Description: Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community. We invited contributions to the overarching topics of data management, data science and data infrastructures. The series of Data Science Symposia is a joint initiative by the three Helmholtz Centers HZG, AWI and GEOMAR Organization: Hela Mehrtens and Daniela Henkel (GEOMAR)

Description: Given the variability of seasonal, annual, and in particular langer time-scales, the dispersal and fate of the river discharge and its influence on the hydrographical and sedimentological settings are the central tasks in understanding the Holocene history of the Laptev Sea shelf. The main goal of this study was to investigate short- and long-term environmental changes in the strongly coupled land-shelf system of the Laptev Sea using isotopic evidence in sediments and biogenic carbonates. In order to trace the modern spatial distribution of terrestrial organic matter, which is strongly affected by the riverine input and the thermal erosion of the ice-rich permafrost coast, stable carbon isotope ratios of total organic carbon in surface sediments were analyzed. The stable carbon isotope composition of surface sediments reveal a dominant impact of terrestrial organic matter on the modern depositional environment of the Laptev Sea shelf with distinct south to north and east to west gradients. Based on downcore 8 13Carg records in radiocarbon-dated sediment cores the spatial and temporal deposition of terrestrial organic matter during the past 12.7 ka is specified and can be related to depositional changes which occurred after the last glacial maximum when this region became flooded due to a global rising sea level. The major changes in the deposition of terrestrial organic matter occurred between 11 and 7 ka BP and comprise the main phase of the southward retreat of the coastline and river depocenters due to the postglacial sea level rise. Stable oxygen and carbon isotope profiles from recent and fossil bivalve shells were investigated in order to trace modern and past hydrographical conditions and their changes during the postglacial history of the Laptev Sea. The serial dissection of bivalve shell valves along their growth axis from the umbo towards the ventral margin provides an isotopic record of hydrographical and physiological changes during the life of the individual specimen. The oxygen isotopic profiles of modern bivalve species of Astarte borealis exhibit amplitude cycles interpreted as recording annual hydrographical cycles. Regarding the well-known relationship between the carbonate 8 180, temperature, and the isotopic composition of water (8180w), it is possible to relate isotopic phases to seasonal hydrographical phases like summer and winter. The within shell isotopic variations are mainly attributed to variations in the isotopic composition and in the salinity of bottom waters in the Laptev Sea. Seasonal temperature changes can be regarded of minor importance. Using a modern linear relationship between 8 180w and salinity of 0.50 %0/salinity, salinity records are reconstructed from the oxygen isotope records of the bivalve shells and can be directly compared with hydrographical parameters at the investigated sites. Carbon isotope profiles from modern specimens reveal a correspondence to the river breakup and to seasonal phytoplankton productivity. Trends towards lighter 8 13 C values through ontogeny suggest the effects of metabolic changes from a juvenile into a mature adult. Differences in the 8 13C of shell carbonate between the sites appear to reflect the regional distribution of the ö 13C of sedimentary organic matter. Given a good conformance between isotope profiles from modern bivalve shells and oceanographic observations, oxygen isotope profiles of radiocarbon bivalve shells from a sediment core from northeast off the Lena Delta are usecl to obtain in formation about passt hydrological conditions. Although isotope profiles from fossil bivalves of the Laptev Sea shelf reflect only a brief interval of time, they may offer new important insights into the paleohydrography during snapshots of the last 8.4 ka and their relation to the Holocene transgression. A reconstructed bottom water salinity of 29.5 at 8.4 ka BP indicates that the particular site was much more affectecl by riverine water than nowaclays causecl by the proximity to the coastline and to the paleo-1iver mouth. Due to the continuing southward retreat of the coastline ancl the Lena River mouth relative to the study site an increase in the bottom water salinity at 7.3 ka BP is reconstructecl. The oxygen isotope shell profile at 7.3 ka BP gives an evidence of a bottom water hydrography which is characterized by a high variability of summer and winter conditions on the level of modern bottom water conditions. The following time slices at 3.6 ka and 1.6 ka BP reveal that modern hydrological conditions are fully established. The presented salinity reconstruction enables us to make further presurnptions on the relative proximity of the study site to the coast and to the river rnouth during snapshot views of the Holocene history and thus can be related to the postglacial transgression of the Laptev Sea shelf.

