Freshwater Fraction Research Articles

Biosynthesis and characterization of silver nanoparticles generated from peels of Solanum tuberosum (potato) and their antibacterial and wastewater treatment potential

Global food production consumes a large fraction of energy budget, land area, and freshwater; however, a larger fraction of the produce is lost or unutilized, which has potential to produce useful products for human use. The biogenic synthesis of silver nanoparticles from such waste food appears to be a promising strategy. A conservative estimate of 70–140 thousand tons of potato peels is produced annually by food-chain companies globally; however, they are primarily utilized to produce substandard feed for livestock or manure. For the formation of highly profitable compounds, enhancement of value, and the process of extraction, such as nanocomposite, organic antioxidants, and organic meal inclusions, potato peels can be used as a cheap, productive, and readily available source of raw material. In the present research, silver nanoparticles (AgNPs) were extracted from the peels of potato (Solanum tuberosum). The fabrication of potato peel-derived AgNPs was established using UV-visible spectroscopy analysis. Approaches like X-ray diffraction (XRD), attenuated total reflection-infrared (ATR-IR) spectroscopy analysis, and field emission scanning electron microscopy (FESEM) were used to determine the characteristics of the AgNPs. Additionally, strains of Gram-positive bacteria such as Staphylococcus aureus (S. aureus) (ATCC 25923) and Gram-negative bacteria such as Escherichia coli (E. coli) (ATCC 25922) were used to determine the antibacterial activity of AgNPs via the disc diffusion technique. The antibacterial properties of AgNPs could help protect food from microbial contamination. Furthermore, AgNPs were tested for their potential application in purification of industrial wastewater. The results revealed that AgNPs derived from the potato peels could be used in industrial and biomedical applications and possess excellent antibacterial activity. Our research suggests that AgNPs can be extracted from a safe and ecofriendly fabrication technique from largely unused potato peels that have a great potential for inhibiting the bacterial growth and for the in situ purification of wastewater in the upcoming years. Therefore, besides value addition to the farm produce, such recycling of potato peels is likely to reduce the burden of the solid waste volumes in agro-centers, kitchen wastes, and food industries across the globe.

Submarine Groundwater Discharge-Derived Nutrient Fluxes in Eckernförde Bay (Western Baltic Sea)

Excess nutrient supply by the rivers and the atmosphere are considered as the major causes for the persistently poor ecological status of the Baltic Sea. More than 97% of the Baltic Sea still suffers from eutrophication due to past and present inputs of nitrogen and phosphorus. One of the poorly quantified nutrient sources in the Baltic Sea is submarine groundwater discharge (SGD). Through seepage meter deployments and a radium mass balance model, a widespread occurrence of SGD along the coastline of Eckernförde Bay was detected. Mean SGD was 21.6 cm d−1 with a calculated freshwater fraction of 17%. Where SGD was detected, pore water sampled by a piezometer revealed a wide range of dissolved inorganic nitrogen (DIN: 0.05–1.722 µmol L−1) and phosphate (PO43−: 0.03–70.5 µmol L−1) concentrations. Mean DIN and PO43− concentrations in non-saline (salinity < 1) pore waters were 59 ± 68 µmol L−1 and 1.2 ± 1.9 µmol L−1, respectively; whereas pore water with salinities > 1 revealed higher values, 113 ± 207 µmol L−1 and 6 ± 12 µmol L−1 for DIN and PO43−, respectively. The nutrient concentrations along the salinity gradient do not suggest that land-derived groundwater is the definitive source of nutrients in the Baltic Sea. Still, SGD may contribute to a major autochthonous nutrient source, resulting from remineralization or dissolution processes of organic matter in the sediments. The DIN and PO43− fluxes derived from SGD rates through seepage meters are 7.9 ± 9.2 mmol m−2 d−1 and 0.5 ± 0.4 mmol m−2 d−1, lower by a factor of ~ 2 and ~ 5 when compared to the fluxes derived with the radium mass balance model (mean DIN: 19 ± 28 mmol m−2 d−1; mean PO43−: 1.5 ± 2.7 mmol m−2 d−1). Assuming that these mean radium-based nutrient fluxes are representative for the coastline of Eckernförde Bay, we arrive at SGD-borne nutrient fluxes of about 1 t km−1 y−1 of nitrogen and 0.2 t km−1 y−1 of phosphorous. These fluxes are lower for DIN and in the same range for phosphorus as compared to the riverine nutrient supply (DIN: 6.3 t km−1 y−1, P: 0.2 km−1 y−1) to the German Baltic Sea identifying SGD-borne nutrients as a secondary nutrient source to the Baltic Sea.

