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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen metabolism by heterotrophic bacterial assemblages in Antarctic coastal waters (1994)
    Springer
    Polar biology 14 (1994), S. 195-204 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Field studies to examine the in situ assimilation and production of ammonium (NH4 +) by bacterial assemblages were conducted in the northern Gerlache Strait region of the Antarctic Peninsula. Short term incubations of surface waters containing 15N-NH4 + as a tracer showed the bacterial population taking up 0.041–0.128 μg-atoms Nl−1d−1, which was 8–25% of total NH4 + uptake rates. The large bacterial uptake of NH4 + occurred even at low bacterial abundance during a rich phytoplankton bloom. Estimates of bacterial production using 3H-leucine and -adenine were l.0μgCl−1 d−1 before the bloom and 16.2 μg Cl−1 d−1 at the bloom peak. After converting bacterial carbon production to an estimate of nitrogen demand, NH4 + was found to supply 35–60% of bacterial nitrogen requirements. Bacterial nitrogen demand was also supported by dissolved organic nitrogen, generally in the form of amino acids. It was estimated, however, that 20–50% of the total amino acids taken up were mineralized to NH4 +. Bacterial production of NH4 + was occurring simultaneously to its uptake and contributed 27–55% of total regenerated NH4 + in surface waters. Using a variety of 15N-labelled amino acids it was found that the bacteria metabolized each amino acid differently. With their large mineralization of amino acids and their relatively low sinking rates, bacteria appear to be responsible for a large portion of organic matter recycling in the upper surface waters of the coastal Antarctic ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240524
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  • 2
    Electronic Resource
    Electronic Resource
    Remineralization Ratios in the Subtropical North Pacific Gyre (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 65-85 
    Details
    ISSN: 1573-1421
    Keywords: Mixing model ; preformed nutrients ; Redfield ratios ; Remineralization ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Based on a new mixing model of two end-members, the water column remineralization ratios of P/N/Corg - O2 = 1/13 ± 1/135 ± 18/170 ± 9 are obtained for the Hawaii Ocean Time-series (HOT) data set at station ALOHA. The traditional Redfield ratios of P/N/Corg/–O2 = 1/16/106/138 have standard deviations of more than 50%, when they are based on the average composition of phytoplankton. Apparently, the remineralization processes in the water column have smoothed out the observed large variability of plankton compositions. A new molar formula for the remineralized plankton may be written as 135H280O105N13P or C25(CH2O)101(CH4)9(NH3)13(H3PO4). Oxidation of this formula results in C25(CH2O)101(CH4)9(NH3)13(H3PO4) + 170O2 → 135CO2 + 132H2O + 13NO3 - + H2PO4 - + 14H+. For comparison, remineralization using Redfield's formula gives: (CH2O)106(NH3)16(H3PO4) + 138O2 → 106CO2 + 122H2O + 16NO3 -+ H2PO4 - + 17H+
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009676300859
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  • 3
    Electronic Resource
    Electronic Resource
    The grounding of the Bahia Paraiso: Microbial ecology of the 1989 Antarctic oil spill (1992)
    Springer
    Microbial ecology 24 (1992), S. 77-89 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On 28 January 1989 the Bahia Paraiso ran aground and sank near Palmer Station, Antarctica. At least 6.8 × 105 liters of diesel fuel arctic (DFA) were released into semi-enclosed Arthur Harbor and deposited in the nearby intertidal regions. Approximately 6 weeks later, a group of scientists was deployed to evaluate the impact of the oil spill on the surrounding coastal marine ecosystem. Microbial hydrocarbon oxidation potential (14CO2 evolved from 14C-labeled hexadecane) was detected throughout both the oil-impacted and control regions. Hexadecane was mineralized at extremely low rates (0.13–1.21 pmol g−1 sediment dry weight day−1); microbiological turnover time exceeded 2 years. The acute effects of DFA (measured over exposure periods of 3–7 days) on the metabolic activities of sedimentary microorganisms appear to be negligible even at seawater saturation concentrations of DFA. Long-term exposure (120 days) to varying concentrations of DFA resulted in significant decreases (〉90%) in total ATP, but had either no effect or a slight stimulatory effect on metabolic activity and production. In contrast to planktonic microbial communities, increasing incubation temperatures of between 0 and 30°C had a positive effect on rates of metabolism and production of sedimentary assemblages. These results may influence the overall weathering rates of hydrocarbons deposited in the intertidal and supratidal regions of Arthur Harbor and other polar regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171972
