Marchant, Hannah
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Preferred name
Marchant, Hannah
Official Name
Marchant, Hannah
Alternative Name
Marchant, H.
Marchant, Hannah K.
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Email
hmarchant@marum.de
hmarchan@mpi-bremen.de
ORCID
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Item-typ:Veröffentlichung, Report and preliminary results of R/V POSEIDON cruise POS531, Las Palmas (Canary Islands) – Mindelo (Cape Verde), 18.01.2019 – 01.02.2019.During the RV POSEIDON research cruise, POS531, from Las Palmas (Canary Islands) to Mindelo (Cape Verde), we studied organic matter transport in the Cape Blanc upwelling region. Cape Blanc upwelling is one of the coastal upwelling regimes of the Eastern Boundary Current Systems (EBUEs), which are the most productive ocean areas and key players in the global carbon cycle and climate change. Pelagic primary production drives the biological pump which, in coastal upwelling regions, is largely controlled by the sinking behaviour and lateral transport of marine snow aggregates and faecal pellets. We still lack a quantitative understanding about the role that zooplankton grazing, sediment processes, and lateral transport play in the transformation and export of particulate organic matter. Further gaps in knowledge exist about the distribution of particles, their size and density and the particle sinking velocities of various biogenic and lithogenic components. Even less is known about what happens when particles reach the sandy seafloor and the role that benthic primary production plays in shallow shelf systems. The sandy seabed is regularly reworked and resuspended and therefore biogeochemical processes in the sediment likely play an important role in nutrient and organic matter transformation. To study how the sandy shelf area is connected to open ocean carbon export and carbon sequestration, we deployed free-drifting sediment traps to study short term variability in mass fluxes and the decay and transformation of large, organic-rich marine snow particles. In addition, the water column was sampled and studied using in situ-pumps, Marine Snow Catchers, particle cameras, and vertical multi-net hauls. To link the pelagic processes with the benthic remineralization and production, we deployed benthic boundary layer samplers and benthic lander systems. This allowed us to study the physical environment near the seabed and elucidate its effects on the biogeochemistry of the sediment, which was quantified through in situ and on-board laboratory rate measurements. The major aim of the research cruise was to better quantify the carbon and nitrogen cycling in the sandy shelf region and to quantify the impact from this cycling on lateral transport to the open ocean.Bericht751 427 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Nitrogen cycling in coastal permeable sediments from eutrophied regions(2014-03-27); ; ; Coastal seas buffer the ocean from anthropogenic pollution such as fixed nitrogen. Much of the coastal zones are comprised of sandy sediments, which are permeable. The interaction between sediment topography and bottom water movement causes advective flow of porewater in the sediment. This enhanced porewater supply leads to intense biogeochemical activity, removing nitrate and reducing it to inert N2. Therefore this work focuses on nitrogen cycling in coastal sands. It was possible to follow the fate of nitrate within the sediment, revealing the surprising importance of eukaryotes to N-loss. Furthermore, in subtidal sediments high rates of nitrification were identified, which coupled to high denitrification rates suggests that sandy sediments play an important role in mediating N-turnover in this region. The fluctuating oxygen and nutrient concentrations lead to an environment, which stimulates the occurrence of aerobic denitrification and allows for high nitrous oxide production, much of which is emitted to the atmosphere.Dissertation370 179 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Report and preliminary results of R/V POSEIDON cruise POS539, Varna (Bulgaria) - Varna (Bulgaria) November 6 - November 21, 2019(2020-10-29); ; ; ; The R/V POSEIDON cruise POS539 took place in the northwestern basin of the Black Sea (42°30’N to 44°N and 29°E to 31°E). The overarching aim of the campaign was to obtain sediment and water samples, including suspended particle material, from the various redox zones of the Black Sea. The campaign lasted between November 6th and November 21st 2019 and the collected samples were taken in order to investigate the activity and physiology of microorganisms involved in the conversion of nitrogen compounds and degradation of organic carbon under various oxygen conditions. The main topics of the cruise were: (a) to quantify the contribution of archaeal nitrifiers to the nitrogen and carbon cycles, b) to measure the production and consumption of the powerful greenhouse gases CH4 and N2O, c) to record palaeoenvironmental changes in high resolution, and d) to describe the complexity and identity of biopolymers. For this, water and sediment samples were retrieved from 10 discrete shelf and slope stations. First, ‘deep water’ transect was conducted, which included three stations with water depths over 2000 m. The second perpendicular transect encompassed stations that gradually transitioned from the deep parts of the slope towards the shelf (ca. 80 m depth). Additionally, two stations were setup north and south of the shelf transect, respectively, for paleoceanographic studies. Throughout the cruise the weather conditions were overwhelmingly good, only towards the end of the campaign gusty winds of 7 Bft were recorded. The recorded oceanographic conditions were in agreement with the expected water properties at all stations. Station activities were completed on November 20th at 14:00 local board time. On November 21st at 10:30 local time, R/V POSEIDON reached the port of Varna, Bulgaria, thus concluding the POS539 expedition. Analyses and results from the samples and experiments will provide a basis for our understanding of the microbial control on the carbon and nitrogen cycle of the Black Sea.Wissenschaftlicher ArtikelBand:3252351 1703