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The Sea of Marmara is the connection between the vast Black Sea-Caspian Sea basin (Pontocaspian) and the Global Ocean via the Mediterranean Sea. Its water levels and water conditions has widely varied over times. Combining two cores in the Sea of Marmara (Turkey) and using organic-walled dinoflagellate cyst assemblages as the main proxy (combined with alkenones, diatoms and benthic foraminifera), allow qualitatively reconstructing water conditions during Marine Isotopic Stage (MIS) 6 and 5, such as salinity and oxygen level. A clear main marine phase is illustrated in MIS 5e. A minor marine incursion occurred during MIS 5c, mostly supported by alkenone data. The rest of the record indicates brackish Pontocaspian conditions, with more Spiniferites inaequalis in MIS 6 and more S. cruciformis in the non-marine parts of MIS 5. At the MIS 6/MIS 5 transition, an earlier initial marine flooding in the Sea of Marmara (dinocyst assemblages) in comparison to the Black Sea was highlighted. The marine reconnection occurred at different moments as seen in the terrestrial vegetation reconstructed from pollen analysis linking the two seas. The sapropels of the Sea of Marmara form when marine water penetrates at depth from the Aegean Sea beneath a layer of lower salinity water. Variations of the residence time of the marine deep water in a stratified Sea of Marmara are potentially an important factor underlying hypoxia/anoxia and sapropel deposition. When combining surface water proxies with benthic foraminifera (test assemblages and presence of inner organic lining), it appears that the successive MIS 5 sapropels formed under decreasing salinity and oxygen availability conditions as the marine inflow was increasingly restricted. Understanding the hydrologic evolution of the Sea of Marmara during MIS 5 implies taking into account that the Bosphorus and Dardanelle straits are hydrodynamically coupled and may not be simplified as on/off switches based on present day sill depths. • Dinocyst analyses of last interglacial and previous glacial in the Sea of Marmara on two long cores. • Marine phase in MIS5e (dinocysts, benthic foraminifera, alkenones) minor in MIS5c • BrackishPontocaspian conditions for rest of sequence although different in MIS6 & 5. • Earlier marine flooding at beginning of MIS5e in Sea of Marmara than in Black Sea. • Three sapropels highlight decreasing anoxic conditions over time. [ABSTRACT FROM AUTHOR]

As all arthropods, microcrustaceans shed their chitinous exoskeleton (cuticule, peritrophic membrane) to develop and grow. While the molting is the most crucial stage in their life cycle, it remains poorly investigated in term of pollutant biodistribution within the organisms. In this paper, we used optical, electronic, and X ray-based microscopies to study the uptake and release of CeO2 nanoparticles by/from Daphnia pulex over a molting stage. We measured that D. pulex molts every 59 ± 21 h (confidence interval) with growth rates about 1.1 or 1.8 μm per stage as a function of the pieces measured. Ingestion via food chain was the main route of CeO2 nanoparticles uptake by D. pulex. The presence of algae during the exposure to nanoparticles (sub-lethal doses) enhanced by a factor of 3 the dry weight concentration of Ce on the whole D. pulex. Nanoparticles were localized in the gut content, in direct contact with the peritrophic membrane, and on the cuticle. Interestingly, the depuration (24 h with Chlorella pseudomonas) was not efficient to remove the nanoparticles from the organisms. From 40% to 100% (depending on the feeding regime during exposure) of the CeO2 taken up by D. pulex is not release after the depuration process. However, we demonstrated for the first time that the shedding of the chitinous exoskeleton was the crucial mechanism governing the released of CeO2 nanoparticles regardless of the feeding regime during exposure., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Chironomids, diatoms and microcrustaceans that inhabit aquatic ecosystems of the Northern Neotropics are abundant and diverse. Some species are highly sensitive to changes in water chemical composition and trophic state. This study was undertaken as a first step in developing transfer functions to infer past environmental conditions in the Northern lowland Neotropics. Bioindicator species abundances were related to multiple environmental variables to exploit their use as environmental and paleoenvironmental indicators. We collected and analyzed water and surface sediment samples from 63 waterbodies located along a broad trophic state gradient and steep gradients of altitude (approximately 0-1 560 m.a.s.l.) and precipitation (approximately 400-3200 mm/y), from NW Yucatán Peninsula (Mexico) to southern Guatemala. We related 14 limnological variables to relative abundances of 282 diatom species, 66 chironomid morphospecies, 51 species of cladocerans, 29 non-marine ostracode species and six freshwater calanoid copepods. Multivariate statistics indicated that bicarbonate is the strongest driver of chironomid and copepod distribution. Trophic state is the second most important factor that determines chironomid distribution. Conductivity, which is related to the precipitation gradient and marine influence on the Yucatán Peninsula, is the main variable that shapes diatom, ostracode and cladoceran communities. Diatoms, chironomids and cladocerans displayed higher diversities (H = 2.4-2.6) than ostracodes and copepods (H = 0.7-1.8). Species richness and diversity were greater at lower elevations (< 450 m.a.s.l.) than at higher elevations in Guatemala. Distribution and diversity of bioindicators are influenced by multiple factors including altitude, precipitation, water chemistry, trophic state and human impact.