Synthesis, characterization, DFT and Td-dfT study of the [Fe(mnt)(L)(t-BuNC) 2] octahedral complex (L = phen, bipy)

FeBr2 has reacted with an equivalent of mnt2- (mnt = cis-1,2-dicyanoethylene-1,2-dithiolate) and the α-diimine L (L = 1,10'-phenantroline, 2,2'-bipyridine) in THF solution, and followed by adding of t-butyl-isocyanide to give [Fe(mnt)(L)(t-BuNC)2] neutral compound. The products were characterized by infrared, UV-visible and Mössbauer spectroscopy, besides thermogravimetric and conductivity data. The geometry in the equilibrium was calculated by the density functional theory and the electronic spectrum by the time-dependent. The experimental and theoretical results in good agreement have defined an octahedral geometry with two isocyanide neighbours. The π→π* intraligand electronic transition was not observed for cis-isomers in the near-IR spectral region

Colonization of a new habitat by copepods: An in situ experiment

Colonization of new habitats by a biological community is conspicuous and this dynamic process is one of the architectural forces of the biogeographical distribution we know today. Within the meiofauna (<1mm), copepods (Crustacea) have successfully adapted to nearly every ecosystem and heir colonization power of permanent habitats is therefore well-established. However, few studies tackled the colonization of new naturally occurring provisional habitats, which are of ecological interest since they are rich in organic material, structurally complex and devoted of native fauna. Hence, the present study investigated the copepod colonization of provisional macrophytodetritus (mainly composed of senescent leaves and drift macroalgae) accumulated on bare sand patches inside a Mediterranean Posidonia oceanica seagrass meadow. General motive of colonization such as food and shelter are well-defined. However, little is known regarding the mode of the colonization and source pool of the associated colonists. Here, an in situ experiment was deployed in order to understand the mode of copepod’s colonization to fauna deprived macrophytodetritus. The objectives were: (1) assessing the adjacent colonist’s source pool (i.e. sediment, water column or P. oceanica canopy), (2) investigating the speed of settlement and (3) quantifying the species composition of the colonizing copepods. In summary: (1) species from every source pool actively colonized the macrophytodetritus through the water column and through the sediment-macrophytodetritus interface. (2) The initial settlement occurred within the first 24 hours. (3) The species composition showed to be different than the source’s composition. After 24h, the composition was similar to 45% of the P. oceanica, 28% of the water column and 25% of the sediments. After 96h, the composition was similar to 24% of the P. oceanica, 13% of the water column and 10% of the sediments. Indicating an evolution towards a macrophytodetritus copepod specific community composed of a mixture of the adjacent habitats first colonizers

Hypoxia in macrophytodetritus accumulation: Species specific harpacticoid copepod adaptation?

Mediterranean Posidonia oceanica seagrass meadows generate high primary production and support large biodiversity of associated fauna and flora. The majority of the foliar material falls on the unvegetated sea floor during the autumnal leaf senescence, fuelling the detrital food web. Whilst laying on the sea floor the freshly formed macrophytodetritus pile up into accumulations according to the local hydrodynamics and seafloor geomorphology. In these litter accumulations, harpacticoid copepods (Crustacea, Copepoda) are the main meiofaunal players (metazoans in the size range of 38µm – 1mm) and show a high specific diversity. They are primarily grazers, but their high specific diversity suggests that they occupy also a large variety of trophic niches. This large morphological and trophic diversity can partly be promoted by the complexity of the phytodetritus in seagrass accumulations. On the other hand, macrophytodetritus degradation and flux of reduced compounds from the sediments is responsible for oxygen consumption inside the accumulation of seagrass litter. Therefore, concentration of oxygen inside the accumulation is very variable and often under the concentration observed in the water column just above the litter. Frequently, oxygen levels reach very low values. The present study aims to link the oxygen variability inside the accumulation to the densities of the five most dominant harpacticoid copepods found living in the P. oceanica litter. Standardized samples were collected seasonally in two contrasting sites of the Calvi Bay (Corsica) during one year. Our results showed no correlation between the oxygen concentrations and harpacticoid community diversity or their total abundances. The five most dominant species showed divergent results, but none had a clear correlation with the oxygen concentration. This contrasts with observation done for sediment meiofaunal community where most harpacticoid copepods are sensitive to oxygen level and where nematodes often dominate the community. This could be explained by their high mobility and the patchiness and variability of the oxygen concentrations present in the accumulations. Harpacticoid copepods, whilst being sensitive to hypoxia and anoxia developed a strategy to live in this fast oxygen changing environment. To conclude, our results underline the importance of species-specific analysis of correlation data. Especially in complex and dynamic environments where a variety of potential trophic niches are present and species competition is very likely to occur. The overall abundance pattern and diversity of the copepod community showed no relation to the oxygen concentration while the most abundant copepod species did not responded to fluctuating oxygen concentrations

