Search

Your search keyword '"Lavik, Gaute"' showing total 525 results
Start Over Author "Lavik, Gaute"
525 results on '"Lavik, Gaute"'

4. Nutrient removal and nitrogen recovery from aquaculture effluents by the edible halophyte <italic>Sesuvium portulacastrum</italic> (L.) in hydroponics and in sand substrate.

Author

Senff, Paula, Lavik, Gaute, Teichberg, Mirta, and Kunzmann, Andreas

Abstract

Aquaculture is important for food security and livelihoods, especially in the developing tropics. Many nutrients supplied by feed degrade water quality, waste resources and lead to nutrient loss. Halophytes have the potential to recover these nutrients from aquaculture effluents. Most studies have focused on temperate species, but there is a need for extractive species suitable for integration in tropical saline aquaculture. Sea purslane Sesuvium portulacastrum is a promising candidate providing biomass for human consumption with potential pharmaceutical applications, but to date, nutrient uptake has not been studied in this species. This study investigated the nutrient removal from milkfish wastewater by systems planted with S. portulacastrum in hydroponics versus planted in sand. Most nutrients were removed from the wastewater within 48 h. Phosphorus and nitrogen were most efficiently removed in treatments with plants and sand and on average lower in the hydroponic incubations. However, in hydroponic systems, plants assimilated 50.2% of the added labelled N with no significant difference in recovery after 48 h when 15NH4 or 15NO3 was added. The recovery of wastewater N into plant biomass was several-fold higher in hydroponics than in sand substrate. Integration of S. portulacastrum into aquaculture turns aquaculture effluents into a valuable resource. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

19. Nitrogen isotope effects induced by anammox bacteria

Author

Brunner, Benjamin, Contreras, Sergio, Lehmann, Moritz F., Matantseva, Olga, Rollog, Mark, Kalvelage, Tim, Klockgether, Gabriele, Lavik, Gaute, Jetten, Mike S. M., Kartal, Boran, and Kuypers, Marcel M. M.

Published
2013

33. Niche partitioning by photosynthetic plankton as a driver of CO2-fixation across the oligotrophic South Pacific Subtropical Ocean

Author

Duerschlag, Julia, primary, Mohr, Wiebke, additional, Ferdelman, Timothy G., additional, LaRoche, Julie, additional, Desai, Dhwani, additional, Croot, Peter L., additional, Voß, Daniela, additional, Zielinski, Oliver, additional, Lavik, Gaute, additional, Littmann, Sten, additional, Martínez-Pérez, Clara, additional, Tschitschko, Bernhard, additional, Bartlau, Nina, additional, Osterholz, Helena, additional, Dittmar, Thorsten, additional, and Kuypers, Marcel M. M., additional

Published
2021
Full Text
View/download PDF

36. The fate of upwelled nitrate off Peru shaped by submesoscale filaments and fronts

Author

Hauschildt, Jaard, Thomsen, Soeren, Echevin, Vincent, Oschlies, Andreas, Jose, Yonss Saranga, Krahmann, Gerd, Bristow, Laura A., Lavik, Gaute, Hauschildt, Jaard, Thomsen, Soeren, Echevin, Vincent, Oschlies, Andreas, Jose, Yonss Saranga, Krahmann, Gerd, Bristow, Laura A., and Lavik, Gaute