Temporal variation of freshwater as control of mangrove in Banyuasin Estuary, South Sumatra, Indonesia

Abstract. Surbakti H, Nurjaya IW, Bengen DG, Prartono T. 2023. Temporal variation of freshwater as control of mangrove in Banyuasin Estuary, South Sumatra, Indonesia. Biodiversitas 24: 1502-1510. The Banyuasin Estuary receives much freshwater, which transports low-salinity water from upstream to the sea through the rivers that flow along the area. The interaction between the freshwater mass from the river and the highly saline seawater mass moving toward the estuary will affect the condition of the mangroves in the region. This study aims to estimate the freshwater runoff from the two main rivers (Musi River and Banyuasin River) into the Banyuasin Estuary in different seasons, at high and low tides, and their impact on the mangroves present in both estuaries. The interaction between the freshwater and seawater masses can be explained using the freshwater fraction and transect methods used for mangrove zonation analysis. This research focuses on the mouth of the Musi River and the Banyuasin River. The present study showed the influence of freshwater fraction at the mouth of the Musi River is very strong in all seasons, dominated by oligohaline and mesohaline conditions. In contrast, the mouth of the Banyuasin River is dominated by mesohaline and polyhaline conditions. Altogether, ten species of mangroves have been found in the Banyuasin Estuary. Of which, low saline tolerant species, namely Nypa fruticans and Sonneratia caseolaris, are predominant, whereas salt tolerant species, namely Avicennia marina, are predominant in the mouth of the Banyuasin River.

The marine carbonate system variability in high meltwater season (Spitsbergen Fjords, Svalbard)

The spatial variability in hydrography (salinity and temperature) and carbonate chemistry (alkalinity - AT, total inorganic carbon concentration - CT, pH, CO2 partial pressure - pCO2, and the saturation state of aragonite - ΩAr) in high meltwater season (summer) was investigated in four Spitsbergen fjords - Krossfjorden, Kongsfjorden, Isfjorden, and Hornsund. It was found that the differences in hydrology entail spatial changes in the CO2 system structure. AT decline with decreasing salinity was evident, hence it is clear that freshwater input generally has a diluting effect and lowers AT in the surface waters of the Spitsbergen fjords. Significant surface water AT variability (1889–2261 µmol kg−1) reveals the complexity of the fjords’ systems with multiple freshwater sources having different alkalinity end-member characteristics and identifies the mean AT freshwater end-member of 595 ± 84 µmol kg−1 for the entire region. The effect of AT fluxes from sediments on the bottom water was rather insignificant, despite high AT values (2288–2666 μmol kg−1) observed in the pore waters. Low pCO2 results in surface water (200–295 μatm) points to intensive biological production, which can strongly affect the CT values, however, is less important for shaping alkalinity. It has also been shown that the freshening of the surface water in the fjords reduces significantly ΩAr (an increase in freshwater fraction contribution by 1% causes a decrease in ΩAr by 0.022). Although during the polar day, due to low pCO2, ΩAr values are still rather far from 1 (they ranged from 1.4 to 2.5), during polar night, when pCO2 values are much higher, ΩAr may drop markedly. This study highlights that the use of salinity to estimate the potential alkalinity can carry a high uncertainty, while good recognition of the surface water AT variability and its freshwater end-members is key to predict marine CO2 system changes along with the ongoing freshening of fjords waters due to climate warming.

Spatial and temporal variations of estuarine stratification and flushing time across the continental U.S.

