Lohrenz Steven E.

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Steven E.

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  • Article
    Carbon cycling in the North American coastal ocean: a synthesis
    (European Geosciences Union, 2019-03-27) Fennel, Katja ; Alin, Simone R. ; Barbero, Leticia ; Evans, Wiley ; Bourgeois, Timothée ; Cooley, Sarah R. ; Dunne, John P. ; Feely, Richard A. ; Hernandez-Ayon, Jose Martin ; Hu, Xinping ; Lohrenz, Steven E. ; Muller-Karger, Frank E. ; Najjar, Raymond G. ; Robbins, Lisa ; Shadwick, Elizabeth H. ; Siedlecki, Samantha A. ; Steiner, Nadja ; Sutton, Adrienne J. ; Turk, Daniela ; Vlahos, Penny ; Wang, Zhaohui Aleck
    A quantification of carbon fluxes in the coastal ocean and across its boundaries with the atmosphere, land, and the open ocean is important for assessing the current state and projecting future trends in ocean carbon uptake and coastal ocean acidification, but this is currently a missing component of global carbon budgeting. This synthesis reviews recent progress in characterizing these carbon fluxes for the North American coastal ocean. Several observing networks and high-resolution regional models are now available. Recent efforts have focused primarily on quantifying the net air–sea exchange of carbon dioxide (CO2). Some studies have estimated other key fluxes, such as the exchange of organic and inorganic carbon between shelves and the open ocean. Available estimates of air–sea CO2 flux, informed by more than a decade of observations, indicate that the North American Exclusive Economic Zone (EEZ) acts as a sink of 160±80 Tg C yr−1, although this flux is not well constrained. The Arctic and sub-Arctic, mid-latitude Atlantic, and mid-latitude Pacific portions of the EEZ account for 104, 62, and −3.7 Tg C yr−1, respectively, while making up 51 %, 25 %, and 24 % of the total area, respectively. Combining the net uptake of 160±80 Tg C yr−1 with an estimated carbon input from land of 106±30 Tg C yr−1 minus an estimated burial of 65±55 Tg C yr−1 and an estimated accumulation of dissolved carbon in EEZ waters of 50±25 Tg C yr−1 implies a carbon export of 151±105 Tg C yr−1 to the open ocean. The increasing concentration of inorganic carbon in coastal and open-ocean waters leads to ocean acidification. As a result, conditions favoring the dissolution of calcium carbonate occur regularly in subsurface coastal waters in the Arctic, which are naturally prone to low pH, and the North Pacific, where upwelling of deep, carbon-rich waters has intensified. Expanded monitoring and extension of existing model capabilities are required to provide more reliable coastal carbon budgets, projections of future states of the coastal ocean, and quantification of anthropogenic carbon contributions.
  • Article
    The United States' next generation of atmospheric composition and coastal ecosystem measurements : NASA's Geostationary Coastal and Air Pollution Events (GEO-CAPE) Mission
    (American Meteorological Society, 2012-10) Fishman, J. ; Iraci, L. T. ; Al-Saadi, J. ; Chance, K. ; Chavez, Francisco P. ; Chin, M. ; Coble, Paula G. ; Davis, Curtiss O. ; DiGiacomo, P. M. ; Edwards, D. ; Eldering, A. ; Goes, Joachim I. ; Herman, J. ; Hu, Chuanmin ; Jacob, Daniel J. ; Jordan, C. ; Kawa, S. Randolph ; Key, R. ; Liu, X. ; Lohrenz, Steven E. ; Mannino, Antonio ; Natraj, V. ; Neil, D. ; Neu, J. ; Newchurch, M. J. ; Pickering, K. ; Salisbury, Joseph E. ; Sosik, Heidi M. ; Subramaniam, A. ; Tzortziou, Maria ; Wang, Jian ; Wang, M.