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  • 4
    Electronic Resource
    Electronic Resource
    A Sea of Change: Biogeochemical Variability in the North Pacific Subtropical Gyre (1999)
    Springer
    Ecosystems 2 (1999), S. 181-214 
    Details
    ISSN: 1435-0629
    Keywords: Key words: oceanography; microbial ecology; nutrients; climate; biodiversity; food webs; microbiology.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT The North Pacific Subtropical Gyre (NPSG) is the largest ecosystem on our planet. However, this expansive habitat is also remote, poorly sampled, and therefore not well understood. For example, the most abundant oxygenic phototroph in the NPSG, Prochlorococcus, was described only a decade ago. Other novel Bacteria, Archaea and Eukarya, recently identified by nucleic acid sequence analysis, have not been isolated. In October 1988, an ocean time-series research program was established to study ecosystem processes in the gyre, including rates and pathways of carbon and energy flow, spatial and temporal scales of variability, and coupling of ocean physics to biogeochemical processes. After a decade of ecosystem surveillance, this sentinel observatory has produced an unprecedented data set and some new views of an old ocean. Foremost is evidence for dramatic changes in microbial community structure and in mechanisms of nutrient cycling in response to large-scale ocean–atmosphere interactions. These and other observations demand reassessment of current views of physical-biogeochemical processes in this and other open-ocean ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900068
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  • 5
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    Short-term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA : a case study of summer 2012 (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: 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): 1145–1164, doi:10.1002/2015GB005141.
    Description: Time-series observations are critical to understand the structure, function, and dynamics of marine ecosystems. The Hawaii Ocean Time-series program has maintained near-monthly sampling at Station ALOHA (22°45′N, 158°00′W) in the oligotrophic North Pacific Subtropical Gyre (NPSG) since 1988 and has identified ecosystem variability over seasonal to interannual timescales. To further extend the temporal resolution of these near-monthly time-series observations, an extensive field campaign was conducted during July–September 2012 at Station ALOHA with near-daily sampling of upper water-column biogeochemistry, phytoplankton abundance, and activity. The resulting data set provided biogeochemical measurements at high temporal resolution and documents two important events at Station ALOHA: (1) a prolonged period of low productivity when net community production in the mixed layer shifted to a net heterotrophic state and (2) detection of a distinct sea-surface salinity minimum feature which was prominent in the upper water column (0–50 m) for a period of approximately 30 days. The shipboard observations during July–September 2012 were supplemented with in situ measurements provided by Seagliders, profiling floats, and remote satellite observations that together revealed the extent of the low productivity and the sea-surface salinity minimum feature in the NPSG.
    Description: NOAA Climate Observation Division; National Science Foundation (NSF) Center for Microbial Oceanography: Research and Education (C-MORE) Grant Numbers: EF0424599, OCE-1153656, OCE-1260164; Gordon and Betty Moore Foundation Marine Microbiology Investigator
    Description: 2016-02-13
    Keywords: Primary productivity ; Microbial ecology ; Station ALOHA ; Temporal variability ; Biogeochemistry
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 6
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    Polyphosphate dynamics at Station ALOHA, North Pacific subtropical gyre (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Association for the Sciences of Limnology and Oceanography, 2015. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 61 (2016): 227–239, doi:10.1002/lno.10206.
