scholarly journals Relationships between phytoplankton light absorption, pigment composition and size structure in offshore areas of the Mediterranean Sea

2011 ◽  
Vol 2 (2) ◽  
pp. 107 ◽  
Author(s):  
Emanuele Organelli ◽  
Caterina Nuccio ◽  
Chiara Melillo ◽  
Luca Massi
Keyword(s):  
Mediterranean Sea ◽  
Cell Size ◽  
Size Structure ◽  
Taxonomic Composition ◽  
Small Range ◽  
Pigment Composition ◽  
Absorption Coefficients ◽  
Phytoplankton Assemblages ◽  
Phytoplankton Absorption ◽  
The Mediterranean

Phytoplankton absorption is mainly determined by pigment composition and packaging into the cell, in turn affected by pigment concentration and cell size and shape. The variations of the chlorophyll-specific absorption coefficients at two selected wavelengths (443 nm and 675 nm) were analysed for offshore areas of the Mediterranean Sea (Alboran, Algerian, Tyrrhenian, Ionian Basins and Sardinia Channel) investigated in autumn 2006, 2007 and 2008. The spatial distribution of Tchl a, accessory pigments, size structure and taxonomic composition of phytoplankton assemblages was diversified among the areas, characterized by higher contribution of photoprotective pigments in oligotrophic surface waters, while accessory chlorophylls increased in deeper layers and where microphytoplankton dominated. (443) values decreased from the oligotrophic waters to the more mesotrophic ones where microphytoplankton prevailed, while for (675) a small range of variation was observed. The differentiation of (443) was explained by the variations in the phytoplankton assemblage mean cell size, that consequently can be assumed as the main factor determining package effect. Comparison with previous parameterizations supported the existence of a Mediterranean differentiation for which the use of global models might determine inaccuracy for predicting phytoplankton absorption coefficients and thus refining ecological models.

scholarly journals Climate change and body size shift in Mediterranean bivalve assemblages: unexpected role of biological invasions

2017 ◽  
Vol 284 (1860) ◽  
pp. 20170357 ◽  
Author(s):  
Rafał Nawrot ◽  
Paolo G. Albano ◽  
Devapriya Chattopadhyay ◽  
Martin Zuschin
Keyword(s):  
Climate Change ◽  
Body Size ◽  
Alien Species ◽  
Mediterranean Sea ◽  
Red Sea ◽  
Size Structure ◽  
Functional Trait ◽  
Taxonomic Composition ◽  
Species Invasions ◽  
The Mediterranean

Body size is a synthetic functional trait determining many key ecosystem properties. Reduction in average body size has been suggested as one of the universal responses to global warming in aquatic ecosystems. Climate change, however, coincides with human-enhanced dispersal of alien species and can facilitate their establishment. We address effects of species introductions on the size structure of recipient communities using data on Red Sea bivalves entering the Mediterranean Sea through the Suez Canal. We show that the invasion leads to increase in median body size of the Mediterranean assemblage. Alien species are significantly larger than native Mediterranean bivalves, even though they represent a random subset of the Red Sea species with respect to body size. The observed patterns result primarily from the differences in the taxonomic composition and body-size distributions of the source and recipient species pools. In contrast to the expectations based on the general temperature–size relationships in marine ectotherms, continued warming of the Mediterranean Sea indirectly leads to an increase in the proportion of large-bodied species in bivalve assemblages by accelerating the entry and spread of tropical aliens. These results underscore complex interactions between changing climate and species invasions in driving functional shifts in marine ecosystems.

Absorption properties of phytoplankton in the Lower Estuary and Gulf of St. Lawrence (Canada)

2008 ◽  
Vol 65 (8) ◽  
pp. 1721-1737 ◽  
Author(s):  
Suzanne Roy ◽  
Frédérick Blouin ◽  
André Jacques ◽  
Jean-Claude Therriault
Keyword(s):  
Spring Bloom ◽  
Size Structure ◽  
Particulate Material ◽  
Dominant Factor ◽  
Pigment Composition ◽  
Ocean Colour ◽  
Absorption Properties ◽  
Ultraviolet Range ◽  
Before And After ◽  
Phytoplankton Absorption

