scholarly journals Bio-optical characterization of subsurface chlorophyll maxima in the Mediterranean Sea from a Biogeochemical-Argo float database

2018 ◽  
Author(s):  
Marie Barbieux ◽  
Julia Uitz ◽  
Bernard Gentili ◽  
Orens Pasqueron de Fommervault ◽  
Alexandre Mignot ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Chlorophyll Concentration ◽  
Environmental Parameters ◽  
Western Basin ◽  
Different Types ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
The Vertical Distribution

Abstract. As commonly observed in oligotrophic stratified waters, a Subsurface (or Deep) Chlorophyll Maximum (SCM) frequently characterizes the vertical distribution of phytoplankton chlorophyll in the Mediterranean Sea. Occurring far from the surface layer seen by ocean color satellites, SCMs are difficult to observe with adequate spatio-temporal resolution and their biogeochemical impact remains unknown. BioGeochemical-Argo (BGC-Argo) profiling floats represent appropriate tools for studying the dynamics of SCMs. Based on data collected from 36 BGC-Argo floats deployed in the Mediterranean Sea, our study aims to address two main questions: (1) What are the different types of SCMs in Mediterranean Sea? (2) Which environmental factors control their occurrence and dynamics? First, we analyzed the seasonal and regional variations of the chlorophyll concentration (Chla), particulate backscattering coefficient (bbp), a proxy of the Particulate Organic Carbon (POC), and environmental parameters (PAR and nitrates) within the SCM layer over the Mediterranean basin. The vertical profiles of Chla and bbp were then statistically classified, and the seasonal occurrence of each of the different types of SCMs quantified. Finally, a case study was performed on two contrasted regions and the environmental conditions at depth were further investigated to understand which parameter controls the SCMs. In the Eastern Basin, SCMs result, at a first order, from photoacclimation process. Conversely, SCMs in the Western Basin reflect a biomass increase at depth benefiting from both light and nitrate resources. Our results also suggest that a variety of intermediate types of SCMs are encountered between these two end-member situations.

scholarly journals Bio-optical characterization of subsurface chlorophyll maxima in the Mediterranean Sea from a Biogeochemical-Argo float database

2019 ◽  
Vol 16 (6) ◽  
pp. 1321-1342 ◽  
Author(s):  
Marie Barbieux ◽  
Julia Uitz ◽  
Bernard Gentili ◽  
Orens Pasqueron de Fommervault ◽  
Alexandre Mignot ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Chlorophyll Concentration ◽  
Environmental Parameters ◽  
Western Basin ◽  
Chl A ◽  
Different Types ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
The Vertical Distribution

Abstract. As commonly observed in oligotrophic stratified waters, a subsurface (or deep) chlorophyll maximum (SCM) frequently characterizes the vertical distribution of phytoplankton chlorophyll in the Mediterranean Sea. Occurring far from the surface layer “seen” by ocean colour satellites, SCMs are difficult to observe with adequate spatio-temporal resolution and their biogeochemical impact remains unknown. Biogeochemical-Argo (BGC-Argo) profiling floats represent appropriate tools for studying the dynamics of SCMs. Based on data collected from 36 BGC-Argo floats deployed in the Mediterranean Sea, our study aims to address two main questions. (1) What are the different types of SCMs in the Mediterranean Sea? (2) Which environmental factors control their occurrence and dynamics? First, we analysed the seasonal and regional variations in the chlorophyll concentration (Chl a), particulate backscattering coefficient (bbp), a proxy of the particulate organic carbon (POC) and environmental parameters (photosynthetically active radiation and nitrates) within the SCM layer over the Mediterranean Basin. The vertical profiles of Chl a and bbp were then statistically classified and the seasonal occurrence of each of the different types of SCMs quantified. Finally, a case study was performed on two contrasted regions and the environmental conditions at depth were further investigated to understand the main controls on the SCMs. In the eastern basin, SCMs result, at a first order, from a photoacclimation process. Conversely, SCMs in the western basin reflect a biomass increase at depth benefiting from both light and nitrate resources. Our results also suggest that a variety of intermediate types of SCMs are encountered between these two endmember situations.

