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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 18151832.
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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Call Number COAPS @ rl18 @ Serial 978
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Author Stukel, M.R.; Kahru, M.; Benitez-Nelson, C.R.; Décima, M.; Goericke, R.; Landry, M.R.; Ohman, M.D.
Title Using Lagrangian-based process studies to test satellite algorithms of vertical carbon flux in the eastern North Pacific Ocean Type $loc['typeJournal Article']
Year 2015 Publication Journal of Geophysical Research: Oceans Abbreviated Journal J. Geophys. Res. Oceans
Volume 120 Issue 11 Pages 7208-7222
Keywords satellite-derived export; carbon export; model algorithms; mesozooplankton grazing; sinking particles; gravitational flux
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ISSN 2169-9275 ISBN Medium
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Call Number COAPS @ mfield @ Serial 113
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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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Call Number COAPS @ user @ Serial 1066
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Author Zeng, H.; Chambers, J.Q.; Negron-Juarez, R.I.; Hurtt, G.C.; Baker, D.B.; Powell, M.D.
Title Impacts of tropical cyclones on U.S. forest tree mortality and carbon flux from 1851 to 2000 Type $loc['typeJournal Article']
Year 2009 Publication Proceedings of the National Academy of Sciences of the United States of America Abbreviated Journal Proc Natl Acad Sci U S A
Volume 106 Issue 19 Pages 7888-7892
Keywords Biodiversity; Biomass; Carbon; *Cyclonic Storms; Ecosystem; Greenhouse Effect; Models, Statistical; Southeastern United States; *Trees; United States
Abstract Tropical cyclones cause extensive tree mortality and damage to forested ecosystems. A number of patterns in tropical cyclone frequency and intensity have been identified. There exist, however, few studies on the dynamic impacts of historical tropical cyclones at a continental scale. Here, we synthesized field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical tropical cyclones from 1851 to 2000 over the continental U.S. Results demonstrated an average of 97 million trees affected each year over the entire United States, with a 53-Tg annual biomass loss, and an average carbon release of 25 Tg y(-1). Over the period 1980-1990, released CO(2) potentially offset the carbon sink in forest trees by 9-18% over the entire United States. U.S. forests also experienced twice the impact before 1900 than after 1900 because of more active tropical cyclones and a larger extent of forested areas. Forest impacts were primarily located in Gulf Coast areas, particularly southern Texas and Louisiana and south Florida, while significant impacts also occurred in eastern North Carolina. Results serve as an important baseline for evaluating how potential future changes in hurricane frequency and intensity will impact forest tree mortality and carbon balance.
Address Department of Ecology and Evolutionary Biology, Tulane University, 400 Boggs Center, New Orleans, LA 70118, USA. hzeng@tulane.edu
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Language English Summary Language Original Title
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Series Volume Series Issue Edition
ISSN 0027-8424 ISBN Medium
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Funding PMID:19416842; PMCID:PMC2683102 Approved $loc['no']
Call Number COAPS @ mfield @ Serial 658
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