Surface Freshwater Research Articles

Occurrence and Evolution of Mesoscale Thermodynamic Phenomena in the Northern Part of the East Sea (Japan Sea) Derived from Satellite Altimeter Data

Based on satellite measurements and oceanic reanalysis data, it has been possible to investigate the spatiotemporal variability of the mesoscale phenomena in the northern part of the East Sea (NES) where direct observations of currents and hydrographical conditions are scarce. For the first time, this study identifies the detailed spatiotemporal structure of the mesoscale features in the NES and the mechanism of its occurrence and evolution, which have important consequences on the distribution of the intermediate water masses in the East Sea. Here, we show that mesoscale thermodynamic phenomena in the northwestern region of the East Sea are characterized by a dipole structure associated with positive and negative sea surface height anomalies. These result in a strong thermal gradient between the seasonally non-persistent anomalies, which emerge and strengthen during late fall and early winter. In contrast to the previous finding of the relationship between winter monsoon winds and mesoscale features in the NES, we found that this relationship is crucial only to the emergence of the mesoscale phenomena. Consequently, we present a new perspective on the evolution mechanism of the mesoscale features in the NES. Of direct significance to the present study, thermohaline transport into the northwestern region of the East Sea regulates the strengthening and weakening of mesoscale features in the NES. Wind forcing may contribute to the emergence of the mesoscale features in the NES and then the intensification of the mesoscale activities is attributed to the intrusion of warm and fresh surface water advected from the southern part of the East Sea.

Experimental study to improve the performance of solar still desalination by hydrophobic condensation surface using cold plasma technology

Improvement of solar still desalination performance has become the agenda of researchers in recent years to be able to make the most of the development of such systems in times of crisis and water scarcity. In the current experimental study, using two solar still desalination systems, the effect of cold plasma coat using Dielectric Barrier Discharge (DBD) on the condensation surface is investigated. To achieve this goal, two still solar systems are tested under the same climatic conditions to demonstrate the effects of the cold plasma coating on the condensation surface wettability and hydrophobicity. Additionally, influence of plasma layer on the internal condensing surface temperature and freshwater production rate is examined. Experimental results show that the contact angle between water droplets and glass cover after using plasma coating will increase, which increases the surface hydrophobicity. Results reveal that the amount of produced fresh water in the uncoated surface desalination system equivalent to 485 ml, while in the system with cold plasma, the maximum productivity with the maximum average solar radiation of 1000 W/m2 and the absorber wall temperature of 70.1 °C, and surface angle of 35° in the experiment day is about 610 mL. Additionally, calculations represent that the produced freshwater using plasma coating increases by 25.7% compared to the uncoated system. The quality of lab-prepared saltwater samples was analyzed before and after desalination, and the results comply with the World Health Organization guidelines for drinking water quality.

How Much Arctic Fresh Water Participates in the Subpolar Overturning Circulation?

AbstractFresh Arctic waters flowing into the Atlantic are thought to have two primary fates. They may be mixed into the deep ocean as part of the overturning circulation, or flow alongside regions of deep water formation without impacting overturning. Climate models suggest that as increasing amounts of freshwater enter the Atlantic, the overturning circulation will be disrupted, yet we lack an understanding of how much freshwater is mixed into the overturning circulation’s deep limb in the present day. To constrain these freshwater pathways, we build steady-state volume, salt, and heat budgets east of Greenland that are initialized with observations and closed using inverse methods. Freshwater sources are split into oceanic Polar Waters from the Arctic and surface freshwater fluxes, which include net precipitation, runoff, and ice melt, to examine how they imprint the circulation differently. We find that 65 mSv (1 Sv ≡ 106 m3 s−1) of the total 110 mSv of surface freshwater fluxes that enter our domain participate in the overturning circulation, as do 0.6 Sv of the total 1.2 Sv of Polar Waters that flow through Fram Strait. Based on these results, we hypothesize that the overturning circulation is more sensitive to future changes in Arctic freshwater outflow and precipitation, while Greenland runoff and iceberg melt are more likely to stay along the coast of Greenland.

