Surface Water Salinity Research Articles

Functional and Compositional Responses of Periphyton Mats to Simulated Saltwater Intrusion in the Southern Everglades

Periphyton plays key ecological roles in karstic, freshwater wetlands and is extremely sensitive to environmental change making it a powerful tool to detect saltwater intrusion into these vulnerable and valuable ecosystems. We conducted field mesocosm experiments in the Florida Everglades, USA to test the effects of saltwater intrusion on periphyton metabolism, nutrient content, and diatom species composition, and how these responses differ between mats from a freshwater versus a brackish marsh. Pulsed saltwater intrusion was simulated by dosing treatment chambers monthly with a brine solution for 15 months; control chambers were simultaneously dosed with site water. Periphyton from the freshwater marsh responded to a 1-ppt increase in surface water salinity with reduced productivity and decreased concentrations of total carbon, nitrogen, and phosphorus. These functional responses were accompanied by significant shifts in periphytic diatom assemblages. Periphyton mats at the brackish marsh were more functionally resilient to the saltwater treatment (~ 2 ppt above ambient), but nonetheless experienced significant shifts in diatom composition. These findings suggest that freshwater periphyton is negatively affected by small, short-term increases in salinity and that periphytic diatom assemblages, particularly at the brackish marsh, are a better metric of salinity increases compared with periphyton functional metrics due to functional redundancy. This research provides new and valuable information regarding periphyton dynamics in response to changing water sources in the southern Everglades that will allow us to extend the use of periphyton, and their diatom assemblages, as tools for environmental assessments related to saltwater intrusion.

Remote sensing and in situ platform based study on impact of Bay of Bengal cyclones (Phailin, Helen, Lehar, and Madi) on ocean chlorophyll and associated physical parameters

Impact of four major cyclones: Phailin, Helen, Lehar, and Madi have been studied in terms of changes in ocean productivity utilizing Indian satellite Oceansat-2 ocean color monitor and MODIS-Aqua data during October–December 2013. The 8-day and monthly composite chlorophyll images have been generated owing to the pre-, during, and post-stages of four cyclones; out of which, three were very severe cyclonic storms and the Helen was severe cyclonic storm. The chlorophyll concentration increased two- to threefolds due to the aftereffect of cyclone in the coastal water, and the concentration was very high (around 2–3 mg/m3). To understand the possible links of cyclones to cooling and upwelling, MODIS-Aqua sea surface temperature (SST) images have been processed. The SST images have shown the cooling effect near the cyclone track pass, over Bay of Bengal. The cooling was observed by 2–3 degree Celsius during the above cyclones. To understand the in situ surface water and water column salinity and temperature variability, the Argo float data are plotted and interpreted. The surface contour shows the lowering of salinity and temperature with effects of cyclones. In addition, the Argo depth profile data have shown possible mixed layer deepening in few profiles around halocline and thermocline depths. This study will be useful for mapping potential fishing zone, ocean biogeochemistry and other useful applications and research.

Responses of the picophytoplankton community to temperature fronts in the northeastern Arabian Sea during the northeast monsoon

We investigated the responses of the picophytoplankton (< 3 µm) community to a temperature filament and front through high resolution spatial (~ 1 NM) sampling (November-23 to December-11, 2012) in the northeastern Arabian Sea (69°E, 18.85°N to 20.25°N). Samples were collected at discrete depths within the 100 m water column. Synechococcus dominated the picophytoplankton community numerically and in terms of biomass along the entire transect. To investigate the patterns of variability in picophytoplankton distribution, depending on the water mass characteristics, the entire transect was divided into four zones (1) south of filament (SFIL) with warm oligotrophic waters, (2) filament (FIL) with cooler and low saline waters, (3) north of filament (NFIL) with relatively cooler waters than the SFIL and (4) front (FRO) with relatively cooler and less saline waters than the FIL. Depth-integrated abundance and biomass of Synechococcus were relatively higher within the FIL and FRO whereas Prochlorococcus and picoeukaryotes were abundant in SFIL and NFIL. Redundancy analysis of environmental variables and picophytoplankton abundance showed that lower saline water mass within the mesoscale features harbored relatively higher Synechococcus abundance and biomass. Two Synechococcus ecotypes were distinguished based on the fluorescence intensity of the accessory pigment, phycoerythrin; the one with higher intensity (open ocean ecotype) dominating in the FIL and the other with lower intensity in the FRO (coastal ecotype). The relatively lower saline surface water mass at the FRO, probably a result of coastal advection, could have introduced the latter ecotype. Vertically, a positive correlation of Prochlorococcus with nutrients and Synechococcus with temperature corroborates their higher and lower abundance and biomass, respectively in the deeper waters. The positive correlation of Synechococcus with the total chlorophyll biomass indicates a similar response to environmental variables within the mesoscale features. This study shows that picophytoplankton contribution (16–24%) to the total phytoplankton carbon biomass in tropical mesoscale features is likely to have important consequences on the planktonic food web function.

