•Ice reduction and changes in oceanography in the Arctic Ocean may result in favourable conditions for increased biological production.•Expected climate-change driven changes in the Northeast ...Atlantic Arctic are reviewed, starting with current status and the history leading up to it.•The entire polar ecosystem is included, from oceanography via plankton and benthos, and finally focus on fish and mammals.•Despite many uncertainties, it is evident that both fish and mammal species may extend their ranges northwards following the observed changes in oceanography and productivity at lower trophic levels.
Global warming drives changes in oceanographic conditions in the Arctic Ocean and the adjacent continental slopes. This may result in favourable conditions for increased biological production in waters at the northern continental shelves. However, production in the central Arctic Ocean will continue to be limited by the amount of light and by vertical stratification reducing nutrient availability. Upwelling conditions due to topography and inflowing warm and nutrient rich Atlantic Water may result in high production in areas along the shelf breaks. This may particularly influence distribution and abundance of sea mammals, as can be seen from analysis of historical records of hunting. The species composition and biomass of plankton, fish and shellfish may be influenced by acidification due to increased carbon dioxide uptake in the water, thereby reducing the survival of some species. Northwards shift in the distribution of commercial species of fish and shellfish is observed in the Barents Sea, especially in the summer period, and is related to increased inflow of Atlantic Water and reduced ice cover. This implies a northward extension of boreal species and potential displacement of lipid-rich Arctic zooplankton, altering the distribution of organisms that depend on such prey. However, euphausiid stocks expanding northward into the Arctic Ocean may be a valuable food resource as they may benefit from increases in Arctic phytoplankton production and rising water temperatures. Even though no scenario modelling or other prediction analyses have been made, both scientific ecosystem surveys in the northern areas, as well as the fisheries show indications of a recent northern expansion of mackerel (Scomber scombrus), cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and capelin (Mallotus villosus). These stocks are found as far north as the shelf-break north of Svalbard. Greenland halibut (Reinhardtius hippoglossoides), redfish (Sebastes spp.) and shrimp (Pandalus borealis) are also present in the slope waters between the Barents Sea and the Arctic Ocean. It is assumed that cod and haddock have reached their northernmost limit, whereas capelin and redfish have potential to expand their distribution further into the Arctic Ocean. Common minke whales (Balaenoptera acutorostrata) and harp seals (Pagophilus groenlandicus) may also be able to expand their distribution into the Arctic Ocean. The abundance and distribution of other species may change as well – to what degree is unknown.
•We found a decoupling of dissolved oxygen and pH in the Changjiang Estuary.•Decoupling of dissolved oxygen and pH reveals “old” algal blooms.•Simulations and end-member models are used to assess how ...“old” the algal bloom.•Estimation revealed the algal bloom preceded our cruise by 6–10 days.
The stoichiometric ratio between seawater CO2 and dissolved oxygen (DO) during phytoplankton metabolism holds significant importance in evaluating ecological and biogeochemical processes. We collected high-resolution underway temperature, salinity, DO, and pH data in the East China Sea inner shelf in May 2017. Our results revealed high pH (8.36) and supersaturated DO (171 %) in the outer Changjiang Estuary, indicating the occurrence of an algal bloom event. They were significantly correlated with a regression slope of 0.0029, which roughly followed the Redfield ratio. In contrast, a much higher ratio (0.0088) manifested in a low-salinity patch on north of the Changjiang Estuary, featuring a pH of 8.40 and oxygen saturation of approximately 123 %. The substantially faster air-sea equilibrium rate of O2 than CO2 probably caused such decoupling, offering insight into the temporal evolutions of algal bloom. Theoretically, a steeper regression slope implies an earlier onset of algal bloom. An end-member mixing model was constructed to exclude the physical mixing influences on dissolved inorganic carbon (ΔDIC) and DO (ΔDO). Furthermore, we conducted simulations to explore the temporal variations of ΔDIC–ΔDO regression slope with time. Comparing slopes derived from simulation and mixing model suggested that the biological signal of the decoupled waters likely preceded our observations by 6–10 days. Satellite results captured high-Chl a waters southwest of the low-salinity patch a week before our observation, potentially transported northward by prevailing southwest wind. Given that oxygen and pH are frequently measured in aquatic environments, their combined assessment could be a valuable method for assessing temporal algal bloom dynamics.
