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Full-Text Articles in Life Sciences
Symbiotic Unicellular Cyanobacteria Fix Nitrogen In The Arctic Ocean, K. Harding, K. A. Turk-Kubo, Rachel E. Sipler, M. M. Mills, D. A. Bronk
Symbiotic Unicellular Cyanobacteria Fix Nitrogen In The Arctic Ocean, K. Harding, K. A. Turk-Kubo, Rachel E. Sipler, M. M. Mills, D. A. Bronk
VIMS Articles
Biological dinitrogen (N2) fixation is an important source of nitrogen (N) in low-latitude open oceans. The unusual N2-fixing unicellular cyanobacteria (UCYN-A)/haptophyte symbiosis has been found in an increasing number of unexpected environments, including northern waters of the Danish Straight and Bering and Chukchi Seas. We used nanoscale secondary ion mass spectrometry (nanoSIMS) to measure 15N2 uptake into UCYN-A/haptophyte symbiosis and found that UCYN-A strains identical to low-latitude strains are fixing N2 in the Bering and Chukchi Seas, at rates comparable to subtropical waters. These results show definitively that cyanobacterial N2 fixation is not constrained to subtropical waters, challenging paradigms and …
The Contribution Of Local And Transport Processes To Phytoplankton Biomass Variability Over Different Timescales In The Upper James River, Virginia, Qubin Quin, Jian Shen
The Contribution Of Local And Transport Processes To Phytoplankton Biomass Variability Over Different Timescales In The Upper James River, Virginia, Qubin Quin, Jian Shen
VIMS Articles
Although both local processes (photosynthesis, respiration, grazing, and settling), and transport processes (advective transport and diffusive transport) significantly affect local phytoplankton dynamics, it is difficult to separate their contributions and to investigate the relative importance of each process to the local variability of phytoplankton biomass over different timescales. A method of using the transport rate is introduced to quantify the contribution of transport processes. By combining the time-varying transport rate and high-frequency observed chlorophyll a data, we can explicitly examine the impact of local and transport processes on phytoplankton biomass over a range of timescales from hourly to annually. For …
Millennial Soil Retention Of Terrestrial Organic Matter Deposited In The Bengal Fan, Kl French, Christopher J. Hein, N Haghipour, L Wacker, Hr Kudrass
Millennial Soil Retention Of Terrestrial Organic Matter Deposited In The Bengal Fan, Kl French, Christopher J. Hein, N Haghipour, L Wacker, Hr Kudrass
VIMS Articles
The abundance of organic carbon (OC) in vegetation and soils (similar to 2,600 PgC) compared to carbon in the atmosphere (similar to 830 PgC) highlights the importance of terrestrial OC in global carbon budgets. The residence time of OC in continental reservoirs, which sets the rates of carbon exchange between land and atmosphere, represents a key uncertainty in global carbon cycle dynamics. Retention of terrestrial OC can also distort bulk OC- and biomarker-based paleorecords, yet continental storage timescales remain poorly quantified. Using "bomb" radiocarbon (C-14) from thermonuclear weapons testing as a tracer, we model leaf-wax fatty acid and bulk OC …
Predicting Marsh Vulnerability To Sea-Level Rise Using Holocene Relative Sea-Level Data, Bp Horton, I Shennan, Sl Bradley, N Cahill, Matthew L. Kirwan, Re Kopp, Ta Shaw
Predicting Marsh Vulnerability To Sea-Level Rise Using Holocene Relative Sea-Level Data, Bp Horton, I Shennan, Sl Bradley, N Cahill, Matthew L. Kirwan, Re Kopp, Ta Shaw
VIMS Articles
Tidal marshes rank among Earth's vulnerable ecosystems, which will retreat if future rates of relative sea-level rise (RSLR) exceed marshes' ability to accrete vertically. Here, we assess the limits to marsh vulnerability by analyzing >780 Holocene reconstructions of tidal marsh evolution in Great Britain. These reconstructions include both transgressive (tidal marsh retreat) and regressive (tidal marsh expansion) contacts. The probability of a marsh retreat was conditional upon Holocene rates of RSLR, which varied between -7.7 and 15.2 mm/yr. Holocene records indicate that marshes are nine times more likely to retreat than expand when RSLR rates are >= 7.1 mm/yr. Coupling …
Numerical Model Of Geochronological Tracers For Deposition And Reworking Applied To The Mississippi Subaqueous Delta, Jj Birchler, Courtney K. Harris, Ta Kniskern, Cr Sherwood
Numerical Model Of Geochronological Tracers For Deposition And Reworking Applied To The Mississippi Subaqueous Delta, Jj Birchler, Courtney K. Harris, Ta Kniskern, Cr Sherwood
VIMS Articles
Measurements of naturally occurring, short-lived radioisotopes from sediment cores on the Mississippi subaqueous delta have been used to infer event bed characteristics such as depositional thicknesses and accumulation rates. Specifically, the presence of Beryllium-7 (Be-7) indicates recent riverine-derived terrestrial sediment deposition; while Thorium-234 (Th-234) provides evidence of recent suspension in marine waters. Sediment transport models typically represent coastal flood and storm deposition via estimated grain size patterns and deposit thicknesses, however, and do not directly calculate radioisotope activities and profiles, which leads to a disconnect between the numerical model and field observations. Here, observed radioisotopic profiles from the Mississippi subaqueous …
Cross-Scale Baroclinic Simulation Of The Effect Of Channel Dredging In An Estuarine Setting, Fei Ye, Harry V. Wang, H Huang, Zg Wang, Z Liu, X Li
Cross-Scale Baroclinic Simulation Of The Effect Of Channel Dredging In An Estuarine Setting, Fei Ye, Harry V. Wang, H Huang, Zg Wang, Z Liu, X Li
