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| Author | Stukel, M.R.; Decima, M.; Kelly, T.B. | ||||
| Title | A new approach for incorporating 15N isotopic data into linear inverse ecosystem models with Markov Chain Monte Carlo sampling | Type | $loc['typeJournal Article'] | ||
| Year | 2018 | Publication | PloS one | Abbreviated Journal | PLoS One |
| Volume | 13 | Issue | 6 | Pages | e0199123 |
| Keywords | Isotopic data; Nitrogen-based ecosystem models; Phytoplankton; Defecation by grazers; Mortality by phytoplankton | ||||
| Abstract | Oceanographic field programs often use delta15N biogeochemical measurements and in situ rate measurements to investigate nitrogen cycling and planktonic ecosystem structure. However, integrative modeling approaches capable of synthesizing these distinct measurement types are lacking. We develop a novel approach for incorporating delta15N isotopic data into existing Markov Chain Monte Carlo (MCMC) random walk methods for solving linear inverse ecosystem models. We test the ability of this approach to recover food web indices (nitrate uptake, nitrogen fixation, zooplankton trophic level, and secondary production) derived from forward models simulating the planktonic ecosystems of the California Current and Amazon River Plume. We show that the MCMC with delta15N approach typically does a better job of recovering ecosystem structure than the standard MCMC or L2 minimum norm (L2MN) approaches, and also outperforms an L2MN with delta15N approach. Furthermore, we find that the MCMC with delta15N approach is robust to the removal of input equations and hence is well suited to typical pelagic ecosystem studies for which the system is usually vastly under-constrained. Our approach is easily extendable for use with delta13C isotopic measurements or variable carbon:nitrogen stoichiometry. | ||||
| Address | Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL, United States of America | ||||
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| Language | English | Summary Language | Original Title | ||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 1932-6203 | ISBN | Medium | ||
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| Funding | strtoupper('2').strtolower('9912928'); strtoupper('P').strtolower('MC6005467') | Approved | $loc['no'] | ||
| Call Number | COAPS @ user @ | Serial | 975 | ||
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| Author | Stukel, M.R.; Décima, M.; Landry, M.R.; Selph, K.E. | ||||
| Title | Nitrogen and isotope flows through the Costa Rica Dome upwelling ecosystem: The crucial mesozooplankton role in export flux | Type | $loc['typeJournal Article'] | ||
| Year | 2018 | Publication | Global Biogeochemical Cycles | Abbreviated Journal | Global Biogeochemical Cycles |
| Volume | 32 | Issue | 12 | Pages | 1815–1832. |
| Keywords | Crustaceans; Diel vertical migration; Nitrogen cycle; Biological carbon pump; Nitrogen isotopes; Linear inverse ecosystem model | ||||
| Abstract | The Costa Rica Dome (CRD) is an open-ocean upwelling ecosystem, with high biomasses of picophytoplankton (especially Synechococcus), mesozooplankton, and higher trophic levels. To elucidate the food web pathways supporting the trophic structure and carbon export in this unique ecosystem, we used Markov Chain Monte Carlo techniques to assimilate data from four independent realizations of δ15N and planktonic rate measurements from the CRD into steady state, multicompartment ecosystem box models (linear inverse models). Model results present well-constrained snapshots of ecosystem nitrogen and stable isotope fluxes. New production is supported by upwelled nitrate, not nitrogen fixation. Protistivory (rather than herbivory) was the most important feeding mode for mesozooplankton, which rely heavily on microzooplankton prey. Mesozooplankton play a central role in vertical nitrogen export, primarily through active transport of nitrogen consumed in the surface layer and excreted at depth, which comprised an average 36-46% of total export. Detritus or aggregate feeding is also an important mode of resource acquisition by mesozooplankton and regeneration of nutrients within the euphotic zone. As a consequence, the ratio of passively sinking particle export to phytoplankton production is very low in the CRD. Comparisons to similar models constrained with data from the nearby equatorial Pacific demonstrate that the dominant role of vertical migrators to the biological pump is a unique feature of the CRD. However, both regions show efficient nitrogen transfer from mesozooplankton to higher trophic levels (as expected for regions with large fish, cetacean, and seabird populations) despite the dominance of protists as major grazers of phytoplankton. | ||||