Increasing Bromine in Intracellular Organic Matter of Freshwater Algae Growing in Bromide-Elevated Environments and Its Impacts on Characteristics of DBP Precursors

Bromide elevation in surface freshwater is unavoidable due to climate change and anthropogenic activities. Freshwater impaired by algal activity and bromide elevation has become problematic worldwide. However, studies of their impact on water quality and treatment practices are limited. This study is the first to demonstrate that genera of freshwater algae (e.g., cyanobacterium Microcystis aeruginosa and green alga Chlorella sp.) can accumulate bromine within their intracellular organic matter (IOM) when bromide occurs in water (i.e., 0, 0.5, 1, and 4 mg/L), which substantially enhances brominated disinfection byproduct (Br-DBP) formation upon chlorination. Using energy-dispersive and X-ray photoelectron spectrometers, we discovered clear bromine signals on algal surfaces in both cultures and natural water. Bromide elevation in source water particularly increased bromine accumulation inside algae cells and intracellularly, with greater than 33%–85% found in IOM. This phenomenon dramatically increased Br-DBP formation from Br-rich IOM precursors to ∼80% of total DBPs at an elevated Br– level of 4 mg/L, resulting in the exponential rise of toxic potency of chlorinated water. These findings are significant to understand the origins of natural organic bromine in freshwater environments and provide further insights into how the co-impairment of algae and bromide elevation may influence finished water quality upon chlorination.

Economic and environmental sustainability of the optimal water resources application for coastal and inland regions

Global water security threatens human health and urbanization, forcing communities to seek ways to tackle water stress problems. Alternative water resources including seawater, desalinated seawater, reclaimed wastewater and desalinated wastewater effluent can replace conventional surface freshwater. Considering alternative water resources, one problem facing policymakers is which one is the most feasible to use under their water and geographical conditions. This study aims to tackle this problem by analyzing the global sensitivity of key influential factors among water and geographic characteristics, assessing water supply systems for coastal and inland regions from both economic and environmental perspectives. The analyzed influential factors are effective population density, population served, daily water demand per capita, water demand of toilet flushing, distance to seaside, and water import distance. The global sensitivity analysis approach is utilized to evaluate the sensitivity index of the influential parameters with respect to each impact category. The analysis demonstrates that the most sensitive influential factors are effective population density and distance to the ocean. By further considering the conditions for extensively applying potential water resources, the analysis illustrates that seawater toilet flushing (SWTF) is the most environmentally friendly option even in areas far away from the seaside with relatively low population density. However, SWTF is only economical in coastal areas with density above 17 000 persons/km2. Wastewater effluent desalination is cheaper for other coastal regions with a lower population density and for inland regions.

Introducing Transversal Connectivity Index (TCI) as a method to evaluate the effectiveness of the blue-green infrastructure at metropolitan scale

This study introduces the Transversal Connectivity Index (TCI) as an ecological indicator for classifying the natural landscape patches by their effective transversal connectivity to the water surfaces. The method applies specifically to urban areas at which the quality of blue-green infrastructure (BGI) is of fundamental importance in reducing the climate change consequences. Effective transversal connectivity among the BGI at the metropolitan scale supplies various ecosystem services in support of nature-based solutions for emerging urban challenges. The TCI value is computed (determined) by integrating a variety of existing and novel landscape indicators into an equation. The connectivity indicators belong to two categories: the intra-patch consists of the isoperimetric quotient, and patch ecological indicator, and the inter-patch ones listed as the band level, the shared border ratio, and the transport fragmentation buffer. The method is tested on the metropolitan zone of Berlin, and the results reveal unconventional findings of the effectiveness of BGI in urbanized landscapes. Despite the abundant green surfaces present in Berlin, only 50% of them have direct access to freshwater surfaces, based on Urban Atlas land use land cover data. The proposed indexing method is reproducible for other metropolitan areas, leading to comparative evaluation of effective BGI, having direct implications with emerging agendas of metropolitan management and policy making like the City Biodiversity Index, the concept of Sponge City, and Sustainable Development Goals.

