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  • Bignert, Anders
    et al.
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Danielsson, Sara
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Ek, Caroline
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Faxneld, Suzanne
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Nyberg, Elisabeth
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Comments Concerning the National Swedish Contaminant Monitoring Programme in Marine Biota, 20172017Report (Other academic)
  • Nyberg, Elisabeth
    et al.
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Faxneld, Suzanne
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Danielsson, Sara
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    Bignert, Anders
    Swedish Museum of Natural History, Department of Environmental research and monitoring.
    The National Swedish Contaminant Monitoring Programme for Freshwater Biota, 20162016Report (Other academic)
  • Fontorbe, G.
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, C. L.
    Hendry, K. R.
    Conley, D. J.
    A silicon depleted North Atlantic since the Palaeogene: Evidence from sponge and radiolarian silicon isotopes2016In: Earth and Planetary Science Letters, Vol. 453, 67-77 p.Article in journal (Refereed)
    Abstract [en]

    Despite being one of Earth's major geochemical cycles, the evolution of the silicon cycle has received little attention and changes in oceanic dissolved silica (DSi) concentration through geologic time remain poorly constrained. Silicon isotope ratios (expressed as delta Si-30) in marine microfossils are becoming increasingly recognised for their ability to provide insight into silicon cycling. In particular, the delta Si-30 of siliceous sponge spicules has been demonstrated to be a useful proxy for past DSi concentrations. We analysed delta Si-30 in radiolarian tests and sponge spicules from the Blake Nose Palaeoceanographic Transect (ODP Leg 171B) spanning the Palaeocene-Eocene (ca. 60-30 Ma). Our delta Si-30 results range from +0.32 to +1.67 parts per thousand and -0.48 to +0.63 parts per thousand for the radiolarian and sponge records, respectively. Using an established relationship between ambient dissolved Si (DSi) concentrations and the magnitude of silicon isotope fractionation in siliceous sponges, we demonstrate that the Western North Atlantic was DSi deplete during the Palaeocene-Eocene throughout the water column, a conclusion that is robust to a range of assumptions and uncertainties. These data can constitute constraints on reconstructions of past-ocean circulation. Previous work has suggested ocean DSi concentrations were higher than modern ocean concentrations prior to the Cenozoic and has posited a drawdown during the Early Palaeogene due to the evolutionary expansion of diatoms. Our results challenge such an interpretation. We suggest here that if such a global decrease in oceanic DSi concentrations occurred, it must predate 60 Ma. (C) 2016 The Authors. Published by Elsevier B.V.

  • Barão, Lúcia
    et al.
    Vandevenne, Floor
    Clymans, Wim
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Ragueneau, Olivier
    Meire, Patrick
    Conley, Daniel J.
    Struyf, Eric
    Alkaline-extractable silicon from land to ocean: A challenge for biogenic silicon determination2015In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, n/a-n/a p.Article in journal (Refereed)
    Abstract [en]

    The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction.

  • Viranta, Suvi
    et al.
    Atickem, Anagaw
    Werdelin, Lars
    Swedish Museum of Natural History, Department of Paleobiology.
    Stenseth, Nils Christian
    Rediscovering a forgotten canid species2017In: BMC Zoology, ISSN 2056-3132Article in journal (Refereed)
    Abstract [en]

    Background

    The African wolf, for which we herein recognise Canis lupaster Hemprich and Ehrenberg, 1832 (Symbolae Physicae quae ex Itinere Africam Borealem er Asoam Occidentalem Decas Secunda. Berlin, 1833) as the valid species name (we consider the older name Canis anthus Cuvier, 1820 [Le Chacal de Sénégal, Femelle. In: Geoffroy St.-Hilaire E, Cuvier F, editors. Histoire Naturelle des Mammifères Paris, A. Belin, 1820] a nomen dubium), is a medium-sized canid with wolf-like characters. Because of phenotypic similarity, specimens of African wolf have long been assigned to golden jackal (Canis aureus Linnaeus, 1758 [Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. Editio decima, reformata, 1758]).

    Results

    Here we provide, through rigorous morphological analysis, a species description for this taxonomically overlooked species. Through molecular sequencing we assess its distribution in Africa, which remains uncertain due to confusion regarding possible co-occurrence with the Eurasian golden jackal. Canis lupasterdiffers from all other Canis spp. including the golden jackal in its cranial morphology, while phylogenetically it shows close affinity to the Holarctic grey wolf (Canis lupus Linnaeus, 1758 [Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis. Tomus I. Editio decima, reformata, 1758]). All sequences generated during this study clustered with African wolf specimens, consistent with previous data for the species.

