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Large organic food falls to the deep sea - such as whale carcasses and wood logs - support the development of reduced, sulfidic niches in an otherwise oxygenated, oligotrophic deep-sea environment. These transient hot spot ecosystems may serve the dispersal of highly adapted chemosynthetic organisms such as thiotrophic bivalves and siboglinid worms. Here we investigated the biogeochemical and microbiological processes leading to the development of sulfidic niches. Wood colonization experiments were carried out for the duration of one year in the vicinity of a cold seep area in the Nile deep-sea fan (Eastern Mediterranean) at depths of 1690 m. Wood logs were deployed in 2006 during the BIONIL cruise (RV Meteor M70/2 with ROV Quest, Marum, Germany) and sampled in 2007 during the Medeco-2 cruise (RV Pourquoi Pas? with ROV Victor 6000, Ifremer, France). Wood-boring bivalves played a key role in the initial degradation of the wood, the dispersal of wood chips and fecal matter around the wood log, and the provision of colonization surfaces to other organisms. Total oxygen uptake measured with a ROV-operated benthic chamber module was higher at the wood (0.5 m away) in contrast to 10 m away at a reference site (25 mmol m-2 d-1 and 1 mmol m-2 d-1, respectively), indicating an increased activity of sedimentary communities around the wood falls. Bacterial cell numbers associated with wood increased substantially from freshly submerged wood to the wood chip/fecal matter layer next to the wood experiments, as determined with Acridine Orange Direct Counts (AODC) and DAPI-stained counts. Microsensor measurements of sulfide, oxygen and pH were conducted ex situ. Sulfide fluxes were higher at the wood experiments when compared to reference measurements (19 and 32 mmol m-2 d-1 vs. 0 and 16 mmol -2 d-1, respectively). Sulfate reduction (SR) rates at the wood experiments were determined in ex situ incubations (1.3 and 2.0 mmol m-2 d-1) and fell into the lower range of SR rates previously observed from other chemosynthetic habitats at cold seeps. There was no influence of wood deposition on phosphate, silicate and nitrate concentrations, but ammonium concentrations were elevated at the wood chip-sediment boundary layer. Concentrations of dissolved organic carbon were much higher at the wood experiments (wood chip-sediment boundary layer) in comparison to measurements at the reference sites, which may indicate that cellulose degradation was highest under anoxic conditions and hence enabled by anaerobic benthic bacteria, e.g. fermenters and sulfate reducers. Our observations demonstrate that, after one year, the presence of wood at the seafloor had led to the creation of sulfidic niches, comparable to what has been observed at whale falls, albeit at lower rates.

This article has been published as a Green Open Access publication. If you are unable to access the full article through the associated journal DOI (https://doi.org/10.1016/j.aquaculture.2020.735614), you may request the full text from the author through its page on ResearchGate. Abstract: Manganese (Mn) is an essential metal for fish and requirements have been established for several finfish but not for gilthead sea bream. Thus, the present study aims to establish the optimal dietary supplementation level of Mn in gilthead sea bream fingerlings fed vegetable based diets. Gilthead sea bream fingerlings (weight 12.6 ± 1.5 g, mean ± S.D.) were fed five practical diets high in vegetable ingredients (fish meal: 10%, fish oil: 6%). The diets were supplemented to contain 19, 27, 30, 41 and 66 mg Mn kg−1 as MnSO4. Four hundred and fifty sea bream fingerlings were randomly distributed in 15 tanks and fed one of the five diets until apparent satiation three times per day for 42 days. Growth parameters including feed intake, thermal growth coefficient and feed conversion ratio were calculated. At the end of the trial, samples were taken for biochemical, mineral, histological and gene expression analyses. After the feeding trial, fish almost tripled their weight, but dietary Mn levels did not affect growth parameters or survival. The high fish meal substitution levels led to high Mn contents in the basal diet (19 mg Mn kg−1 diet), that seemed to be sufficient to promote sea bream growth. Body lipid composition, protein and ash were not affected by the dietary Mn. Similarly, whole body, liver and vertebrae mineral contents were not affected by Mn supplementation. Morphological characteristics of liver had no significant differences among dietary Mn levels. However, increase of Mn contents beyond 30 mg Mn kg−1 down-regulated mnsod expression. Expression of cat gene was not affected. Overall, results suggest that the Mn content present in the basal diet (19 mg Mn kg−1) was sufficient to cover the requirements in juvenile gilthead sea bream fed practical plant-based diets, although results from oxidative status markers might point out the need to increase supplementation levels beyond this point when fish are under conditions that may affect their oxidative status.

