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  • Biodiversity Research  (6)
  • 1
    Online Resource
    Online Resource
    ACKNOWLEDGEMENT OF REVIEWERS
    Elsevier BV ; 2011
    In:  Clinical Microbiology and Infection Vol. 17, No. 1 ( 2011-01), p. 102-103
    Details
    In: Clinical Microbiology and Infection, Elsevier BV, Vol. 17, No. 1 ( 2011-01), p. 102-103
    Type of Medium: Online Resource
    ISSN: 1198-743X
    URL: Article
    DOI: 10.1111/j.1469-0691.2010.03428.x
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2011
    detail.hit.zdb_id: 2020034-1
    SSG: 12
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  • 2
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    The fate of upwelled nitrate off Peru shaped by submesoscale filaments and fronts
    Copernicus GmbH ; 2021
    In:  Biogeosciences Vol. 18, No. 12 ( 2021-06-17), p. 3605-3629
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 18, No. 12 ( 2021-06-17), p. 3605-3629
    Abstract: Abstract. Filaments and fronts play a crucial role for a net offshore and downward nutrient transport in Eastern Boundary Upwelling Systems (EBUSs) and thereby reduce regional primary production. Most studies on this topic are based on either observations or model simulations, but only seldom are 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 (Coastal and Regional Ocean Community model, CROCO) and biogeochemical (Pelagic Interaction Scheme for Carbon and Ecosystem Studies, 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 in 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 of 4 lower than at the upwelling front, while surface primary production is a factor of 2 higher. The simulation exhibits filaments that are similar in horizontal and vertical scale compared to the observed filament. Nitrate concentrations and primary production 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 % of upwelled floats and 40 % of upwelled nitrate are subducted within 20 d after upwelling, which corresponds to an increase in nitrate subduction compared to a mesoscale-resolving (1/9∘) simulation by 14 %. Taking model biases into account, we give a best estimate for subduction of upwelled nitrate off Peru between 30 %– 40 %. Our results suggest that submesoscale processes further reduce primary production by amplifying the downward and offshore export of nutrients found in previous mesoscale studies, which are thus likely to underestimate the reduction in primary production due to eddy fluxes. Moreover, this downward and offshore transport could also enhance the export of fresh organic matter below the euphotic zone and thereby potentially stimulate microbial activity in regions of the upper offshore oxygen minimum zone.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-18-3605-2021
    DOI: 10.5194/bg-18-3605-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2158181-2
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  • 3
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    Sediment release of dissolved organic matter to the oxygen minimum zone off Peru
    Copernicus GmbH ; 2020
    In:  Biogeosciences Vol. 17, No. 18 ( 2020-09-25), p. 4663-4679
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 17, No. 18 ( 2020-09-25), p. 4663-4679
    Abstract: Abstract. The eastern tropical South Pacific (ETSP) represents one of the most productive areas in the ocean that is characterised by a pronounced oxygen minimum zone (OMZ). Particulate organic matter (POM) that sinks out of the euphotic zone is supplied to the anoxic sediments and utilised by microbial communities, and the degradation of POM is associated with the production and reworking of dissolved organic matter (DOM). The release of DOM to the overlying waters may, therefore, represent an important organic matter escape mechanism from remineralisation within sediments but has received little attention in OMZ regions so far. Here, we combine measurements of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) with DOM optical properties in the form of chromophoric (CDOM) and fluorescent (FDOM) DOM from pore waters and near-bottom waters of the ETSP off Peru. We evaluate diffusion-driven fluxes and net in situ fluxes of DOC and DON to investigate processes affecting DOM cycling at the sediment–water interface along a transect at 12∘ S. To our knowledge, these are the first data for sediment release of DON and pore water CDOM and FDOM for the ETSP off Peru. Pore water DOC accumulated with increasing sediment depth, suggesting an imbalance between DOM production and remineralisation within sediments. High DON accumulation resulted in very low pore water DOC ∕ DON ratios (≤1) which could be caused by an “uncoupling” in DOC and DON remineralisation. Diffusion-driven fluxes of DOC and DON exhibited high spatial variability and ranged from 0.2±0.1 to 2.5±1.3 mmolm-2d-1 and from -0.04±0.02 to 3.3±1.7 mmolm-2d-1, respectively. Generally low net in situ DOC and DON fluxes, as well as a steepening of spectral inclination (S) of CDOM and an increase in humic-like DOM at the sediment–water interface over time, indicated active microbial DOM utilisation. The latter may potentially be stimulated by the presence of nitrate (NO3-) and nitrite (NO2-) in the water column. The microbial DOC utilisation rates, estimated in our study, are potentially sufficient to support denitrification rates of 0.2–1.4 mmolm-2d-1, suggesting that the sediment release of DOM may on occasion contribute to nitrogen loss processes in the ETSP off Peru.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    URL: Article
    DOI: 10.5194/bg-17-4663-2020
    DOI: 10.5194/bg-17-4663-2020-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2158181-2
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  • 4
    Online Resource
    Online Resource
    Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans
    Copernicus GmbH ; 2016
    In:  Biogeosciences Vol. 13, No. 12 ( 2016-06-20), p. 3585-3606
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 13, No. 12 ( 2016-06-20), p. 3585-3606
