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AbstractThis paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet.The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets.

ABSTRACT Despite considerable technological advances in recent decades that have enabled the ecosystems of the deeper parts of the oceans to be discovered and explored, large knowledge gaps still exist on the biology and ecology of such ecosystems. This is largely due to challenges related to observation and experimentation in situ, and to maintaining deepwater species under ex situ experimental conditions. Deep-sea organisms have evolved life strategies and physiological adaptations (e.g. slow metabolism and growth rates, high longevity, and late maturity) that allow them to succeed in the cold and generally food-limited deep-sea environment but that may partially impair their ability to physiologically compensate for and adapt to changes in climate. Therefore, a deeper understanding of species’ biological and ecological traits, as well as their tolerance thresholds to single and cumulative climatic stressors (e.g. temperature and nutrition, pH and O2) is much needed. Most experiments to date have been conducted under short-term (i.e. acute) conditions, thereby hindering the mechanisms potentially involved in species resilience and acclimation. Studies addressing the impact of climate change on species gametogenesis, reproductive output, or larval development and physiology are also largely lacking. While efforts continue to build a knowledge base on the impacts over the physiological and ecological processes affecting individual species, it is also necessary to start to address the impacts that climate change will have on wider ecosystem functioning.

Marine space is three dimensional, the turnover of life forms is rapid, defining a fourth dimension: time. The definition of ecologically significant spatial units calls for the spatio-temporal framing of significant ecological connections in terms of extra-specific (biogeochemical cycles), intra-specific (life cycles), and inter-specific (food webs) fluxes. The oceanic volume can be split in sub-systems that can be further divided into smaller sub-units where ecosystem processes are highly integrated. The volumes where oceanographic and ecological processes take place are splittable into hot spots of ecosystem functioning, e.g., upwelling currents triggering plankton blooms, whose products are then distributed by horizontal currents, so defining Cells of Ecosystem Functioning (CEFs), whose identification requires the collaboration of physical and chemical oceanography, biogeochemistry, marine geology, plankton, nekton and benthos ecology and biology, food web dynamics, marine biogeography. CEFs are fuzzy objects that reflect the instability of marine systems.

AbstractThere is strong evidence of an increase in primary production (PP) in the Arctic Ocean (AO) over the last two decades. Further increases will depend on the interplay between decreasing light limitation for primary producers, as the sea ice extent and thickness decrease, and the availability of nutrients, which is controlled by, but not limited to, inputs from the Atlantic and the Pacific Oceans. While these inputs are the major nutrient sources to the AO, ocean vertical mixing is required to bring the nutrients into the photic zone. We analyze data collected in the Western Eurasian Basin (WEB) between 1980 and 2016 and characterize the nutrient climatology of the various water masses. We conclude that there were no significant trends in the concentrations of the two macronutrients that typically limit PP in the AO (nitrate and silicic acid, in the case of diatoms), except a decreasing trend for silicic acid in Polar Surface Water (PSW), which is consistent with the reported increase in PP in the AO. We suggest that the Whalers Bay polynya, located in the northwestern corner of Svalbard, may act as a mixing hotspot, creating patches of nutrient replenished PSW. These patches may then be advected to higher latitudes under the ice pack, later boosting PP upon release from light limitation or else, keeping a nutrient reservoir that may be used in a subsequent growth season. It is likely that this remaining nutrient reservoir will decrease as sea ice cover retreats and light limitation alleviates.

The effects of climate change (CC) on contaminants and their potential consequences to marine ecosystem services and human wellbeing are of paramount importance, as they pose overlapping risks. Here, we discuss how the interaction between CC and contaminants leads to poorly constrained impacts that affects the sensitivity of organisms to contamination leading to impaired ecosystem function, services and risk assessment evaluations. Climate drivers, such as ocean warming, ocean deoxygenation, changes in circulation, ocean acidification, and extreme events interact with trace metals, organic pollutants, excess nutrients, and radionuclides in a complex manner. Overall, the holistic consideration of the pollutants-climate change nexus has significant knowledge gaps, but will be important in understanding the fate, transport, speciation, bioavailability, toxicity, and inventories of contaminants. Greater focus on these uncertainties would facilitate improved predictions of future changes in the global biogeochemical cycling of contaminants and both human health and marine ecosystems.

Abstract A 30 kW fixed-guide-vanes biradial turbine-generator set was designed by Instituto Superior Tecnico (IST) and manufactured by Kymaner, within the framework of the H2020 European project OPERA, for open sea testing at the Mutriku breakwater oscillating water column (OWC) power plant and at the IDOM MARMOK-A-5 OWC spar-buoy, deployed at BiMEP, Basque Country, Spain. The paper reports the design and construction of the prototype, and its dry testing at IST, in a variable-flow test rig, simulating the oscillating flow induced by irregular waves. Results show that the turbine exhibits a peak efficiency of 70% under steady-state conditions and an average efficiency of 56% for the control laws tested.

AbstractGroundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium‐to‐high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science‐policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change.