О некоторых проблемных вопросах реализации прокурорами надзорных полномочий в области охраны поверхностных пресноводных объектов в Российской Федерации при выявлении затонувших в акваториях водоемов судов и иного затонувшего имущества

The article examines certain problematic issues that arise in prosecutorial practice in the process of exercising supervisory powers in the field of protection of surface freshwater objects in the Russian Federation when specialized prosecutors identify vessels and other sunken property that have sunk in water areas. On the basis of an analysis of the norms of federal legislation, materials of supervisory and judicial practice, the author formulated specific proposals for solving existing problems in order to increase the efficiency of work in the field of environmental protection and ensuring the safety of navigation.

Three-bestseller pesticides in Brazil: Freshwater concentrations and potential environmental risks

Agricultural production in Brazil is favored by weather conditions and by the large amount of available land. Therefore, currently, Brazil is the second largest exporter of agricultural products globally. Pesticides are widely used in Brazilian crops due to their high efficiency, their low cost, and permissive legislation. However, pesticides tend to reach water resources threatening organisms and the water quality. Thereby, we aimed to review the surface freshwater concentrations of the three-bestseller pesticides in Brazil (glyphosate, 2,4D, and atrazine), and discuss the results with sales, legislation, toxicity and potential risks. For that, we performed a systematic review of quantitative studies of glyphosate, atrazine, and 2,4D in Brazilian freshwater and included monitoring data provided by the Brazilian Ministry of Health in our analysis. Finally, we calculated the risk assessment for the three pesticides. Only a few scientific studies reported concentrations of either of the three-bestseller pesticides in Brazilian freshwaters. Between 2009 and 2018, an increase in the sales of 2,4D, atrazine, and glyphosate was observed. It was not possible to evaluate the relation between concentrations and sales, due to limited number of studies, lack of standard criteria for sampling, individual environmental properties, and type of pesticide. Atrazine showed a higher toxicity compared to 2,4D and glyphosate. Regarding the environmental risks, 65%, 72%, and 94% of the Brazilian states had a medium to high risk to 2,4D, atrazine, and glyphosate, respectively. Finally, 80% of the Brazilian states evaluated showed a high environmental risk considering a mixture of the three pesticides. Although most of the environmental concentrations registered were below the allowed limits according to the Brazilian legislation, they are already enough to pose a high risk for the aquatic ecosystems. We, therefore, strongly recommend a revaluation of the maximum allowed values in the national surface freshwater Brazilian legislation.

CYCLOCIM: A 4-D variational assimilation system for the climatological mean seasonal cycle of the ocean circulation

We describe a new 4-D variational assimilation system, called CYCLOCIM, to estimate the climatological seasonal cycle of the residual mean ocean circulation. CYCLOCIM assimilates monthly mean potential temperature and salinity data from the World Ocean Atlas, and CFC-11, CFC-12 and natural radiocarbon measurements for the deep ocean from the Global Data Analysis Project, Version 2. CYCLOCIM’s control parameters include: (i) a seasonally varying 3-D field of unresolved eddy-stress divergences that appear in the horizontal momentum equations, (ii) seasonally varying 2-D correction fields for the surface heat and freshwater fluxes, and (iii) a constant scaling factor for the air–sea flux of CFCs. The influence of initial conditions on a fully spun-up ocean model vanishes. Thus, unlike other 4-D variational assimilation systems, CYCLOCIM does not include initial conditions as control parameters. A Bayesian procedure is used to formulate the inverse problem, which is solved by finding the maximum of the posterior probability distribution. The optimization process used to find the maximum includes a forward simulation to calculate the flow velocities and tracer distributions followed by a backward (“adjoint” ) simulation to compute the gradient of the posterior. A quasi-Newton search algorithm is used to find the set of parameters to maximize the posterior probability. We find that by resolving the seasonal cycle the model is able to better fit the observations in the upper ocean compared to a previous steady-state version of the model. The main output from CYCLOCIM is a set of 12 data-constrained monthly tracer transport matrices that will provide a useful circulation model for global marine biogeochemical cycle studies.