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The San Jorge Gulf was declared an area of national economic, commercial, conservation and diversity interest. To contribute to its study, the southern coastal sector of the gulf was characterised in ...physical and chemical parameters in spring campaigns (November 2016 and 2017). Samples were taken on board the oceanographic vessel Puerto Deseado in three perpendicular to the coast transects and another one to the southeast of the gulf, which crosses a thermohaline front. The perpendicular to the coast transects showed a similar pattern of distribution of physical and chemical properties in the water column. At nearshore stations, the water column was homogeneous and the nutrient concentrations between the surface and bottom layers were similar. At offshore stations, the water column was stratified and the nutrient concentrations were higher near the bottom than at surface. In 2016, a wind induced upwelling front was observed in the southwest of the gulf. Both sides of the thermohaline front did not show significant chemical differences. Throughout the study area, silicic acid and nitrate limited primary production. Satellite chlorophyll-a data and fluorescence profiles showed that the southern sector of the gulf has a high biomass of phytoplankton during November. We conclude that the southern sector of the SJG has different features depending on the external forcing caused by the front. The presence of fronts stimulates the growth of phytoplankton biomass through the injection of nutrients from the homogeneous part to the stratified sector. This would affect phytoplankton community and, thus, the productivity of the system.
The trisaccharide, 2′-fucosyllactose (Fucα1-2Galβ1-4Glc; 2′-FL), is the most abundant oligosaccharide in human milk. It has numerous significant biological properties including prebiotics, ...antibacterial, antiviral, and immunomodulating effects, and has been approved as "generally recognized as safe" (GRAS) by the Food and Drug Administration (FDA) and as a novel food (NF) by the European Food Safety Authority (EFSA). 2′-FL not only serves as a food ingredient added in infant formula, but also as a dietary supplement and medical food material in food bioprocesses. There is considerable commercial interest in 2′-FL for its irreplaceable nutritional applications. This review aims at systematically elaborating key functional properties of 2′-FL as well as its applications. In addition, several approaches for 2′-FL production are described in this review, including chemical, chemo-enzymatical, and cell factory approaches, and the pivotal research results also have been summarized. With the rapid development of metabolic engineering and synthetic biology strategies, using the engineered cell factory for 2′-FL large-scale production might be a promising approach. From an economic and safety point of view, microbial selection for cell factory engineering in 2′-FL bioprocess also should be taken into consideration.
•Annual mean seawater pCO2 has not increased between 2002 and 2016 at the PAP site.•The winter-summer seasonality of seawater pCO2 has however increased with time.•The study area was a carbon sink ...with increasing CO2 flux into the ocean.•Redfieldian carbon consumption was observed during the spring blooms.•Gas exchange, biological production and mixing explain most of the pCO2 variability.
The ocean is currently a significant net sink for anthropogenically remobilised CO2, taking up around 24% of global emissions. Numerical models predict a diversity of responses of the ocean carbon sink to increased atmospheric concentrations in a warmer world. Here, we tested the hypothesis that increased atmospheric forcing is causing a change in the ocean carbon sink using a high frequency observational dataset derived from underway pCO2 (carbon dioxide partial pressure) instruments on ships of opportunity (SOO) and a fixed-point mooring between 2002 and 2016. We calculated an average carbon flux of 0.013 Pg yr−1 into the ocean at the Porcupine Abyssal Plain (PAP) site, consistent with past estimates. In spite of the increase in atmospheric pCO2, monthly average seawater pCO2 did not show a statistically significant increasing trend, but a higher annual variability, likely due to the decreasing buffer capacity of the system. The increasing ΔpCO2 led to an increasing trend in the estimated CO2 flux into the ocean of 0.19 ± 0.03 mmol m−2 day−1 per year across the entire 15 year time series, making the study area a stronger carbon sink. Seawater pCO2 variability is mostly influenced by temperature, alkalinity and dissolved inorganic carbon (DIC) changes, with 77% of the annual seawater pCO2 changes explained by these terms. DIC is in turn influenced by gas exchange and biological production. In an average year, the DIC drawdown by biological production, as determined from nitrate uptake, was higher than the DIC increase due to atmospheric CO2 dissolution into the surface ocean. This effect was enhanced in years with high nutrient input or shallow mixed layers. Using the rate of change of DIC and nitrate, we observed Redfieldian carbon consumption during the spring bloom at a C:N ratio of 6.2 ± 1.6. A comparison between SOO and PAP sustained observatory data revealed a strong agreement for pCO2 and DIC. This work demonstrates that the study area has continued to absorb atmospheric CO2 in recent years with this sink enhancing over time. Furthermore, the change in pCO2 per unit nitrate became larger as surface buffer capacity changed.