    Conclusions

    We suggest that the estimated current geographic range of golden jackal in Africa represents the African wolf range. Further research is needed in eastern Egypt, where a hybrid zone between Eurasian golden jackal and African wolf may exist. Our results highlight the need for improved studies of geographic range and population surveys for the taxon, which is classified as ‘least concern’ by the IUCN due to its erroneous identification as golden jackal. As a species exclusively distributed in Africa, investigations of the biology and threats to African wolf are needed.

  • Clymans, W.
    et al.
    Conley, D. J.
    Battles, J. J.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Koppers, M. M.
    Likens, G. E.
    Johnson, C. E.
    Silica uptake and release in live and decaying biomass in a northern hardwood forest2016In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 11, 3044-3057 p.Article in journal (Refereed)
    Abstract [en]

    In terrestrial ecosystems, a large portion (20-80%) of the dissolved Si (DSi) in soil solution has passed through vegetation. While the importance of this terrestrial Si filter is generally accepted, few data exist on the pools and fluxes of Si in forest vegetation and the rate of release of Si from decomposing plant tissues. We quantified the pools and fluxes of Si through vegetation and coarse woody debris (CWD) in a northern hardwood forest ecosystem (Watershed 6, W6) at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA. Previous work suggested that the decomposition of CWD may have significantly contributed to an excess of DSi reported in stream-waters following experimental deforestation of Watershed 2 (W2) at the HBEF. We found that woody biomass (wood+bark) and foliage account for approximately 65% and 31%, respectively, of the total Si in biomass at the HBEF. During the decay of American beech (Fagus grandifolia) boles, Si loss tracked the whole-bole mass loss, while yellow birch (Betula alleghaniensis) and sugar maple (Acer saccharum) decomposition resulted in a preferential Si retention of up to 30% after 16yr. A power-law model for the changes in wood and bark Si concentrations during decomposition, in combination with an exponential model for whole-bole mass loss, successfully reproduced Si dynamics in decaying boles. Our data suggest that a minimum of 50% of the DSi annually produced in the soil of a biogeochemical reference watershed (W6) derives from biogenic Si (BSi) dissolution. The major source is fresh litter, whereas only similar to 2% comes from the decay of CWD. Decay of tree boles could only account for 9% of the excess DSi release observed following the experimental deforestation of W2. Therefore, elevated DSi concentrations after forest disturbance are largely derived from other sources (e.g., dissolution of BSi from forest floor soils and/or mineral weathering).

  • Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, Christina
    Struyf, Eric
    van Pelt, Dimitri
    Schoelynck, Jonas
    Hudson, Mike Murray
    Gondwe, Mangaliso J.
    Wolski, Piotr
    Mosimane, Keotsheple
    Gray, William
    Schaller, Jörg
    Conley, Daniel J.
    Tracing silicon cycling in the Okavango Delta, a sub-tropical flood-pulse wetland using silicon isotopes2014In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 142, no 0, 132-148 p.Article in journal (Refereed)
    Abstract [en]

    Chemical weathering of silicate minerals releases elements into solution whereas the neoformation of secondary minerals works in the opposite direction, potentially confounding estimates of silicate weathering rates. Silicon isotopes (δ30Si) may be a useful tool to investigate these processes. Here, we present 82 δ30Si measurements from surface waters, pore waters, biogenic silica (BSi), clays, sand and vegetation from the Okavango Delta, Botswana, a freshwater sub-tropical, flood-pulse wetland. Hydrologically, the Okavango is dominated by evapotranspiration water losses to the atmosphere. It receives an annual pulse of water that inundates seasonal floodplains, while river baseflow is sufficient to maintain a permanent floodplain. δ30Si in dissolved silica (DSi) in surface waters along a 300 km transect at near-peak flood show a limited range (0.36–1.19‰), implying the Delta is well buffered by a balance of processes adding and removing DSi from the surface water. A key control on DSi concentrations is the uptake, production of BSi and recycling of Si by aquatic vegetation, although the net isotopic effect is necessarily small since all BSi re-dissolves on short timescales. In the sediments, BSi δ30Si (n = 30) ranges from −1.49‰ to +0.31‰ and during dissolution, residual BSi tends towards higher δ30Si. The data permit a field-based estimate of the fractionation associated with BSi dissolution, ε30BSi-DSi = −0.26‰, though it is unclear if this is an artefact of the process of dissolution. Clay δ30Si ranges from −0.97‰ to +0.10‰, (n = 15, mean = −0.31‰) and include the highest values yet published, which we speculate may be due to an equilibrium isotope effect during diagenetic transformation of BSi. Two key trends in surface water DSi δ30Si merit further examination: declining δ30Si in an area roughly corresponding to the permanent floodplains despite net DSi removal, and increasing δ30Si in the area corresponding to the seasonal floodplains. We infer that evaporative enrichment of surface waters creates two contrasting regimes. Chemical weathering of low δ30Si phases releases low δ30Si DSi in the relatively dilute waters of the permanent floodplains, whereas silicon removal via clay formation or vegetation uptake is the dominant process in the more enriched, seasonal floodplains.

  • Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Clymans, W.
    Fontorbe, G.
    Gray, W.
    Chakrapani, G. J.
    Conley, D. J.
    De La Rocha, C.
    Silicate weathering in the Ganges alluvial plain2015In: Earth and Planetary Science Letters, Vol. 427, 136-148 p.Article in journal (Refereed)
    Abstract [en]

    The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km(-2) yr(-1), respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as delta Si-30) varies from +0.8 parts per thousand in the Ganges mainstem at the Himalaya front to +3.0 parts per thousand in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher delta Si-30 values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km(-2) yr(-1), for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively). (C) 2015 The Authors. Published by Elsevier B.V.

  • Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Clymans, Wim
    Conley, Daniel J.
    Amorphous Silica Transport in the Ganges Basin: Implications for Si Delivery to the Oceans2014In: Procedia Earth and Planetary Science, Vol. 10, no 0, 271-274 p.Article in journal (Refereed)
    Abstract [en]

    Rivers transport ∽6 x1012 mol yr-1 of dissolved Si (DSi) from the continents to the oceans. They also carry amorphous silica (ASi), solid phases likely to dissolve in seawater. Unfortunately, the magnitude of this flux is poorly constrained at a global scale. We present 92 new ASi values from suspended particulate matter (SPM) from the Ganges basin. Bulk SPM is ∽1.2% ASi, and mean ASi concentrations are ∽65 μM, of comparable magnitude to DSi concentrations. Our results also indicate a) ASi is not evenly distributed in the water column of large rivers, b) the ASi is not a wholly biogenic Si endmember and c) the ASi flux is, to a first order, a function of the SPM load. Our results suggest that the ASi particulate load is much greater than previously believed, rivaling that of the DSi load with important implications for the global Si cycle and oceanic Si isotopic budget.

  • Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Fontorbe, G.
    Clymans, W.
    De La Rocha, C. L.
    Conley, D.J.
    The continental Si cycle and its impact on the ocean Si isotope budget2016In: Chemical Geology, Vol. 425, 12-36 p.Article in journal (Refereed)
  • Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Clymans, Wim
    Jeppesen, Erik
    Lauridsen, Torben L
    Struyf, Eric
    Conley, Daniel J
    Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration2014In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 117, no 2-3, 255-277 p.Article in journal (Refereed)
  • Hålenius, Ulf
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hatert, Frédéric
    Université de Liège, Belgium..
    Pasero, Marco
    Università di Pisa, Italy..
    Mills, Stuart J.
    Museum Victoria, Melbourne, Australia..
    IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) Newsletter 362017In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 81, no 2, 403-409 p.Article in journal (Other academic)
  • Bengtson, Stefan
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Sallstedt, Therese
    Swedish Museum of Natural History, Department of Paleobiology.
    Belivanova, Veneta
    Swedish Museum of Natural History, Department of Paleobiology.
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Three-dimensional preservation of cellular and subcellular structures suggests 1.6 billion-year-old crown-group red algae2017In: PLoS biology, ISSN 1544-9173, E-ISSN 1545-7885, Vol. 15, no 3, 1-38 p., e2000735Article in journal (Refereed)
    Abstract [en]

    The ~1.6 Ga Tirohan Dolomite of the Lower Vindhyan in central India contains phosphatized stromatolitic microbialites. We report from there uniquely well-preserved fossils interpreted as probable crown-group rhodophytes (red algae). The filamentous form Rafatazmia chitrakootensis n. gen, n. sp. has uniserial rows of large cells and grows through diffusely distributed septation. Each cell has a centrally suspended, conspicuous rhomboidal disk interpreted as a pyrenoid. The septa between the cells have central structures that may represent pit connections and pit plugs. Another filamentous form, Denaricion mendax n. gen., n. sp., has coin-like cells reminiscent of those in large sulfur-oxidizing bacteria but much more recalcitrant than the liquid-vacuole-filled cells of the latter. There are also resemblances with oscillatoriacean cyanobacteria, although cell volumes in the latter are much smaller. The wider affinities of Denaricion are uncertain. Ramathallus lobatus n. gen., n. sp. is a lobate sessile alga with pseudoparenchymatous thallus, “cell fountains,” and apical growth, suggesting florideophycean affinity. If these inferences are correct, Rafatazmia and Ramathallus represent crown-group multicellular rhodophytes, antedating the oldest previously accepted red alga in the fossil record by about 400 million years.