kormas ◽  
Alexandre B. De Menezes ◽  
Paraskevi N. Polymenakou ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Oil Spills ◽  
Eastern Mediterranean ◽  
Sole Source ◽  
Eastern Mediterranean Sea ◽  
Deep Waters ◽  
Degradation Rates ◽  
Polycyclic Aromatic ◽  
Set Up

The diversity and degradation capacity of hydrocarbon-degrading consortia from surface and deep waters of the Eastern Mediterranean Sea were studied in time-series experiments. Microcosms were set up in ONR7a medium at in situ temperatures of 25 °C and 14 °C for the Surface and Deep consortia, respectively, and crude oil as the sole source of carbon. The Deep consortium was additionally investigated at 25 °C to allow the direct comparison of the degradation rates to the Surface consortium. In total, ~50% of the alkanes and ~15% of the polycyclic aromatic hydrocarbons were degraded in all treatments by Day 24. Approximately ~95% of the total biodegradation by the Deep consortium took place within 6 days regardless of temperature, whereas comparable levels of degradation were reached on Day 12 by the Surface consortium. Both consortia were dominated by well-known hydrocarbon-degrading taxa. Temperature played a significant role in shaping the Deep consortia communities with Pseudomonas and Pseudoalteromonas dominating at 25 °C and Alcanivorax at 14 °C. Overall, the Deep consortium showed a higher efficiency for hydrocarbon degradation within the first week following contamination, which is critical in the case of oil spills, and thus merits further investigation for its exploitation in bioremediation technologies tailored to the Eastern Mediterranean Sea.

scholarly journals Parasites of the head of Scomber colias (Osteichthyes: Scombridae) from the western Mediterranean Sea

2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Salvatore Mele ◽  
Maria Pennino ◽  
Maria Piras ◽  
José Bellido ◽  
Giovanni Garippa ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Parasite Fauna ◽  
Point Of View ◽  
Published Data ◽  
Multivariate Techniques ◽  
Western Mediterranean Sea ◽  
Scomber Colias ◽  
Non Parametric

AbstractThe metazoan parasite assemblage of the head of 30 specimens of the Atlantic chub mackerel (Scomber colias) from the western Mediterranean Sea was analysed. Eight species of parasites were found, four mazocraeid monogeneans: Grubea cochlear (prevalence = 10%), Kuhnia scombercolias (59%), K. scombri (52%), Pseudokuhnia minor (86%); three didymozoid trematodes: Nematobothrium cf. faciale (21%), N. filiforme (41%), N. scombri (7%); and one laerneopodid copepod: Clavelissa scombri (7%). Results were compared with previously published data from 14 localities of the eastern Mediterranean Sea and the Atlantic Ocean, using non-parametric univariate and multivariate analyses, and the whole parasite fauna of S. colias was compared with that of the congeners (S. australasicus, S. japonicus and S. scombrus). Parasites showed to reflect the biogeographical and phylogenetic history of host. From a methodological point of view, the use of both non-parametric univariate and multivariate techniques proved to be effective tools to detect dissimilarities between parasite assemblages.

scholarly journals Will deep water formation collapse in the North Western Mediterranean Sea by the end of the 21st century?

2021 ◽  
Author(s):  
Iván Manuel Parras Berrocal ◽  
Ruben Vazquez ◽  
William David CabosNarvaez ◽  
Dimitry Sein ◽  
Oscar Alvarez Esteban ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
21St Century ◽  
Deep Water ◽  
Western Mediterranean ◽  
Deep Water Formation ◽  
The North ◽  
Western Mediterranean Sea ◽  
Water Formation ◽  
North Western

scholarly journals Impact of moderately energetic fine-scale dynamics on the phytoplankton community structure in the western Mediterranean Sea

2021 ◽  
Vol 18 (24) ◽  
pp. 6455-6477
Author(s):  
Roxane Tzortzis ◽  
Andrea M. Doglioli ◽  
Stéphanie Barrillon ◽  
Anne A. Petrenko ◽  
Francesco d'Ovidio ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Phytoplankton Community ◽  
World Ocean ◽  
Western Mediterranean ◽  
Water Masses ◽  
Ocean Dynamics ◽  
Western Boundary ◽  
Fine Scale ◽  
Western Mediterranean Sea

Abstract. Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only a few in situ-based studies at fine scales have been performed, and most of them concern western boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea (WMS), in the region south of the Balearic Islands. Taking advantage of near-real-time satellite information, we defined a sampling strategy in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the research vessel, on a towed vehicle and on an ocean glider were used to sample physical and biogeochemical variables at a high spatial resolution. Particular attention was given to adapting the sampling route in order to estimate the vertical velocities in the frontal area also. This strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different concentrations of chlorophyll a and O2. Here, we focus on moderately energetic fronts induced by fine-scale circulation. Moreover, we explore physical–biological coupling in an oligotrophic region. Our results show that the fronts induced by the fine-scale circulation, even if weaker than the fronts occurring in energetic and nutrient-rich boundary current systems, maintain nevertheless a strong structuring effect on the phytoplankton community by segregating different groups at the surface. Since oligotrophic and moderately energetic regions are representative of a very large part of the world ocean, our results may have global significance when extrapolated.

scholarly journals On the Circulation and Thermohaline Properties of the Eastern Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Milena Menna ◽  
Riccardo Gerin ◽  
Giulio Notarstefano ◽  
Elena Mauri ◽  
Antonio Bussani ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Mixed Layer ◽  
Eastern Mediterranean ◽  
Mixed Layer Depth ◽  
Eastern Mediterranean Sea ◽  
Salt Fingers ◽  
Main Circulation ◽  
Satellite Altimetry Data

The circulation of the Eastern Mediterranean Sea is characterized by numerous recurrent or permanent anticyclonic structures, which modulate the pathway of the main currents and the exchange of the water masses in the basin. This work aims to describe the main circulation structures and thermohaline properties of the Eastern Mediterranean with particular focus on two anticyclones, the Pelops and the Cyprus gyres, using in-situ (drifters and Argo floats) and satellite (altimetry) data. The Pelops gyre is involved in the circulation and exchange of Levantine origin surface and intermediate waters and in their flow toward the Ionian and the Adriatic Sea. The Cyprus Gyre presents a marked interannual variability related to the presence/absence of waters of Atlantic origin in its interior. These anticyclones are characterized by double diffusive instability and winter mixing phenomena driven by salty surface waters of Levantine origin. Conditions for the salt finger regime occur steadily and dominantly within the Eastern Mediterranean anticyclones. The winter mixing is usually observed in December–January, characterized by instability conditions in the water column, a gradual deepening of the mixed layer depth and the consequent downward doming of the isohalines. The mixing generally involves the first 200 m of the water column (but occasionally can affect also the intermediate layer) forming a water mass with well-defined thermohaline characteristics. Conditions for salt fingers also occur during mixing events in the layer below the mixed layer.

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