Diurnal sediment resuspension and settling: impact on the coupled physical and biogeochemical dynamics of dissolved oxygen and carbon in a shallow water body

2009 ◽  
Vol 60 (7) ◽  
pp. 669 ◽  
Author(s):  
Brett F. Branco ◽  
Thomas Torgersen
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Hot Spot ◽  
Sediment Resuspension ◽  
Biogeochemical Model ◽  
Mirror Lake ◽  
Frequency Monitoring ◽  
Tightly Coupled ◽  
Biogeochemical Transformations ◽  
Shallow Water Body ◽  
Inland Water Bodies

Small, shallow, inland water bodies are ubiquitous on the landscape and may be significant hotspots for biogeochemical transformations. However, the coupled physical and biogeochemical dynamics of these systems have received little attention compared with larger and deeper systems. Here, we examine the coupling between physical dynamics, sediment dynamics and oxygen–carbon dynamics in Mirror Lake, a small shallow pond in Storrs, CT, USA, using high frequency monitoring data and a simple coupled physical–biogeochemical model. The physical dynamics are characterised by a diurnal pattern of daytime thermal stratification and nighttime mixing. Observations show that the distribution of oxygen is tightly coupled with both the diurnal physical dynamics and photosynthesis–respiration reactions. Two 24-h periods in the summer of 2003 with similar meteorological conditions but distinctly different oxygen dynamics were simulated with a coupled physical–biogeochemical model. The model results suggest that the dynamics of sediment resuspension during nighttime convective overturn and subsequent settling during daytime stratification are critical in explaining the observed oxygen and dissolved inorganic carbon distributions. The diurnal dynamics provide a biogeochemical hot spot and hot moment by coupling meterologic forcing, resuspension of sediments, physical mixing and biological activity to hypoxia and anoxia in Mirror Lake.

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

scholarly journals Air-sea CO<sub>2</sub> fluxes and the controls on ocean surface <i>p</i>CO<sub>2</sub> seasonal variability in the coastal and open-ocean southwestern Atlantic Ocean: a modeling study

2015 ◽  
Vol 12 (19) ◽  
pp. 5793-5809 ◽  
Author(s):  
R. Arruda ◽  
P. H. R. Calil ◽  
A. A. Bianchi ◽  
S. C. Doney ◽  
N. Gruber ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Seasonal Variability ◽  
Dissolved Inorganic Carbon ◽  
Open Ocean ◽  
Atmospheric Co2 ◽  
Biogeochemical Model ◽  
Southwestern Atlantic ◽  
Biological Production ◽  
The North ◽  
Southwestern Atlantic Ocean

Abstract. We use an eddy-resolving, regional ocean biogeochemical model to investigate the main variables and processes responsible for the climatological spatio-temporal variability of pCO2 and the air-sea CO2 fluxes in the southwestern Atlantic Ocean. Overall, the region acts as a sink of atmospheric CO2 south of 30° S, and is close to equilibrium with the atmospheric CO2 to the north. On the shelves, the ocean acts as a weak source of CO2, except for the mid/outer shelves of Patagonia, which act as sinks. In contrast, the inner shelves and the low latitude open ocean of the southwestern Atlantic represent source regions. Observed nearshore-to-offshore and meridional pCO2 gradients are well represented by our simulation. A sensitivity analysis shows the importance of the counteracting effects of temperature and dissolved inorganic carbon (DIC) in controlling the seasonal variability of pCO2. Biological production and solubility are the main processes regulating pCO2, with biological production being particularly important on the shelves. The role of mixing/stratification in modulating DIC, and therefore surface pCO2, is shown in a vertical profile at the location of the Ocean Observatories Initiative (OOI) site in the Argentine Basin (42° S, 42° W).

