24 research outputs found
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Suspended particulate matter transport of polycyclic aromatic hydrocarbons in the lower Columbia River and its estuary
Analysis of suspended particulate material (SPM) collected from the Columbia River and its estuary in 2007–2008 revealed the ubiquitous presence of polycyclic aromatic hydrocarbons (PAHs) from several distinct sources. The two dominant ones were: (1) a suite of non-alkylated, three to five-ringed compounds derived from high temperature combustion and (2) perylene, a compound of diagenetic origin. A particle-selective, hydrodynamic trapping process explains how both PAH types become concentrated on both a particle weight and organic carbon basis in the estuarine turbidity maximum (ETM) by as much as 10 times relative to the riverborne particle source. The ETM is a transient sedimentary feature at the land-to-sea interface of river-dominated estuarine systems which, in the case of our study region, is located remotely from the likely site of initial PAH input. Particle normalized concentrations for PAH of notable environmental concern, such as fluoranthene, chrysene, and benzo[a]pyrene, exceeded the EPA-defined threshold effects level in all cases and were typically at, or above, the probable effects level. Comparison with results from studies for other waterways around the world indicates PAH concentrations in ETM-trapped particles from the Columbia River estuary are higher than those documented for SPM in waters of many far more industrialized and populated regions. Our refined understanding of PAH behavior in the Columbia River and its estuary should prove valuable for reliably modeling the transport and dispersal mechanism that is characteristic of other hydrophobic, particle associated persistent organic pollutants prevalent in this system, and for other river-dominated estuarine systems.This is the publisher’s final pdf. The article is copyrighted by Association for the Sciences of Limnology and Oceanography and published by John Wiley & Sons, Inc. It can be found at: http://www.aslo.org/lo/index.htm
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A Synthesis of Year-Round Interdisciplinary Mooring Measurements in the Bering Strait (1990-2014) and the RUSALCA Years (2004-2011)
The flow through the Bering Strait, the only Pacific-Arctic oceanic gateway, has dramatic local, regional, and global impacts. Advanced year-round moored technology quantifies challengingly large temporal (subdaily, seasonal, and interannual) and spatial variability in the ~85 km wide, two-channel strait. The typically northward flow, intensified seasonally in the ~10–20 km wide, warm, fresh, nutrient-poor Alaskan Coastal Current (ACC) in the east, is otherwise generally homogeneous in velocity throughout the strait, although with higher salinities and nutrients and lower temperatures in the west. Velocity and water properties respond rapidly (including flow reversals) to local wind, likely causing most of the strait’s approximately two-layer summer structure (by “spilling” the ACC) and winter water-column homogenization. We identify island-trapped eddy zones in the central strait; changes in sea-ice properties (season mean thicknesses from 2 m); and increases in annual mean volume, heat, and freshwater fluxes from 2001 to present (2013). Tantalizing first results from year-round bio-optics, nitrate, and ocean acidification sensors indicate significant seasonal and spatial change, possibly driven by the spring bloom. Moored acoustic recorders show large interannual variability in sub-Arctic whale occurrence, related perhaps to water property changes. Substantial daily variability demonstrates the dangers of interpreting section data and the necessity for year-round interdisciplinary time-series measurements.This is the publisher’s final pdf. The published article is copyrighted by the Oceanography Society and can be found at: http://tos.org/oceanography/article/a-synthesis-of-year-round-interdisciplinary-mooring-measurements-in-the-ber Bering Strait physical oceanographic data are available via http://psc.apl.washington.edu/BeringStrait.html and the National Oceanographic Data Center (https://www.nodc.noaa.gov); ocean acidification data, via http://aoncadis.org; and marine mammal acoustic data, via http://aoncadis.org and http://AOOS.org
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Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific
Summertime carbon, nitrogen, and biogenic silica export was examined using ²³⁴Th:²³⁸U disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps (ISP) within the Eastern Tropical North Pacific and the Gulf of California. Fine scale ISP sampling provides evidence that in this system, particulate carbon (PC) and particulate nitrogen (PN) concentrations were more rapidly attenuated relative to ²³⁴Th activities in small particles compared to large particles, converging to 1–5 µmol dpm⁻¹ by 100 m. Comparison of elemental particle composition, coupled with particle size distribution analysis, suggests that small particles are major contributors to particle flux. While absolute PC and PN export rates were dependent on the method used to obtain the element/²³⁴Th ratio, regional trends were consistent across measurement techniques. The highest C fixation rates were associated with diatom-dominated surface waters. Yet, the highest export efficiencies occurred in picoplankton-dominated surface waters, where relative concentrations of diazotrophs were also elevated. Our results add to the increasing body of literature that picoplankton- and diazotroph-dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton, e.g., diatoms, in low productivity pico/nanoplankton-dominated regions, where small particles are major contributors to particle export. Findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate. Therefore, we argue the necessity of collecting multiple particle sizes used to convert ²³⁴Th fluxes into carbon or other elemental fluxes, including <50 µm, since they can play an important role in vertical fluxes, especially in oligotrophic environments. Our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method.This is the publisher’s final pdf. The article is copyrighted by American Geophysical Union and published by John Wiley & Sons, Inc. It can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-9224