Estuarine circulation attributes such as stratification and flushing time significantly influence estuarine ecological processes. Stratification reflects how much vertical mixing occurs in an estuary, while flushing time can describe the exchange rate of pollutants between the estuary and ocean. A recently developed estuarine characterization framework used estuarine geophysical attributes and water exchange datasets to characterize estuarine circulation for 360 estuaries in the continental U.S. between 1950 and 2015. The estuaries were grouped into nine ecoregions according to the Marine Ecoregions of the World. In the Gulf of Mexico and along the East Coast, most estuaries were well-mixed (63–93%), with 3–5% strongly-stratified estuaries. Along the West Coast, strongly-stratified estuaries dominated (46–63%), with the exception of the Puget Trough basin and the southern CA ecoregion with 83% and 75% well-mixed estuaries. The stratification type of some estuaries varied seasonally. Generally, they were more stratified winter through spring, then mixed during the summer, with the exception of southern FL, which had a reverse pattern due to the positive correlation between the stratification parameter and freshwater inflow (97% estuaries with R2 > 0.9). The flushing times of the 300 well-mixed and partially-stratified estuaries were estimated using Tidal Prism (TPM) and Freshwater Fraction Methods (FFM). Flushing time seasonal variation exhibited a negative correlation with freshwater inflow (R2 > 0.8 for 50% of estuaries using TPM). Generally, estuarine flushing times were short in winter and long in summer (reversed in FL and a portion of the Gulf of Mexico). On the West Coast, estuaries tended to flush quickly compared with estuaries in other regions, even though they usually had low freshwater inflows, since other factors, e.g., the estuarine volume, affected the flushing time as well. To ensure appropriate interpretation of responses to change in nutrient loading, the significant intra- and interannual variations in stratification and flushing time need to be incorporated into management and assessment of estuaries.

ROFI Zone (Region of Freshwater Influence) and Its Impact on Total Dissolved Solids in the Coastal District of Sukadana Kayong Utara

Coastal areas are characterized by complex dynamics between freshwater entering through the estuary from land and seawater from open water. This study aims to calculate the salinity anomaly found on the sandy coast of Mayang, estimate the number of fractions and the volume of mass transport of fresh water entering the waters through the river flow and measure the total dissolved solids (TDS) in the west season. Water mass characteristics data collection using Water Checker. The determination of 17 data collection stations is assumed to be representative in representing the overall condition of the research location. The results of the anomaly salinity calculation show the low anomalous salinity values that are distributed horizontally on the coast. The distribution of salinity as anomaly values transversely on lines 1 to 4 ranges from -1 to -15. Freshwater fraction is concentrated as far as 1.16 km from the coast of Pasir Mayang with concentration values ranging from 0.44% to 0.13%. The mass transport of fresh water in the Pasir Mayang coastal waters is 1,130 m3s -1. The value of the transport volume of fresh water depends on rainfall and the flow of fresh water through rivers and then into sea waters. The total dissolved solids at the study site at each station ranged from 7.88 ppm to 17.8 ppm.

Glacial Ice Melting Stimulates Heterotrophic Prokaryotes Production on the Getz Ice Shelf in the Amundsen Sea, Antarctica

AbstractExtensive oceanographic data sets were combined with microbiological parameters to elucidate the tight coupling between glacial meltwater and heterotrophic bacterial production (BP) on the Getz Ice Shelf (GtzIS) in the Amundsen Sea. BP in the eastern GtzIS (EG; 85.8 pM Leu. h−1), where basal glacier meltwater upwells, was significantly higher than BP measured in the western GtzIS (WG; 50.6 pM Leu. h−1) and the Amundsen Sea Polynya (ASP; 27.8 pM Leu. h−1). BP in the EG accounted for 49% of primary production, which was greater than that of the WG (10%) and ASP (9.2%). Enhanced BP in the eastern GtzIS was not coupled with phytoplankton biomass, but correlated significantly with the freshwater fraction containing meltwater‐derived dissolved organic carbon (MW‐DOC). These results suggest that warming‐induced glacier melting weakens carbon sequestration efficiency in Antarctic coastal waters by stimulating heterotrophic metabolism that converts MW‐DOC to CO2.

The calculation of flushing time for the upper Pasur River Estuary, Bangladesh

Estimation of estuarine flushing time, a time required to transport of pollutants or any other properties from estuaries to the coast, is very important for its resource management. In this study, we estimated flushing time (T) of the upper Pasur River Estuary (UPRE) for understanding the water quality condition in the dry and wet seasons. High-resolution salinity data were collected from the PRE at high water in the dry and wet seasons in 2014 and 2019. Flushing time was calculated using the freshwater fraction method (FFM) as well as e-folding flushing time scales was estimated empirically using the salinity (non-reactive conservative) and monthly river discharge data. System flushing during the dry season was thirteen times weaker than flushing during the wet season owing to decreasing river discharge by nearly 94%. In addition, the daily exchange volume was decreased by eight times during the dry season than during the wet season. As a consequence, the conditions of the UPRE are more dynamic during the wet season due to receiving huge amount of river discharge. During the dry season, only the e-folding time scales showed higher values in the salinity maximum zone (salt plug area). This implied that the e-folding time scale is an empirical approach and was able to encompass the tidal dispersion process whereas the FFM was unable to include that process. As the PRE is a macrotidal estuary, the tide assists to flush dissolved substances from the UPRE to the coast during the dry season having negligible river discharge. In addition, there was no significant variation in water quality parameter between the salt plug area (SP) and downstream of salt plug area (DSP) during the dry season. In order to have more accuracy, a three-dimensional hydrodynamic model would be useful to compute estuarine time scales precisely.

