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Oxygen Minimum Zones prevail in most of the world’s oceans and are particularly extensive in Eastern Boundary Upwelling Ecosystems such as the Humboldt and the Benguela upwelling systems. In these regions, euphausiids are an important trophic link between primary producers and higher trophic levels. The species are known as pronounced diel vertical migrators, thus facing different levels of oxygen and temperature within a 24 h cycle. Declining oxygen levels may lead to vertically constrained habitats in euphausiids, which consequently will affect several trophic levels in the food web of the respective ecosystem. By using the regulation index (RI), the present study aimed at investigating the hypoxia tolerances of different euphausiid species from Atlantic, Pacific as well as from Polar regions. RI was calculated from 141 data sets and used to differentiate between respiration strategies using median and quartile (Q) values: low degree of oxyregulation (0.25 < RI median < 0.5); high degree of oxyregulation (0.5 < RI median < 1; Q1 > 0.25 or Q3 > 0.75); and metabolic suppression (RI median, Q1 and Q3 < 0). RI values of the polar (Euphausia superba, Thysanoessa inermis) and sub-tropical (Euphausia hanseni, Nyctiphanes capensis, and Nematoscelis megalops) species indicate a high degree of oxyregulation, whereas almost perfect oxyconformity (RI median ≈ 0; Q1 < 0 and Q3 > 0) was identified for the neritic temperate species Thysanoessa spinifera and the tropical species Euphausia lamelligera. RI values of Euphausia distinguenda and the Humboldt species Euphausia mucronata qualified these as metabolic suppressors. RI showed a significant impact of temperature on the respiration strategy of E. hanseni from oxyregulation to metabolic suppression. The species’ estimated hypoxia tolerances and the degree of oxyconformity vs. oxyregulation were linked to diel vertical migration behavior and the temperature experienced during migration. The results highlight that the euphausiid

Migrant biomass and carbon fux of vertically migrating meso- and macrozooplankton was calculated for shelf (< 200 m bottom depth) and oceanic (> 200 m bottom depth) regions in the northern Benguela upwelling system. Active carbon fux is based on migrant biomass and respiration rates. Especially in upwelling regions, oxygen minimum zones (OMZ) are a common feature and thus the impact of low oxygen concentrations (i.e. hypoxia) on metabolic rates also should be considered. Copepods were sampled with a 0.25 m2 multiple opening and closing net (Multinet midi), while a larger net (1 m MOCNESS) was used for the collection of euphausiids and decapods. Copepods were dominant in the upper 50 m of shelf areas with a migrant biomass between 23 and 47 mg C m-2, whereas euphausiids were more abundant at oceanic regions with up to 1437 mg C m-2. Decapods were absent at the shelf but important in greater depth at oceanic stations (> 150 mg C m-2). Mass-specifc respiration rates of individuals from the OMZ were reduced by 46-64% as compared to metabolic rates of specimens from surface waters. The resulting active carbon fux out of the upper 100 m by vertically migrating species was estimated with 4.3 mg C m-2 d-1 for shelf regions and 11.2 mg C m-2 d-1 for oceanic areas, which is equivalent to 4% and 35% of sinking POC, respectively. These data emphasize the crucial role of the OMZ for future developments of realistic carbon budgets under climate change scenarios.

Modern Oxygen Minimum Zones (OMZs) are extensive and prevail in most of the world oceans. Anthropogenic and climate induced changes will cause OMZs to expand, while coastal hypoxia is assumed to increase in extent and severity. Particularly in Eastern Boundary Upwelling Ecosystems (EBUEs), such as the Humboldt and the Benguela upwelling system, severe OMZs prevail. Animals living in these areas have to physiologically and/or behaviourally adapt to the low oxygen levels or will be excluded from these areas or at least their vertical distribution ranges will be limited. It is assumed that some areas may experience a shift from an abundant and diverse regime to one that is lean and dominated by vertical migrators. Further, temperature is known to impact the hypoxia tolerance of animals negatively. Euphausiids are known as pronounced diel vertical migrators, thus facing different levels of oxygen and temperature within 12 hours and are an important trophic link between primary producers and higher trophic levels throughout the world oceans. The critical oxygen pressure (Pcrit) and the regulation index (RI), as a method to differentiate between oxygen conformity and regulation, were used to assess hypoxia tolerances of different species from different ecosystems. Furthermore, diel vertical migration behaviour was monitored in some species. We will present and compare hypoxia tolerances of different dominant euphausiids species, show how oxygen availability may affect their vertical migration behaviour and assess how future climate scenarios (warming waters and decreasing oxygen content) may alter horizontal and/or vertical distribution of these species.

