Fish Farming Effects on Chemical and Microbial Variables of the Water Column: A Spatio-temporal Study Along the Mediterranean Sea

Hydrobiologia ◽  
2006 ◽  
Vol 563 (1) ◽  
pp. 99-108 ◽  
Author(s):  
P. Pitta ◽  
E. T. Apostolaki ◽  
T. Tsagaraki ◽  
M. Tsapakis ◽  
I. Karakassis
Keyword(s):  
Mediterranean Sea ◽  
Water Column ◽  
Fish Farming ◽  
Temporal Study ◽  
The Mediterranean ◽  
Spatio Temporal

scholarly journals The spatio-temporal distribution of lightning over Israel and the neighboring area and its relation to regional synoptic systems

2011 ◽  
Vol 11 (8) ◽  
pp. 2125-2135 ◽  
Author(s):  
S. Shalev ◽  
H. Saaroni ◽  
T. Izsak ◽  
Y. Yair ◽  
B. Ziv
Keyword(s):  
Spatial Distribution ◽  
Mediterranean Sea ◽  
Temporal Distribution ◽  
Lightning Activity ◽  
Eastern Coast ◽  
Synoptic Situation ◽  
Lightning Flash ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
Neighboring Area

Abstract. The spatio-temporal distribution of lightning flashes over Israel and the neighboring area and its relation to the regional synoptic systems has been studied, based on data obtained from the Israel Lightning Location System (ILLS) operated by the Israel Electric Corporation (IEC). The system detects cloud-to-ground lightning discharges in a range of ~500 km around central Israel (32.5° N, 35° E). The study period was defined for annual activity from August through July, for 5 seasons in the period 2004–2010. The spatial distribution of lightning flash density indicates the highest concentration over the Mediterranean Sea, attributed to the contribution of moisture as well as sensible and latent heat fluxes from the sea surface. Other centers of high density appear along the coastal plain, orographic barriers, especially in northern Israel, and downwind from the metropolitan area of Tel Aviv, Israel. The intra-annual distribution shows an absence of lightning during the summer months (JJA) due to the persistent subsidence over the region. The vast majority of lightning activity occurs during 7 months, October to April. Although over 65 % of the rainfall in Israel is obtained during the winter months (DJF), only 35 % of lightning flashes occur in these months. October is the richest month, with 40 % of total annual flashes. This is attributed both to tropical intrusions, i.e., Red Sea Troughs (RST), which are characterized by intense static instability and convection, and to Cyprus Lows (CLs) arriving from the west. Based on daily study of the spatial distribution of lightning, three patterns have been defined; "land", "maritime" and "hybrid". CLs cause high flash density over the Mediterranean Sea, whereas some of the RST days are typified by flashes over land. The pattern defined "hybrid" is a combination of the other 2 patterns. On CL days, only the maritime pattern was noted, whereas in RST days all 3 patterns were found, including the maritime pattern. It is suggested that atmospheric processes associated with RST produce the land pattern. Hence, the occurrence of a maritime pattern in days identified as RST reflects an "apparent RST". The hybrid pattern was associated with an RST located east of Israel. This synoptic type produced the typical flash maximum over the land, but the upper-level trough together with the onshore winds it induced over the eastern coast of the Mediterranean resulted in lightning activity over the sea as well, similar to that of CLs. It is suggested that the spatial distribution patterns of lightning may better identify the synoptic system responsible, a CL, an "active RST" or an "apparent RST". The electrical activity thus serves as a "fingerprint" for the synoptic situation responsible for its generation.

scholarly journals Is Posidonia oceanica regression a general feature in the Mediterranean Sea?

2013 ◽  
Vol 14 (1) ◽  
pp. 193 ◽  
Author(s):  
M. BONACORSI ◽  
C. PERGENT-MARTINI ◽  
N. BREAND ◽  
G. PERGENT
Keyword(s):  
Mediterranean Sea ◽  
Temporal Evolution ◽  
Posidonia Oceanica ◽  
Aerial Photographs ◽  
Human Pressure ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
Mapping Techniques ◽  
Significant Regression ◽  
Ancient Maps

Over the last few years, a widespread regression of Posidonia oceanica meadows has been noticed in the Mediterranean Sea. However, the magnitude of this decline is still debated. The objectives of this study are (i) to assess the spatio-temporal evolution of Posidonia oceanica around Cap Corse (Corsica) over time comparing available ancient maps (from 1960) with a new (2011) detailed map realized combining different techniques (aerial photographs, SSS, ROV, scuba diving); (ii) evaluate the reliability of ancient maps; (iii) discuss observed regression of the meadows in relation to human pressure along the 110 km of coast. Thus, the comparison with previous data shows that, apart from sites clearly identified with the actual evolution, there is a relative stability of the surfaces occupied by the seagrass Posidonia oceanica. The recorded differences seem more related to changes in mapping techniques. These results confirm that in areas characterized by a moderate anthropogenic impact, the Posidonia oceanica meadow has no significant regression and that the changes due to the evolution of mapping techniques are not negligible. However, others facts should be taken into account before extrapolating to the Mediterranean Sea (e.g. actually mapped surfaces) and assessing the amplitude of the actual regression.