Abstract

Filaments and fronts play a crucial role for a net offshore and downward nutrient transport in Eastern Boundary Upwelling Regions (EBUS) and thereby reduce primary production. Often studies are either based on observations or model simulations but seldom both approaches are combined quantitatively to assess the importance of filaments for primary production and nutrient transport. Here we combine targeted interdisciplinary shipboard observations of a cold filament off Peru with submesoscale-permitting (1/45°) coupled physical (CROCO) and biogeochemical (PISCES) model simulations to (i) evaluate the model simulations in detail, including the timescales of biogeochemical modification of the newly upwelled water and (ii) quantify the net effect of submesoscale fronts and filaments on primary production of the Peruvian upwelling system. The observed filament contains relatively cold, fresh and nutrient-rich waters originating in the coastal upwelling. Enhanced nitrate concentrations and offshore velocities of up to 0.5 m s−1 within the filament suggest an offshore transport of nutrients. Surface chlorophyll in the filament is a factor 4 lower than at the upwelling front while surface primary production is a factor 2 higher, highlighting the additional value of direct rate measurements for model validation. The simulation exhibits filaments that are similar in horizontal and vertical scale compared to the observed filament. Nitrate concentrations and primary pro- duction within filaments in the model are comparable to observations as well, justifying further analysis of nitrate uptake and subduction using the model. Virtual Lagrangian floats were released in the subsurface waters along the shelf and biogeochemical variables tracked along the trajectories of floats upwelled near the coast. In the submesoscale-permitting (1/45°) simulation 43.0 % of upwelled floats and 40.6 % of upwelled nitrate is subducted within 20 days after upwelling, which corresponds to an increase

Published
2021
Full Text
View/download PDF

37. Doubling of marine dinitrogen-fixation rates based on direct measurements

Author

Grosskopf, Tobias, Mohr, Wiebke, Baustian, Tina, Schunck, Harald, Gill, Diana, Kuypers, Marcel M.M., Lavik, Gaute, Schmitz, Ruth A., Wallace, Douglas W.R., and LaRoche, Julie

Subjects
Atlantic Ocean -- Environmental aspects, Nitrogen -- Fixation, Carbon fixation -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Biological dinitrogen fixation provides the largest input of nitrogen to the oceans, therefore exerting important control on the ocean's nitrogen inventory and primary productivity (1-3). Nitrogen-isotope data from ocean sediments [...]

Published
2012
Full Text
View/download PDF

42. Detoxification of sulphidic African shelf waters by blooming chemolithotrophs

Author

Lavik, Gaute, Stuhrmann, Torben, Bruchert, Volker, Van der Plas, Anja, Mohrholz, Volker, Lam, Phyllis, Mussmann, Marc, Fuchs, Bernhard M., Amann, Rudolf, Lass, Ulrich, and Kuypers, Marcel M.M.

Subjects
Marine bacteria -- Properties -- Methods -- Environmental aspects, Water bloom -- Environmental aspects -- Methods -- Control, Hydrogen sulfide -- Environmental aspects -- Methods, Eutrophication -- Control -- Environmental aspects -- Methods, Environmental issues, Science and technology, Zoology and wildlife conservation, Control, Properties, Methods, Environmental aspects
Abstract

Coastal waters support ~90 per cent of global fisheries and are therefore an important food reserve for our planet (1). Eutrophication of these waters, due to human activity, leads to [...]

Published
2009

43. Sulfur cycling in oceanic oxygen minimum zones

Author

Callbeck, Cameron M., primary, Canfield, Donald E., additional, Kuypers, Marcel M. M., additional, Yilmaz, Pelin, additional, Lavik, Gaute, additional, Thamdrup, Bo, additional, Schubert, Carsten J., additional, and Bristow, Laura A., additional

Published
2021
Full Text
View/download PDF

44. Versatile cyanobacteria control the timing and extent of sulfide production in a Proterozoic analog microbial mat

Author

Klatt, Judith M., Gomez-Saez, Gonzalo V., Meyer, Steffi, Pop Ristova, Petra, Yilmaz, Pelin, Granitsiotis, Michael S., Macalady, Jennifer L., Lavik, Gaute, Polerecky, L., Bühring, Solveig I., Geochemistry, and Bio-, hydro-, and environmental geochemistry