    Description: Polyphosphate (polyP) was examined within the upper water column (≤ 150 m) of Station ALOHA (22° 45′N, 158° 00′W) during two cruises conducted in May–June 2013 and September 2013. Phosphorus molar ratios of particulate polyP to total particulate phosphorus (TPP) were relatively low, similar to previously reported values from the temperate western North Atlantic, and did not exhibit strong vertical gradients, reflecting a lack of polyP recycling relative to other forms of TPP with depth. Furthermore, relationships among polyP:TPP, soluble reactive phosphorus (SRP), and alkaline phosphatase activity (APA) were also consistent with previous observations from the Atlantic Ocean. To ascertain potential mechanisms of biological polyP production and utilization, surface seawater was incubated following nutrient additions. Results were consistent with polyP:TPP enrichment under opposite extremes of APA, suggesting diverse polyP accumulation/retention mechanisms. Addition of exogenous polyP (45 ± 5 P atoms) to field incubations did not increase chlorophyll content relative to controls, suggesting that polyP was not bioavailable to phytoplankton at Station ALOHA. To clarify this result, phytoplankton cultures were screened for the ability to utilize exogenous polyP. PolyP bioavailability was variable among model diatoms of the genus Thalassiosira, yet chain length did not influence polyP bioavailability. Thus, microbial community composition may influence polyP dynamics in the ocean, and vice versa.
    Description: This work was supported by a Postdoctoral Fellowship from the Ford Foundation (JMD), the National Science Foundation under grants OCE 1225801 (JMD), OCE 1316036 (STD), EF 04-24599 (DMK), the Woods Hole Oceanographic Coastal Ocean Institute, the Center for Microbial Oceanography: Research and Education, and the Gordon and Betty Moore Foundation (DMK). Additional support was provided by grants from the Simons Foundation to DMK and STD.
    Repository Name: Woods Hole Open Access Server
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  • 7
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    Quantifying subtropical North Pacific gyre mixed layer primary productivity from Seaglider observations of diel oxygen cycles (2015)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geophysical Research Letters 42 (2015): 4032–4039, doi:10.1002/2015GL063065.
    Description: Using autonomous underwater gliders, we quantified diurnal periodicity in dissolved oxygen, chlorophyll, and temperature in the subtropical North Pacific near the Hawaii Ocean Time-series (HOT) Station ALOHA during summer 2012. Oxygen optodes provided sufficient stability and precision to quantify diel cycles of average amplitude of 0.6 µmol kg−1. A theoretical diel curve was fit to daily observations to infer an average mixed layer gross primary productivity (GPP) of 1.8 mmol O2 m−3 d−1. Cumulative net community production (NCP) over 110 days was 500 mmol O2 m−2 for the mixed layer, which averaged 57 m in depth. Both GPP and NCP estimates indicated a significant period of below-average productivity at Station ALOHA in 2012, an observation confirmed by 14C productivity incubations and O2/Ar ratios. Given our success in an oligotrophic gyre where biological signals are small, our diel GPP approach holds promise for remote characterization of productivity across the spectrum of marine environments.
    Description: The authors acknowledge support from the National Science Foundation (NSF) through an NSF Science and Technology Center, the Center for Microbial Oceanography Research and Education (C-MORE; NSF EF-0424599). D.N. also was supported by NSF (OCE-1129644) and an Independent Study Award from the Woods Hole Oceanographic Institution (WHOI). D.M.K. was also supported by the Gordon and Betty Moore Foundation. WHOI Summer Student Fellow Cole Stites-Clayton, Stanford University, contributed to early stages of Seaglider data analysis and was supported by an NSF REU grant to WHOI (OCE-1156952).
    Keywords: Primary productivity ; Glider ; Diel ; Oxygen ; Net community production ; Hawaii
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Diversity and productivity of photosynthetic picoeukaryotes in biogeochemically distinct regions of the South East Pacific Ocean (2016)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography 61 (2016): 806–824, doi:10.1002/lno.10255.
