ALBERT

Description: Ocean observation systems, such as Argo floats or the modular ocean laboratory MoLab, produce an increasing amount of time series data. Both, statistical data mining techniques and manual exploration via visualization are necessary for oceanographers to extract scientific knowledge from such vast datasets. Therefore, scientists require a platform to explore and analyze data visually, supporting their collaboration and research. To deliver results and foster the impact of publications, such platform should facilitate automatic and interactive access to research results for scientists, their peers and the public. Our software platform OceanTEA (Oceanographic TimeSeries Exploration and Analysis) supports oceanographers in their research and publication efforts. The platform leverages modern web technology to support the interactive exploration and analysis of high-dimensional datasets. OceanTEA relies on a microservice architecture which can be deployed on desktops and on cloud computing infrastructure.

Description: In oxic environments, nitrogen (N) is frequently a limiting nutrient for primary production and hence a controlling element in marine ecosystems. The fixed form of N, i.e. bioavailable N for primary production, is primarily in the oxidized form of nitrate (NO3-). However, in the sub-oxic environments of oxygen minimum zones (OMZs), N-species are biochemically converted to biogenic N2 gas which is then released, or lost, to the atmosphere. N-cycling under sub-oxic conditions thus diminishes the oceanic pool of bioavailable N. It has been suggested that although OMZs constitute only about 1% of global ocean volume, they account for about 20-40% of global oceanic N loss. However, to date these estimates are subject to largely uncertainties. Here, we quantify the rate of N-cycling and the associated N-loss by evaluating all terms of a benthic-pelagic nutrient transport budget at the continental margin off Peru using observations from an extensive measurement program conducted along the continental slope and shelf region at 12°S. The data set was collected during austral summer in 2013 and consists of nutrient, microstructure and CTD/O 2 profiles as well as shipboard velocity data from two research cruises, a glider swarm experiment and current time series from a moored array. To constrain the benthic contribution to the nutrient budget, benthic nutrient fluxes were measured in benthic chambers using Biogeochemical Observatory (BIGO) landers. Detailed budget determinations were performed on the upper continental slope and shelf break as well as at the shelf. Both regions were anoxic but different with regard to nutrient distribution as well as benthic nutrient release rates. Three major conclusions can be inferred from the study: (1) Unexpectedly, the results showed that diapycnal nutrient fluxes, driven by turbulent mixing caused by the breaking of non-linear internal waves, was one to two orders of magnitude larger than advective and lateral-diffusive fluxes. (2) The relative contribution of benthic nutrient fluxes to nutrient cycling was between 30% and 50%. (3) Nitrogen conversion rates on the shelf (50m-100m water depth) were an order of magnitude larger that at the continental slope (200m-300m water depth). The strong differences in the magnitude of the nutrient cycling rates most likely originate from the presence of sulfidic bottom waters that were observed on the shelf

Description: While oxygen minimum zones (OMZ) are frequently referred to as ‘dead zones’ from a biological standpoint, coastal OMZ can actually be highly dynamic in regard to nutrient cycling. Under the low-oxygen conditions (≤ 10 µM O2) that define OMZ , nutrients are released from the sediment to the water and can contribute to increased primary production in surface water. However, considerable nitrogen (N) loss to the atmosphere, one of the key processes limiting primary productivity, can also occur. Diapycnal mixing due to internal waves, coastal upwelling and lateral advective and diffusive transport can significantly enhance these processes by accelerating nutrient supply to the near-surface layers. There are conflicting opinions on which biochemical processes (e.g., denitrification, dissimilatory nitrate reduction to ammonium, and/or anammox) control N cycling within OMZ . Furthermore, while it is known that internal waves can significantly affect nutrient fluxes, hydrodynamics in coastal OMZ can be highly variable and effects on the nutrient distribution are not currently understood. We thus performed a process study focusing on the Peruvian OMZ in the Eastern Tropical South Pacific boundary current system, a region which is characterized by both (1) an extreme N deficit due to N loss and (2) elevated non-linear internal waves. Paired microstructure and CTD data were used to assess water-column turbulence and nutrient concentrations, respectively, and benthic chambers were used to evaluate nutrient fluxes from the sediment. Velocity and hydrographic time series from a mooring array allowed for investigation of advective and eddy nutrient transport. With these data, a nutrient budget was determined by quantifying water-column flux divergences of N species at the upper continental slope and shelf regions. Together with N fluxes from the sediment, we established an overall N balance which we then used to evaluate which biochemical processes were likely contributors to N cycling in this critical region.