Models of ocean colour rely on information about phytoplankton absorption, which varies according to community composition and photoacclimation. Here we show that pigment packaging, which is strongly determined by the size structure of local algal populations, represents a dominant factor in the Estuary and Gulf of St. Lawrence, accounting for ~50%–80% of the reduction in phytoplankton absorption at 440 nm during the spring bloom periods and for 24%–48% before and after the blooms. This is consistent with the importance of diatoms in this environment. Comparison between three methods of estimating packaging gave average values within less than 20% of each other during the blooms. Changes in pigment composition, which also affect phytoplankton absorption, were more important outside bloom periods (particularly in the Gulf), although this influence was relatively modest (11%–13%). This was accompanied by an increase in photoprotective pigments and an absorption peak in the ultraviolet range (~330 nm). Regional variations in phytoplankton absorption reflected bloom conditions, whereas detrital particulate material was highest in the upstream Saguenay region (often more than 60% of the absorption of total particulate material at 440 nm (ap(440))) and was at least 20%–30% elsewhere. This information is a first step towards the development of regional models of ocean colour.

scholarly journals Multiple transgressions and slow evolution shape the phylogeographic pattern of the blind cave-dwelling shrimp Typhlocaris

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5268 ◽  
Author(s):  
Tamar Guy-Haim ◽  
Noa Simon-Blecher ◽  
Amos Frumkin ◽  
Israel Naaman ◽  
Yair Achituv
Keyword(s):  
Molecular Evolution ◽  
Mediterranean Sea ◽  
Divergence Time ◽  
Evolutionary Rates ◽  
Radiometric Dating ◽  
Small Range ◽  
Biogeographic Patterns ◽  
Blind Cave ◽  
The Mediterranean ◽  
Slow Evolution

Background Aquatic subterranean species often exhibit disjunct distributions, with high level of endemism and small range, shaped by vicariance, limited dispersal, and evolutionary rates. We studied the disjunct biogeographic patterns of an endangered blind cave shrimp, Typhlocaris, and identified the geological and evolutionary processes that have shaped its divergence pattern. Methods We collected Typlocaris specimens of three species (T. galilea, T. ayyaloni, and T. salentina), originating from subterranean groundwater caves by the Mediterranean Sea, and used three mitochondrial genes (12S, 16S, cytochrome oxygnese subunit 1 (COI)) and four nuclear genes (18S, 28S, internal transcribed spacer, Histon 3) to infer their phylogenetic relationships. Using the radiometric dating of a geological formation (Bira) as a calibration node, we estimated the divergence times of the Typhlocaris species and the molecular evolution rates. Results The multi-locus ML/Bayesian trees of the concatenated seven gene sequences showed that T. salentina (Italy) and T. ayyaloni (Israel) are sister species, both sister to T. galilea (Israel). The divergence time of T. ayyaloni and T. salentina from T. galilea was 7.0 Ma based on Bira calibration. The divergence time of T. ayyaloni from T. salentina was 5.7 (4.4–6.9) Ma according to COI, and 5.8 (3.5–7.2) Ma according to 16S. The computed interspecific evolutionary rates were 0.0077 substitutions/Myr for COI, and 0.0046 substitutions/Myr for 16S. Discussion Two consecutive vicariant events have shaped the phylogeographic patterns of Typhlocaris species. First, T. galilea was tectonically isolated from its siblings in the Mediterranean Sea by the arching uplift of the central mountain range of Israel ca. seven Ma. Secondly, T. ayyaloni and T. salentina were stranded and separated by a marine transgression ca. six Ma, occurring just before the Messinian Salinity Crisis. Our estimated molecular evolution rates were in one order of magnitude lower than the rates of closely related crustaceans, as well as of other stygobiont species. We suggest that this slow evolution reflects the ecological conditions prevailing in the highly isolated subterranean water bodies inhabited by Typhlocaris.

scholarly journals Parameterization of chlorophyll-specific phytoplankton absorption coefficients for productive lake waters

2016 ◽  
Author(s):  
Birgot Paavel ◽  
Kersti Kangro ◽  
Helgi Arst ◽  
Anu Reinart ◽  
Tiit Kutser ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Chlorophyll Concentration ◽  
Algal Species ◽  
Optical Measurements ◽  
Model Parameters ◽  
Water Type ◽  
Total Chlorophyll ◽  
Absorption Coefficients ◽  
Phytoplankton Assemblages ◽  
Phytoplankton Absorption