Assessment of carbon fluxes to coastal area during persistent drought conditions

This study assesses the seasonal and hydrological factors controlling carbon fluxes and quality of organic matter through the maximum turbidity zone (MTZ) of a tropical semiarid estuary under extreme drought, the Jaguaribe River estuary located in northeast Brazil. Dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations decreased in the Jaguaribe River estuary during the past ten years, reflecting drought intensification and river damming. DOC and POC behavior were strongly correlated to the freshwater residence time and freshwater fraction. Correlations with Chl-a indicated that the biological activity did not regulate DOC but did POC. Stable isotope ratios (δ13C and δ15N) of POC showed that it was predominantly terrestrial-derived, suggesting mangrove as an important POC source. Dissolved inorganic carbon concentrations reflected the seasonal variability of the semiarid climate, being higher in the dry season due to the negative water balance during this period. The Jaguaribe River estuary’s MTZ behaved as a retainer of POC (-1.5 ± 0.2 × 104 tons.year −1), DOC (-1.0 × 105 tons.year −1) and DIC (-4.8 ± 3.3 × 105 tons.year −1) during the dry season and as an exporter of DOC (+ 2 x 104 tons.year −1) and DIC (+1.4 × 105 tons.year −1) in the rainy season. However, the reduced freshwater supply to the estuary resulted in carbon concentrations 50% lower than those reported in 2004 and carbon fluxes smaller than expected for a tropical region. This study indicates that, under a scenario of climatic changes, the intensification of droughts in NE Brazil can further increase carbon retention in the estuary, reducing its exportation to the ocean.

Rethinking tracer-based (Ra, Rn, salinity) approaches to estimate point-source submarine groundwater discharge (SGD) into coastal systems

Submarine groundwater discharge (SGD) has been shown to potentially be a more important source of solutes to the global ocean than river flow. As a result, the accuracy of predictions of the magnitude and seasonal variability of SGD to the sea is critical for the management of coastal marine ecosystems. For a model site (Kinvarra Bay, Ireland) dominated by point source SGD inputs, we show that the difference between estimates provided by different marine tracer-based methods can be large, depending on the way water residence time within the system and water exchange across its boundaries are described. For example, results from tidal-prism and freshwater fraction models, the most widely used approaches to quantify freshwater fluxes into marine areas of restricted exchange, vary by one order of magnitude depending on the way the water exchange across the outer system boundaries is considered and whether Lagrangian or Eulerian data is used. We show that SGD estimates based on single point time series (Eulerian) outside of a retention area can lead to consistently lower estimates than when using transect data (Langrangian). Moreover, the outcome of radon (222Rn) based SGD estimates is dependent on the way the effect of water age variability on radon decay and degassing is accounted for. We provide a solution to this conceptual problem by developing a correction to 222Rn budgetary approaches to estimate SGD, based on the spatial variation of water ages estimated from radium isotopes (223Ra, 224Ra) in solution. We use new data to compare the different sets of approaches while examining the validity of their underlying assumptions to verify internal consistency and use the substantial range of published data on Kinvarra bay to assess the quality of results produced with the new method.