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| Funding | Approved | $loc['no'] | |||
| Call Number | COAPS @ rl18 @ | Serial | 978 | ||
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| Author | Stukel, M.R.; Ohman, M.D.; Kelly, T.B.; Biard, T. | ||||
| Title | The Roles of Suspension-Feeding and Flux-Feeding Zooplankton as Gatekeepers of Particle Flux Into the Mesopelagic Ocean in the Northeast Pacific | Type | $loc['typeJournal Article'] | ||
| Year | 2019 | Publication | Frontiers in Marine Science | Abbreviated Journal | Front. Mar. Sci. |
| Volume | 6 | Issue | Pages | ||
| Keywords | biological pump; carbon export; remineralization length scale; mesozooplankton ecology; pteropods; marine biogeochemistry; sinking particles; marine snow | ||||
| Abstract | Zooplankton are important consumers of sinking particles in the ocean's twilight zone. However, the impact of different taxa depends on their feeding mode. In contrast to typical suspension-feeding zooplankton, flux-feeding taxa preferentially consume rapidly sinking particles that would otherwise penetrate into the deep ocean. To quantify the potential impact of two flux-feeding zooplankton taxa [Aulosphaeridae (Rhizaria), and Limacina helicina (euthecosome pteropod)] and the total suspension-feeding zooplankton community, we measured depth-stratified abundances of these organisms during six cruises in the California Current Ecosystem. Using allometric-scaling relationships, we computed the percentage of carbon flux intercepted by flux feeders and suspension feeders. These estimates were compared to direct measurements of carbon flux attenuation (CFA) made using drifting sediment traps and U-238-Th-234 disequilibrium. We found that CFA in the shallow twilight zone typically ranged from 500 to 1000 m mol organic C flux remineralized per 10-m vertical depth bin. This equated to approximately 6-10% of carbon flux remineralized/10 m. The two flux-feeding taxa considered in this study could account for a substantial proportion of this flux near the base of the euphotic zone. The mean flux attenuation attributable to Aulosphaeridae was 0.69%/10 m (median = 0.21%/10 m, interquartile range = 0.04-0.81%) at their depth of maximum abundance (similar to 100 m), which would equate to similar to 10% of total flux attenuation in this depth range. The maximum flux attenuation attributable to Aulosphaeridae reached 4.2%/10 m when these protists were most abundant. L. helicina, meanwhile, could intercept 0.45-1.6% of carbon flux/10 m, which was slightly greater (on average) than the Aulosphaeridae. In contrast, suspension-feeding zooplankton in the mesopelagic (including copepods, euphausiids, appendicularians, and ostracods) had combined clearance rates of 2-81 L m(-3) day(-1) (mean of 19.6 L m(-3) day(-1)). This implies a substantial impact on slowly sinking particles, but a negligible impact on the presumably rapidly sinking fecal pellets that comprised the majority of the material collected in sediment traps. Our results highlight the need for a greater research focus on the many taxa that potentially act as flux feeders in the oceanic twilight zone. | ||||
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| ISSN | 2296-7745 | ISBN | Medium | ||
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| Funding | Approved | $loc['no'] | |||
| Call Number | COAPS @ user @ | Serial | 1066 | ||
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| Author | Subrahmanyam, B.; Babu, V.R.; Murty, V.S.N.; Rao, L.V.G. | ||||
| Title | Surface circulation off Somalia and western equatorial Indian Ocean during summer monsoon of 1988 from Geosat altimeter data | Type | $loc['typeJournal Article'] | ||
| Year | 1996 | Publication | International Journal of Remote Sensing | Abbreviated Journal | International Journal of Remote Sensing |