<p>We examined and parameterized chlorophyll-specific phytoplankton absorption coefficients (<em>a</em><sup>*</sup><sub>ph</sub>(<em>λ</em>)) for three turbid productive Estonian lakes on the basis of bio-optical measurements in 2005-2013. A new model parameterization was created that enables to reconstruct the spectra of <em>a</em><sup>*</sup><sub>ph</sub>(<em>λ</em>) for turbid productive waters with the higher reliability than previous parameterizations for ocean and coastal waters. The coefficients <em>A</em>(<em>λ</em>) and <em>B</em>(<em>λ</em>) of our model differ from those found in seas, coastal waters and other types of lakes. For any water type separately the increase of total chlorophyll concentration accompanied with the decrease of <em>a</em><sup>*</sup><sub>ph</sub>. Our results showed significant seasonal differences between the model parameters due to diversity of the phytoplankton assemblages. This suggests that season-specific models should be developed and validated. Improving the modelling of chlorophyll-specific phytoplankton absorption spectra for hypertrophic lakes is still pending on the availability of a larger dataset, which includes simultaneous measurements of chlorophyll concentrations, phytoplankton absorption coefficients and phytoplankton species composition. Our results implied that total chlorophyll concentration is not a universal predictor of the magnitude of chlorophyll-specific phytoplankton absorption coefficient. The <em>a</em><sub>ph</sub>(<em>λ</em>) models are also likely site and season dependent. Further research is needed for quantifying the role of accessory pigments and other optical constituents as well as the cell size of dominant algal species for considering their influence on the modelling outputs.</p>

scholarly journals Vertical distribution of the prokaryotic cell size in the Mediterranean Sea

2012 ◽  
Vol 66 (4) ◽  
pp. 635-650 ◽  
Author(s):  
R. La Ferla ◽  
G. Maimone ◽  
M. Azzaro ◽  
F. Conversano ◽  
C. Brunet ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Mediterranean Sea ◽  
Cell Size ◽  
Prokaryotic Cell ◽  
The Mediterranean

scholarly journals Bathymetrical distribution and size structure of cold-water coral populations in the Cap de Creus and Lacaze-Duthiers canyons (northwestern Mediterranean)

2013 ◽  
Vol 10 (3) ◽  
pp. 2049-2060 ◽  
Author(s):  
A. Gori ◽  
C. Orejas ◽  
T. Madurell ◽  
L. Bramanti ◽  
M. Martins ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Cold Water ◽  
Size Structure ◽  
First Record ◽  
Lophelia Pertusa ◽  
Submarine Canyons ◽  
Remotely Operated Vehicle ◽  
Coral Colony ◽  
The Mediterranean ◽  
Water Coral

Abstract. Submarine canyons are known as one of the seafloor morphological features where living cold-water coral (CWC) communities develop in the Mediterranean Sea. We investigated the CWC community of the two westernmost submarine canyons of the Gulf of Lions canyon system: the Cap de Creus Canyon (CCC) and Lacaze-Duthiers Canyon (LDC). Coral associations have been studied through video material recorded by means of a manned submersible and a remotely operated vehicle. Video transects have been conducted and analyzed in order to obtain information on (1) coral bathymetric distribution and density patterns, (2) size structure of coral populations, and (3) coral colony position with respect to the substrate. Madrepora oculata was the most abundant CWC in both canyons, while Lophelia pertusa and Dendrophyllia cornigera mostly occurred as isolated colonies or in small patches. An important exception was detected in a vertical cliff in LDC where a large L. pertusa framework was documented. This is the first record of such an extended L. pertusa framework in the Mediterranean Sea. In both canyons coral populations were dominated by medium and large colonies, but the frequent presence of small-sized colonies also indicate active recruitment. The predominant coral orientation (90° and 135°) is probably driven by the current regime as well as by the sediment load transported by the current flows. In general, no clear differences were observed in the abundance and in the size structure of the CWC populations between CCC and LDC, despite large differences in particulate matter between canyons.

scholarly journals Modelling spatio-temporal patterns of fish community size structure across the northern Mediterranean Sea: an analysis combining MEDITS survey data with environmental and anthropogenic drivers