    The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission was recommended by the National Research Council's (NRC's) Earth Science Decadal Survey to measure tropospheric trace gases and aerosols and coastal ocean phytoplankton, water quality, and biogeochemistry from geostationary orbit, providing continuous observations within the field of view. To fulfill the mandate and address the challenge put forth by the NRC, two GEO-CAPE Science Working Groups (SWGs), representing the atmospheric composition and ocean color disciplines, have developed realistic science objectives using input drawn from several community workshops. The GEO-CAPE mission will take advantage of this revolutionary advance in temporal frequency for both of these disciplines. Multiple observations per day are required to explore the physical, chemical, and dynamical processes that determine tropospheric composition and air quality over spatial scales ranging from urban to continental, and over temporal scales ranging from diurnal to seasonal. Likewise, high-frequency satellite observations are critical to studying and quantifying biological, chemical, and physical processes within the coastal ocean. These observations are to be achieved from a vantage point near 95°–100°W, providing a complete view of North America as well as the adjacent oceans. The SWGs have also endorsed the concept of phased implementation using commercial satellites to reduce mission risk and cost. GEO-CAPE will join the global constellation of geostationary atmospheric chemistry and coastal ocean color sensors planned to be in orbit in the 2020 time frame.
  • Working Paper
    The development of ocean test beds for ocean technology adaptation and integration into the emerging U.S. offshore wind energy industry
    (Woods Hole Oceanographic Institution, 2018-05) Kirincich, Anthony R. ; Borkland, Jay ; Hines, Eric W. ; Lohrenz, Steven E.
    The landscape of applied ocean technology is rapidly changing with forces of innovation emerging from basic ocean science research methodologies as well as onshore high tech sectors. There is a critical need for ocean-related industries to continue to modernize via the adoption of state-of-the-art practices to advance rapidly changing industry objectives, maintain competitiveness, and be careful stewards of the ocean as a common resource. These objectives are of national importance for the dynamic ocean energy sector, and a mechanism by which new and promising technologies can be validated and adopted in an open and benchmarked process is needed. POWER-US seeks to develop Ocean Test Beds as research and development infrastructure capable of driving innovative observations, modeling, and monitoring of the physical, biological, and use characteristics present in offshore wind energy installation areas.
  • Working Paper
    A science plan for carbon cycle research in North American coastal waters. Report of the Coastal CARbon Synthesis (CCARS) community workshop, August 19-21, 2014
    (Ocean Carbon & Biogeochemistry Program, 2016) Benway, Heather M. ; Alin, Simone R. ; Boyer, Elizabeth ; Cai, Wei-Jun ; Coble, Paula G. ; Cross, Jessica N. ; Friedrichs, Marjorie A. M. ; Goni, Miguel ; Griffith, Peter C. ; Herrmann, Maria ; Lohrenz, Steven E. ; Mathis, Jeremy T. ; McKinley, Galen A. ; Najjar, Raymond G. ; Pilskaln, Cynthia H. ; Siedlecki, Samantha A. ; Smith, Richard A.
    Relative to their surface area, continental margins represent some of the largest carbon fluxes in the global ocean, but sparse and sporadic sampling in space and time makes these systems difficult to characterize and quantify. Recognizing the importance of continental margins to the overall North American carbon budget, terrestrial and marine carbon cycle scientists have been collaborating on a series of synthesis, carbon budgeting, and modeling exercises for coastal regions of North America, which include the Gulf of Mexico, the Laurentian Great Lakes (LGL), and the coastal waters of the Atlantic, Pacific, and Arctic Oceans. The Coastal CARbon Synthesis (CCARS) workshops and research activities have been conducted over the past several years as a partner activity between the Ocean Carbon and Biogeochemistry (OCB) Program and the North American Carbon Program (NACP) to synthesize existing data and improve quantitative assessments of the North American carbon budget.
  • Thesis
    Primary production of particulate protein amino acids : algal protein metabolism and its relationship to the composition of particulate organic matter
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1985-04) Lohrenz, Steven E.
