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Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro-nutrient data (hereafter termed nutrients) in Antarctic pack ice (306 ice-cores collected from 19 research cruises). Dissolved inorganic nitrogen and silicic acid concentrations change with time, as expected from a seasonally productive ecosystem. In winter, salinity-normalized nitrate and silicic acid concentrations (C∗) in sea ice are close to seawater concentrations (Cw), indicating little or no biological activity. In spring, nitrate and silicic acid concentrations become partially depleted with respect to seawater (C∗ Cw). The phosphate excess could be explained by a greater allocation to phosphorus-rich biomolecules during ice algal blooms coupled with convective loss of excess dissolved nitrogen, preferential remineralization of phosphorus, and/or phosphate adsorption onto metal-organic complexes. Ammonium also appears to be efficiently adsorbed onto organic matter, with likely consequences to nitrogen mobility and availability. This dataset supports the view that the sea ice microbial community is highly efficient at processing nutrients but with a dynamic quite different from that in oceanic surface waters calling for focused future investigations. info:eu-repo/semantics/published SCOPUS: ar.j

Synechococcus, the second most abundant oxygenic phototroph in the marine environment, harbors the largest pigment diversity known within a single genus of cyanobacteria, allowing it to exploit a wide range of light niches. Some strains are capable of Type IV chromatic acclimation (CA4), a process by which cells can match the phycobilin content of their phycobilisomes to the ambient light quality. Here, we performed extensive genomic comparisons to explore the diversity of this process within the marine Synechococcus radiation. A specific gene island was identified in all CA4-performing strains, containing two genes (fciA/b) coding for possible transcriptional regulators and one gene coding for a phycobilin lyase. However, two distinct configurations of this cluster were observed, depending on the lineage. CA4-A islands contain the mpeZ gene, encoding a recently characterized phycoerythrobilin lyase-isomerase, and a third, small, possible regulator called fciC. In CA4-B islands, the lyase gene encodes an uncharacterized relative of MpeZ, called MpeW. While mpeZ is expressed more in blue light than green light, this is the reverse for mpeW, although only small phenotypic differences were found among chromatic acclimaters possessing either CA4 island type. This study provides novel insights into understanding both diversity and evolution of the CA4 process. International audience

Significantly reduced ice coverage in Greenland and West Antarctica during the warmer-than-present Pliocene could account for ∼10 m of global mean sea level rise. Any sea level increase beyond this would require contributions from the East Antarctic Ice Sheet (EAIS). Previous studies have presented low-resolution geochemical evidence from the geological record, suggesting repeated ice advance and retreat in low-lying areas of the EAIS such as the Wilkes Subglacial Basin. However, the rates and mechanisms of retreat events are less well constrained. Here we present orbitally-resolved marine detrital sediment provenance data, paired with ice-rafted debris and productivity proxies, during three time intervals from the middle to late Pliocene at IODP Site U1361A, offshore of the Wilkes Subglacial Basin. Our new data reveal that Pliocene shifts in sediment provenance were paralleled by increases in marine productivity, while the onset of such changes was marked by peaks in ice-rafted debris mass accumulation rates. The coincidence of sediment provenance and marine productivity change argues against a switch in sediment delivery between ice streams, and instead suggests that deglacial warming triggered increased rates of iceberg calving, followed by inland retreat of the ice margin. Timescales from the onset of deglaciation to an inland retreated ice margin within the Wilkes Subglacial Basin are on the order of several thousand years. This geological evidence corroborates retreat rates determined from ice sheet modeling, and a contribution of ∼3 to 4 m of equivalent sea level rise from one of the most vulnerable areas of the East Antarctic Ice Sheet during interglacial intervals throughout the middle to late Pliocene. Provenance analysis was supported by a Kristian Gerhard Jebsen PhD Scholarship and NERC UK IODP grants (NE/H025162/1 and NE/H014144/1). Biogenic silica data was supported by a Royal Society of New Zealand Marsden FastStart grant (#UOO-1315) and a University of Otago PhD Scholarship. Support for sedimentology analysis was provided by the Royal Society of New Zealand Rutherford Discovery Fellowship (RDF-13-VUW-003). XRF work was supported by the Ministry of Science and Innovation Grant CTM2014-60451-C2-1-P co-financed by the European Regional Development Fund (FEDER). Samples were provided by the Integrated Ocean Drilling Program. The authors acknowledge two anonymous reviewers whose thoughtful comments helped improve the manuscript.

0.564 mm. Larval EC shows a long nucleus with thorn-like extravaginations toward the cytoplasm, numerous electron-dense and -lucent secretory granules spanning from the perinuclear to subplasmalemmal space, an elevated number of free ribosomes, small, spherical mitochondria with few cristae and a laminated matrix, small and few Golgi apparatuses, and few endoplasmic reticula, with wide cisternae complexes. Ultrastructure suggests that anaerobic glycolysis is the main metabolic pathway, obtained through nutrient endocytosis across the pseudocoelomic surface of the EC plasmalemma and its endocytic canaliculi. Thorn-like extravaginations of EC karyotheca likely mediate specific processes (Ca2+ signaling, gene expression, transport, nuclear lipid metabolism) into the extremely wide EC cytosol, enabling focal delivery of a signal to specific sites in a short time. These functional annotations of parasitic EC should help to clarify anisakiasis pathogenesis. Excretory and secretory products are crucial for parasite infectivity and host immunomodulation, but the functioning and ultrastructure of the excretory gland cell (EC) that produces these products are still scarcely understood and described. In light of growing reports on anisakiasis cases in Europe, we aimed to characterise the EC of larval Anisakis pegreffii and adult Pseudoterranova azarasi. In the latter, EC starts 0.85 mm from the head tip, measuring 1.936 ×

