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: Gelatinous zooplankton (Cnidaria, Ctenophora, and Urochordata, namely, Thaliacea) are ubiquitous members of plankton communities linking primary production to higher trophic levels and the deep ocean by serving as food and transferring “jelly‐carbon” (jelly‐C) upon bloom collapse. Global biomass within the upper 200 m reaches 0.038 Pg C, which, with a 2–12 months life span, serves as the lower limit for annual jelly‐C production. Using over 90,000 data points from 1934 to 2011 from the Jellyfish Database Initiative as an indication of global biomass (JeDI: http://jedi.nceas.ucsb.edu, http://www.bco‐dmo.org/dataset/526852), upper ocean jelly‐C biomass and production estimates, organism vertical migration, jelly‐C sinking rates, and water column temperature profiles from GLODAPv2, we quantitatively estimate jelly‐C transfer efficiency based on Longhurst Provinces. From the upper 200 m production estimate of 0.038 Pg C year−1, 59–72% reaches 500 m, 46–54% reaches 1,000 m, 43–48% reaches 2,000 m, 32–40% reaches 3,000 m, and 25–33% reaches 4,500 m. This translates into ~0.03, 0.02, 0.01, and 0.01 Pg C year−1, transferred down to 500, 1,000, 2,000, and 4,500 m, respectively. Jelly‐C fluxes and transfer efficiencies can occasionally exceed phytodetrital‐based sediment trap estimates in localized open ocean and continental shelves areas under large gelatinous blooms or jelly‐C mass deposition events, but this remains ephemeral and transient in nature. This transfer of fast and permanently exported carbon reaching the ocean interior via jelly‐C constitutes an important component of the global biological soft‐tissue pump, and should be addressed in ocean biogeochemical models, in particular, at the local and regional scale.

Beschreibung: The model SEAPODYM (Spatial Ecosystem And Population Dynamics) has now reached a degree of maturity allowing to use it for testing management scenarios and to implement operational monitoring. It is proposed to implement an operational forecast system for the Atlantic albacore tuna. The system will use physical field (temperature, currents and primary production) from Copernicus CMEMS. The sensitivity to improved physical variables with data assimilation will be analysed and the interest of this operational production of tuna stock distributions evaluated in collaboration with colleagues involved in the management of tuna fisheries at ICCAT and FAO, and the AtlantOS fitness for this modelling analysed [D8.9]

Beschreibung: Report on the current observing status in the North Atlantic subpolar gyre and the South Atlantic subtropical gyre, containing the results of the investigation on regional observing activities, systems, and connectivity in relation to climate and ecosystems

Beschreibung: Distinct differences were observed in geochemical signatures in sediments from two sites drilled in the upper plate of the Costa Rica margin during Integrated Ocean Drilling Program (IODP) Expedition 334. The upper 80 m at Site U1379, located on the outer shelf, show pore water non‐steady state conditions characteristic of a declining methane flux. These contrast with analyses of the upper sediment layers at the middle slope site (U1378) that reflect steady state conditions. Distinct carbonate‐rich horizons up to 11 meters thick were recovered between 63 and 310 meters below seafloor at Site U1379 but were not found at Site U1378. The carbonates and dissolved inorganic carbon from Site U1379 have a depleted carbon stable isotope signal (up to ‐25‰) that indicates anaerobic methane oxidation. This inference is further supported by distinct δ34S‐pyrite and magnetic susceptibility records that reveal fluctuations of the sulfate‐methane transition in response to methane flux variations. Tectonic reconstructions of this margin document a marked subsidence event after arrival of the Cocos Ridge, 2.2 ± 0.2 million years ago (Ma), followed by increased sedimentation rates and uplift. As the seafloor at Site U1379 rose from ~2000 m to the present water depth of ~126 m, the site moved out of the gas hydrate stability zone (GHSZ) at ~1.1 Ma, triggering upward methane advection, methane oxidation, and the onset of massive carbonate formation. Younger carbonate occurrences and the non‐steady state pore profiles at Site U1379 reflect continued episodic venting likely modulated by changes in the underlying methane reservoir.

Beschreibung: The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.

Beschreibung: The potential of Coastal Ocean Alkalinization (COA), a carbon dioxide removal (CDR) climate engineering strategy that chemically increases ocean carbon uptake and storage, is investigated with an Earth system model of intermediate complexity. The CDR potential and possible environmental side effects are estimated for various COA deployment scenarios, assuming olivine as the alkalinity source in ice-free coastal waters (about 8.6% of the global ocean's surface area), with dissolution rates being a function of grain size, ambient seawater temperature and pH. Our results indicate that for a large-enough olivine deployment of small-enough grain sizes (10 μm), atmospheric CO2 could be reduced by more than 800 GtC by the year 2100. However, COA with coarse olivine grains (1000 μm) has little CO2 sequestration potential on this time scale. Ambitious CDR with fine olivine grains would increase coastal aragonite saturation Ω to levels well beyond those that are currently observed. When imposing upper limits for aragonite saturation levels (Ωlim) in the grid boxes subject to COA (Ωlim = 3.4 and 9 chosen as examples), COA still has the potential to reduce atmospheric CO2 by 265 GtC (Ωlim=3.4) to 790 GtC (Ωlim=9) and increase ocean carbon storage by 290 Gt (Ωlim=3.4) to 913 Gt (Ωlim=9) by year 2100.

Beschreibung: Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) is a multinational program initiated in 1997 in the tropical Atlantic to improve our understanding and ability to predict ocean-atmosphere variability. PIRATA consists of a network of moored buoys providing meteorological and oceanographic data transmitted in real time to address fundamental scientific questions as well as societal needs. The network is maintained through dedicated yearly cruises, which allow for extensive complementary shipboard measurements and provide platforms for deployment of other components of the Tropical Atlantic Observing System. This paper describes network enhancements, scientific accomplishments and successes obtained from the last 10 years of observations, and additional results enabled by cooperation with other national and international programs. Capacity building activities and the role of PIRATA in a future Tropical Atlantic Observing System that is presently being optimized are also described.

Beschreibung: Analysis of the capacities and gaps of the present Atlantic Ocean Observing System