Aquaculture is the fastest growing food production industry, and the vast majority of aquaculture products are derived from Asia. The quantity of aquaculture products directly consumed is now greater ...than that resulting from conventional fisheries. The nutritional value of aquatic products compares favourably with meat from farm animals because they are rich in micronutrients and contain high levels of healthy omega-3 fatty acids. Compared with farm animals, fish are more efficient converters of energy and protein. If the aquaculture sector continues to expand at its current rate, production will reach 132million tonnes of fish and shellfish and 43million tonnes of seaweed in 2020. Future potential for marine aquaculture production can be estimated based on the length of coastline, and for freshwater aquaculture from available land area in different countries. The average marine production in 2005 was 103tonnes per km coastline, varying from 0 to 1721 (China). Freshwater aquaculture production in 2005 averaged 0.17tonnes/ha, varying from 0 to close to 6tonnes per ha (Bangladesh), also indicating potential to dramatically increase freshwater aquaculture output. Simple estimations indicate potential for a 20-fold increase in world aquaculture production. Limits imposed by the availability of feed resources would be lessened by growing more herbivorous species and by using more of genetically improved stocks.
Aquaculture generally trails far behind plant and farm animal industries in utilizing selective breeding as a tool to improve the biological efficiency of production. It is estimated that at present less than 10% of aquaculture production is based on genetically improved stocks, despite the fact that annual genetic gains reported for aquatic species are substantially higher than that of farm animals. With an average genetic gain in growth rate of 12.5% per generation, production may be dramatically increased if genetically improved animals are used. Importantly, animals selected for faster growth have also been shown to have improved feed conversion and higher survival, implying that increased use of selectively bred stocks leads to better utilization of limited resources such as feed, labour, water, and available land and sea areas.
► We demonstrate existence of vast potential for increased aquaculture production. ► The largest potential for aquaculture lies in the marine environment. ► Selection responses in aquaculture species are higher than for conventional livestock. ► More use of genetically improved stocks may dramatically increase aquaculture output. ► Genetically improved stocks are critical for better utilization of limited resources.
Upwelling is critical to the biological production, acidification, and deoxygenation of the ocean's major eastern boundary current ecosystems. A leading conceptual hypothesis projects that the winds ...that induce coastal upwelling will intensify in response to increased land‐sea temperature differences associated with anthropogenic global warming. We examine this hypothesis using an ensemble of coupled, ocean‐atmosphere models and find limited evidence for intensification of upwelling‐favorable winds or atmospheric pressure gradients in response to increasing land‐sea temperature differences. However, our analyses reveal consistent latitudinal and seasonal dependencies of projected changes in wind intensity associated with poleward migration of major atmospheric high‐pressure cells. Summertime winds near poleward boundaries of climatological upwelling zones are projected to intensify, while winds near equatorward boundaries are projected to weaken. Developing a better understanding of future changes in upwelling winds is essential to identifying portions of the oceans susceptible to increased hypoxia, ocean acidification, and eutrophication under climate change.
Key Points
Comprehensive assessment of pressures, temperatures, and coastal upwelling winds in CMIP5 models
Poleward shift in distribution of coastal upwelling‐favorable winds projected with climate change
Changes due to displacement of high‐pressure systems, not land‐sea surface air temperature contrasts
d-Allulose, an epimer of d-fructose, is a rare monosaccharide that exists in extremely small quantities in nature. It is an ideal substitute for sucrose, because it has 70% of the sweetness of ...sucrose and ultra-low the energy. In addition, it has received sustained attention because of its unique physiological functions and potential health benefits. However, it is scarce in nature, and difficult to chemically synthesize.