It is well known that modern resting cysts with morphologies matching those of species of the fossil genus Spiniferites germinate into motile cells of the genus Gonyaulax. Different Spiniferites species have been connected to a single Gonyaulax species, raising the question of whether they are over-classified. Through germination experiments of cysts with the morphological features of four species of Spiniferites, viz. S. bentorii, S. hyperacanthus, S. ramosus and S. scabratus, we established cyst-theca relationships. Cysts with the morphology of S. bentorii gave rise to vegetative, motile cells of Gonyaulax nezaniae sp. nov., which is characterized by two stout antapical spines. Cysts with S. hyperacanthus and S. ramosus morphologies germinated into Gonyaulax whaseongensis and G. spinifera, respectively. Cysts with S. scabratus morphology lacked a ventral pore and were attributed to Gonyaulax cf. spinifera. Gene sequences for SSU, LSU and/or ITS-5.8S rRNA were obtained from these four species, and from cysts with the morphology of Spiniferites belerius, S. mirabilis, S. lazus, Spiniferites cf. bentorii and Tectatodinium pellitum. The maximum likelihood and Bayesian inference analyses based on LSU and SSU rRNA gene sequences revealed that cysts assignable to Spiniferites formed a polyphyletic group, intermingled with Tectatodinium, Bitectatodinium, Ataxiodinium and Impagidinium, whereas Gonyaulax species appeared as monophyletic. From our results we inferred the phylogenetic positions of S. bentorii, S. mirabilis, S. lazus, S. scabratus, Tectatodinium pellitum and Gonyaulax digitale for the first time, supporting the idea that Spiniferites species are not over-classified and each of them may correspond to different Gonyaulax species.

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Goswami, Vineet Haley, Brian A. Hathorne, Ed C. Hemming, Sidney R. Henderson, Gideon M. Jeandel, Catherine Jones, Kevin Kreissig, Katharina Lacan, Francois Lambelet, Myriam Martin, Ellen E. Newkirk, Derrick R. Obata, Haijme Pena, Leopoldo Piotrowski, Alexander M. Pradoux, Catherine Scher, Howie D. Schoberg, Hans Singh, Sunil Kumar Stichel, Torben Tazoe, Hirofumi Vance, Derek Yang, Jingjing Lacan, Francois/B-8032-2009; Scher, Howie/C-4927-2013; Pena, Leopoldo/B-8140-2013; Crocket, Kirsty/G-6327-2013 Crocket, Kirsty/0000-0003-2171-3010 NSF [OCE-07-52402]; Marie Curie International Reintegration [IRG 230828]; NERC [NE/F016751/1]; U.S. National Science Foundation [OCE-927285] We would like to extend a special word of thanks to Bob Anderson, Marty Fleisher, and Tim Kenna for being a great team to work with during this GEOTRACES intercalibration. Thanks also to crew and colleagues who sailed on the two intercalibration cruises on the R/V Knorr, and to Greg Cutter, Ken Bruland, and Rob Sherrell for leading the GEOTRACES intercalibration effort. Thermo Fisher Scientific and Gideon Henderson are thanked for providing the unknown Nd isotope and REE standards. Wafa Abouchami, associate editor Peter Croot, and two anonymous reviewers are thanked for providing constructive reviews. Funding was provided by NSF grant OCE-07-52402 to TvdF and KP, and by Marie Curie International Reintegration grant IRG 230828 and NERC grantNE/F016751/1 to TvdF. This paper is part of the Intercalibration in Chemical Oceanography special issue of L&O Methods that was supported by funding from the U.S. National Science Foundation, Chemical Oceanography Program (Grant OCE-927285 to G. Cutter). 14 AMER SOC LIMNOLOGY OCEANOGRAPHY WACO LIMNOL OCEANOGR-METH One of the key activities during the initial phase of the international GEOTRACES program was an extensive international intercalibration effort, to ensure that results for a range of trace elements and isotopes (TEIs) from different cruises and from different laboratories can be compared in a meaningful way. Here we present the results from the intercalibration efforts on neodymium isotopes and rare earth elements in seawater and marine particles. Fifteen different laboratories reported results for dissolved Nd-143/Nd-144 ratios in seawater at three different locations (BATS 15 m, BATS 2000 m, SAFe 3000 m), with an overall agreement within 47 to 57 ppm (2 sigma standard deviation of the mean). A similar agreement was found for analyses of an unknown pure Nd standard solution carried out by 13 laboratories (56 ppm), indicating that mass spectrometry is the main variable in achieving accurate and precise Nd isotope ratios. Overall, this result is very satisfactory, as the achieved precision is a factor of 40 better than the range of Nd isotopic compositions observed in the global ocean. Intercalibration for dissolved rare earth element concentrations (REEs) by six laboratories for two water depths at BATS yielded a reproducibility of 15% or better for all REE except Ce, which seems to be the most blank-sensitive REE. Neodymium concentrations from 12 laboratories show an agreement within 9%, reflecting the best currently possible reproducibility. Results for Nd isotopic compositions and REE concentrations on marine particles are inconclusive, and should be revisited in the future.