Controls on oxygen response to climate change on the Northwest European Continental Shelf

2020 ◽  
Author(s):  
Sarah L. Wakelin ◽  
Yuri Artioli ◽  
Momme Butenschön ◽  
Jason Holt ◽  
Jeremy Blackford
Keyword(s):  
Climate Change ◽  
Continental Shelf ◽  
Water Column ◽  
Ecosystem Processes ◽  
Phytoplankton Production ◽  
Biogeochemical Model ◽  
Biological Cycling ◽  
Increasing Temperature ◽  
The Impact ◽  
Oxygen Concentrations

<p>Dissolved oxygen in the ocean is an indicator of water quality and low concentrations can threaten ecosystem health. The main sources of marine oxygen are diffusion from the atmosphere and phytoplankton photosynthesis. Biological respiration and decomposition act to reduce oxygen concentrations. Under conditions of vertical stratification, the water column below the pycnocline is isolated from oxygen exchange with the atmosphere, photosynthesis may be limited by light availability and oxygen concentrations decrease. Climate change influences the oxygen cycle in two ways: 1) changing the hydrodynamic climate and 2) affecting rates of biogeochemical processes. The hydrodynamic climate affects the nutrient supply and so controls phytoplankton production while changes to water column stratification affects vertical mixing. Gas solubility decreases with increasing temperature so that oxygen uptake from the atmosphere is expected to decrease under increasing oceanic temperatures. Biological cycling rates increase with increasing temperature affecting photosynthesis, respiration and bacterial decomposition. It is not obvious whether changes in oxygen concentrations due to changing ecosystem processes will mitigate or reinforce the projected reduction from solubility changes.</p><p>The Northwest European Continental shelf (NWES) is a region of the northeast Atlantic that experiences seasonal stratification. We use the physics-biogeochemical model NEMO-ERSEM to study near-bed oxygen concentrations on the NWES under a high greenhouse gas emissions scenario (Representative Concentration Pathway (RCP) 8.5). We show that much of the NWES could experience low oxygen concentrations by 2100 and assess the relative impacts of changing temperature and ecosystem processes. Until about 2040 the impact of solubility dominates the oxygen change. The mean near-bed oxygen concentration is projected to decrease by 6.3% by 2100, of which 73% is due to solubility changes and the remainder to changes in the ecosystem. In the oxygen-depleted region in the eastern North Sea, 77% of the near-bed oxygen reduction is due to ecosystem processes.</p>

Evidence that increased nitrogen efflux from wave-influenced marine sediment enhances pelagic phytoplankton production on the inner continental shelf of Western Australia

2010 ◽  
Vol 61 (5) ◽  
pp. 625 ◽  
Author(s):  
Jim Greenwood
Keyword(s):  
Continental Shelf ◽  
Surface Waves ◽  
Water Column ◽  
Chlorophyll A ◽  
Wave Height ◽  
Western Australia ◽  
Regional Scale ◽  
Reaction Rates ◽  
Phytoplankton Production ◽  
Biogeochemical Model

Increased biological and chemical reaction rates within permeable continental-shelf sediment can result from the action of passing surface waves, especially when the seabed is rippled. The effect of this on the exchange of nitrogen between the sediment and water column is the focus of the present paper. The continental shelf of Western Australia is used as an example. A time series of chlorophyll a is compared with surface-wave height revealing seasonal and sub-seasonal correlation between the two variables. At the same time, results from a coupled pelagic–benthic biogeochemical model show that temperature-controlled changes in sedimentary nitrogen efflux cannot account for the observed seasonal changes in chlorophyll a in the overlying water column. It is proposed that enhanced pore-water circulation within the sediment, caused by the action of passing surface waves, results in an increase in the efflux of nitrogen from the sediment during winter, supporting higher pelagic phytoplankton production. The parameterisation of sedimentary nitrogen mineralisation as a function of the square of wave height is suggested for the inclusion of this effect in regional-scale continental shelf models.

scholarly journals Variation of Runoff and Runoff Components of the Upper Shule River in the Northeastern Qinghai–Tibet Plateau under Climate Change

Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3357
Author(s):  
Jinkui Wu ◽  
Hongyuan Li ◽  
Jiaxin Zhou ◽  
Shuya Tai ◽  
Xueliang Wang
Keyword(s):  
Climate Change ◽  
Sustainable Use ◽  
Reduction Rate ◽  
Northwest China ◽  
Tibet Plateau ◽  
Glacier Area ◽  
Rainfall Runoff ◽  
Total Runoff ◽  
Increasing Temperature ◽  
The Impact