In this report, the investigation of wind farm control with the objective to meet power systems requirements is reported. It is shown that the full range of ancillary services including frequency support can be provided at the farm level. The architecture of the wind farm controller is hierarchical, decentralised and scalable. Although, only very weak feedback control is introduced at the turbine level, reasonably tight control is achieved at the wind farm level. It is demonstrated that offshore wind farms can be made to operate as virtual conventional plant through the Generator Response Following concept, whereby the power output of the farm is slaved to the power output from a small synchronous generator situated at the onshore end of the connection-to-shore. The sensitivity to communication delays and mitigating strategies are explored. The StrathFarm simulation tool has been used extensively in this work to evaluate the loads each turbine experiences when farm level control is used to provide ancillary services.

Changes in marine net primary productivity (PP) and export of particulate organic carbon (EP) are projected over the 21st century with four global coupled carbon cycle-climate models. These include representations of marine ecosystems and the carbon cycle of different structure and complexity. All four models show a decrease in global mean PP and EP between 2 and 20% by 2100 relative to preindustrial conditions, for the SRES A2 emission scenario. Two different regimes for productivity changes are consistently identified in all models. The first chain of mechanisms is dominant in the low- and mid-latitude ocean and in the North Atlantic: reduced input of macro-nutrients into the euphotic zone related to enhanced stratification, reduced mixed layer depth, and slowed circulation causes a decrease in macro-nutrient concentrations and in PP and EP. The second regime is projected for parts of the Southern Ocean: an alleviation of light and/or temperature limitation leads to an increase in PP and EP as productivity is fueled by a sustained nutrient input. A region of disagreement among the models is the Arctic, where three models project an increase in PP while one model projects a decrease. Projected changes in seasonal and interannual variability are modest in most regions. Regional model skill metrics are proposed to generate multi-model mean fields that show an improved skill in representing observation-based estimates compared to a simple multi-model average. Model results are compared to recent productivity projections with three different algorithms, usually applied to infer net primary production from satellite observations.

The present study provides new knowledge about the so far largely unexplored Coral Patch seamount which is located in the NE Atlantic Ocean half-way between the Iberian Peninsula and Madeira. For the first time a detailed hydroacoustic mapping (MBES) in conjunction with video surveys (ROV, camera sled) were performed to describe the sedimentological and biological characteristics of this sub-elliptical ENE-WSW elongated seamount. Video observations were restricted to the southwestern summit area of Coral Patch seamount (water depth: 560–760 m) and revealed that this part of the summit is dominated by exposed hard substrate, whereas soft sediment is just a minor substrate component. Although exposed hardgrounds are dominant for this summit area and, thus, offer suitable habitat for settlement by benthic organisms, the benthic megafauna shows rather scarce occurrence. In particular, scleractinian framework-building cold-water corals are apparently rare with very few isolated and small-sized live occurrences of the species Lophelia pertusa and Madrepora oculata. In contrast, dead coral framework and coral rubble are more frequent pointing to a higher abundance of cold-water corals on Coral Patch during the recent past. This is even supported by the observation of fishing lines that got entangled with rather fresh-looking coral frameworks. Overall, long lines and various species of commercially important fish were frequently observed emphasising the potential of Coral Patch as an important target for fisheries that may have impacted the entire benthic community. Hydroacoustic seabed classification covered the entire summit of Coral Patch and its northern and southern flanks (water depth: 560–2660 m) and revealed extended areas dominated by mixed and soft sediments at the northern flank and to a minor degree at its easternmost summit and southern flank. Nevertheless, these data also predict most of the summit area to be dominated by exposed bedrock which would offer suitable habitat for benthic organisms. By comparing the locally restricted video observations and the broad-scale monitoring of a much larger and deeper seafloor area as derived by hydroacoustic seabed classification, it becomes obvious that habitat information obtained by in situ sampling may provide a rather scattered pattern about the entire seamount ecosystem. Solely with a combination of both methods, a satisfactory approach to describe the diverse characteristics of a seamount ecosystem can be derived which is in turn indispensable for future scientific monitoring campaigns as well as management and conservation purposes.