Abstract

Cyanobacterial mats were hotspots of biogeochemical cycling during the Precambrian. However, mechanisms that controlled O2 release by these ecosystems are poorly understood. In an analog to Proterozoic coastal ecosystems, the Frasassi sulfidic springs mats, we studied the regulation of oxygenic and sulfide-driven anoxygenic photosynthesis (OP and AP) in versatile cyanobacteria, and interactions with sulfur reducing bacteria (SRB). Using microsensors and stable isotope probing we found that dissolved organic carbon (DOC) released by OP fuels sulfide production, likely by a specialized SRB population. Increased sulfide fluxes were only stimulated after the cyanobacteria switched from AP to OP. O2 production triggered migration of large sulfur-oxidizing bacteria from the surface to underneath the cyanobacterial layer. The resultant sulfide shield tempered AP and allowed OP to occur for a longer duration over a diel cycle. The lack of cyanobacterial DOC supply to SRB during AP therefore maximized O2 export. This mechanism is unique to benthic ecosystems because transitions between metabolisms occur on the same time scale as solute transport to functionally distinct layers, with the rearrangement of the system by migration of microorganisms exaggerating the effect. Overall, cyanobacterial versatility disrupts the synergistic relationship between sulfide production and AP, and thus enhances diel O2 production.

Published
2020

45. EUREC4A Campaign, Cruise No. MSM89, 17. January - 20. February 2020, Bridgetown (Barbados) - Bridgetown (Barbados), The ocean mesoscale component in the EUREC4A++ field study

Author

Karstensen, Johannes, Lavik, Gaute, Acquistapace, Claudia, Baghen, Gholamhossein, Begler, Christian, Bendinger, Arne, Bodenschatz, Eberhard, Böck, Tobias, Güttler, Johannes, Hall, Kashawn, Körner, Mareike, Kopp, Andreas, Lange, Diego, Mehlmann, Melina, Nordsiek, Freja, Reus, Klaus, Ribbe, Joachim, Philippi, Miriam, Piosek, Sandra, Ritschel, Markus, Tschitschko, Bernhard, and Wiskandt, Jonathan

Abstract

The MSM89 expedition of Maria S Merian was a contribution to the international research initiative EUREC4A (www.eurec4a.eu). The cruise was carried out in concert with the M161 campaign on RV METEOR (Germany) and the EUREC4A-OA campaign on NO L’ATALANTE (France). Airplane and drone operations as well as well as continuous observations from the ground-based site on the Island of Barbados (BCO) were considered during the MSM89 campaign. Moreover, the cruise was coordinated with ships and Saildrone© operations in the context of the US American ATOMIC project. The overall goal of the EUREC4A field campaign was to collect observational data that will enable research on dynamic and thermodynamic processes in the atmosphere and ocean that will bring the understanding of the role of clouds in the climate system to a new level. MSM89 had its focus on the ocean/atmosphere coupling across ocean mesoscale vortices. For this purpose, both ocean and atmosphere profile measurements were carried out to observe the temporal evolution and spatial heterogeneity of the atmospheric and oceanic boundary layer. Autonomous observing platforms (underwater glider) and a ship towed platform (Cloudkite) augmented the ship-based observations. Incubation experiments were performed to determine Nitrogen fixation rates, the gas exchange for carbon dioxide and oxygen uptake.

Published
2020

46. Linking crenarchaeal and bacterial nitrification to anammox in the Black Sea

Author

Lam, Phyllis, Jensen, Marlene M., Lavik, Gaute, McGinnis, Daniel F., Muller, Beat, Schubert, Carsten J., Amann, Rudolf, Thamdrup, Bo, and Kuypers, Marcel M.M.

Subjects
Black Sea -- Environmental aspects, Gene expression -- Research, Marine fauna -- Research, Marine fauna -- Environmental aspects, Nitrification -- Research, Science and technology
Abstract