Quantifying the impact of climate change on hydrologic features is essential for the scientific planning, management and sustainable use of water resources in Northwest China. Based on hydrometeorological data and glacier inventory data, the Spatial Processes in Hydrology (SPHY) model was used to simulate the changes of hydrologic processes in the Upper Shule River (USR) from 1971 to 2020, and variations of runoff and runoff components were quantitatively analyzed using the simulations and observations. The results showed that the glacier area has decreased by 21.8% with a reduction rate of 2.06 km2/a. Significant increasing trends in rainfall runoff, glacier runoff (GR) and baseflow indicate there has been a consistent increase in total runoff due to increasing rainfall and glacier melting. The baseflow has made the largest contribution to total runoff, followed by GR, rainfall runoff and snow runoff, with mean annual contributions of 38%, 28%, 18% and 16%, respectively. The annual contribution of glacier and snow runoff to the total runoff shows a decreasing trend with decreasing glacier area and increasing temperature. Any increase of total runoff in the future will depend on an increase of rainfall, which will exacerbate the impact of drought and flood disasters.

scholarly journals The impact of climate change on fish infectious diseases (a review)

2020 ◽  
pp. 78-110
Author(s):  
Yu. Rud ◽  
◽  
O. Zaloilo ◽  
L. Buchatsky ◽  
I. Hrytsyniak ◽  
...  
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Infectious Diseases ◽  
Climate Change Impacts ◽  
Fish Farms ◽  
Impact Of Climate Change ◽  
Key Words Climate Change ◽  
Temperature Climate ◽  
Increasing Temperature ◽  
The Impact

Purpose. As the climate change impacts freshwater and marine ecosystems, and rising ocean temperatures and acidification continue to this moment, our aim was to analyze the literature and summarize information on the development of fish infectious diseases in the light of global warming. Findings. Even a slight increase in temperature affects the life cycle, physiology, behavior, distribution and structure of populations of aquatic bioresources, especially fish. Recent studies show that some infectious diseases of fish spread much faster with increasing temperature. Climate change contributes to pathogens spread in both marine and freshwater areas. In particular, rising water temperatures can expand the range of diseases. Aquatic bioresources have high cumulative mortality from infectious diseases, and pathogens are rapidly progressing, and these phenomena may be powered by climate change, leading to the geographical spread of virulent pathogens to fisheries and aquaculture facilities, threatening much of global production and food security. The article presents data on the impact of climate change and global warming on aquaculture and fisheries. The list of the main pathogens of fish of various etiology in Ukraine, including viral, bacterial and parasitic diseases is presented. The impact of infectious agents on modern aquaculture is described and the main ideas about the possible long-term consequences of climate change for fish farms are given. Practical Value. The review may be useful for specialists in veterinary medicine, epizootology and ichthyopathology. Key words: climate change, infectious diseases of fish, pathogenesis.

scholarly journals Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

2021 ◽  
Vol 8 ◽  
Author(s):  
Kostas Tsiaras ◽  
Yannis Hatzonikolakis ◽  
Sofia Kalaroni ◽  
Annika Pollani ◽  
George Triantafyllou
Keyword(s):  
Water Column ◽  
Wind Wave ◽  
Hot Spot ◽  
Sea Surface ◽  
Biogeochemical Model ◽  
Near Surface ◽  
Size Classes ◽  
Basin Scale ◽  
The Mediterranean ◽  
The Impact