scholarly journals Metazooplankton diversity, community structure and spatial distribution across the Mediterranean Sea in summer: evidence of ecoregions

2011 ◽  
Vol 8 (2) ◽  
pp. 3081-3119 ◽  
Author(s):  
A. Nowaczyk ◽  
F. Carlotti ◽  
D. Thibault-Botha ◽  
M. Pagano
Keyword(s):  
Vertical Distribution ◽  
Mediterranean Sea ◽  
Mesh Size ◽  
Specific Pattern ◽  
Strongly Correlated ◽  
Western Basin ◽  
Order Of Magnitude ◽  
The Mediterranean ◽  
Abundance And Diversity ◽  
The Vertical Distribution

Abstract. The diversity and distribution of metazooplankton across the Mediterranean Sea was studied along a 3000 km long transect from the eastern to the western basins during the BOUM cruise in summer 2008. Metazooplankton were sampled using both a 120 μm mesh size bongo net and Niskin bottles at 17 stations. Here we report on the stock, the composition and the structure of the metazooplankton community. The abundance was 4 to 8 times higher than in several previously published studies, whereas the biomass remained within the same order of magnitude. An eastward decrease in abundance was evident, although biomass was variable. Spatial (horizontal and vertical) distribution of metazooplankton abundance and biomass was strongly correlated to chlorophyll-a concentration. In addition, a clear association was observed between the vertical distribution of nauplii and small copepods and the depth of the deep chlorophyll maximum. The role of environmental factors is also discussed. Cluster analysis allowed us to define a regionalization of the Mediterranean Sea based on the abundance and diversity of metazooplankton. We found a north-south distinction in the western basin and a longitudinal homogeneity in the eastern basin. The Sicily Channel appeared as an intermediate region. The specific pattern of distribution of remarkable species was also described.

scholarly journals A primer on rhythm quantification for fish sounds: a Mediterranean case study

2021 ◽  
Vol 8 (9) ◽  
pp. 210494
Author(s):  
Lara S. Burchardt ◽  
Marta Picciulin ◽  
Eric Parmentier ◽  
Marta Bolgan
Keyword(s):  
Fourier Analysis ◽  
Mediterranean Sea ◽  
Temporal Structure ◽  
Critical Aspect ◽  
Fish Sounds ◽  
Temporal Succession ◽  
Sound Sequence ◽  
The Mediterranean

We have used a lately established workflow to quantify rhythms of three fish sound types recorded in different areas of the Mediterranean Sea. So far, the temporal structure of fish sound sequences has only been described qualitatively. Here, we propose a standardized approach to quantify them, opening the path for assessment and comparison of an often underestimated but potentially critical aspect of fish sounds. Our approach is based on the analysis of inter-onset-intervals (IOIs), the intervals between the start of one sound element and the next. We calculate exact beats of a sequence using Fourier analysis and IOI analysis. Furthermore, we report on important parameters describing the variability in timing within a given sound sequence. Datasets were chosen to depict different possible rhythmic properties: Sciaena umbra sounds have a simple isochronous—metronome-like—rhythm. The /Kwa/ sound type emitted by Scorpaena spp. has a more complex rhythm, still presenting an underlying isochronous pattern. Calls of Ophidion rochei males present no rhythm, but a random temporal succession of sounds. This approach holds great potential for shedding light on important aspects of fish bioacoustics. Applications span from the characterization of specific behaviours to the potential discrimination of yet not distinguishable species.

scholarly journals Spatio-temporal patterns of macrourid fish species in the northern Mediterranean Sea

2020 ◽  
Vol 83 (S1) ◽  
pp. 117
Author(s):  
Cristina García-Ruiz ◽  
Manuel Hidalgo ◽  
Paolo Carpentieri ◽  
Ulla Fernandez-Arcaya ◽  
Palma Gaudio ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Trawl Survey ◽  
Western Basin ◽  
Entire Study ◽  
Mediterranean Countries ◽  
The Mean ◽  
The Mediterranean ◽  
Spatio Temporal ◽  
First Time ◽  
Entire Study Area