High-resolution dataset assessing methane concentrations and modelling the carbon dynamics within Europe's second largest delta, the Danube River Delta

2020 ◽  
Author(s):  
Anna Canning ◽  
Arne Körtzinger
Keyword(s):  
High Resolution ◽  
Dissolved Inorganic Carbon ◽  
Hot Spot ◽  
River Delta ◽  
Danube River ◽  
The Black Sea ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Diel Variation ◽  
The Danube River

&lt;p&gt;Wetlands are known to be significant sources for CH&lt;sub&gt;4&lt;/sub&gt;, yet vary between potential sources and sinks for CO&lt;sub&gt;2&lt;/sub&gt;. However, in regards to the budgets and processes, they are still considered to have high uncertainties, inconsistencies and a general lack of data overall. One key wetland region in Europe is the Danube River Delta. It is the second largest delta in Europe, consisting of the vastest compact reed bed zone in the world, intertwined with rivers, lakes and channels. It is sourced with water from a drainage basin of 817,000 km&lt;sup&gt;2&lt;/sup&gt;, with the Danube River originating in Germany before travelling 2,857 km to the Black Sea. However, considering the potential pollution effects within this terminal zone, as well as the delta being one of the most important wetlands in Europe for its ecological value alone (and therefore fragile), few studies have focused on the dynamics within the carbon cycle. During 2017, three field campaigns across three seasons measured high resolution, small-scale spatial and temporal variability for pCO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, O&lt;sub&gt;2&lt;/sub&gt; and ancillary parameters within the lakes, rivers and channels with the use of a surface water flow-through package. Given the flexibility of the system, we were able to conduct day-night cycles and extensive mapping transects. We discovered day-night cycles showing significant variation of CH&lt;sub&gt;4&lt;/sub&gt; concentrations within the lakes and channels, as well &amp;#8216;hot spot&amp;#8217; anomalies showing potential ground water sourcing and extreme CH&lt;sub&gt;4&lt;/sub&gt; concentrations flowing in from the reed beds. Although reasoning for supersaturation in surface waters are under continuous debate, we conclude a potential reason for such dynamic diel variation within the lake may be due to biomass decomposition and extensive macrophyte concentrations creating a temporarily anoxic zone during the day with mixing during the night, such as previously suggested. On top of this, with the use of discrete data collected from the same water source simultaneously, we were able to model alkalinity, dissolved inorganic carbon and pH to examine both 24 h cycles across lakes and day-night dynamics, giving an in-depth glimpse into the carbonate system. Through the extensive mapping, we successful extracted diel variations for pCO&lt;sub&gt;2&lt;/sub&gt; and the carbonate species across the lakes with the use of just day-light data, allowing for spatial and temporal variations to be distinguished. We confirm the boundaries between channels and lakes are intertwined as much as they are with the wetlands, and how small extreme anomalies can only begin to be explained with such high-resolution data, even more so in combination with modelled data.&lt;/p&gt;

scholarly journals Isotope data improve the predictive capabilities of a marine biogeochemical model

2012 ◽  
Vol 9 (7) ◽  
pp. 9453-9486 ◽  
Author(s):  
T. Van Engeland ◽  
A. De Kluijver ◽  
K. Soetaert ◽  
F. J. R. Meysman ◽  
J. J. Middelburg
Keyword(s):  
Stable Isotope ◽  
Marine Ecosystem ◽  
Mesocosm Experiment ◽  
Added Value ◽  
Biogeochemical Model ◽  
Isotope Tracer ◽  
Isotope Data ◽  
Powerful Research Tool ◽  
Mesocosm Experiments ◽  
Biogeochemical Transformations

Abstract. Mesocosm experiments combined with biogeochemical modeling provide a powerful research tool to better understand marine ecosystem processes. Using an extended Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model, we investigated the added value of stable isotope tracer additions to constrain biogeochemical transformations within a mesocosm experiment that was designed to study ocean acidification effects on the marine ecosystem. Markov-Chain Monte-Carlo simulations revealed that even when isotope data were available for the majority of the components, not all parameters in the model could be constrained by calibration. However, when isotope tracer data were deliberately excluded from the calibration, the overparameterisation was even stronger. More specifically, it led to unconstrained fluxes through the zooplankton and detritus compartment, and different relative contributions of these two compartments to phytoplankton biomass loss produced equally plausible results. It is concluded that model uncertainty due to overparameterisation can be considerably reduced by explicitly resolving stable isotope dynamics. Therefore, this mesocosm experiment has benefitted substantially from isotope tracer additions to unravel carbon cycling under varying CO2 regimes.