The Mediterranean is considered a hot-spot for plastic pollution, due to its semi-enclosed nature and heavily populated coastal areas. In the present study, a basin-scale coupled hydrodynamic/particle drift model was used to track the pathways and fate of plastics from major land-based sources (coastal cities and rivers), taking into account of the most important processes (advection, stokes drift, vertical and horizontal mixing, sinking, wind drag, and beaching). A hybrid ensemble Kalman filter algorithm was implemented to correct the near- surface circulation, assimilating satellite data (sea surface height, temperature) in the hydrodynamic model. Different size classes and/or types of both micro- and macroplastics were considered in the model. Biofouling induced sinking was explicitly described, as a possible mechanism of microplastics removal from the surface. A simplified parameterization of size-dependent biofilm growth has been adopted, as a function of bacterial biomass (obtained from a biogeochemical model simulation), being considered a proxy for the biofouling community. The simulated distributions for micro- and macroplastics were validated against available observations, showing reasonable agreement, both in terms of magnitude and horizontal variability. An 8-year simulation was used to identify micro- and macroplastics accumulation patterns in the surface layer, water column, seafloor and beaches. The impact of different processes (vertical mixing, biofouling, and wind/wave drift) was identified through a series of sensitivity experiments. For both micro- and macroplastics, distributions at sea surface were closely related to the adopted sources. The microplastics concentration was drastically reduced away from source areas, due to biofouling induced sinking, with their size distribution dominated by larger (>1 mm) size classes in open sea areas, in agreement with observations. High concentration patches of floating plastics were simulated in convergence areas, characterized by anticyclonic circulation. The distribution of macroplastics on beaches followed the predominant southeastward wind/wave direction. In the water column, a sub-surface maximum in microplastics abundance was simulated, with increasing contribution of smaller particles in deeper layers. Accumulation of microplastics on the seafloor was limited in relatively shallow areas (<500 m), with bottom depth below their relaxation depth due to defouling. The simulated total amount of floating plastics (∼3,760 tonnes) is comparable with estimates from observations.

The use of artificial oxygenation to reduce nutrient availability in the Canning River, Western Australia

2001 ◽  
Vol 43 (9) ◽  
pp. 133-144 ◽  
Author(s):  
B. Greenop ◽  
K. Lovatt ◽  
M. Robb
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Western Australia ◽  
Algal Blooms ◽  
Positive Impact ◽  
Monitoring Program ◽  
Nutrient Concentrations ◽  
Nitrogen And Phosphorus ◽  
The Impact ◽  
Oxygen Concentrations

Artificial oxygenation has been used for two summer periods to improve the water quality of the Canning River in Perth, Western Australia. The project is part of the Swan Canning Cleanup Program, which aims to reduce the frequency and severity of nuisance and toxic algal blooms in the Swan-Canning estuary. The trials have proved that oxygenation has increased the dissolved oxygen concentrations in the water column, particularly in the bottom waters where dissolved oxygen concentrations are frequently below a critical level of three milligrams per litre. Oxygenation has had a positive impact on nutrient concentrations in the water column and nitrogen cycling processes. Reductions in nutrient concentrations were highlighted by drops in ammonium and total phosphorus concentrations of 97% and 64% following the recommencement of oxygenation after a plant shutdown. Results of a microbiological study combined with the data analysis indicate that the number of nitrifying microbes have increased due to oxygenation. However, comparisons between oxygenated and control areas were inconclusive about the ability of the oxygenation plant to reduce total nitrogen and phosphorus levels. This could be explained by factors such as spatial variability, water flow during the trials and measurement limitations in the monitoring program. Future work will concentrate on assessing the impact of the oxygenation plant on nutrient concentrations.

scholarly journals Effects of large-scale floating (solar photovoltaic) platforms on hydrodynamics and primary production in a coastal sea from a water column model

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 195-208
Author(s):  
Thodoris Karpouzoglou ◽  
Brigitte Vlaswinkel ◽  
Johan van der Molen
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Large Scale ◽  
Net Primary Production ◽  
Biogeochemical Model ◽  
Solar Photovoltaic ◽  
Column Model ◽  
Coastal Sea ◽  
Floating Platforms ◽  
The Impact