    Description: Picophytoplankton, including photosynthetic picoeukaryotes (PPE) and unicellular cyanobacteria, are important contributors to plankton biomass and primary productivity. In this study, phytoplankton composition and rates of carbon fixation were examined across a large trophic gradient in the South East Pacific Ocean (SEP) using a suite of approaches: photosynthetic pigments, rates of 14C-primary productivity, and phylogenetic analyses of partial 18S rRNA genes PCR amplified and sequenced from flow cytometrically sorted cells. While phytoplankton 〉10 μm (diatoms and dinoflagellates) were prevalent in the upwelling region off the Chilean coast, picophytoplankton consistently accounted for 55–92% of the total chlorophyll a inventories and 〉60% of 14C-primary productivity throughout the sampling region. Estimates of rates of 14C-primary productivity derived from flow cytometric sorting of radiolabeled cells revealed that the contributions of PPE and Prochlorococcus to euphotic zone depth-integrated picoplankton productivity were nearly equivalent (ranging 36–57%) along the transect, with PPE comprising a larger share of picoplankton productivity than cyanobacteria in the well-lit (〉15% surface irradiance) region compared with in the lower regions (1–7% surface irradiance) of the euphotic zone. 18S rRNA gene sequence analyses revealed the taxonomic identities of PPE; e.g., Mamiellophyceae (Ostreococcus) were the dominant PPE in the upwelling-influenced waters, while members of the Chrysophyceae, Prymnesiophyceae, Pelagophyceae, and Prasinophyceae Clades VII and IX flourished in the oligotrophic South Pacific Subtropical Gyre. Our results suggest that, despite low numerical abundance in comparison to cyanobacteria, diverse members of PPE are significant contributors to carbon cycling across biogeochemically distinct regions of the SEP.
    Description: Support for this work derived from U.S. National Science Foundation grants to C-MORE (EF-0424599; DMK) and OCE-1241263 (MJC). Additional support was received from the University of Hawai'i Denise B. Evans Research Fellowship in Oceanography (YMR), the Gordon and Betty Moore Foundation (DMK), and the Simons Foundation via the Simons Collaboration on Ocean Processes and Ecology (SCOPE: DJR, MJC, and DMK).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    Allochthonous sources and dynamic cycling of ocean dissolved organic carbon revealed by carbon isotopes (2017)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 44 (2017): 2407–2415, doi:10.1002/2016GL071348.
    Description: We present concentration and isotopic profiles of total, size, and polarity fractionated dissolved organic carbon (DOC) from Station ALOHA (A Long-term Oligotrophic Habitat Assessment), an oligotrophic site in the North Pacific Ocean. The data show that, between the surface and 3500 m, low molecular weight (LMW) hydrophilic DOC, LMW hydrophobic DOC, and high molecular weight (HMW) DOC constitute 22–33%, 45–52%, and 23–35% of DOC, respectively. LMW hydrophilic DOC is more isotopically depleted (δ13C of −23.9‰ to −31.5‰ and Δ14C of −304‰ to −795‰; mean age of 2850 to 15000 years) than the LMW hydrophobic DOC (δ13C of −22‰ to −23‰ and Δ14C of −270‰ to −568‰; 2470 to 6680 years) and HMW DOC (δ13C of ~−21‰ and Δ14C of −24‰ to −294‰; 135–2700 years). Our analyses suggest that a large fraction of DOC may be derived from allochthonous sources such as terrestrial and hydrothermal DOC and cycle on much longer time scales of 〉10000 years or enter the ocean as preaged carbon.
    Description: NSF Cooperative Agreement for the Operation of a National Ocean Sciences Accelerator Mass Spectrometry Facility Grant Number: OCE-0753487; Gordon and Betty Moore Foundation Grant Numbers: GBMF3298, GBMF3794; Simons Foundation Grant Number: 329108
    Description: 2017-09-07
    Keywords: Carbon cycling ; Carbon isotopes ; Radiocarbon ; Biogeochemical cycles
    Repository Name: Woods Hole Open Access Server
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  • 10
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    Minireviews: A Sea of Change: Biogeochemical Variability in the North Pacific Subtropical Gyre (1999)
    Springer
    Details
    Publication Date: 1999-05-01
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
    Published by Springer
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