    Abstract: Abstract. Recent modeling results suggest that oceanic oxygen levels will decrease significantly over the next decades to centuries in response to climate change and altered ocean circulation. Hence, the future ocean may experience major shifts in nutrient cycling triggered by the expansion and intensification of tropical oxygen minimum zones (OMZs), which are connected to the most productive upwelling systems in the ocean. There are numerous feedbacks among oxygen concentrations, nutrient cycling and biological productivity; however, existing knowledge is insufficient to understand physical, chemical and biological interactions in order to adequately assess past and potential future changes. In the following, we summarize one decade of research performed in the framework of the Collaborative Research Center 754 (SFB754) focusing on climate–biogeochemistry interactions in tropical OMZs. We investigated the influence of low environmental oxygen conditions on biogeochemical cycles, organic matter formation and remineralization, greenhouse gas production and the ecology in OMZ regions of the eastern tropical South Pacific compared to the weaker OMZ of the eastern tropical North Atlantic. Based on our findings, a coupling of primary production and organic matter export via the nitrogen cycle is proposed, which may, however, be impacted by several additional factors, e.g., micronutrients, particles acting as microniches, vertical and horizontal transport of organic material and the role of zooplankton and viruses therein.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-13-3585-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2158181-2
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  • 5
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    Diapycnal dissolved organic matter supply into the upper Peruvian oxycline
    Copernicus GmbH ; 2019
    In:  Biogeosciences Vol. 16, No. 9 ( 2019-05-15), p. 2033-2047
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 16, No. 9 ( 2019-05-15), p. 2033-2047
    Abstract: Abstract. The eastern tropical South Pacific (ETSP) hosts the Peruvian upwelling system, which represents one of the most productive areas in the world ocean. High primary production followed by rapid heterotrophic utilization of organic matter supports the formation of one of the most intense oxygen minimum zones (OMZs) in the world ocean, where dissolved oxygen (O2) concentrations reach less than 1 µmol kg−1. The high productivity leads to an accumulation of dissolved organic matter (DOM) in the surface layers that may serve as a substrate for heterotrophic respiration. However, the importance of DOM utilization for O2 respiration in the Peruvian upwelling system in general and for shaping the upper oxycline in particular remains unclear so far. This study reports the first estimates of diapycnal fluxes and supply of O2, dissolved organic carbon (DOC), dissolved organic nitrogen, dissolved hydrolysable amino acids (DHAA) and dissolved combined carbohydrates (DCCHO) for the ETSP off Peru. Diapycnal flux and supply estimates were obtained by combining measured vertical diffusivities and solute concentration gradients. They were analysed together with the molecular composition of DCCHO and DHAA to infer the transport of labile DOM into the upper OMZ and the potential role of DOM utilization for the attenuation of the diapycnal O2 flux that ventilates the OMZ. The observed diapycnal O2 flux (50 mmol O2 m−2 d−1 at maximum) was limited to the upper 80 m of the water column; the O2 supply of ∼1 µmol kg−1 d−1 was comparable to previously published O2 consumption rates for the North and South Pacific OMZs. The diapycnal DOM flux (31 mmol C m−2 d−1 at maximum) was limited to ∼30 m water depth, suggesting that the labile DOM is extensively consumed within the upper part of the shallow oxycline off Peru. The analyses of DCCHO and DHAA composition support this finding, suggesting that DOM undergoes comprehensive remineralization within the upper part of the oxycline, as the DOM within the core of the OMZ was found to be largely altered. Estimated by a simple equation for carbon combustion, aerobic respiration of DCCHO and DHAA, supplied by diapycnal mixing (0.46 µmol kg−1 d−1 at maximum), could account for up to 38 % of the diapycnal O2 supply in the upper oxycline, which suggests that DOM utilization plays a significant role for shaping the upper oxycline in the ETSP.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-16-2033-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2158181-2
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  • 6
    Online Resource
    Online Resource
    Remote and local drivers of oxygen and nitrate variability in the shallow oxygen minimum zone off Mauritania in June 2014
    Copernicus GmbH ; 2019
    In:  Biogeosciences Vol. 16, No. 5 ( 2019-03-13), p. 979-998
    Details
    In: Biogeosciences, Copernicus GmbH, Vol. 16, No. 5 ( 2019-03-13), p. 979-998
    Abstract: Abstract. Upwelling systems play a key role in the global carbon and nitrogen cycles and are also of local relevance due to their high productivity and fish resources. To capture and understand the high spatial and temporal variability in physical and biogeochemical parameters found in these regions, novel measurement techniques have to be combined in an interdisciplinary manner. Here we use high-resolution glider-based physical–biogeochemical observations in combination with ship-based underwater vision profiler, sensor and bottle data to investigate the drivers of oxygen and nitrate variability across the shelf break off Mauritania in June 2014. Distinct oxygen and nitrate variability shows up in our glider data. High-oxygen and low-nitrate anomalies were clearly related to water mass variability and probably linked to ocean transport. Low-oxygen and high-nitrate patches co-occurred with enhanced turbidity signals close to the seabed, which suggests locally high microbial respiration rates of resuspended organic matter near the sea floor. This interpretation is supported by high particle abundance observed by the underwater vision profiler and enhanced particle-based respiration rate estimates close to the seabed. Discrete in situ measurements of dissolved organic carbon and amino acids suggest the formation of dissolved organic carbon due to particle dissolution near the seabed fueling additional microbial respiration. During June an increase in the oxygen concentration on the shelf break of about 15 µmol kg−1 was observed. These changes go along with meridional circulation changes but cannot be explained by typical water mass property changes. Thus our high-resolution interdisciplinary observations highlight the complex interplay of remote and local physical–biogeochemical drivers of oxygen and nitrate variability off Mauritania, which cannot be captured by classical shipboard observations alone.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    URL: Article
    DOI: 10.5194/bg-16-979-2019
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2158181-2
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