In the framework of the GENUS –“Geochemistry and Ecology of the Namibian Upwelling System” research program, trophic interactions and carbon pathways throughout the food web of the coastal upwelling system are being quantified. In contrast to earlier studies, special focus is been given to lower trophic levels in higher taxonomic resolution. Energy demands of various zooplankton taxa, including copepods, euphausiids, decapods and fish larvae, have been quantified with standardized methodology via optode respirometry. Dietary spectra and trophic levels were analyzed by trophic biomarker approaches based on fatty acid composition and stable isotopes (15N, 13C), respectively. All empirical data are assembled for an Ecopath with Ecosim (EwE) food-web model. The EwE model distinguishes between shelf and offshore communities. The conceptual food‐web model consists of three groups of primary producers, i.e. diatoms, dinoflagellates, and cyanobacteria, as well as many consumers such as Calanoides carinatus as the key herbivorous copepod in the Benguela upwelling system, other copepods, Euphausia hanseni, other zooplankton, and pelagic fishes including sardine, anchovy, and horse mackerel. Empirical data show that zooplankton and particularly copepods encompass a wider range of trophic levels from herbivory to secondary or even tertiary consumers (δ15N from 4 to 12‰), while anchovy had rather low δ15N of about 7‰. Respiration rates and metabolic activities of copepods could be parameterized for the model by an energy budget approach based on ambient temperature, body mass, and activity level. Calanoid copepods consumed 78mg C m‐2 d‐1 in shelf regions and 21mg C m‐2 d‐1 in oceanic regions. Locally, C. carinatus could remove up to 90% of the diatom biomass per day. The community consumption of pelagic decapods ranged from 7 mg C m‐2 d‐1 to >20mg C m‐2 d‐1 with highest values in the northernmost part of the study area. Overall, pelagic decapods apparently play a more prominent

The prevailing vertical transport of carbon produced by phytoplankton in the upper water layers of the ocean to deeper zones takes place by sinking of particulate organic carbon (POC). Several processes mediated by the zooplankton community can either enhance or limit the vertical carbon flux and regulate the efficiency of the biological carbon pump. Main biological pathways by which carbon is exported to deeper water layers are the active transport of carbon by vertical migration of pelagic animals and the passive transport of faecal pellets. Vertically migrating zooplankton may in this way significantly contribute to the dissolved inorganic carbon (DIC) pool by respiration and the dissolved organic carbon (DOC) pool by excretion. In the northern Benguela Upwelling System (BUS) jellyfish, krill, copepods, decapods and occasionally salps dominate the mesozooplankton community in terms of biomass. We will present a conceptual model, combining diel vertical migration (DVM) patterns of dominant krill species, with environmental parameters such as temperature, food availability and with physiological constraints such as species-specific respiration rates that may explain seasonal adaptations of DVM to changes in water temperature, oxygen and food availability. Additionally, we will show how the different taxa contribute to the downward transport of organic carbon by vertical migration (Krill, copepods and decapods) or through high amounts of fast sinking faeces (salps). Variable spatial and temporal distributions, such as a high patchiness of krill, decapods and salps and a more homogenous horizontal distribution of copepods will lead to seasonal and regional differences in the export of organic carbon. Furthermore, high primary production in the upper water layers related to upwelling intensity enhances the carbon export due to phytoplankton sinking after a bloom and/or faecal pellet production and grazing by zooplankton. Overall, we will estimate the role of zooplankt