Chemical contamination along the Mediterranean French coast using Posidonia oceanica (L.) Delile above-ground tissues: a multiple trace element study

Levels of Be, Al, V, Mn, Co, As, Se, Mo, Ag, Sn, Sb, Bi as well as of Cr, Fe, Ni, Cu, Zn, Cd and Pb in Posidonia oceanica (L.) Delile from the Mediterranean French coast were analysed using DRC ICP-MS. The first twelve elements have not been well studied and can be considered to be potential pollutants as a result of potentially increased levels resulting from anthropogenic activities. Spatial variation and/or compartmentalization were found for all trace elements. Except for Al, Cr, Fe, Cu and Ag, most trace elements were preferentially accumulated in photosynthetic tissues, suggesting uptake from the water column. Moreover, for Be, V, Mn, Co, Ni, As, Mo, Sb, Sn and Pb, adult leaves had higher levels than intermediate leaves, suggesting low kinetics of accumulation. Levels in the third intermediate leaf were representative of the average levels of the integral shoot, and thus can be used alone in chemical biomonitoring. For most of the twelve little-studied trace elements, the background levels of the northwestern Mediterranean Sea can be measured, and their spatial variation can be related to anthropogenic activities. Levels of the seven widely studied trace elements seem to decrease or stabilize over time, probably due to their reduced anthropogenic use. These observations show that P. oceanica is a sensitive bioindicator for the monitoring of chemical contamination of a large number of trace elements.PhD thesis. Coastal pollution of the Mediterranean and extension of its biomonitoring to trace elements of emerging concer

Assessment of Mytilus galloprovincialis to monitor 19 trace elements in the Calvi Bay

Mussel caging with Mytilus galloprovincialis has been successively used to monitor classic trace metal (Cd, Cu, Zn, Cr, Fe, Ni, Pb) pollution of Mediterranean coastal waters at spatial scales ranging from 10 to 100km. However, its relevance as bioindicator at smaller scales (100 m - 1 km) is poorly known. Moreover, the levels of some little studied trace elements (Al, V, Mn, Sb, Sn, Ag, Mo, Se, As, Co, Be, Bi), recently identified as potential pollutants of coastal environments, have not yet been assessed in that species. In this work, M. galloprovincialis was used to monitor the 19 listed trace elements at the scale of the Calvi Bay (NW Corsica, France). Additionally, we investigated decontamination kinetics and trace element tissue speciation before and after spawning. Mytilus galloprovincialis trace element levels reflect the good water quality of the Calvi Bay, showing little spatial variations either at 100m or 1km scales. Filter feeders are only influenced by their relatively homogeneous pelagic environment (dissolved trace elements and suspended particulate matters), in contrast to organisms which inhabit typically heterogeneous benthic habitats. This bioindicator, a convincing candidate for the monitoring of the 12 little studied trace elements, effectively accumulates the 19 studied elements to 105 seawater concentrations. Mytilus galloprovincialis rapidly equilibrates (within days) with its environment, and is therefore a good indicator of chronic and stable chemical pollutions. Tissue speciation shows that the most relevant organ to monitor trace elements is the hepatopancreas. However, the important variability induced by the reproductive cycle of mussels requires using this bioindicator during its sexual dormancy.Évolution de la pollution en éléments traces dans le milieu marin suite aux modifications récentes de leur production et de leur utilisation par l'homme: cas de la Méditerranée occidentale