scholarly journals Fleshy Red Algae Mats Influence Their Environment in the Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Neele Schmidt ◽  
Yusuf C. El-Khaled ◽  
Felix I. Roßbach ◽  
Christian Wild
Keyword(s):  
Environmental Factors ◽  
Light Intensity ◽  
Water Temperature ◽  
Mediterranean Sea ◽  
Water Column ◽  
Red Algae ◽  
Water Movement ◽  
Ecosystem Engineer ◽  
Overlying Water ◽  
The Mediterranean

In the Mediterranean Sea, the fleshy red alga Phyllophora crispa forms dense mats of up to 15 cm thickness, mainly located on rocky substrates in water depths below 20 m. Because of the observed density of these mats and some first observations, we hypothesize that P. crispa is a yet undescribed ecosystem engineer that provides a multitude of ecological niches for associated organisms along small-scale environmental gradients. Therefore, we conducted an in-situ pilot study in the Western Mediterranean Sea to assess potential influence of the algae mats on the key environmental factors water movement, temperature and light intensity. We comparatively and simultaneously measured in P. crispa mats, in neighboring Posidonia oceanica seagrass meadows, on neighboring bare rocky substrates without algae mats, and in the directly overlying water column. We used several underwater logging sensors and gypsum clod cards. Findings revealed that P. crispa significantly reduced water movement by 41% compared to the overlying water column, whereas water movement was not affected by P. oceanica meadows and bare rocky substrates. Surprisingly, P. crispa increased the water temperature by 0.3°C relative to the water column, while the water temperature in P. oceanica and on bare rocky substrates was reduced by 0.5°C. Light intensity inside the red algae mats was reduced significantly by 69% compared to the water column. This was similar to measured light reduction of 77% by P. oceanica. These findings highlight the strong influence of the dense red algae mats on some key environmental factors. Their influence is obviously similar or even higher than for the well-known seagrass ecosystem engineer. This may be a factor that facilitates associated biodiversity similarly as described for P. oceanica.

scholarly journals Large-scale spatio-temporal monitoring highlights hotspots of demersal fish diversity in the Mediterranean Sea

2015 ◽  
Vol 130 ◽  
pp. 65-74 ◽  
Author(s):  
Victoria Granger ◽  
Jean-Marc Fromentin ◽  
Nicolas Bez ◽  
Giulio Relini ◽  
Christine N. Meynard ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Large Scale ◽  
Demersal Fish ◽  
Fish Diversity ◽  
The Mediterranean ◽  
Spatio Temporal

scholarly journals Sinking microplastics in the water column: simulations in the Mediterranean Sea

Ocean Science ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 431-453
Author(s):  
Rebeca de la Fuente ◽  
Gábor Drótos ◽  
Emilio Hernández-García ◽  
Cristóbal López ◽  
Erik van Sebille
Keyword(s):  
Vertical Distribution ◽  
Mediterranean Sea ◽  
Water Column ◽  
Large Scale ◽  
Circulation Model ◽  
Small Scale ◽  
The Mediterranean ◽  
Scale Turbulence ◽  
Non Gaussian ◽  
The Vertical Distribution

Abstract. We study the vertical dispersion and distribution of negatively buoyant rigid microplastics within a realistic circulation model of the Mediterranean sea. We first propose an equation describing their idealized dynamics. In that framework, we evaluate the importance of some relevant physical effects (inertia, Coriolis force, small-scale turbulence and variable seawater density), and we bound the relative error of simplifying the dynamics to a constant sinking velocity added to a large-scale velocity field. We then calculate the amount and vertical distribution of microplastic particles on the water column of the open ocean if their release from the sea surface is continuous at rates compatible with observations in the Mediterranean. The vertical distribution is found to be almost uniform with depth for the majority of our parameter range. Transient distributions from flash releases reveal a non-Gaussian character of the dispersion and various diffusion laws, both normal and anomalous. The origin of these behaviors is explored in terms of horizontal and vertical flow organization.

DOM DYNAMICS IN THE MEDITERRANEAN SEA. Can a new fluorescence SENSOR contribute to its understanding?