2020 ◽  
Vol 83 (S1) ◽  
pp. 141
Author(s):  
Isabella Bitetto ◽  
Giovanni Romagnoni ◽  
Angeliki Adamidou ◽  
Gregoire Certain ◽  
Manfredi Di Lorenzo ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Fish Community ◽  
Size Structure ◽  
Anthropogenic Impacts ◽  
Maximum Length ◽  
Dynamic Factor ◽  
Central Mediterranean ◽  
Commercial Fish ◽  
The Mediterranean ◽  
Typical Length

The state of marine systems subject to natural or anthropogenic impacts can be generally summarized by suites of ecological indicators carefully selected to avoid redundancy. Length-based indicators capture the status of fish community structure, fulfilling the Marine Strategy Framework Directive (MSFD) requirement for Descriptor 3 (status of commercial fish species). Although the MSFD recommends the development of regional indicators, a comparison among alternative length-based indicators is so far missing for the Mediterranean Sea. Using principal component analysis and dynamic factor analysis, we identified the most effective subset of length-based indicators, whether or not based on maximum length. Indicator trends and time series of fishing effort and environmental variables are also compared in order to highlight the individual and combined capability of indicators to track system changes across geographical sub-areas. Two indicators, typical length and mean maximum length, constitute the smallest set of non-redundant indicators, capturing together 87.45% of variability. Only in combination can these indicators disentangle changes in the fish community composition from modifications of size structure. Our study supports the inclusion of typical length among the regional MSFD Descriptor 3 indicators for the Mediterranean Sea. Finally, we show dissimilarity between the western and eastern-central Mediterranean, suggesting that there are sub-regional differences in stressors and community responses.

scholarly journals Multiple transgressions and slow evolution shape the phylogeographic pattern of the blind cave-dwelling shrimp Typhlocaris

2018 ◽  
Author(s):  
Tamar Guy-Haim ◽  
Noa Simon-Blecher ◽  
Amos Frumkin ◽  
Israel Naaman ◽  
Yair Achituv
Keyword(s):  
Molecular Evolution ◽  
Mediterranean Sea ◽  
Evolutionary Rates ◽  
Radiometric Dating ◽  
Small Range ◽  
Mountain Range ◽  
Biogeographic Patterns ◽  
Blind Cave ◽  
The Mediterranean ◽  
Slow Evolution

Background. Aquatic subterranean species often exhibit disjunct distributions, with high level of endemism and small range, shaped by vicariance, limited dispersal, and evolutionary rates. We studied the disjunct biogeographic patterns of an endangered blind cave shrimp, Typhlocaris, and identified the geological and evolutionary processes that have shaped its divergence pattern. Methods. We collected Typlocaris specimens of three species (T. galilea, T. ayyaloni, and T. salentina), originating from subterranean groundwater caves by the Mediterranean Sea, and used three mitochondrial genes (12S, 16S, COI) and four nuclear genes (18S, 28S, ITS, H3) to infer their phylogenetic relationships. Using the radiometric dating of a geological formation (Bira) as a calibration node, we estimated the divergence times of the Typhlocaris species and the molecular evolution rates. Results. The multi-locus ML/Bayesian trees of the concatenated seven gene sequences showed that T. salentina (Italy) and T. ayyaloni (Israel) are more closely related than T. galilea (Israel). The divergence time of T. ayyaloni and T. salentina from T. galilea was according to COI – 6.0 [4.5-7.2] Ma and according to 16S – 5.9 [3.6-7.4] Ma. The computed interspecific evolutionary rates for COI – 0.0074 substitutions/Myr and for 16S – 0.0041 substitutions/Myr. Discussion. Two consecutive vicariant events have shaped the phylogeographic patterns of Typhlocaris species. First, T. galilea was tectonically isolated from its siblings in the Mediterranean Sea by the arching uplift of the central mountain range of Israel ca. 7 Ma. Secondly, T. ayyaloni and T. salentina were stranded and separated by a marine transgression ca. 6 Ma, occurring just before the Messinian Salinity Crisis. Our estimated molecular evolution rates were in one order of magnitude lower than the rates of closely related crustaceans, as well as of other stygobiont species. We suggest that this slow evolution reflects the ecological conditions prevailing in the highly isolated subterranean enclosures inhabited by Typhlocaris.

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