Quantifying water quality and flow in multi-branched urban estuaries for a rainfall event with mass balance method

In this study, field observations were conducted after a heavy rainfall event in the Sumida and Shakujii rivers in Tokyo, Japan. The flow dynamics and fluxes of salt, suspended sediment (SS), and dissolved oxygen (DO) were investigated with the mass balance method. The fractions of fresh water and saltwater in seaward and landward flows were separated. The maximum salt flux in the Shakujii River was 53.8 kg/s during the flood tide, and those in the Sumida River were 680.3 kg/s at the upstream station and 703.7 kg/s at the downstream station. The trends of SS and DO fluxes were similar in both rivers. In the Shakujii River, the highest SS (3.1 kg/s) and DO (0.4 kg/s) fluxes appeared during the flood tide after rainfall. In the Sumida River, the maximum SS fluxes (6.1 and 6.3 kg/s at the upstream and downstream stations, respectively) and DO fluxes (1.15 and 1.21 kg/s at the upstream and downstream stations, respectively) appeared during the ebb tide. The mass balance method was used to estimate discharge, salinity, SS concentration, and DO concentration at a station with missing data. The results show that the estimated salinity and SS concentration had a significant correlation with the on-site observations, with correlation coefficients (R) of 0.950 and 0.835, respectively, but not for DO concentration (R = 0.638). The disparity between the computed and measured data may be explained by the differences in velocity, salinity, topography, sedimentation, and the presence of organic matter. The analysis based on the advective salt transport components found a lower salt flux per unit width in the Shakujii River (0.36 kg/(m·s)) in comparison with that in the Sumida River (2.88 kg/(m·s)). This indicates a higher probability for salt retention in the Shakujii River.

Influence of estuarine tidal mixing on structure and spatial scales of large river plumes

Abstract. The Yenisei and Khatanga rivers are among the largest estuarine rivers that inflow to the Arctic Ocean. Discharge of the Yenisei River is 1 order of magnitude larger than that of the Khatanga River. However, spatial scales of buoyant plumes formed by freshwater runoff from the Yenisei and Khatanga gulfs are similar. This feature is caused by different tidal forcing in these estuaries, which have similar sizes, climate conditions, and geomorphology. The Khatanga discharge experiences strong tidal forcing that causes formation of a diluted bottom-advected plume in the Khatanga Gulf. This deep and weakly stratified plume has a small freshwater fraction and therefore occupies a large area on the shelf. The Yenisei Gulf, on the other hand, is a salt-wedge estuary that receives a large freshwater discharge and is less affected by tidal mixing due to low tidal velocities. As a result, the low-salinity and strongly stratified Yenisei plume has a large freshwater fraction and its horizontal size is relatively small. The results show that estuarine tidal mixing determines freshwater fraction in these river plumes, which governs their depth and area after they spread from estuaries to coastal sea. Therefore, the influence of estuarine mixing on spatial scales of a large river plume can be of the same importance as the roles of river discharge rate and wind forcing. In particular, plumes with similar areas can be formed by rivers with significantly different discharge rates, as illustrated by the Yenisei and Khatanga plumes.

The calculation of estuarine flushing times in convergent estuaries using fresh-water fraction method

ABSTRACT The flushing time in an estuary is important for water quality analysis, and it is one of the major transport time scales used in estuaries to quantify the hydrodynamic processes and for water resources management strategies. The purpose of this paper is to investigate the influence of tidal amplitude, river discharge, and salinity stratification on the spatially varying flushing time of the two selected Moroccan Atlantic semi-closed estuaries, i.e. Bouregreg and Loukkos. A freshwater fraction method (FFM) was used to calculate flushing time for both estuaries using a spatially varying freshwater fraction. The results showed that the flushing time varies from 2.7 to 6.3 days for a river discharge ranges from 17 to 22 m3s−1 during spring tide, and from 3.4 to 11.2 days for a river discharge ranges from 17 to 31 m3s−1 during neap tide in Bouregreg estuary, and varies from 10 to 13.6 days for a river discharge ranges from 3.47 to 5.12 m3s−1 during spring tide, and from 9.11 to 13.1 days for a river discharge ranges from 3.47 to 5.48 m3s−1 at neap tide in Loukkos estuary. In addition, the flushing time near the mouth for both estuaries is shorter during spring tide than during neap tide because of the larger amplitude of the spring tide. At the estuary mouth (e.g. Bouregreg estuary), the potential energy anomaly of the water column is negligible (<4 J m−3).