2020 ◽  
Author(s):  
Simona Retelletti Brogi ◽  
Marta Furia ◽  
Giancarlo Bachi ◽  
Vanessa Cardin ◽  
Giuseppe Civitarese ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Water Column ◽  
Fluorescence Sensor ◽  
Global Ocean ◽  
Intermediate Water ◽  
Physical Processes ◽  
Open Sea ◽  
The Mediterranean

<p>The Mediterranean Sea (Med Sea) can be considered as a natural laboratory for the study of dissolved organic matter (DOM) dynamics. Despite its small size, it is characterized by the same physical processes and dissolved organic carbon (DOC) concentration and distribution as the global ocean. The Med Sea deep water DOC pool is however older than the Atlantic one and differences in the microbial loop and in DOM dynamics have been observed between the eastern (EMED) and western (WMED) basins. Fluorescence is a fast, cheap and highly sensitive tool to study DOM dynamics, it can therefor give useful information about the main processes affecting DOM distribution.</p><p>The main aims of this study were: (i) to investigate DOM dynamics in both Med Sea basins, in relation to the physical processes (e.g. vertical stratification, irradiation); and (ii) to validate the use of a new fluorescence sensor, developed in the framework of the SENSOR project (POR FESR, Tuscany Region), for the rapid, in-situ measurements of open-sea fluorescent DOM (FDOM). DOM dynamics was investigated by measuring dissolved organic carbon (DOC) and the fluorescence of FDOM. Samples were collected from surface to bottom in 26 stations during the trans-Mediterranean cruise “MSM72”, carried out on board the R/V MARIA S.MERIAN (Institut für Meereskunde der Universität Hamburg). The stations cover both the EMED and the WMED, from Gibraltar to the Crete Island.</p><p>Six fluorescent components were identified by applying the parallel factorial analysis (PARAFAC) to the measured excitation-emission matrices (EEMs). Two components were identified as marine humic-like, two as terrestrial humic-like, one as protein-like and one as polycyclic aromatic hydrocarbon-like (PAH-like).</p><p>Temperature and salinity increased moving from the WMED to the EMED. A surface minimum in salinity, was observed in the WMED, indicating the occurrence of the Atlantic Water (AW), whereas the presence of the Levantine Intermediate Water (LIW) was observed south of Crete. The vertical distribution of both DOC and humic-like FDOM was strongly affected by the water masses circulation and water column stratification. In the upper 200 m, DOC markedly increased from 50 to 80 μM moving eastward, likewise the protein-like component dominates the upper layer and increased moving from Gibraltar to Crete. In contrast, the humic-like components showed a minimum in the surface layer, and a decreasing moving eastward, probably due to photobleaching. The PAH-like component showed its maximum in correspondence with the areas characterized by intensive naval traffic. The accumulation of DOC, observed in the EMED, could be explained by a change in DOM quality, supported by the differences in FDOM.</p><p>In 2 selected stations, the fluorescence of humic-like and protein-like compounds was also measured along the water column by using the new fluorescence sensor and compared with PARAFAC results, in order to evaluate its performance for open sea waters.</p>

scholarly journals Ocean Currents Reconstruction from a Combination of Altimeter and Ocean Colour Data: A Feasibility Study

2021 ◽  
Vol 13 (12) ◽  
pp. 2389
Author(s):  
Daniele Ciani ◽  
Elodie Charles ◽  
Bruno Buongiorno Buongiorno Nardelli ◽  
Marie-Hélène Rio ◽  
Rosalia Santoleri
Keyword(s):  
Mediterranean Sea ◽  
Time Window ◽  
Ocean Surface ◽  
Global Scale ◽  
Biogeochemical Model ◽  
Surface Currents ◽  
Ocean Surface Currents ◽  
Marine Surface ◽  
The Mediterranean ◽  
Spatio Temporal

Measuring the ocean surface currents at high spatio-temporal resolutions is crucial for scientific and socio-economic applications. Since the early 1990s, the synoptic and global-scale monitoring of the ocean surface currents has been provided by constellations of radar altimeters. By construction, altimeter constellations provide only the geostrophic component of the marine surface currents. In addition, given the effective spatial-temporal resolution of the altimeter-derived products (O (100 km) and O (10 days), respectively), only the largest ocean mesoscale features can be resolved. In order to enhance the altimeter system capabilities, we propose a synergistic use of high resolution sea surface Chlorophyll observations (Chl) and altimeter-derived currents’ estimates. The study is focused on the Mediterranean Sea, where the most energetic signals are found at spatio-temporal scales up to 10 km and a few days. The proposed method allows for inferring the marine surface currents from the evolution of the Chl field, relying on altimeter-derived currents as a first-guess estimate. The feasibility of this approach is tested through an Observing System Simulation Experiment, starting from biogeochemical model outputs distributed by the European Copernicus Marine Service. Statistical analyses based on the 2017 daily data showed that our approach can improve the altimeter-derived currents accuracy up to 50%, also enhancing their effective spatial resolution up to 30 km. Moreover, the retrieved currents exhibit larger temporal variability than the altimeter estimates over annual to weekly timescales. Our method is mainly limited to areas/time periods where/when Chl gradients are larger and are modulated by the marine currents’ advection. Its application is thus more efficient when the surface Chl evolution is not dominated by the biological activity, mostly occurring in the mid-February to mid-March time window in the Mediterranean Sea. Preliminary tests on the method applicability to satellite-derived data are also presented and discussed.

Sign in / Sign up

Export Citation Format

Share Document