Small phytoplankton drive high summertime carbon and nutrient export in the Gulf of California and Eastern Tropical North Pacific
Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 29 (2015): 1309–1332, doi:10.1002/2015GB005134.Summertime carbon, nitrogen, and biogenic silica export was examined using 234Th:238U disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps (ISP) within the Eastern Tropical North Pacific and the Gulf of California. Fine scale ISP sampling provides evidence that in this system, particulate carbon (PC) and particulate nitrogen (PN) concentrations were more rapidly attenuated relative to 234Th activities in small particles compared to large particles, converging to 1–5 µmol dpm−1 by 100 m. Comparison of elemental particle composition, coupled with particle size distribution analysis, suggests that small particles are major contributors to particle flux. While absolute PC and PN export rates were dependent on the method used to obtain the element/234Th ratio, regional trends were consistent across measurement techniques. The highest C fixation rates were associated with diatom-dominated surface waters. Yet, the highest export efficiencies occurred in picoplankton-dominated surface waters, where relative concentrations of diazotrophs were also elevated. Our results add to the increasing body of literature that picoplankton- and diazotroph-dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton, e.g., diatoms, in low productivity pico/nanoplankton-dominated regions, where small particles are major contributors to particle export. Findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate. Therefore, we argue the necessity of collecting multiple particle sizes used to convert 234Th fluxes into carbon or other elemental fluxes, including <50 µm, since they can play an important role in vertical fluxes, especially in oligotrophic environments. Our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method.NSF Grant Numbers: OCE-0726290, OCF-0962362, OCE-0726543, OCE-0726422; EU Grant Number: FP7-MC-IIF-220485; MEC Grant Number: CTM2007-31241-E/MAR; ICREA Academia; MERS Grant Number: 2014 SGR – 1356; Spain's Ministerio de Educación y Ciencia Grant Numbers: AP-2009-4733, BES-2004-3348; NASA New Investigator Award Grant Number: NNX10AQ81G; Sloan Research Fellowship2016-02-2
Small Phytoplankton Drive High Summertime Carbonand Nutrient Export in the Gulf of California and Eastern Tropical North Pacific
Summertime carbon, nitrogen, and biogenic silica export was examined using 234Th:238U disequilibria combined with free floating sediment traps and fine scale water column sampling with in situ pumps (ISP) within the Eastern Tropical North Pacific and the Gulf of California. Fine scale ISP sampling provides evidence that in this system, particulate carbon (PC) and particulate nitrogen (PN) concentrations were more rapidly attenuated relative to 234Th activities in small particles compared to large particles, converging to 1–5 µmol dpm−1 by 100 m. Comparison of elemental particle composition, coupled with particle size distribution analysis, suggests that small particles are major contributors to particle flux. While absolute PC and PN export rates were dependent on the method used to obtain the element/234Th ratio, regional trends were consistent across measurement techniques. The highest C fixation rates were associated with diatom‐dominated surface waters. Yet, the highest export efficiencies occurred in picoplankton‐dominated surface waters, where relative concentrations of diazotrophs were also elevated. Our results add to the increasing body of literature that picoplankton‐ and diazotroph‐dominated food webs in subtropical regions can be characterized by enhanced export efficiencies relative to food webs dominated by larger phytoplankton, e.g., diatoms, in low productivity pico/nanoplankton‐dominated regions, where small particles are major contributors to particle export. Findings from this region are compared globally and provide insights into the efficiency of downward particle transport of carbon and associated nutrients in a warmer ocean where picoplankton and diazotrophs may dominate. Therefore, we argue the necessity of collecting multiple particle sizes used to convert 234Th fluxes into carbon or other elemental fluxes, including \u3c50 \u3eµm, since they can play an important role in vertical fluxes, especially in oligotrophic environments. Our results further underscore the necessity of using multiple techniques to quantify particle flux given the uncertainties associated with each collection method
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Distribution of membrane lipids of planktonic Crenarchaeota in the Arabian Sea
Intact core tetraether membrane lipids of marine planktonic Crenarchaeota were quantified in water column-suspended particulate matter obtained from four depth intervals (~70, 500, 1,000 and 1,500 m) at seven stations in the northwestern Arabian Sea to investigate the distribution of the organisms at various depths. Maximum concentrations generally occurred at 500 m, near the top of the oxygen minimum zone, and the concentrations at this depth were, in most cases, slightly higher than those in surface waters. In contrast, lipids derived from eukaryotes (cholesterol) and from eukaryotes and bacteria (fatty acids) were at their highest concentrations in surface waters. This indicates that these crenarchaeotes are not restricted to the photic zone of the ocean, which is consistent with the results of recent molecular biological studies. Since the Arabian Sea has a strong oxygen minimum zone between 100 and 1,000 m, with minimum oxygen levels of <1 μM, the abundance of crenarchaeotal membrane lipids at 500 m suggests that planktonic Crenarchaeota are probably facultative anaerobes. The cell numbers we calculated from the concentrations of membrane lipids are similar to those reported for the Central Pacific Ocean, supporting the recent estimation of M. B. Karner, E. F. DeLong, and D. M. Karl (Nature 409:507–510, 2001) that the world’s oceans contain ca. 10²⁸ cells of planktonic Crenarchaeota
Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record
© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 483-511, doi: 10.5194/bg-7-483-2010The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments.