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 (&gt;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 (&lt;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.

scholarly journals Long-term variations in ocean acidification indices in the Northwest Pacific from 1993 to 2018

2021 ◽  
Vol 168 (3-4) ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
Observational Data ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Kuroshio Extension ◽  
Biogeochemical Model ◽  
Northwest Pacific ◽  
Subarctic Region ◽  
Long Term Variations

AbstractLong-term variations in ocean acidification indices in the Northwest Pacific were examined using observational data and a biogeochemical model with an operational ocean model product for the period 1993–2018. The model and observational data for the surface ocean (< 100-m depth) exhibit consistent patterns of ocean acidification in the subtropical and Kuroshio Extension regions and relative alkalinization (i.e., reduced acidification) in the subarctic region of the Northwest Pacific. Below 100-m depth, acidification dominated in the subtropical regions and alkalinization in the subarctic regions. We attribute the excess acidification in the subtropical and Kuroshio regions to the vertical mixing of dissolved inorganic carbon (DIC) exceeding the DIC release by air–sea exchange. These regional differences in acidification and alkalinization are attributed to spatially variable biological processes in the upper ocean and horizontal and vertical physical redistribution of DIC. Our model and observational results have implications for the spatial extent and pattern of ocean acidification, along with the strength of the ocean carbon sink, which are key aspects of global climate change.

Long-term variation in dissolved inorganic carbon and ocean acidification indices in the Northwest Pacific from 1993 to 2018: A study of a biogeochemical model with an operational ocean model product and observational evidence

2021 ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Kuroshio Extension ◽  
Vertical Mixing ◽  
Ocean Model ◽  
Biogeochemical Model ◽  
Northwest Pacific ◽  
Subarctic Region ◽  
Surface Ocean

Abstract The multi-decadal variation in ocean acidification indices in the Northwest Pacific was examined using a biogeochemical model with an operational ocean model product for the period 1993–2018. We found that ocean acidification varied regionally in the Northwest Pacific. The surface ocean (above 100 m depth) underwent acidification that progressed more quickly in the subtropical region and the Kuroshio extension than in the subarctic region due to vertical mixing of the dissolved inorganic carbon (DIC) supply exceeding DIC release by air–sea exchange. Below 100 m depth, acidification and alkalinization occurred in the subtropical and subarctic regions, respectively. We attribute these regional differences in acidification and alkalinization to spatially variable biological processes in the upper layer and physical redistribution of DIC, both horizontally and vertically.

scholarly journals Coral Mucus Is a Hot Spot for Viral Infections

2015 ◽  
Vol 81 (17) ◽  
pp. 5773-5783 ◽  
Author(s):  
Hanh Nguyen-Kim ◽  
Yvan Bettarel ◽  
Thierry Bouvier ◽  
Corinne Bouvier ◽  
Hai Doan-Nhu ◽  
...  
Keyword(s):  
Viral Infections ◽  
Hot Spot ◽  
Life Strategy ◽  
Surrounding Water ◽  
Coral Mucus ◽  
Content Type ◽  
Nha Trang Bay ◽  
Tightly Coupled ◽  
Viral Communities ◽  
Coral Health

ABSTRACTThere is increasing suspicion that viral communities play a pivotal role in maintaining coral health, yet their main ecological traits still remain poorly characterized. In this study, we examined the seasonal distribution and reproduction pathways of viruses inhabiting the mucus of the scleractiniansFungia repandaandAcropora formosacollected in Nha Trang Bay (Vietnam) during an 11-month survey. The strong coupling between epibiotic viral and bacterial abundance suggested that phages are dominant among coral-associated viral communities. Mucosal viruses also exhibited significant differences in their main features between the two coral species and were also remarkably contrasted with their planktonic counterparts. For example, their abundance (inferred from epifluorescence counts), lytic production rates (KCN incubations), and the proportion of lysogenic cells (mitomycin C inductions) were, respectively, 2.6-, 9.5-, and 2.2-fold higher in mucus than in the surrounding water. Both lytic and lysogenic indicators were tightly coupled with temperature and salinity, suggesting that the life strategy of viral epibionts is strongly dependent upon environmental circumstances. Finally, our results suggest that coral mucus may represent a highly favorable habitat for viral proliferation, promoting the development of both temperate and virulent phages. Here, we discuss how such an optimized viral arsenal could be crucial for coral viability by presumably forging complex links with both symbiotic and adjacent nonsymbiotic microorganisms.