Active expression of putative ammonia monooxygenase gene subunit A (amoA) of marine group I Crenarchaeota has been detected in the Black Sea water column. It reached its maximum, as quantified by reverse-transcription quantitative PCR, exactly at the nitrate maximum or the nitrification zone modeled in the lower oxic zone. Crenarchaeal amoA expression could explain 74.5% of the nitrite variations in the lower oxic zone. In comparison, amoA expression by [gamma]-proteobacterial ammonia-oxidizing bacteria (AOB) showed two distinct maxima, one in the modeled nitrification zone and one in the suboxic zone. Neither the amoA expression by crenarchaea nor that by [beta]-proteobacterial AOB was significantly elevated in this latter zone. Nitrification in the suboxic zone, most likely microaerobic in nature, was verified by [sup.15]N[O.sup.-.sub.2] and [sup.15]N[sup.15]N production in [sup.15]N[H.sup.+.sub.4] incubations with no measurable oxygen. It provided a direct local source of nitrite for anammox in the suboxic zone. Both ammonia-oxidizing crenarchaea and [gamma]-proteobacterial AOB were important nitrifiers in the Black Sea and were likely coupled to anammox in indirect and direct manners respectively. Each process supplied about half of the nitrite required by anammox, based on [sup.15]N-incubation experiments and modeled calculations. Because anammox is a major nitrogen loss in marine suboxic waters, such nitrification--anammox coupling potentially occurring also in oceanic oxygen minimum zones would act as a short circuit connecting regenerated ammonium to direct nitrogen loss, thus reducing the presumed direct contribution from deep-sea nitrate. ammonia-oxidizing bacteria | amoA gene expression | marine group | Crenarchaeota | marine nitrogen loss

Published
2007

47. Versatile cyanobacteria control the timing and extent of sulfide production in a Proterozoic analog microbial mat

Author

Geochemistry, Bio-, hydro-, and environmental geochemistry, Klatt, Judith M., Gomez-Saez, Gonzalo V., Meyer, Steffi, Pop Ristova, Petra, Yilmaz, Pelin, Granitsiotis, Michael S., Macalady, Jennifer L., Lavik, Gaute, Polerecky, L., Bühring, Solveig I., Geochemistry, Bio-, hydro-, and environmental geochemistry, Klatt, Judith M., Gomez-Saez, Gonzalo V., Meyer, Steffi, Pop Ristova, Petra, Yilmaz, Pelin, Granitsiotis, Michael S., Macalady, Jennifer L., Lavik, Gaute, Polerecky, L., and Bühring, Solveig I.

Published
2020

50. Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation

Author

Kuypers, Marcel M.M., Lavik, Gaute, Woebken, Dagmar, Schmid, Markus, Fuchs, Bernhard M., Amann, Rudolf, Jorgensen, Bo Barker, and Jetten, Mike S.M.

Subjects
Ocean -- Research, Nitrogen in the body -- Research, Phytoplankton -- Research, Science and technology
Abstract

In many oceanic regions, growth of phytoplankton is nitrogen-limited because fixation of [N.sub.2] cannot make up for the removal of fixed inorganic nitrogen (N[H.sup.+.sub.4], N[O.sup.-.sub.2], and N[O.sup.-.sub.3]) by anaerobic microbial processes. Globally, 30-50% of the total nitrogen loss occurs in oxygen-minimum zones (OMZs) and is commonly attributed to denitrification (reduction of nitrate to [N.sub.2] by heterotrophic bacteria). Here, we show that instead, the anammox process (the anaerobic oxidation of ammonium by nitrite to yield [N.sub.2]) is mainly responsible for nitrogen loss in the OMZ waters of one of the most productive regions of the world ocean, the Benguela upwelling system. Our in situ experiments indicate that nitrate is not directly converted to [N.sub.2] by heterotrophic denitrification in the suboxic zone. In the Benguela system, nutrient profiles, anammox rates, abundances of anammox cells, and specific biomarker lipids indicate that anammox bacteria are responsible for massive losses of fixed nitrogen. We have identified and directly linked anammox bacteria to the removal of fixed inorganic nitrogen in the OMZ waters of an open-ocean setting. We hypothesize that anammox could also be responsible for substantial nitrogen loss from other OMZ waters of the ocean. anammox | denitrification | oceanic nitrogen cycle | oxygen-minimum zone

Published
2005

Catalog

Books, media, physical & digital resources
See catalog results