Abstract. An improved understanding of the effects of floating solar platforms on the ecosystem is necessary to define acceptable and responsible real-world field implementations of this new marine technology. This study examines a number of potential effects of offshore floating solar photovoltaic (PV) platforms on the hydrodynamics and net primary production in a coastal sea for the first time. Three contrasting locations within the North Sea (a shallow and deeper location with well-mixed conditions and a seasonally stratifying location) have been analysed using a water column physical–biogeochemical model: the General Ocean Turbulence Model coupled with the European Regional Seas Ecosystem Model – Biogeochemical Flux Model (GOTM-ERSEM-BFM). The results show strong dependence on the characteristics of the location (e.g. mixing and stratification) and on the density of coverage with floating platforms. The overall response of the system was separated into contributions by platform-induced light deficit, shielding by the platforms of the sea surface from wind and friction induced by the platforms on the currents. For all three locations, light deficit was the dominant effect on the net primary production. For the two well-mixed locations, the other effects of the platforms resulted in partial compensation for the impact of light deficit, while for the stratified location, they enhanced the effects of light deficit. For up to 20 % coverage of the model surface with platforms, the spread in the results between locations was relatively small, and the changes in net primary production were less than 10 %. For higher percentages of coverage, primary production decreased substantially, with an increased spread in response between the sites. The water column model assumes horizontal homogeneity in all forcings and simulated variables, also for coverage with floating platforms, and hence the results are applicable to very-large-scale implementations of offshore floating platforms that are evenly distributed over areas of at least several hundreds of square kilometres, such that phytoplankton remain underneath a farm throughout several tidal cycles. To confirm these results, and to investigate more realistic cases of floating platforms distributed unevenly over much smaller areas with horizontally varying hydrodynamic conditions, in which phytoplankton can be expected to spend only part of the time underneath a farm and effects are likely to be smaller, spatial detail and additional processes need to be included. To do so, further work is required to advance the water column model towards a three-dimensional modelling approach.

scholarly journals Effects of floating (solar PV) platforms on hydrodynamics and primary production in a coastal sea

2019 ◽  
Author(s):  
Thodoris Karpouzoglou ◽  
Brigitte Vlaswinkel ◽  
Johan van der Molen
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Net Primary Production ◽  
Strong Dependence ◽  
Biogeochemical Model ◽  
Solar Pv ◽  
Column Model ◽  
Coastal Sea ◽  
Floating Platforms ◽  
The Impact

Abstract. An improved understanding of the effects of floating solar platforms on the ecosystem is necessary to define acceptable and responsible real-world field implementations of this new marine technology. This study examines a number of potential effects of offshore floating solar PV platforms on the hydrodynamics and net primary production in a coastal sea for the first time. Three contrasting locations within the North Sea (a shallow and deeper location with well-mixed conditions and a summer-stratifying location) have been analysed using a water column physical-biogeochemical model (GOTM-ERSEM-BFM). The results show strong dependence on the characteristics of the location (e.g. mixing and stratification) and on the density of coverage with floating platforms. The overall response of the system was separated into contributions by platform shadow, shielding by the platforms of the sea surface from wind, and friction induced by the platforms on the currents. For all three locations, platform shadow was the dominant effect on the net primary production. For the two well-mixed locations, the other effects of the platforms resulted in partial compensation for the impact of platform shadow, while for the stratified location, they enhanced the effects of platform shadow. For up to 20 % coverage of the model surface with platforms, the spread in the results between locations was relatively small, and the changes in net primary production were less than 10 %. For higher percentages of coverage, primary production decreased substantially, with an increased spread in response between the sites. The water-column model assumes horizontal homogeneity in all forcings and simulated variables, also for coverage with floating platforms, and hence the results are applicable to very large-scale implementations of offshore floating platforms that are evenly distributed over areas of at least several hundreds of square kilometres. To confirm these results, and to investigate more realistic cases of floating platforms distributed unevenly over much smaller areas with horizontally varying hydrodynamic conditions, in which phytoplankton can be expected to spend only part of the time underneath a farm, spatial detail and additional processes need to be included. To do so, further work is required to advance the water-column model towards a 3D modelling approach.

scholarly journals Potential consequences of climate change for primary production and fish production in large marine ecosystems

2012 ◽  
Vol 367 (1605) ◽  
pp. 2979-2989 ◽  
Author(s):  
Julia L. Blanchard ◽  
Simon Jennings ◽  
Robert Holmes ◽  
James Harle ◽  
Gorka Merino ◽  
...  
Keyword(s):  
Climate Change ◽  
Individual Species ◽  
Phytoplankton Production ◽  
Biogeochemical Model ◽  
Fish Production ◽  
Large Marine Ecosystems ◽  
The North ◽  
Shelf Seas ◽  
Ecological Mechanisms ◽  
Food Web Model

Existing methods to predict the effects of climate change on the biomass and production of marine communities are predicated on modelling the interactions and dynamics of individual species, a very challenging approach when interactions and distributions are changing and little is known about the ecological mechanisms driving the responses of many species. An informative parallel approach is to develop size-based methods. These capture the properties of food webs that describe energy flux and production at a particular size, independent of species' ecology. We couple a physical–biogeochemical model with a dynamic, size-based food web model to predict the future effects of climate change on fish biomass and production in 11 large regional shelf seas, with and without fishing effects. Changes in potential fish production are shown to most strongly mirror changes in phytoplankton production. We project declines of 30–60% in potential fish production across some important areas of tropical shelf and upwelling seas, most notably in the eastern Indo-Pacific, the northern Humboldt and the North Canary Current. Conversely, in some areas of the high latitude shelf seas, the production of pelagic predators was projected to increase by 28–89%.