VIMS Articles
Holistic simulation approaches are often required to assess human impacts on a river-estuary-coastal system, due to the intrinsically linked processes of contrasting spatial scales. In this paper, a Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) is applied in quantifying the impact of a proposed hydraulic engineering project on the estuarine hydrodynamics. The project involves channel dredging and land expansion that traverse several spatial scales on an ocean-estuary-river-tributary axis. SCHISM is suitable for this undertaking due to its flexible horizontal and vertical grid design and, more importantly, its efficient high-order implicit schemes applied in both the momentum and transport calculations. These …
Discerning Autotrophy, Mixotrophy And Heterotrophyin Marine Tack Archaea From The North Atlantic, L M. Seyler, L. R. Mcguinness, J. A. Gilbert, J. F. Biddle, Donglai Gong, L. J. Kerkhof
Discerning Autotrophy, Mixotrophy And Heterotrophyin Marine Tack Archaea From The North Atlantic, L M. Seyler, L. R. Mcguinness, J. A. Gilbert, J. F. Biddle, Donglai Gong, L. J. Kerkhof
VIMS Articles
DNA stable isotope probing (SIP) was used to track the uptake of organic and inorganic carbon sources for TACK archaea(Thaumarchaeota/Aigarchaeota/Crenarchaeota/Korarchaeota) on a cruise of opportunity in the North Atlantic. Due to water limitations, duplicate samples from the deep photic (60–115 m), the mesopelagic zones (local oxygen minimum; 215–835 m)and the bathypelagic zone (2085–2835 m) were amended with various combinations of12C- or13C-acetate/urea/bicarbonate to assess cellular carbon acquisition. The SIP results indicated the majority of TACK archaeal operational taxonomic units(OTUs) incorporated13C from acetate and/or urea into newly synthesized DNA within 48 h. A small fraction (16%) of the OTUs, often representing the …
Accuracy And Precision Of Tidal Wetland Soil Carbon Mapping In The Conterminous United States, Jr Holmquist, L Windham-Myers, N Bliss, S Crooks, Jt Morris, W. G. Reay, Et Al.
Accuracy And Precision Of Tidal Wetland Soil Carbon Mapping In The Conterminous United States, Jr Holmquist, L Windham-Myers, N Bliss, S Crooks, Jt Morris, W. G. Reay, Et Al.
VIMS Articles
Tidal wetlands produce long-term soil organic carbon (C) stocks. Thus for carbon accounting purposes, we need accurate and precise information on the magnitude and spatial distribution of those stocks. We assembled and analyzed an unprecedented soil core dataset, and tested three strategies for mapping carbon stocks: applying the average value from the synthesis to mapped tidal wetlands, applying models fit using empirical data and applied using soil, vegetation and salinity maps, and relying on independently generated soil carbon maps. Soil carbon stocks were far lower on average and varied less spatially and with depth than stocks calculated from available soils …
Spatial Distribution And Morphological Responses To Predation In The Salt Marsh Periwinkle, Aj Rietl, Mg Sorrentino, Bj Roberts
Spatial Distribution And Morphological Responses To Predation In The Salt Marsh Periwinkle, Aj Rietl, Mg Sorrentino, Bj Roberts
VIMS Articles
The salt marsh periwinkle (Littoraria irrorata) is a common and often abundant mollusk in marshes of the Gulf and Atlantic coasts of the United States. Several studies have focused on the effects of periwinkles on Spartina alterniflora production and the effects of oil on periwinkle survivability, yet the general ecology of the snail has been underreported. In this study, we measured spatial distributions, biomass, shell repair frequency, and a suite of morphological characteristics of L. irrorata at three sites in each of five regions spanning the southeastern Louisiana Coast between the Atchafalaya and Mississippi rivers. Sampling was conducted along 50 …
Time Trends Of Polybrominated Diphenyl Ethers (Pbdes) In Antarctic Biota, E Markham, Ek Brault, M Khairy, Ar Robuck, Me Goebel, Mg Cantwell, Rm Dickhut, R Lohmann
Time Trends Of Polybrominated Diphenyl Ethers (Pbdes) In Antarctic Biota, E Markham, Ek Brault, M Khairy, Ar Robuck, Me Goebel, Mg Cantwell, Rm Dickhut, R Lohmann
VIMS Articles
Polybrominated diphenyl ethers (PBDEs) are "emerged" contaminants that were produced and used as flame retardants in numerous consumer and industrial applications for decades until banned. They remain ubiquitously present in the environment today. Here, a unique set of >200 biotic samples from the Antarctic was analyzed for PBDEs, including phytoplankton, krill, fish, and fur seal milk, spanning several sampling seasons over 14 years. PBDE-47 and -99 were the dominant congeners determined in all samples, constituting > 60% of total PBDEs. A temporal trend was observed for Sigma 7PBDE concentrations in fur seal milk, where concentrations significantly increased (R-2 = 0.57, p < 0.05) over time (2000-2014). Results for krill and phytoplankton also suggested increasing PBDE concentrations over time. Trends of PBDEs in fur seal milk of individual seals sampled 1 or more years apart showed no clear temporal trends. Overall, there was no indication of PBDEs decreasing in Antarctic biota yet, whereas numerous studies have reported decreasing trends in the northern hemisphere. Similar PBDE concentrations in perinatal versus nonperinatal milk implied the importance of local PBDE sources for bioaccumulation. These results indicate the need for continued assessment of contaminant trends, such as PBDEs, and their replacements, in Antarctica.