In situ sampling of pore waters from seagrass meadows

A routine and low cost method to collect pore water in a seagrass meadow in situ and underwater is here proposed. The method consists of direct-suction filtered sampling allowing the determination of nutrient concentrations in the sampled water. Data ranges of nutrient (NO2-+NO3-; HPO4 2- and NH4+) concentrations in a P. oceanica meadow are also discusse

Carbon dioxide daily variations and atmospheric fluxes over the Great Bahama Bank using a novel autonomous measuring system

peer reviewedA novel autonomous measuring device that acquires the partial pressure of CO2 (pCO2) by equilibration and several other parameters is described. This device, the Floating Equilibrator System (FES) was tested in field conditions for the first time in the Great Bahama Bank, in December 2000. We successfully carried out two 24 h cycles in Norman’s Pond, one in front of the Caribbean Marine Research Centre (CMRC) and another one near Bock Cay. Over-saturation of CO2 with respect to atmospheric equilibrium was observed systematically at the three sites, although significantly more marked at Norman’s Pond. The higher values of pCO2 and atmospheric CO2 fluxes obtained at Norman’s Pond, than in the adjacent open waters of the Great Bahama Bank, suggest a comparatively stronger heterotrophy at Norman’s Pond. This is most likely related to the organic carbon inputs to the water column and sediments from the dense mangrove forest surrounding Norman’s Pond. The larger amplitude of pCO2 daily variations observed, during the Norman’s Pond 24 h cycles, is probably due to higher biological activity than in the adjacent open waters of the Great Bahama Bank. This is corroborated by a tentative estimation of Gross Primary Production based on simple computations. We speculate that calcification could also contribute to some extent to different amplitude of the pCO2 daily variations between the mangrove pond and the open waters of the Great Bahama Bank

Posidonia oceanica, a usefull tool to biomonitor the pollution of Mediterranean coastal areas by trace elements

Évolution de la pollution en éléments traces dans le milieu marin suite aux modifications récentes de leur production et de leur utilisation par l'homme: cas de la Méditerranée occidental

Trace element kinetics in contaminated Posidonia oceanica meadow

The seagrass Posidonia oceanica (L.) Delile is widely used since the mid-70th to biomonitor trace elements (TEs). However, there is a lack of knowledge regarding to pollutant kinetics in that species. Posidonia oceanica were in situ contaminated by a mix of 15 TEs (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Ag, Cd, Pb and Bi) at experimental levels equivalent to 10 (moderate) and 100 (acute) times seawater average concentrations. TEs concentrations were measured by ICP-MS in P. oceanica leaves and rhizomes sampled at regular time intervals, in epiphytes, in water and in sediment. Posidonia oceanica immediately accumulated pollutants from the beginning of experiments; once contaminations ended, TE concentrations came back to their original levels within two weeks, or at least showed a clear decrease. Leaves exhibited different uptake kinetics for many elements (e.g. Cr, Cu, Ag, Bi etc.): the younger growing leaves forming new tissues incorporated chemicals more rapidly than the older senescent leaves. Rhizomes did not show any clear trend, except for Cu, Zn and Bi. Results demonstrate that P. oceanica is a very sensitive sentinel to immediately delineate punctual pollutions similar to what might be measured in contaminated Mediterranean waters. The good response of P. oceanica leaves to pollutant short-term expositions suggests their routine use in regularly scheduled monitoring programs. Nevertheless, to by-pass P. oceanica leaves deciduous character and their capability to detoxify rapidly, long term accumulation recordings would also necessitate belowground tissues analyses