Monitoring the impact of sand extraction on the bathy-morphology and the seabed sediment in the Belgian part of the North Sea: Lessons of fifteen years of MBES measurements and current innovation.

2020 ◽  
Author(s):  
Koen Degrendele ◽  
Marc Roche
Keyword(s):  
Time Series ◽  
Continental Shelf ◽  
Water Column ◽  
Real Time ◽  
Fine Sediment ◽  
Fishing Vessels ◽  
Amplitude Data ◽  
Belgian Continental Shelf ◽  
The Impact ◽  
Sand Extraction

<p>For several decades the Belgian Continental Shelf (BCS) has been exploited for its sand. As this exploitation intensified over the years, according with the environmental regulation both on national and European levels, evaluating the extraction impact on the seabed bathymetry and morphology as well as on the sediment nature itself is a legal obligation.</p><p>The impact assessment of sand extraction is based on multiple types of data: statistics derived from the extraction registers, data from the Electronic Monitoring Systems (EMS = “black-boxes”) on board the dredging vessels, bathymetric and backscatter time series derived from regular MBES surveys, and ground truth data. In this framework, the most extracted areas have been surveyed several times each year for more than 15 years, enabling the development of well-controlled highly valuable and informative time series. In addition to this local approach, regular but less frequent surveys along straight lines, parallel and perpendicular to the sandbanks and the gullies, provide valuable information on the global evolution of the bathymetry and the sediment allowing a comparison between extracted and non-extracted areas. This multi-scale approach combining various types of data provides a 4D (space and time) overview of the evolution of the extraction and leads to robust and pragmatic conclusions about the impact of the sand extraction on the bathymetry, the morphology and the seabed habitats.</p><p>The long MBES bathymetric and BS time series on several monitoring areas inside the extraction sectors demonstrate the direct and non cumulative impact of the extraction on the bathymetry of the sandbanks and the unsustainable character of the sand resource. However, several questions remain regarding how the extraction impacts the seabed morphology and sedimentology in real time. Dredging by suction generates fine sediment plumes which could, after transport and sedimentation, modify the habitats within a certain radius around the extraction sites. Although the plumes generated during dredging operations have been the subject of numerous publications, few projects have been attempted to visualize these plumes and quantify the volume of fine sediment by using MBES water column amplitude data.</p><p>Specific series of acoustic measurements using the Kongsberg EM2040 MBES installed on the RV Simon Stevin were carried out following dredging vessels on the Belgian Continental Shelf. The resulting high quality dataset allows the evaluation of the real time impact of the extraction on the seabed and the water column in a 4D visualization. Another goal of this research is to evaluate the feasibility to use the MBES water column amplitude data to characterize and quantify the sediment plumes generated by the dredging operation. In a second experiment the scope was extended to plumes from fishing vessels and an evaluation of the impact of tidal currents on the water column measurements. The results of the simultaneous measurements with several acoustic and optical instruments and water sampling will contribute to the establishment of a methodology which will extend the present monitoring program to include the important impact on the seabed from the extraction technique itself.</p>

scholarly journals Coupled physical/biogeochemical modeling including O<sub>2</sub>-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

2013 ◽  
Vol 10 (6) ◽  
pp. 3559-3591 ◽  
Author(s):  
E. Gutknecht ◽  
I. Dadou ◽  
B. Le Vu ◽  
G. Cambon ◽  
J. Sudre ◽  
...  
Keyword(s):  
Sensitivity Analyses ◽  
Global Ocean ◽  
Biogeochemical Model ◽  
Ammonium Oxidation ◽  
N Loss ◽  
Total N ◽  
Eastern Boundary ◽  
Parameter Values ◽  
The Impact ◽  
Oxygen Concentrations

Abstract. The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela) using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox) as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen concentrations are driven by the poleward meridional advection of oxygen-depleted waters offshore of a 300 m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. In the OMZ off Namibia, the magnitude of N2O outgassing and of N loss is comparable. Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50%) for the global ocean.

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