Occurrence of caffeine, fluoxetine, bezafibrate and levothyroxine in surface freshwater of São Paulo State (Brazil) and risk assessment for aquatic life protection.

The prioritization of active pharmaceutical ingredients (APIs) for monitoring programmes and/or environmental risk assessment (ERA) purposes is based on several criteria, including environmental occurrence data. However, data on API occurrence in Brazilian surface freshwaters are still scarce. The Brazilian Unified Health System (SUS) provides several medicines free-of-charge, including medications that have bezafibrate, fluoxetine and levothyroxine as the API. Thus, our objective was to investigate the occurrence of bezafibrate, fluoxetine and levothyroxine in samples collected at sampling sites included in the surface freshwater monitoring program of the São Paulo State Environmental Agency (CETESB); caffeine was also included in the analysis because it is commonly used as an anthropogenic marker of aquatic environment contamination. Monitoring results showed that levothyroxine was not found in any of the analysed samples. Caffeine was ubiquitous in the analysed samples, thus indicating anthropic contamination in the studied water bodies. Caffeine and bezafibrate presented risk quotient (RQ) < 1 for all the sampling sites and periods evaluated in this study. For fluoxetine, RQs > 1 were found in all water samples in which this API was found, indicating a potential risk for freshwater pelagic biota. Thus, fluoxetine should be regulated in São Paulo State in order to protect the aquatic biota. Additional occurrence studies in other Brazilian states are still needed to evaluate if fluoxetine is a nationwide pollutant.

Fluorophores in surface freshwaters: importance, likely structures, and possible impacts of climate change.

Fluorescence spectroscopy is one of the most useful techniques currently available for the characterisation of organic matter in natural water samples, because it combines easy availability of instrumentation, high sensitivity and limited requirements for sample treatment. The main fluorophores that can be found in natural waters are usually proteins (and/or free amino acids) and humic substances (humic and fulvic acids). The identification of these fluorescent compounds in water samples helps to obtain information about, among others, biological activity in the water body, possible transport of organic matter from soil, and the phenomenon of photobleaching that decreases both the absorbance and (usually) the fluorescence of natural organic matter. Interestingly, all these phenomena can be affected by climate change, which could alter to different extents the ratio between aquagenic and pedogenic fluorophores. Several events induced by warming in natural waters (and especially lake water) could enhance algal growth, thereby also enhancing the production of aquagenic organic matter. Intense precipitation events could increase the export of pedogenic material to surface waters, while photobleaching would be enhanced in the epilimnion of lakes when summer stratification becomes longer and more stable because of higher temperatures. Interestingly, photobleaching affects humic substances to a higher extent compared to protein-like material, thus protein fluorescence signals could be more preserved in stratified waters.

КАДМИЙ В ВОДЕ ПО КОНТИНУУМУ «ЭСТУАРИЙ Р. МИУС – ТАГАНРОГСКИЙ ЗАЛИВ АЗОВСКОГО МОРЯ»

We have studied the distribution of concentrations of bulk cadmium, as well as dissolved and suspended forms of its migration, along the continuum ‘the Mius estuary – the Taganrog Bay of the Azov Sea’. Within this area, there are located two barrier zones – the zone of the Mius River waters mixing with the Miussky Liman waters and the zone of the estuary waters mixing with the waters of the Taganrog Bay. In these barrier zones, the concentrations of all forms of cadmium increased significantly, which was due to the high wind activity observed during the study period, as a result of which, the silt deposit was stirred up, and a significant part of the cadmium previously deposited on the geochemical barriers migrated into the water. In general, in the water of the studied continuum, we observed a positive correlation of concentrations of all forms of cadmium not only with each other but also with the values of pH and salinity. For the entire studied system, the dissolved form of cadmium migration slightly prevailed over the suspended form and ranged from 50 to 75% (on average, 57%) of its gross content. At the same time, the absolute content of the dissolved form of cadmium migration did not go beyond the maximum values of the range of its concentrations in fresh surface and sea waters of the globe, as well as the MPC values for the corresponding environments.

