Beschreibung: 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.

Beschreibung: 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.

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