The present study describes for the first time the spatial distribution of five macrourid species throughout the Mediterranean Sea and analyses depth, geographical and time-related trends regarding their abundance, biomass and mean fish weight. The data were collected as part of the MEDITS annual bottom trawl survey carried out by several European Mediterranean countries from 1994 to 2015, using the same standardized gear and sampling protocol. The most represented species in terms of abundance and biomass was Coelorinchus caelorhincus. The bathymetric trend was different for each species. The shallowest occurring species was C. caelorhincus, followed by Hymenocephalus italicus and Nezumia sclerorhynchus, while Nezumia aequalis and Trachyrincus scabrus were the deepest. Overall, the mean weight of all the species increased with depth. C. caelorhincus and H. italicus occurred in the entire study area: the first species showed relatively high catches in most areas, while the second was more abundant in the central and easternmost areas. N. aequalis and T. scabrus were mainly reported in the western basin, and N. sclerorhynchus in the central-eastern areas of the Mediterranean. An increasing inter-annual trend in abundance was only detected for C. caelorhincus and N. sclerorhynchus, while variable fluctuations were observed in the other species.

scholarly journals Ecology of aerobic anoxygenic phototrophic bacteria along an oligotrophic gradient in the Mediterranean Sea

2011 ◽  
Vol 8 (4) ◽  
pp. 973-985 ◽  
Author(s):  
D. Lamy ◽  
C. Jeanthon ◽  
M. T. Cottrell ◽  
D. L. Kirchman ◽  
F. Van Wambeke ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Bacterial Growth ◽  
Growth Response ◽  
Anoxygenic Phototrophic Bacteria ◽  
Carbon Limitation ◽  
Organic Substrates ◽  
Western Basin ◽  
Eastern Basin ◽  
Nutrient Additions ◽  
The Mediterranean

Abstract. Aerobic anoxygenic phototrophic (AAP) bacteria are photoheterotrophic prokaryotes able to use both light and organic substrates for energy production. They are widely distributed in coastal and oceanic environments and may contribute significantly to the carbon cycle in the upper ocean. To better understand questions regarding links between the ecology of these photoheterotrophic bacteria and the trophic status of water masses, we examined their horizontal and vertical distribution and the effects of nutrient additions on their growth along an oligotrophic gradient in the Mediterranean Sea. Concentrations of bacteriochlorophyll-a (BChl-a) and AAP bacterial abundance decreased from the western to the eastern basin of the Mediterranean Sea and were linked with concentrations of chlorophyll-a, nutrient and dissolved organic carbon. Inorganic nutrient and glucose additions to surface seawater samples along the oligotrophic gradient revealed that AAP bacteria were nitrogen- and carbon-limited in the ultraoligotrophic eastern basin. The intensity of the AAP bacterial growth response generally differed from that of the total bacterial growth response. BChl-a quota of AAP bacterial communities was significantly higher in the eastern basin than in the western basin, suggesting that reliance on phototrophy varied along the oligotrophic gradient and that nutrient and/or carbon limitation favors BChl-a synthesis.

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 Creating and evaluating web-based visualizations of multi-dimensional spatiotemporal data

2019 ◽  
Vol 2 ◽  
pp. 1-8
Author(s):  
Jan Wilkening ◽  
Keni Han ◽  
Mathias Jahnke
Keyword(s):  
Spatiotemporal Data ◽  
Weather Data ◽  
Temporal Data ◽  
Web Based ◽  
Animated Maps ◽  
Different Types ◽  
Weather Parameters ◽  
Spatio Temporal ◽  
The Web

<p><strong>Abstract.</strong> In this article, we present a method for visualizing multi-dimensional spatio-temporal data in an interactive web-based geovisualization. Our case study focuses on publicly available weather data in Germany. After processing the data with Python and desktop GIS, we integrated the data as web services in a browser-based application. This application displays several weather parameters with different types of visualisations, such as static maps, animated maps and charts. The usability of the web-based geovisualization was evaluated with a free-examination and a goal-directed task, using eye-tracking analysis. The evaluation focused on the question how people use static maps, animated maps and charts, dependent on different tasks. The results suggest that visualization elements such as animated maps, static maps and charts are particularly useful for certain types of tasks, and that more answering time correlates with less accurate answers.</p>

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.

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