ALBERT

Description: The magnitude of nutrient and trace metal cycling in oxygen minimum zones (OMZ) and the involved loss of fixed nitrogen is crucial for the ocean’s nutrient budget, particularly in light of the ongoing expansion of OMZs. The major focus of the measurement program that was carried out in the frame of the DFG Collaborative Research Centre (SFB) 754 „Climate-biogeochemical interactions in the tropical ocean“, was to advance interdisciplinary understanding of benthic and pelagic nutrient and trace metal cycling processes in the OMZ off Peru and to quantify loss of nitrogen nutrients. Further objectives were to determine ventilation rates by submesoscale processes, quantify export fluxes of particulate organic matter, determine production and decay rates of dissolved organic material, and investigate mechanisms of iron stabilization, removal and cycling. The physical-biogeochemical measurement program focused on a transect perpendicular to the coastline at 12°S. Additionally, a transect at 14°S was completed and a submesoscale process study in an upwelling filament structure was carried out in the region of 15°S, 77°W. The coordinated sampling scheme included CTD profiling and water sampling stations, shipboard turbulence and velocity observations, a glider swarm experiment, moored velocity and hydrography observations, in situ benthic flux measurements using landers, sediment retrieval with a multiple corer, drifting sediment trap deployments and recovery and in situ pump deployments. The measurement program that was closely linked to the follow-up cruise M137 was successfully completed and all data sets were acquired as planned

Description: 15.05 – 30.05.2019 The AL522 cruise extended a long-term data series on (eco-)system composition and functioning of the Baltic Sea, with a focus on the deeper basins. The series has been collected in similar form since 1986. A key characteristic of the cruise is the integration of oceanographic and biological information to enhance understanding of environmental and (fish) population fluctuations, and evolutionary processes in this system. The resulting data- and sample sets support ongoing projects in the Research Unit Marine Evolutionary Ecology at GEOMAR, as well as the EU Horizon 2020 project GoJelly and several international collaborations. The spatial focus lay on the Bornholm Basin as most important spawning area of Baltic cod, but also included the Western Baltic Sea, Arkona and Gotland Basin, Gdansk Deep, and Stolpe Trench. Specific investigations included a detailed hydrological survey (oxygen, salinity, temperature) of the cruise area, plankton surveys (zoo- and ichthyplankton including gelatinous plankton, with the goal to determine the composition and the abundance and vertical and horizontal distribution of species, and to take samples for later measurements of nutritional condition), and pelagic fishery hauls. The latter served to determine stock structure, gonadal maturation, stomach contents, and egg production of sprat and cod, and to sample tissue and otolith samples for individual-level genetic and ecological analyses of cod. The abundance and distribution of fishes in the cruise area was also assessed with hydroacoustic methods. Additional cruise components were: (i) cod gonad and liver sampling for fecundity + parasite studies, (ii) vertically resolved plankton sampling for studies of plankton phenology (iii) depth-resolved sampling of microplastic using an neuston sledge (iv) sampling and experimental work of photosynthesis rates of different phytoplankton fractions (v) eDNA filter sampling to compare with traditional net based methods.

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: The status report has two separate volumes. Vol. I presents the scientific achievements of GEOMAR since the beginning of 2013.

Description: Vol. II contains a selection of CVs of scientific staff as well as a set of quantitative indicators for the years 2013 to 2016. The Helmholtz Association and its Research Field Earth and Environment decided to limit the number of CVs based on the size of the scientific staff of each institute (resulting in 24 CVs for GEOMAR) and to a maximum size of one page per CV. In addition, general guidelines were set out concerning what the CVs should contain, including limiting the number of listed publications to five. All publication data/indices originate from Web of Science.

Description: A recent optimality-based model for phytoplankton growth and diazotrophy was applied at two stations located in the oligotrophic western and the ultra-oligotrophic eastern subtropical North Atlantic. Contrary to the common view that diazotrophy is favoured by nitrogen (N) depletion relative to the Redfield equivalent of phosphorus (P), we find that optimality-based diazotrophy could explain N fixation in both regions in spite of relatively high N:P supply ratios. This is possible because the availability of an additional source of N for diazotrophs makes them strong competitors for P under oligotrophic conditions. The best reproduction of observations, especially of net primary production, is only achieved with preferential remineralization of P relative to N and atmospheric deposition. In line with observations, a higher rate of nitrogen fixation is predicted for the eastern site, owing to a larger niche for diazotrophs resulting from stronger oligotrophy and lower N:P supply ratios due to weaker atmospheric N deposition. Because the competitive advantage of diazotrophs under nutrient starvation diminishes with increasing supply N:P ratio, the predicted increase of atmospheric N deposition due to anthropogenic activity could negatively affect N2 fixation in the Atlantic Ocean.

Description: M130, Mindelo - Recife 28.08.- 03.10.2016 1. Wochenbericht vom 28.08.2016

Description: M130, Mindelo - Recife 28.08.- 03.10.2016 2. Wochenbericht vom 04.09.2016

Description: M130, Mindelo - Recife 28.08.- 03.10.2016 6. Wochenbericht vom 02.10.2016