Factors Determining the Natural Fresh‐Salt Groundwater Distribution in Deltas

AbstractMost river deltas are densely populated areas with intensive agriculture. The increased shortage of fresh surface water that results from rising demands are expected to lead to increased groundwater pumping, which leads to sea water intrusion. To correctly project the future of fresh groundwater resources in deltas, knowing the current fresh‐salt groundwater distribution is a prerequisite. However, uncertainties about these distributions and their drivers are large. To understand these uncertainties, we conducted a global sensitivity analysis of a complex three‐dimensional variable‐density groundwater model of a synthetic delta, simulating the effect of the last glacial low stand and the subsequent marine transgression. The analysis is unique in its wide range of geometries, hydrogeological parameterizations, and boundary conditions analyzed, making it representative for a large number of deltas worldwide. We find that the aquifer hydraulic conductivity is the most uncertain input and has a strong nonmonotonous effect on the total salt mass onshore. The calculated fresh‐salt groundwater distributions were classified into five classes and compared to real‐world case studies. We find that salinity inversions occur in deltaic systems with high representative system anisotropies as a remnant of a marine transgression. These salinity inversions were observed in half of the real‐world cases, indicating that their fresh‐salt groundwater distributions are not in a dynamic equilibrium. We conclude that it is very likely that past marine transgressions are still reflected in the current fresh‐salt groundwater distributions in deltas. This makes paleo‐groundwater modeling a prerequisite for effective simulation of present‐day groundwater salinity distributions in these systems.

Water Security and Sustainability in India

Water is valuable for life, livelihood, economy and ecosystem services, but distributed unevenly. Water scarcity in general and water quality in the particular region, are posing risks to sustainability and quality of life. Indian economy and agricultural practices depend on its rivers, as per an estimate about 80 percent of fresh surface water and 60 percent of ground water have been used by the agricultural sector, but rivers and other water bodies are facing problems of contamination due to domestic waste, sewage, agriculture effluents of chemical fertilizers and discharge of industrial effluents. Domestic waste is drained out as waste and ends up flowing into various water bodies which leads to pollution of water sources. The careful utilizing of river water is the biggest challenge. Losses are also due to traditional way of irrigation which increases the problem of water scarcity. For sustainability of livelihood and maintaining quality of life, it is essential to have sufficient water availability even in the phase of climate change. The national drinking water programme and accelerated urban water supply programme aim to provide universal and equitable access to safe and affordable drinking water for all by 2030. It is time to value every drop of water and rejuvenate our traditional water bodies, clean rivers, recharge ground water, collect rain water and successful implementation of technology for achieving water resource management.

Water quality indicators of the Nima Creek, and potential for sustainable urban agriculture in Ghana

ABSTRACT Urban and peri-urban agriculture, a widely accepted practice of food cultivation in urban centers contributes to positive environment. It has the benefits of job creation, increased access to healthy and affordable food, and important means of improving community health. Use of wastewater or disturbed surface water for urban agriculture is a common practice in the developing world due to lack of adequate infrastructure and widespread poverty. This study assessed the urban water quality parameters of the Nima Creek, a major water resource for peri-urban and urban farming in Southeastern Accra. Water sampled from six locations along the NE – SW stretch of the creek were evaluated for physicochemical parameters including pH, conductivity, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), cations, zinc, iron, oil and grease, Biological Oxygen demand (BOD), Chemical Oxygen demand (COD). Results show high enrichment of nutrients, ammonia (NH3), nitrate (NO3), and phosphate (PO4) as well as elevated levels of BOD, COD, and grease at sites receiving solid and liquid wastes. The physicochemical parameters such as conductivity, TSS, and TDS exhibited periods of elevated values that were congruent with seasonal rainfall patterns within the catchment area. Sodium concentration ranged from 32 to 297 mg/L. Nitrate levels generally ranged from 1.5 to 7.13 mg/L. The cation concentrations showed broad temporal and spatial variation characteristic of disturbed surface freshwater. Principal component analysis of the data discriminated four distinct components accounting for 63.6% of the total variance. The component plots constrained three major classes explaining the physical quality of the water and two other groups defining nutrient and alkalinity levels in the water.