Description: Reefs are in situ organic deposits which exhibit different sizes from few cubic meters to several hundreds of kilometers length and even several hundreds of meters in thickness (Spalding et al., 2001). Modern reefs are formed predominantly by stony corals which is the equivalent of the taxonomic order Scleractinia. Corals and other calcifying organisms produce hard skeletons, which lead to the accumulation of biogenic carbonates as a result of individual growth, bioerosion, sedimentation, and cementation due to wave energy during several hundreds of years. On millennial and much longer timescales, sea-level changes are the major driving force of reef growth. Today coral reefs cover more than 284,000 km2 (Spalding et al., 2001) and they are the largest marine structures on earth formed by biota, having a long geological record and ...

Description: Sclerochronology is the record of different periodicities expressed as chemical and physical variations in mineralized endo- or exoskeletons of living, fossil, and even extinct aquatic organisms. Sclerochronological periodicities are documented in growth increments of different shapes and sizes, depending on the time span they represent (Schöne and Surge, 2005). Such increments may portray days, lunar cycles, months, or years. Their individual width and pattern reflect either specific taxonomically related and therefore biologically controlled signals or environmental conditions in which the organism grew. These skeletal chronologies may comprise individual lifetimes of organisms ranging from several decades to several hundreds of years. Prominent organisms are scleractinian corals, calcified sponges, mollusk shells, or otoliths from fish. Along with the record of growth increments, the chemical composition of the mineralized skeleton based on elemental ratios such as Sr/Ca and Mg/Ca or ...

Description: Maio Island is situated in the eastern part of Cape Verde archipelago, and comprises early Mesozoic MORB-type pillow lavas and deep-sea sediments, and Miocene-Pliocene igneous rocks. The island is deeply eroded, indicating several phases of intensive erosion and collapse both during and after igneous growth. Maio exposes a central intrusive complex of Miocene age, which is surrounded by Lower Cretaceous pelagic limestones that were uplifted from the surrounding seafloor by igneous and tectonic activity1. The limestones were intruded by dykes and sills during the Miocene (12-8 Ma), with a peak in activity around 11 Ma2. These successions are overlain by lava flows and conglomerates of the Casas Velhas Formation (Fm.) and the Pedro Vaz Fm., which formed between 12-11 Ma, and by plateau lavas of the Malhada Pedra Fm. (9-7 Ma)2. The youngest volcanic units exposed on the island are lava flows of the Monte Penoso Fm., which formed a stratovolcano and have been K-Ar dated at 6.9 ± 0.4 Ma and 6.7 ± 0.4 Ma (2σ )2. At the base of the Monte Penoso Fm., polymict conglomerates up to 100 m thick, which we interpret as landslide deposits, occur at several locations. They contain well rounded clasts of various lithologies. Fresh biotite grains from a xenolith-rich basanite clast within the conglomerate were analysed. Single crystal laser total fusion biotite 40Ar-39Ar ages range from 8.50 ± 0.03 Ma to 11.55 ± 0.34 Ma (2σ, using the decay constants and atmospheric ratio of 3, and age standard TCS2 (27.87 ± 0.04 Ma; 1σ)). The older biotite ages are probably xenocrysts, but the youngest biotites yield a well constrained weighted mean 40Ar-39Ar age of 8.50 ± 0.02 Ma (2σ; n=22). Combining the K-Ar ages of the overlying Monte Penoso Fm.2 and our 40Ar-39Ar single biotite ages for the conglomerate clast, the Miocene period of large scale collapse and erosion on Maio can be confined to a period between 8.50-6.80 Ma, before the final phase of volcanism on the island began with the formation of the Monte Penoso stratovolcano. References: 1 Stillman, C.J. et al. (1982) J. Geol. Soc. 139 (3), 347–361. 2 Mitchell, J.G. et al. (1983) EPSL 64, 61–76. 3 Steiger R.H. & Jäger E. (1977) EPSL 36, 359–362.