    The biochemical and physiological bases underlying primary production of particulate protein amino acids were investigated in an effort to understand the relationship between algal protein metabolism and particulate organic matter composition. In order to examine biochemical processes associated with conversion of inorganic carbon and nitrogen into protein, the effects of NH+4 limitation on free amino acid and protein composition and incorporation of inorganic 14C were studied in the marine chlorophyte, Nannochloris sp. (clone GSB Nanna). Free amino acid metabolism was sensitive to changes in steady state NH+4-limited growth rates. Reduced carbon and nitrogen flux into protein resulting from nitrogen limitation of growth was associated with reductions in proportions of cellular carbon and nitrogen in the intracellular free amino acid (IFAA) pool. Growth rate-dependent changes IFAA pool composition reflected changes in rate limiting steps which were intermediate between assimilation of inorganic nitrogen and the incorporation of nitrogen into macromolecules. The proportion of cellular carbon in both protein and pools of free amino acids decreased with decreasing growth rate. Distributions of incorporated inorganic 14C among free amino acids and protein provided qualitative descriptions of growth related compositional variations. Saturation rates of (IFAA) carbon with dissolved inorganic 14C did not significantly change as growth rates decreased. In contrast, saturation rates of free glutamate, glycine + alanine and valine did decrease with growth rate. At low growth rate, specific activities of the newly assimilated glutamate, valine, and glycine + alanine in protein were higher than specific activities of their corresponding free amino acid pools. This was likely a consequence of metabolic segregation and more rapid saturation of protein precursor pools. Enrichment of NH+4-limited steady state cultures of Nannochloris sp. with NH+4 led to a dramatic time dependent increase in free glutamine concentrations accompanied by differential increases in other free amino acids. Patterns of isotope incorporation into the free amino acids reflected real changes in concentrations. Increases were associated with the diversion of photosynthetically fixed carbon from lipophilic material towards amino acid biosynthesls, and signalled the onset of increased protein synthesis. Preliminary investigations of two other marine phytoplankton species, Dunaliella tertiolecta (clone Dun) and Thalassiosira weissflogii (clone Actin), suggested that the nature and timing of the biochemical response to NH+4 enrichment is different among different species. At high light intensity, increased NH+4 limitation of Nannochloris sp. was associated with decreases in cellular protein, protein to carbon ratios, and protein to chlorophyll a ratios. At low light intensities, cellular protein and protein to carbon ratios did not decrease with increasing NH+4 limitation. Chlorophyll a to protein ratios were generally higher at low light intensity and decreased with increasing NH+4 limitation, suggesting that nitrogen limitation suppressed low light enhancement of chlorophyll a production. Observed incorporation rates of inorganic 14C exceeded predicted rates for glycine and alanine in protein under combined conditions of light and nitrogen limitation, an indication that protein turnover in excess of net synthesis was important under these conditions. The characteristics of protein composition and incorporation of inorganic 14C were examined in steady state NH+4-limited cultures of three other species of marine phytoplankton. The species studied included Chaetoceros simplex (clone BBSM). Chattonella luteus (clone Olisth), and Chroomonas salina (clone 3C). Saturation of protein precursors was different for different species and for different protein amino acids. Nannochloris sp. displayed the most rapid and complete equilibration, while C. simplex exhibited relatively slow or incomplete saturation and high sensitivity to nitrogen depletion. Intermediate patterns were observed for the other species. For all species examined, protein glycine and alanine demonstrated relatively rapid and complete equilibration of precursor pools, and were least sensitive to nitrogen depletion. With the knowledge that these selected amino acids consistently demonstrated relatively rapid and complete equilibration of precursor pools with 14C-inorganlc carbon in several taxonomically distinct marine algae, primary production of particulate protein amino acids and its relationship to the composition of particulate organic matter was investigated in the epilimnion of a semi-enclosed marine basin, Salt Pond, MA. Studies were conducted previous to and throughout a major bloom of Olisthodiscus magnus. Before the bloom, the ratio of particulate protein amino acid (PPAA) production to particulate organic carbon (POC) production was not significantly different from the relative proportions of PPAA and POC in the particulate organic matter. Comparisons between estimated production and observed concentration changes indicated residence times of POC and PPAA were similar (10 - 20 days). Thus with respect to POC and PPAA, particulate organic matter composition reflected the composition of organic matter being produced by photoautotrophs. During the bloom decline, the PPAA/POC production ratio, a reflection of the activities of the metabolically active algal population, was significantly less than the PPAA/POC ratio of the particulate organic matter. This discrepancy can be attributed either to increased turnover of protein associated with the low inorganic nitrogen concentrations and in situ light intensities, or selective removal of PPAA carbon by secondary transformational processes.