Solar-driven, self-sustainable electrolysis for treating eutrophic river water: Intensified nutrient removal and reshaped microbial communities

River ecosystems are the most important resource of surface freshwater, but they have frequently been contaminated by excessive nutrient input of nitrogen (N) and phosphorus (P) in particular. An efficient and economic river water treatment technology that possesses the capacity of simultaneous N and P removal is urgently required. In this study, a solar-driven, self-sustainable electrolytic treatment was conducted in situ to intensify N and P removal from eutrophic river water. Solar panel was applied to provide the electrolysis setups with energy (voltage 10 ± 0.5 V), and the current density was controlled to be 0.06 ± 0.02 mA cm−2. Results indicated that the average removal efficiencies of total N (TN) and total P (TP) under electrolysis conditions reached 72.4 ± 11.7 and 13.8 ± 5.3 mg m−2 d−1, which were 3.7- and 4.7-fold higher compared to untreated conditions. Enhanced TN removal mainly reflected the abatement of nitrate N (NO3−-N) (80.6 ± 4.1%). The formation of ferric ions through the electro-dissolution of the sacrificial iron anode improved TP removal by coprecipitation with SPS. Combined high-throughput sequencing and statistical analyses revealed that electrolysis significantly reshaped the microbial communities in both the sediment-water interface and suspended sediment (SPS), and hydrogenotrophic denitrifiers (e.g., Hydrogenophaga) were highly enriched under electrolysis conditions. These findings indicated that in situ electrolysis is a feasible and effective technology for intensified nutrient removal from river water.

Upper-ocean physical and biological features associated with Hudhud cyclone: A bio-physical modelling study

Abstract The east coast of India is highly prone towards the devastation by the cyclonic storms. The Bay of Bengal (BoB) basin in the northeastern Indian Ocean is characterized to provide adequate conditions to the cyclogenesis. The cyclogenesis is more active during pre- and post-monsoon seasons over the BoB. The post-monsoon season shows highest storm occurrence in the region due to presence of warm and freshwater in the upper-ocean which helps to maintain deep barrier layer and supports cyclogenesis. The very severe cyclonic storm, Hudhud was a post-monsoonal storm occurred during 07th–14th October 2014 over the BoB. Hudhud made landfall near Visakhapatnam coast at noon of 12th October 2014. The present study utilized a three dimensional coupled bio-physical model for the analysis of biogeochemical response of the upper-ocean to Hudhud cyclone. The different surface and subsurface physical and biological features along the track of Hudhud has depicted a cyclone-generated surface phytoplankton bloom and its associated decline of surface dissolved oxygen. The study aims at a better understanding of the spatial and temporal variability of the upper-ocean parameters in response to the passage of tropical cyclone (TC) Hudhud. It is found that the intense cyclonic wind stress caused upwelling in the wake of cyclone track about 1550 km from its genesis location. The excess surface freshwater flux due to precipitation establishes stronger stratification in the coastal region. This enhanced stratification found to restrict the supply of nutrients to the euphotic zone and, hence, limiting the surface primary productivity in the coastal region.

Safeguarding the threatened hydrogeo-cultural heritage of Majuli Island in Assam, India: A case study