The goal of the GENUS project (Geochemistry and Ecology of the Namibian Upwelling System) is to analyse the interrelationships between climate change, oceanic nutrients, greenhouse gases and the ecosystem structure in the coastal upwelling area off Namibia. The biological/ecological work package focused on the structure of the Northern Benguela Upwelling System (NBUS) and its energy flows under changing environmental conditions. Physiological constraints and adaptations were detected in several taxonomic groups investigated within the project, such as several copepod species, euphausiids and fish larvae. Temperature and oxygen distribution in the water column were identified as main drivers in modulating the distribution and ecology of many species. The extension and position of the Oxygen Minimum Zone (OMZ) seems to have a significant impact on the life cycles, vertical distribution and trophic condition of various species. In copepods we find a variety of adaptation mechanisms. While some species avoid the OMZ, others use it for resting and predator avoidance during daytime. Such vertical migrations contribute significantly to vertical carbon flux. The same holds true for decapods (4.4 mg C m‐2 d‐1). Respiration rates of 16 copepod species were determined to average 54.6 ±32.8 ml O2 d‐1 gDM‐1. Calanoides carinatus diapausing C5 stages reduced respiration at depth by 82% compared to surface activity. Further adaptations were found in euphausiid species: While Euphausia hanseni is capable to use the OMZ as a retreat by reducing its metabolic activity at lower temperatures and unfavourable trophic conditions, Nematoscelis megalops generally maintains a low level metabolism adapted to a constant life in the OMZ, and avoids crossing the thermocline. Special features of early life stages of Trachurus capensis, the fish species actually showing highest commercial landings, were analysed to elucidate their potential advantages in life performance, compared to other small

In the highly productive northern Benguela Upwelling System (nBUS), euphausiids can dominate the zooplankton community and may contribute substantially to the vertical flux of carbon. The predominant vertical transport of carbon produced by phytoplankton in the upper water layers of the ocean to deeper layers takes place by sinking of particulate organic carbon (POC). Several processes mediated by the zooplankton community can either enhance or limit the vertical carbon flux and regulate the efficiency of the biological carbon pump. Main biological pathways by which carbon is exported to deeper water layers are the active transport of carbon by vertical migration of pelagic animals, such as krill, and the passive transport of faecal pellets. A conceptual model will be introduced, combining diel vertical migration (DVM) patterns of dominant krill species, with environmental parameters such as temperature, food availability and with physiological constraints such as species-specific respiration rates, which may explain seasonal adaptations of DVM to changes in water temperature, oxygen and food availability. Energetic considerations based on the DVM model showed that temperature acted as the controlling and limiting factor with food abundance further modifying the vertical positioning of krill species. Variable spatial and temporal distributions of krill will lead to seasonal and regional differences in the export of carbon to deeper water layers. We will show how the different krill species contribute to the downward transport of carbon by vertical migration, and assess its importance relative to other vertical carbon fluxes in the nBUS.

The oxygen concentration within the oxygen minimum zone in the Angola Gyre is almost constant over long times, where ventilation balances oxygen consumption by mineralization of organic material. A simple physical explanation is that the turbulent oxygen flux is governed by Fick’s law, where the oxygen flux is proportional to the oxygen concentration gradient. Here, we discuss an alternative feedback mechanism from the zooplankton respiration towards ambient oxygen concentration by vertical migration of zooplankton. This idea is based on model results from a coupled biogeochemical model, respiration, hypoxia tolerance and acoustic measurements showing in how far zooplankton avoids low oxygen waters. Zooplankton vertical migration implies considerable transport of organic matter. Zooplankton respiration as well as nitrification of excreted ammonium is an essential sink of oxygen. If zooplankton is avoiding oxygen exhausted water bodies, oxygen consumption from respiration and nitrification is reduced considerably there. For the biogeochemical model considered this feedback is an essential component to produce a realistic oxygen minimum zone, whereas a simple bulk zooplankton significantly overestimates its extent and apparent oxygen utilization. Keywords: Oxygen minimum, zooplankton, ecosystem model