Description: Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community.

Description: Abstract Legal requirement in Europe asks for Ecosystem-Based Fisheries Management (EBFM) in European seas, including considerations of trophic interactions and minimization of negative impacts of fishing on food webs and ecosystem functioning. Focusing on the interaction between fisheries and ecosystem components, the trophic model presented here shows for the first time the “big picture” of the western Baltic Sea (WBS) food web by quantifying structure and flows between all trophic elements and the impact of fisheries that were and are active in the area, based on best available recent data. Model results show that fishing pressures exerted on the WBS since the early nineties of the past century forces not only top predators such as harbour porpoises and seals but also cod and other demersal fish to heavily compete for fish as food and to cover their dietary needs by shifting to organisms lower in the trophic web, mainly to benthic macrofauna and / or search for suitable prey in adjacent ecosystems such as Kattegat, Skagerrak, central Baltic Sea and North Sea. While common sense implementations of EBFM have been proposed, such as fishing all stocks below Fmsy and reducing fishing pressure even further for forage fish such as herring and sprat, few studies compared such fishing to alternative scenarios. Different options for EBFM, with regards to recovery of depleted stocks and sustainable future catches, are presented here based on the WBS ecosystem model, the legal framework given by the new Common Fisheries Policy (CFP) and the Marine Strategy Framework Directive (MSFD) of the European Union. The model explores four legally valid future fishery scenarios: 1) business as usual, 2) maximum sustainable fishing (F = Fmsy), 3) half of Fmsy, and 4) EBFM with F = 0.5 Fmsy for forage fish and F = 0.8 Fmsy for other fish. In addition, a “No-fishing” scenario demonstrates, that neither individual stocks nor the whole system would collapse when all fishing activities from 2017 on would cease. Simulations show that “Business as usual” would perpetuate low 2016 catches from depleted stocks in an unstable ecosystem where endangered species may be lost. In contrast, an “EBFM” scenario - with herring and sprat fished at 0.5 Fmsy level and cod and other stocks fished at 0.8 Fmsy level - allows the recovery of all stocks with strongly increased catches close to the maximum (at Fmsy) for cod and flatfish and catches similar to the 2016 level for herring and sprat but with strongly reduced fishing effort. Model and methodology presented here are considered suitable to assess MSFD Criterion D4C2 in the WBS.

Description: A physical - biogeochemical survey was carried out in the northeastern tropical Atlantic and in the western tropical South Atlantic. The main objective of the works in the oxygen minimum zone of the eastern tropical North Atlantic was to improve oxygen budget estimates. Additional objectives were to investigate the role of zooplankton for fluxes of particulate and dissolved organic matter and to advance quantitative understanding of nitrogen fixation in the tropical Atlantic. The main objective of the measurements program in the western tropical South Atlantic was to investigate the variability of transport and water mass properties of the western boundary circulation. A major component of the work program was the recovery of nine and the redeployment of eight moorings. The moorings positioned off Cape Verde, in the tropical northeastern Atlantic and at the western boundary off Brazil are collecting velocity, oxygen, temperature, and salinity time series since several years. All moorings were successfully recovered and redeployed. Section work focused on 23°W from 15°N to 5.5°S, on 11.5°S from 32°W to the coast of Brazil and on 5°S from 29.5°W to the coast of Brazil. Parameters measured along the sections included temperature-salinity-depth, oxygen and turbulence profiles, lowered acoustic Doppler current profiles, underwater vision profiles, shipboard velocity profiles, multinet and Working Party 2 net casts, and photosynthetically active radiation profiles. Water samples were analyzed for numerous variables including salinity, oxygen concentrations, tracer concentrations (CFC-12, SF6, CF3SF5), nutrients in micro and nano range, and halocarbons. Filtered samples were taken for NanoSIMS, flow cytometry, dissolved organic phosphorus, DNA/RNA, particulate organic matter, particulate organic nitrogen, and chlorophyll a. Samples of Heme content and dissolved iron were taken from a towed trace metal clean fish. Furthermore, on-board incubations to quantify nitrogen and carbon fixation and primary productivity were performed. The measurement program was successfully completed and all data sets were acquired as planned.

Description: Laufzeit des Vorhabens: 01.01.2014-31.12.2017 : Berichtszeitraum: 01.01.2014-31.12.2017