Water resources are basic need for life, and it has a vital role on any riverine island and its diverse culture and heritage. Majuli, the riverine island in Assam is distinctive for its origin, characteristic water resources, hydrogeological manifestations as well as its cultural heritage. River Brahmaputra, the lifeline of Assam, transverses through Assam’s valley, resulting in the deposition of alluvial sediments and forming one of India’s most potential aquifer systems. Every year, the state is prone to frequent natural disasters like massive floods and riverbank erosion in the valley during the monsoon months. Majuli Island is the cultural heritage site of Assam, which is often highlighted as the ‘Cultural Capital’ of the state. It is termed as the largest river island of India and one of the largest inhabited riverine islands in the world. In combination with cultural aspects, the island holds typical hydrogeological heritage, consisting of encircled fresh surface water bodies, wetlands, beels, various sub-surface aquifer systems, and water quality issues. However, the existence of the hydrogeo-cultural heritage in the island is under acute threat due to frequent floods, land erosion by the Brahmaputra and its tributaries, surface water and groundwater quality deterioration. Hence, the present study has emphasized the changing hydrogeological scenario of Majuli over the last decades and the correlation of diverse cultural perspectives followed by the establishment of mutual interrelationships between hydrogeology and cultures, which have not been addressed so far. The paper also aims at understanding the demographic status, landscape pattern, hydro-geomorphological characteristics, biodiversity and ethnic diversity perspectives, which would facilitate to adopt the effective measures for protection of the island from further environmental degradation and thereby to recommend a sustainable management strategy to uphold the multidimensional cultural heritage perspectives of the island.

Quasi‐Biweekly Mode of the Asian Summer Monsoon Revealed in Bay of Bengal Surface Observations

AbstractAsian summer monsoon has a planetary‐scale, westward propagating “quasi‐biweekly” mode of variability with a 10–25 day period. Six years of moored observations at 18°N, 89.5°E in the north Bay of Bengal (BoB) reveal distinct quasi‐biweekly variability in sea surface salinity (SSS) during summer and autumn, with peak‐to‐peak amplitude of 3–8 psu. This large‐amplitude SSS variability is not due to variations of surface freshwater flux or river runoff. We show from the moored data, satellite SSS, and reanalyses that surface winds associated with the quasi‐biweekly monsoon mode and embedded weather‐scale systems, drive SSS and coastal sea level variability in 2015 summer monsoon. When winds are calm, geostrophic currents associated with mesoscale ocean eddies transport Ganga‐Brahmaputra‐Meghna river water southward to the mooring, salinity falls, and the ocean mixed layer shallows to 1–10 m. During active (cloudy, windy) spells of quasi‐biweekly monsoon mode, directly wind‐forced surface currents carry river water away to the east and north, leading to increased salinity at the moorings, and rise of sea level by 0.1–0.5 m along the eastern and northern boundary of the bay. During July–August 2015, a shallow pool of low‐salinity river water lies in the northeastern bay. The amplitude of a 20‐day oscillation of sea surface temperature (SST) is two times larger within the fresh pool than in the saltier ocean to the west, although surface heat flux is nearly identical in the two regions. This is direct evidence that spatial‐temporal variations of BoB salinity influences sub‐seasonal SST variations, and possibly SST‐mediated monsoon air‐sea interaction.

Detectability and Abundance of Snowy Plovers at Salt Plains National Wildlife Refuge, Oklahoma

AbstractIn the past two decades, Salt Plains National Wildlife Refuge has been increasingly recognized as important habitat for both breeding and migratory shorebirds. North American snowy plovers Charadrius nivosus in particular rely on the nearly 5,000-ha salt flat at Salt Plains National Wildlife Refuge, which thousands use as breeding and stopover habitat. Elsewhere on the Southern Great Plains, decadal declines up to 75% within snowy plover subpopulations have been documented and attributed to vegetation encroachment, increased rates of nest predation, and decreased availability of fresh surface water. Despite many attempts to estimate this species' abundance across the continent, to date, no known attempt at distance sampling of snowy plovers has occurred. To address this paucity of data, we assessed feasibility of distance sampling methods to accurately estimate snowy plover abundance and detectability. Distance sampling surveys (2017–2018) indicated high detection probability (P = 0.80) and the population abundance estimate across the salt flat extrapolated to 3,307 individuals. The distance-sampling population abundance estimate is lower than population abundance estimates determined by two previous studies within the past decade but far greater than 2,105 estimated for a study in 2006. Overall, distance sampling snowy plovers at Salt Plains National Wildlife Refuge proved to be an effective addition to pre-established survey protocols but further investigation is needed to compare accuracy and precision of methods used in this study, annual surveys conducted by Salt Plains National Wildlife Refuge, and other potential snowy plover surveys.