Fires have influenced atmospheric composition and climate since the rise of vascular plants, and satellite data have shown the overall global extent of fires. Our knowledge of historic fire emissions has progressively improved over the past decades due mostly to the development of new proxies and the improvement of fire models. Currently, there is a suite of proxies including sedimentary charcoal records, measurements of fire-emitted trace gases and black carbon stored in ice and firn, and visibility observations. These proxies provide opportunities to extrapolate emission estimates back in time based on satellite data starting in 1997, but each proxy has strengths and weaknesses regarding, for example, the spatial and temporal extents over which they are representative. We developed a new historic biomass burning emissions dataset starting in 1750 that merges the satellite record with several existing proxies and uses the average of six models from the Fire Model Intercomparison Project (FireMIP) protocol to estimate emissions when the available proxies had limited coverage. According to our approach, global biomass burning emissions were relatively constant, with 10-year averages varying between 1.8 and 2.3 Pg C yr−1. Carbon emissions increased only slightly over the full time period and peaked during the 1990s after which they decreased gradually. There is substantial uncertainty in these estimates, and patterns varied depending on choices regarding data representation, especially on regional scales. The observed pattern in fire carbon emissions is for a large part driven by African fires, which accounted for 58 % of global fire carbon emissions. African fire emissions declined since about 1950 due to conversion of savanna to cropland, and this decrease is partially compensated for by increasing emissions in deforestation zones of South America and Asia. These global fire emission estimates are mostly suited for global analyses and will be used in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations.

First results of a coupled modelling and forecasting system for fisheries on habitat-bound stocks are being presented. The system consists currently of three mathematically, fundamentally different model subsystems coupled offline: POLCOMS providing the physical environment implemented in the domain of the north-west European shelf, the SPAM model which describes sandeel stocks in the North Sea, and the third component, the SLAM model, which connects POLCOMS and SPAM by computing the physical–biological interaction. Our major experience by the coupling model subsystems is that well-defined and generic model interfaces are very important for a successful and extendable coupled model framework. The integrated approach, simulating ecosystem dynamics from physics to fish, allows for analysis of the pathways in the ecosystem to investigate the propagation of changes in the ocean climate and to quantify the impacts on the higher trophic level, in this case the sandeel population, demonstrated here on the basis of hindcast data. The coupled forecasting system is tested for some typical scientific questions appearing in spatial fish stock management and marine spatial planning, including determination of local and basin-scale maximum sustainable yield, stock connectivity and source/sink structure. Our presented simulations indicate that sandeel stocks are currently exploited close to the maximum sustainable yield, even though periodic overfishing seems to have occurred, but large uncertainty is associated with determining stock maximum sustainable yield due to stock inherent dynamics and climatic variability. Our statistical ensemble simulations indicates that the predictive horizon set by climate interannual variability is 2–6 yr, after which only an asymptotic probability distribution of stock properties, like biomass, are predictable.

Organic compounds represent a significant fraction of submicrometer atmospheric aerosol mass. Even if most of these compounds are semi-volatile in atmospheric concentrations, the ambient organic aerosol volatility is quite uncertain. The most common volatility measurement method relies on the use of a thermodenuder (TD). The aerosol passes through a heated tube where its more volatile components evaporate, leaving the less volatile components behind in the particulate phase. The typical result of a thermodenuder measurement is the mass fraction remaining (MFR), which depends, among other factors, on the organic aerosol (OA) vaporization enthalpy and the accommodation coefficient. We use a new method combining forward modeling, introduction of "experimental" error, and inverse modeling with error minimization for the interpretation of TD measurements. The OA volatility distribution, its effective vaporization enthalpy, the mass accommodation coefficient and the corresponding uncertainty ranges are calculated. Our results indicate that existing TD-based approaches quite often cannot estimate reliably the OA volatility distribution, leading to large uncertainties, since there are many different combinations of the three properties that can lead to similar thermograms. We propose an improved experimental approach combining TD and isothermal dilution measurements. We evaluate this experimental approach using the same model, and show that it is suitable for studies of OA volatility in the lab and the field.