Because of its scarcity, bioconversion of d-allulose is attractive to researchers. It has been demonstrated that ketose 3-epimerase plays an irreplaceable role in the bioconversion of d-fructose to d-allulose. Herein, an overview of recent advances regarding the physiological functions as well as the biological production of d-allulose is provided. Additionally, a comparison of the biochemical properties and a structural analysis of ketose 3-epimerases are also reviewed in detail in this paper.
Up to now, ketose 3-epimerase has been experimentally identified and characterized from only twelve types of microorganisms. In addition, 4 types of crystal structures from ketose 3-epimerases have been already solved, and the catalytic mechanism has also been proposed. However, the researches on molecular modification of ketose 3-epimerase are very few. In the future, molecular modification to improve the enzyme activity and thermostability through site-directed mutagenesis or directed evolution must be the research focus.
•d-Allulose is an ideal substitute of sucrose, with high sweetness and low calorie.•d-Allulose is a rare sugar, with distinct physiological health functions.•Bioconversion of d-allulose using ketose 3-epimerase is the research focus now.•The enzyme properties are characterized and comprehensively reviewed.•The crystal structures are solved, and the active sites are explored.
Oxygen loss in the ocean, termed deoxygenation, is a major consequence of climate change and is exacerbated by other aspects of global change. An average global loss of 2% or more has been recorded ...in the open ocean over the past 50-100 years, but with greater oxygen declines in intermediate waters (100-600 m) of the North Pacific, the East Pacific, tropical waters, and the Southern Ocean. Although ocean warming contributions to oxygen declines through a reduction in oxygen solubility and stratification effects on ventilation are reasonably well understood, it has been a major challenge to identify drivers and modifying factors that explain different regional patterns, especially in the tropical oceans. Changes in respiration, circulation (including upwelling), nutrient inputs, and possibly methane release contribute to oxygen loss, often indirectly through stimulation of biological production and biological consumption. Microbes mediate many feedbacks in oxygen minimum zones that can either exacerbate or ameliorate deoxygenation via interacting nitrogen, sulfur, and carbon cycles. The paleo-record reflects drivers of and feedbacks to deoxygenation that have played out through the Phanerozoic on centennial, millennial, and hundred-million-year timescales. Natural oxygen variability has made it difficult to detect the emergence of a climate-forced signal of oxygen loss, but new modeling efforts now project emergence to occur in many areas in 15-25 years. Continued global
deoxygenation is projected for the next 100 or more years under most emissions scenarios, but with regional heterogeneity. Notably, even small changes in oxygenation can have significant biological effects. New efforts to systematically observe oxygen changes throughout the open ocean are needed to help address gaps in understanding of ocean deoxygenation patterns and drivers.
The Kuroshio Current carries a large amount of nutrients in dark subsurface layer along the southern coast of Japan. However, due to lack of sufficient multidisciplinary high‐resolution observations, ...it has been unclear whether and how the subsurface nutrients are injected to sunlit layers on the continental shelf. In this study, using a state‐of‐the‐art tow‐yo microstructure profiler and nitrate measurements, we show that the Kuroshio flowing on the shelfbreak induces very strong turbulent dissipation rate ∼O(10−7W·kg−1) and diffusivity ∼O(10−3 m2·s−1) over an across frontal scale of 20–30 km. This strong turbulence could provide a diffusive nitrate flux to euphotic zone of >O(1 mmol N·m−2·day−1). As the Kuroshio steadily runs on the continental shelves along the path, the nutrient injection found in this study is a very important supply for biological production on the continental margin along the southern coast of Japan.
Key Points
Very strong turbulence is observed in the Kuroshio Current near shelfbreak over 30 km in the across frontal direction
Turbulence is caused by banded internal wave shear amplified between the Kuroshio Current and the continental slope
Turbulent mixing causes a large diapycnal diffusive nitrate flux to the euphotic zone over 30 km
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