Freshwater intrusion during ebb and flood tide in the Balikpapan Bay

The Balikpapan Bay waters is influenced by freshwater discharge from many rivers and its distribution is affected by tidal current. This study aims to estimate seawater intrusion during flood and ebb tides, using the box model and freshwater fraction methods. The data used in this study for calculating freshwater fraction and its transport volume were 45 conductivity- temperature-depth CTD casts and single moored ADCP current measurement, carried out between 17 and 25 May 2018. The budget of the box model system is calculated using evaporation and precipitation data. The results show that estimated freshwater fraction and transport volume during flood tide vary between 16.92 and 36.26%, and between 2.048 and 9.661x109 m3day−1, respectively. Near the entrance of the bay, seawater flux urges freshwater westward with surface salinity budget of -95.352x106 psu.m3day−1. Furthermore, during ebb tide, freshwater fraction and transport volume are estimated to be 19.33 – 34.5% and 2.048–9.661x109 m3day−1, respectively. Near the mouth of estuary, freshwater pushes seawater toward east side of the bay with salinity budget of -186.187x106 psu.m3day−1. During flood tide (ebb tide) estimated surface salinity budget in transect 5 that came out from the system is about -135.512x106 psu.m3day−1 (-143.794x106 psu.m3day−1) toward the southern bay.

Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean

In siliciclastic systems, submarine groundwater discharge (SGD) provides a fraction of freshwater and nutrients delivered to coastal waters, but in many carbonate karst terrains SGD represents the predominant source of terrestrial water and solutes. Water compositions may be modified by reactions in subterranean estuaries, altering chemical fluxes via SGD. In carbonate settings, feedbacks between organic carbon remineralization and calcium carbonate mineral (CaCO3) dissolution and precipitation may alter carbon dioxide (CO2) and phosphorus (P) concentrations and fluxes associated with SGD. To assess these effects, we sampled water from multiple submarine springs along the east coast of the Yucatan peninsula, as well as inland cenotes, and a coastal groundwater well. We measured ammonium (NH4), phosphate (PO4), major element, dissolved inorganic and organic carbon concentrations (DIC and DOC), fluorescent characteristics of colored dissolved organic matter (CDOM) and modeled calcite saturation indices (SIcal) and the partial pressure of dissolved CO2 (PCO2). These data indicate that reactions along a hypothetical flow path to the coast control the composition of terrestrial fresh water entering the subterranean estuary. Non-conservative mixing between brackish groundwater and lagoon water reflect changes to groundwater compositions within the subterranean estuary from CO2 produced during organic matter remineralization and CaCO3 dissolution. Although both organic matter remineralization and carbonate dissolution should liberate P, molar N:P ratios in spring discharge are higher than the Redfield Ratio of 16:1, suggesting sequestration of remineralized P through sorption to carbonate minerals within the STE. This result indicates that SGD, the primary source of water and nutrient to this coastal zone, results in P limitation in coastal water and is a source of CO2 despite buffering by CaCO3 dissolution. This result also emphasizes the importance of biogeochemical reactions within subterranean estuaries for estimates of SGD solute delivery to the oceans and impacts to the coastal carbon cycle.

“Freshwater” in the Ocean is Not a Useful Parameter in Climate Research

AbstractOcean water is freshwater with salt. The distribution of salt concentration in the ocean changes by addition and removal of freshwater in the form of precipitation, continental runoff, and evaporation, and by a flow of saline ocean water that gives rise to a salt flux divergence. Often, changes in salinity are described in terms of “freshwater content” changes and oceanic “freshwater transports,” defined as fractions of freshwater. But these freshwater fractions are arbitrary, because they are defined by a nonunique reference salinity. Also all temporal and spatial comparisons and anomalies of such freshwater fractions in the ocean depend on the choice of reference salinity in a nonlinear way, because in the definition of the fraction it appears in the denominator. Consequently, any conclusion based on the comparison of freshwater fractions is ambiguous. Since there is no definite physical constraint for a unique reference salinity, freshwater fractions are declared not useful for the assessment of the state of ocean regions and the associated changes. In the light of ongoing changes in the water cycle and the global nature of climate science, scientific results need to be expressed in a way so that they can be easily compared and integrated in a global perspective. To this end, we recommend to avoid freshwater fraction as a parameter describing the ocean state. Instead, one should use the terms of the salt budget to obtain unique results for quantifying and comparing salinity.