scholarly journals Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO<sub>2</sub> flux induced by mineralization of terrestrial organic carbon

2017 ◽  
Author(s):  
Erik Gustafsson ◽  
Christoph Humborg ◽  
Göran Björk ◽  
Christian Stranne ◽  
Leif G. Anderson ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Organic Carbon ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Atmospheric Co2 ◽  
Arctic Shelf ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Siberian Arctic

Abstract. Measurements from the SWERUS-C3 and ISSS-08 Arctic expeditions were used to calibrate and validate a new physical-biogeochemical model developed to quantify key carbon cycling processes on the East Siberian Arctic Shelf (ESAS). The model was used in a series of experimental simulations with the specific aim to investigate the pathways of terrestrial dissolved and particulate organic carbon (DOCter and POCter) supplied to the shelf. Rivers supply on average 8.5 Tg C yr−1 dissolved inorganic carbon (DIC), and further 8.5 and 1.1 Tg C yr−1 DOCter and POCter respectively. Based on observed and simulated DOC concentrations and stable isotope values (δ13CDOC) in shelf waters, we estimate that only some 20 % of the riverine DOCter is labile. According to our model results, an additional supply of approximately 14 Tg C yr−1 eroded labile POCter is however required to describe the observed stable isotope values of DIC (δ13CDIC). Degradation of riverine DOCter and POCter results in a 1.8 Tg C yr−1 reduction in the uptake of atmospheric CO2, while degradation of eroded POCter results in an additional 10 Tg C yr−1 reduction. Our calculations indicate nevertheless that the ESAS is an overall small net sink for atmospheric CO2 (1.7 Tg C yr−1). The external carbon sources are largely compensated by a net export from the shelf to the Arctic Ocean (31 Tg C yr−1), and to a smaller degree by a permanent burial in the sediments (2.7 Tg C yr−1).

scholarly journals The role of N<sub>2</sub>-fixation to simulate the <i>p</i>CO<sub>2</sub> observations from the Baltic Sea

2005 ◽  
Vol 2 (3) ◽  
pp. 609-636 ◽  
Author(s):  
A. Leinweber ◽  
T. Neumann ◽  
B. Schneider
Keyword(s):  
Baltic Sea ◽  
Inorganic Carbon ◽  
Spring Bloom ◽  
Dissolved Inorganic Carbon ◽  
Inorganic Nitrogen ◽  
Biogeochemical Model ◽  
Winter Period ◽  
State Variables ◽  
Nitrogen Fixing ◽  
C:P Ratio

Abstract. Measurements in the central Baltic Sea have shown that dissolved inorganic carbon (DIC) concentrations in the upper water column continue to decrease even after complete depletion of dissolved inorganic nitrogen (DIN). To explain this observation, a new external supply of nitrogen is required without a concomitant supply of inorganic carbon. The primary proposed candidate process is N2-fixation. In order to address this question in the eastern Gotland Sea, a biogeochemical model containing nine state variables including diatoms, flagellates, and nitrogen fixing cyanobacteria, was coupled to a 1D physical model. The results from the winter period until the onset of the spring bloom of 1997 gave reasonable surface water values for partial pressure of CO2 (pCO2) compared with measurements of the pCO2. However, the model failed to simulate the observed pCO2 drawdown for the period from the end of the spring bloom until late summer. Even after introducing a seasonal dissolved organic carbon (DOC) excess production and varying different process parameterization the simulated pCO2 values did not improve. Only the shift from a sharp to a moderate temperature dependency in addition to an increase in the C:P ratio of the nitrogen fixing cyanobacteria made it possible for the model to match the pCO2 observations. The resulting total nitrogen fixation (167 mmol m-2 a-1) exceeds previous measurement-based estimates but is in good agreement with recent rate measurement based estimates.

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