| Volume | 17 | Issue | 4 | Pages | 761-770 |
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| ISSN | 0143-1161 | ISBN | Medium | ||
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| Funding | Approved | $loc['no'] | |||
| Call Number | COAPS @ mfield @ | Serial | 713 | ||
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| Author | Subrahmanyam, B.; Legler, D. M.; Barnier, B.; de Miranda, A. P.; O'Brien, J. J. | ||||
| Title | Sensitivity of the North Atlantic circulation to momentum forcing using SPEM | Type | $loc['typeConference Article'] | ||
| Year | 2000 | Publication | IGARSS 2000, Honolulu, Hawaii, USA | Abbreviated Journal | |
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| Call Number | COAPS @ mfield @ | Serial | 797 | ||
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| Author | Subrahmanyam, B.; Legler, D. M.; Barnier, B.; O'Brien, J. J.; de Miranda, A. P.; Bourassa, M. | ||||
| Title | Sensitivity of an ocean general circulation model to changes in surface momentum forcing | Type | $loc['typeConference Article'] | ||
| Year | 2001 | Publication | Abbreviated Journal | ||
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| Series Editor | Series Title | WMO WORLD Climate Research Programme, CAS/JSC Working Group on Numerical Experimentation, Research Activities in Atmospheric and Oceanic Modeling | Abbreviated Series Title | ||
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| Call Number | COAPS @ mfield @ | Serial | 822 | ||
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| Author | Subrahmanyam, B.; Legler, D. M.; O'Brien, J. J. | ||||
| Title | ), Indian Ocean Circulation using TOPEX/POSEIDION Altimetry and Model Simulations | Type | $loc['typeReport'] | ||
| Year | 1999 | Publication | Abbreviated Journal | ||
| Volume | 28 | Issue | Pages | ||
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| Publisher | Place of Publication | Editor | Ritchie, H. | ||
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| Series Editor | Series Title | Research activities in Atmospheric and Oceanic Modeling | Abbreviated Series Title | ||
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| Call Number | COAPS @ mfield @ | Serial | 776 | ||
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| Author | Subrahmanyam, B.; Legler, D. M.; O'Brien, J. J. | ||||
| Title | Response of the North Atlantic circulation with surface momentum forcing using SPEM Model | Type | $loc['typeReport'] | ||
| Year | 2000 | Publication | Abbreviated Journal | ||
| Volume | Issue | Pages | 9.13-9.14 | ||
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| Publisher | Place of Publication | Editor | Ritchie, H. | ||
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| Series Editor | Series Title | WMO World Climate Research Programme, CAS/JSC Working Group on Numerical Experimentation, Research Activities in Atmospheric and Oceanic Modeling, Report No. 30 (WMO/TD-No.987) | Abbreviated Series Title | ||
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| Call Number | COAPS @ mfield @ | Serial | 801 | ||
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| Author | Subrahmanyam, B.; Manghanai, V.; O'Brien, J. J.; Morrison, J. M.; Xie, L. | ||||
| Title | A study of the Indian Ocean Dipole Mode Dynamics using satellite observations and MICOM simulations | Type | $loc['typeConference Article'] | ||
| Year | 2001 | Publication | Abbreviated Journal | ||
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| Publisher | Place of Publication | San Diego, California, USA | Editor | ||
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| Call Number | COAPS @ mfield @ | Serial | 823 | ||
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| Author | Subrahmanyam, B.; Murty, V. S. N.; O'Brien, J. J. | ||||
| Title | New Sea Surface Salinity Product in the Tropical Indian Ocean | Type | $loc['typeReport'] | ||
| Year | 2005 | Publication | Abbreviated Journal | ||
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| Series Editor | Series Title | CAS/JSC Working Group on Numerical Experimentation | Abbreviated Series Title | ||
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| Call Number | COAPS @ mfield @ | Serial | 897 | ||
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