Euphausiids are distributed ubiquitously across the globe and many krill species are represented in extraordinarily high numbers in various ecosystems. Their biomass, physiological plasticity and importance as a trophic link between primary production and higher trophic levels enable these animals to fill key positions in marine ecosystems. Knowledge about their distribution, abundance, life-history traits, growth patterns, physiological and behavioural adaptations to short- and long-term changes in their environment will help to understand both spatial and temporal variability found in krill populations. Changes in krill distribution and abundance may significantly impact the food web and ecosystem structure and functioning. One ecosystem, where euphausiids play a pivotal role and can dominate the zooplankton biomass, is the Northern Benguela Current (NBC) also called the northern Benguela upwelling system (nBus). The NBC is a nutritionally poly-pulsed, highly productive and stratified coastal upwelling system. High fishery yields and large populations of fish, birds and seals point to the economic and ecological importance of this area. Several physical and biological changes have occurred over the last decades in this Eastern Boundary Upwelling Ecosystem (EBUE). As a component keystone species in the food web of the NBC the dominant krill species may serve as indicators for ongoing changes in the environment since they are known to react quickly to changes in abiotic and biotic conditions. It is therefore crucial to enhance our understanding of the biology and life-history of the dominant krill species in this area and to investigate their physiological constraints and behavioural adaptations to the prevailing conditions. Most notable and important areas for further investigations are adaptations to highly fluctuating abiotic parameters, such as temperature and dissolved oxygen , as well as metabolic and life-history adaptations to short-term upwelling pulses and

Das nördliche Benguelaauftriebsgebiet vor der Westküste Namibias ist eines der vier großen Auftriebsgebiete der Weltmeere und von hoher ökologischer und sozio-ökonomischer Bedeutung. Euphausiiden nehmen in diesem Gebiet eine Schlüsselstellung im Nahrungsnetz ein und können die Biomasse dominieren. Das Vertikalwanderungsverhalten verschiedener Krillarten wurde untersucht und mit Hilfe eines konzeptuellen Models dessen Energiebilanzen quantifiziert. Hierzu wurden Verhaltensbeobachtungen mit physiologischen Raten und hydrografischen Messungen kombiniert. Artspezifische physiologische Anpassungen an die starken Temperaturgradienten spiegeln sich dabei direkt in unterschiedlichem Wanderungsverhalten wieder. Einige Euphausiidenarten wandern in die im Benguelasystem ausgeprägte Sauerstoffmangelschicht ein und nutzen diese als ökologische Nische. Eine Analyse der zugrunde liegenden Triebkräfte zeigte, dass die Temperatur einen kontrollierenden und manchmal auch begrenzenden Einfluss auf das Wanderungsverhalten der Tiere hat, welches zusätzlich von der vorherrschenden trophischen Situation beeinflusst wird.

Rates of respiration and ammonia excretion of Euphausia hanseni and Nematoscelis megalops were determined experimentally at four temperatures representative of conditions encountered by these euphausiid species in the northern Benguela upwelling environment. The respiration rate increased from 7.7 μmol O2 h–1 gww–1 at 5 °C to 18.1 μmol O2 h–1 gww –1 at 20 °C in E. hanseni and from 7.0 μmol O2 h–1 gww–1 (5 °C) to 23.4 μmol O2 h–1 gww –1 (20 °C) in N. megalops. The impact of temperature on oxygen uptake of the two species differed significantly. Nematoscelis megalops showed thermal adaptations to temperatures between 5 °C and 10 °C (Q10 = 1.9) and metabolic constraint was evident at higher temperatures (Q10 = 2.6). In contrast, E. hanseni showed adaptations to temperatures of 10–20 °C (Q10 = 1.5) and experienced metabolic depression below 10 °C (Q10 = 2.6). Proteins were predominantly metabolised by E. hanseni in contrast to lipids by N. megalops. Carbon demand of N. megalops between 5 and 15 °C was lower than in E. hanseni versus equal food requirements at 20 °C. It is concluded that the two species display different physiological adaptations, based on their respective temperature adaptations, which are mirrored in their differential vertical positioning in the water column.