It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown.
To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation.
Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more accurate reconstruction of past productivity and bottom water oxygenation.
Given the cost and effort associated with programs to recover sediment cores for paleoclimatological studies, as well as with generating proxy records, it would seem wise to develop a detailed sedimentological and diagenetic context for interpretation of these records. With respect to the latter, parallel acquisition of data that inform on the fidelity of the proxy signatures and reveal potential diagenetic biases would be of clear value.We acknowledge
generous financial support by the DFG Research Center/Cluster of
Excellence MARUM “The Ocean in the Earth System”, the International
Graduate College EUROPROX and the Alfred Wegener
Institute for Polar and Marine Research enabling the realisation
of the “Workshop on Selective Preservation of Organic Matter:
Processes and Impact on the Fossil Record” which formed the basis
of this paper. GJMV acknowledges support by the German Science
Foundation (DFG grant VE486/2)
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Red Waters of Myrionecta rubra are Biogeochemical Hotspots for the Columbia River Estuary with Impacts on Primary/Secondary Productions and Nutrient Cycles
The localized impact of blooms of the mixotrophic ciliate Myrionecta rubra in the Columbia River estuary during 2007-2010 was evaluated with biogeochemical, light microscopy, physiological, and molecular data. M. rubra affected surrounding estuarine nutrient cycles, as indicated by high and low concentrations of organic nutrients and inorganic nitrogen, respectively, associated with red waters. M. rubra blooms also altered the energy transfer pattern in patches of the estuarine water that contain the ciliate by creating areas characterized by high primary production and elevated levels of fresh autochthonous particulate organic matter, therefore shifting the trophic status in emergent red water areas of the estuary from net heterotrophy towards autotrophy. The pelagic estuarine bacterial community structure was unaffected by M. rubra abundance, but red waters of the ciliate do offer a possible link between autotrophic and heterotrophic processes since they were associated with elevated dissolved organic matter and showed a tendency for enhanced microbial secondary production. Taken together, these findings suggest that M. rubra red waters are biogeochemical hotspots of the Columbia River estuary.Keywords: Myrionecta rubra, Biogeochemical cycles, Red waters, Mesodinium rubrum, Columbia River estuar
14C and 13C characteristics of higher plant biomarkers in Washington margin surface sediments
Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 105 (2013): 14-30, doi:10.1016/j.gca.2012.11.034.Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their 13C and 14C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for 14C analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the 13C and 14C compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both δ13C (-28.3 to -37.5 ‰) and ∆14C values (-204 to +2 ‰), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar δ13C values (between -30 to -34 ‰) and a relatively narrow range of ∆14C values (-45 to -150 ‰; HPLC-based mesurement) that were similar to, or younger than, bulk OM (-195 to -137 ‰). Moreover, lignin phenol 14C age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average ~500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol 14C measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics.
Key words: 14C and 13C composition, radiocarbon age, plant wax lipids, lignin phenols, Washington margin, marine carbon cycling, terrestrial organic matterGrants OCE-9907129, OCE-0137005, and OCE-0526268 (to TIE) from the National Science Foundation (NSF) supported this research
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Co-variation of crenarchaeol and branched GDGTs in globally-distributed marine and freshwater sedimentary archives
Two major types of glycerol dialkyl glycerol tetraethers (GDGTs) are commonly
used in paleoecological and paleoclimatological reconstructions: isoprenoidal and
branched GDGTs. In aquatic environments, it was originally assumed that isoprenoidal
GDGTs, especially crenarchaeol, derive mainly from aquatic Thaumarchaeota, whilst
branched GDGTs are an allochthonous input derived from soil Bacteria. Recently,
direct co-variation of crenarchaeol and branched GDGTs has been described in two
marine sedimentary records, and this observation suggests in situ production of
branched GDGTs is possible at least in some aquatic environments. After investigating
30 published and unpublished data sets from downcore and surface sediments as well as
sediment traps from 19 distinct regions around the world, we found a widespread
significant correlation between concentrations of branched GDGTs and crenarchaeol
(p<0.01; r²=0.57-0.99), even when normalized against TOC, where available. These
data sets include freshwater and marine environments with varying distances from the
shore, varying redox conditions and different terrestrial matter input pathways. Our
findings from this large-scale data set suggest that a common or mixed source for both
GDGT types is actually commonplace in lacustrine and marine settings.Keywords: Branched GDGTs,
Oceans,
Crenarchaeol,
Archaea,
Isoprenoid GDGTs,
Lakes,
In situ production