Marine CO2 system variability in a high arctic tidewater-glacier fjord system, Tempelfjorden, Svalbard

The marine CO2 system in Tempelfjorden (Svalbard) was investigated between August 2015 and December 2017 using total alkalinity, pH, temperature, salinity, oxygen isotopic ratio, and nutrient data. Primary production resulted in the largest changes that were observed in the partial pressure of CO2 (pCO2, 140 μatm) and the saturation state of aragonite (ΩAr, 0.9). Over the period of peak freshwater discharge (June to August), the freshwater addition and air-sea CO2 uptake (on average 15.5 mmol m−2 day−1 in 2017) governed the surface pCO2. About one fourth of the uptake was driven by the freshening. The sensitivity of ΩAr to the freshwater addition was investigated using robust regressions. If the effect of air-sea CO2 exchange was removed from ΩAr, a freshwater fraction larger than 50% (lower range of uncertainty) was needed to provide aragonite undersaturated waters. This study shows that ΩAr and freshwater fraction relationships that are derived from regression techniques and the interpretation thereof are sensitive to the effect of air-sea CO2 exchange. Since the freshening in itself only drives a fraction of the air-sea CO2 uptake, studies that do not account for this exchange will overestimate the impact of freshwater on ΩAr. Finally, in the summer an excess in the salinity normalized dissolved inorganic carbon, corrected for aerobic primary production/respiration, of on average 86 μmol kg−1 was found in the deepest water of the fjord. This excess is suggested to be a result of enhanced CO2 uptake and brine release during the period of sea ice growth.

Dramatic hydrodynamic and sedimentary responses in Galveston Bay and adjacent inner shelf to Hurricane Harvey

Hurricane Harvey, one of the worst hurricanes that hit the United States in recent history, poured record-breaking rainfall across the Houston metropolitan area. Based on a comprehensive set of data from various sources, we examined the dramatic responses in hydrodynamic and sedimentary processes of Galveston Bay to this extreme event. Using a freshwater fraction method that circumvents the uncertainties in surface runoff and groundwater discharge, the freshwater load into the bay during Harvey and the following month was estimated to be 11.1 × 109 m3, about 3 times the bay volume, which had completely refreshed the entire bay. Harvey also delivered 9.86 × 107 metric tons of sediment into the bay, equivalent to 18 years of average annual sediment load. At a site inside the San Jacinto Estuary, acute bed erosion of 48 cm followed by deposition of 22 cm of new sediment was observed from the sediment cores. Slow salinity recovery (~2 month) and a thick flood deposit (~10.5 cm average over the entire bay) had likely impacted the ecosystem in the bay and the adjacent inner shelf. Estuaries with similar bathymetric and geometric characteristics, i.e., shallow bathymetry with narrow outlets, are expected to experience similar dramatic estuarine responses while extreme precipitation events are expected to occur more frequently under the warming climate.

Impacts of Nearshore Wave‐Current Interaction on Transport and Mixing of Small‐Scale Buoyant Plumes

AbstractSmall‐scale buoyant outflows have the potential to impact beach contamination, nutrient exchange, productivity, larval recruitment, and carbon chemistry in the nearshore region where surface gravity waves influence momentum and energy transport. This study aims to understand the dynamics leading to the fate and structure of an idealized small‐scale outflow in the presence of surface waves using a fully coupled 3‐D hydrodynamic and spectral wave model. Wave‐current interactions significantly alter plume structure when compared to hydrodynamics‐only simulations. Wave dissipation injected into the water column as a flux of turbulent kinetic energy at the sea surface mixes the plume in the surf zone, while wave‐driven velocities reduce offshore plume propagation and enhance alongshore spreading. A series of simulations varying flow rate and offshore wave height indicate a log linear relationship between the surf zone volume‐integrated freshwater fraction and the ratio of wave to outflow momentum fluxes.

Seasonally physical characteristics of ROFI zone (Region of Freshwater Influence) in Pelabuhan Ratu Bay

Coastal waters have many oceanographic phenomena are still being studied. One such phenomenon is how the influence of freshwater to the water mass in coastal waters. This study aims to calculate freshwater fraction, volume transport of freshwater and water mass stability. Physical water characteristics were measured by CTD (Conductivity, Temperature and Depth) deployed in 15 locations for temperature, salinity and density. The results of freshwater fraction analysis show that the west season had a greater on water fraction than the east season with value ranging from 0.40 % - 0.70 % with the amount 18.07 %, while the east season had a value of 0.02 % - 0.28 % with the amount is 7.30 %. The transport of freshwater volume in west season is 1.429.244 m3s-1 while in the east season it is 1.066 m3s-1. Water mass stability of water column in the research location has static stability with its average N2 in west and east monsoon are 0.008 cycl/s and 0.7 × 103 cycl/s, respectively. Those analyses above infer that freshwater input hugely influences physical water mass of ROFI zone in research location.