Antarctic krill Euphausia superba (hereafter ‘krill’) occur in regions undergoing rapid environmental change, particularly loss of winter sea ice. During recent years, harvesting of krill has increased, possibly enhancing stress on krill and Antarctic ecosystems. Here we review the overall impact of climate change on krill and Antarctic ecosystems, discuss implications for an ecosystem-based fisheries management approach and identify critical knowledge gaps. Sea ice decline, ocean warming and other environmental stressors act in concert to modify the abundance, distribution and life cycle of krill. Although some of these changes can have positive effects on krill, their cumulative impact is most likely negative. Recruitment, driven largely by the winter survival of larval krill, is probably the population parameter most susceptible to climate change. Predicting changes to krill populations is urgent, because they will seriously impact Antarctic ecosystems. Such predictions, however, are complicated by an intense inter-annual variability in recruitment success and krill abundance. To improve the responsiveness of the ecosystem-based management approach adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), critical knowledge gaps need to be filled. In addition to a better understanding of the factors influencing recruitment, management will require a better understanding of the resilience and the genetic plasticity of krill life stages, and a quantitative understanding of under-ice and benthic habitat use. Current precautionary management measures of CCAMLR should be maintained until a better understanding of these processes has been achieved.

Purpose To report on long-term outcomes of patients treated with active surveillance (AS) for localized prostate cancer (PCa) in the daily routine setting. Methods HAROW (2008-2013) was a non-interventional, health service research study about the management of localized PCa in the community setting, with 86% of the study centers being office-based urologists. A follow-up examination of all patients who opted for AS as primary treatment was carried out. Overall, cancer-specific, and metastasis-free survival, as well as discontinuation rates, were determined. Results Of 329 patients, 62.9% had very-low- and 21.3% low-risk tumours. The median follow-up was 7.7 years (IQR 4.7-9.1). Twenty-eight patients (8.5%) died unrelated to PCa, of whom 19 were under AS or watchful waiting (WW). Additionally, seven patients (2.1%) developed metastasis. The estimated 10-year overall and metastasis-free survival was 86% (95% CI 81.7-90.3) and 97% (95% CI 94.6-99.3), respectively. One hundred eighty-seven patients (56.8%) discontinued AS changing to invasive treatment: 104 radical prostatectomies (RP), 55 radiotherapies (RT), and 28 hormonal treatments (HT). Another 50 patients switched to WW. Finally, 37.4% remained alive without invasive therapy (22.2% AS and 15.2% WW). Intervention-free survival differed between the risk groups: 47.8% in the very-low-, 33.8% in the low- and 34.6% in the intermediate-/high-risk-group (p = 0.008). On multivariable analysis, PSA-density >= 0.2 ng/ml(2)was significantly predictive for receiving invasive treatment (HR 2.55;p = 0.001). Conclusion Even in routine care, AS can be considered a safe treatment option. Our results might encourage office-based urologists regarding the implementation of AS and to counteract possible concerns against this treatment option.

Purpose To report on long-term outcomes of patients treated with active surveillance (AS) for localized prostate cancer (PCa) in the daily routine setting. Methods HAROW (2008-2013) was a non-interventional, health service research study about the management of localized PCa in the community setting, with 86% of the study centers being office-based urologists. A follow-up examination of all patients who opted for AS as primary treatment was carried out. Overall, cancer-specific, and metastasis-free survival, as well as discontinuation rates, were determined. Results Of 329 patients, 62.9% had very-low- and 21.3% low-risk tumours. The median follow-up was 7.7 years (IQR 4.7-9.1). Twenty-eight patients (8.5%) died unrelated to PCa, of whom 19 were under AS or watchful waiting (WW). Additionally, seven patients (2.1%) developed metastasis. The estimated 10-year overall and metastasis-free survival was 86% (95% CI 81.7-90.3) and 97% (95% CI 94.6-99.3), respectively. One hundred eighty-seven patients (56.8%) discontinued AS changing to invasive treatment: 104 radical prostatectomies (RP), 55 radiotherapies (RT), and 28 hormonal treatments (HT). Another 50 patients switched to WW. Finally, 37.4% remained alive without invasive therapy (22.2% AS and 15.2% WW). Intervention-free survival differed between the risk groups: 47.8% in the very-low-, 33.8% in the low- and 34.6% in the intermediate-/high-risk-group (p = 0.008). On multivariable analysis, PSA-density >= 0.2 ng/ml(2)was significantly predictive for receiving invasive treatment (HR 2.55;p = 0.001). Conclusion Even in routine care, AS can be considered a safe treatment option. Our results might encourage office-based urologists regarding the implementation of AS and to counteract possible concerns against this treatment option.