Cohesive And Mixed Sediment In The Regional Ocean Modeling System (Roms V3.6) Implemented In The Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System (Coawst R1234), Cr Sherwood, Al Aretxabaleta, Courtney K. Harris, Jp Rinehimer, R Verney, B Ferre
Cohesive And Mixed Sediment In The Regional Ocean Modeling System (Roms V3.6) Implemented In The Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System (Coawst R1234), Cr Sherwood, Al Aretxabaleta, Courtney K. Harris, Jp Rinehimer, R Verney, B Ferre
VIMS Articles
We describe and demonstrate algorithms for treating cohesive and mixed sediment that have been added to the Regional Ocean Modeling System (ROMS version 3.6), as implemented in the Coupled Ocean-Atmosphere-Wave- Sediment Transport Modeling System (COAWST Subversion repository revision 1234). These include the following: floc dynamics (aggregation and disaggregation in the water column); changes in floc characteristics in the seabed; erosion and deposition of cohesive and mixed (combination of cohesive and non-cohesive) sediment; and biodiffusive mixing of bed sediment. These routines supplement existing noncohesive sediment modules, thereby increasing our ability to model fine-grained and mixed-sediment environments. Additionally, we describe changes to …
The Competing Impacts Of Climate Change And Nutrient Reductions On Dissolved Oxygen In Chesapeake Bay, Id Irby, Marjorie A.M. Friedrichs, F Da, Ke Hinson
The Competing Impacts Of Climate Change And Nutrient Reductions On Dissolved Oxygen In Chesapeake Bay, Id Irby, Marjorie A.M. Friedrichs, F Da, Ke Hinson
VIMS Articles
The Chesapeake Bay region is projected to experience changes in temperature, sea level, and precipitation as a result of climate change. This research uses an estuarine-watershed hydrodynamic-biogeochemical modeling system along with projected mid-21st-century changes in temperature, freshwater flow, and sea level rise to explore the impact climate change may have on future Chesapeake Bay dissolved-oxygen (DO) concentrations and the potential success of nutrient reductions in attaining mandated estuarine water quality improvements. Results indicate that warming bay waters will decrease oxygen solubility year-round, while also increasing oxygen utilization via respiration and remineralization, primarily impacting bottom oxygen in the spring. Rising sea …
Assimilating Bio-Optical Glider Data During A Phytoplankton Bloom In The Southern Ross Sea, De Kaufman, Marjorie A.M. Friedrichs, Jcp Hemmings, Walker O. Smith Jr.
Assimilating Bio-Optical Glider Data During A Phytoplankton Bloom In The Southern Ross Sea, De Kaufman, Marjorie A.M. Friedrichs, Jcp Hemmings, Walker O. Smith Jr.
VIMS Articles
The Ross Sea is a region characterized by high primary productivity in comparison to other Antarctic coastal regions, and its productivity is marked by considerable variability both spatially (1-50 km) and temporally (days to weeks). This variability presents a challenge for inferring phytoplankton dynamics from observations that are limited in time or space, which is often the case due to logistical limitations of sampling. To better understand the spatio-temporal variability in Ross Sea phytoplankton dynamics and to determine how restricted sampling may skew dynamical interpretations, high-resolution bio-optical glider measurements were assimilated into a one-dimensional biogeochemical model adapted for the Ross …
Early-Holocene Greening Of The Afro-Asian Dust Belt Changed Sources Of Mineral Dust In West Asia, A Sharifi, Ln Murphy, A Pourmand, Ac Clement, Elizabeth A. Canuel
Early-Holocene Greening Of The Afro-Asian Dust Belt Changed Sources Of Mineral Dust In West Asia, A Sharifi, Ln Murphy, A Pourmand, Ac Clement, Elizabeth A. Canuel
VIMS Articles
Production, transport and deposition of mineral dust have significant impacts on different components of the Earth systems through time and space. In modern times, dust plumes are associated with their source region(s) using satellite and land -based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleodust, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr-Nd-Hf isotopes and …