Factors influencing the behaviour of Irrawaddy dolphins Orcaella brevirostris (Owen in Gray, 1866) in Brunei Bay, Malaysia

The population of Irrawaddy dolphins in Brunei Bay, Malaysia is little studied. This study aimed at contributing information on how abiotic and other factors influence different aspects of their behaviour displayed at the water surface. Several behaviours, i.e. foraging, travelling, foraging behind trawler, milling and socializing were observed during boat-based line transect surveys (2013–2016). The behaviours of individuals and groups were filmed or noted, and the abiotic factors of the habitat were registered at the same time. The number of “travelling” individuals was negatively correlated with surface water salinity (p value = 0.04) and positively correlated with turbidity (p value = 0.01). Fisher’s exact test also revealed that the behaviours of dolphin groups significantly differed with the ranges of several abiotic factors, i.e. foraging behind trawler with depth (p value = 0.001), travelling with surface water salinity (p value = 0.05), travelling and foraging behind trawler with turbidity (p value = 0.04, 0.01). The results for foraging behind trawler differed significantly between the groups with calves and those without calves (χ2 test, p value = 0.04), where groups with calves were less likely to forage behind trawlers. Significant differences were observed among group sizes for travelling, milling and socializing (χ2 test, p value < 0.05), with large groups (11–20 individuals) more frequently foraging, milling and socializing, compared to smaller ones. The current study is the first behavioural observation for Irrawaddy dolphins in Brunei Bay and these findings will help researchers, conservationists, local marine park managers and policy makers in developing effective conservation and management plans for the area.

Effects of Hydroclimatic Change and Rehabilitation Activities on Salinity and Mangroves in the Ci\xe9naga Grande de Santa Marta, Colombia

The Ciénaga Grande de Santa Marta (CGSM), Colombia is possibly the wetland that has experienced the largest mangrove mortality on record due to modification of hydrologic connectivity and consequent hypersaline conditions. We used hydroclimatic, salinity and mangrove basal area data collected in five stations from 1993 to 2015 to study the relation between ongoing mangrove recovery, changes in salinity in the wetland and hydroclimatic changes in precipitation, potential evapotranspiration and freshwater inputs. We found that until 2015, the mangrove ecosystems in CGSM are in general terms in a path of recovery due to the combined effect of favorable hydroclimatic conditions and management operations to increase freshwater inputs into the wetland. We observed in three stations that the annual growth of mangrove basal area increased as pore water salinity decreased. Regarding surface water salinity, El Niño/Southern Oscillation explained most of the inter-annual variability in the wet season by regulating freshwater and in the dry season by regulating potential evaporation from the wetland. However, persistent channel reopening appeared to be the cause for the largest salinity decreases, whereas lack of persistent dredging slowed recovery in other areas. The monitoring of the mangrove-salinity-hydroclimate system must continue in order to increase its understanding and to avoid more recurring episodes of mangrove mortality.

Parametric Assessment of Pre-Monsoon Agricultural Water Scarcity in Bangladesh

This study assesses the geographical distribution of agricultural water scarcity in Bangladesh in order to streamline the adaptation measures. The agricultural water scarcity was assumed to be a system with five subsystems, namely, groundwater depth, surface water availability, rainfall availability, groundwater salinity for irrigation, and surface water salinity for irrigation. The catastrophe-theory-based multi-criteria decision making approach was used for the estimation of agricultural water scarcity index from five subsystem indices. The obtained results showed that agriculture in about 6.3% of the area of the country is experiencing very high-risk water scarcity, 19.1% with high water scarcity, 37.2% with moderate water risk, and the rest is low or no risk of water scarcity for agriculture. Results showed that the western part of Bangladesh was more vulnerable to agricultural water scarcity. The analysis of the results showed that higher agriculture water scarcity in the northwest region resulted from water unavailability, and in the southwest region it was closely related to poor water quality. The severe areas of water scarcity are very similar to those that are usually regarded as water-scarce. The approach presented in this study can be used for rapid but fair assessment of water scarcity with readily available data, which can be further improved by incorporating other factors related to water scarcity.

Effect of Water Surface Salinity on Evaporation: The Case of a Diluted Buoyant Plume Over the Dead Sea

AbstractEvaporation from water bodies strongly depends on surface water salinity. Spatial variation of surface salinity of saline water bodies commonly occurs across diluted buoyant plumes fed by freshwater inflows. Although mainly studied at the pan evaporation scale, the effect of surface water salinity on evaporation has not yet been investigated by means of direct measurement at the scale of natural water bodies. The Dead Sea, a large hypersaline lake, is fed by onshore freshwater springs that form local diluted buoyant plumes, offering a unique opportunity to explore this effect. Surface heat fluxes, micrometeorological variables, and water temperature and salinity profiles were measured simultaneously and directly over the salty lake and over a region of diluted buoyant plume. Relatively close meteorological conditions prevailed in the two regions; however, surface water salinity was significantly different. Evaporation rate from the diluted plume was occasionally 3 times larger than that of the main salty lake. In the open lake, where salinity was uniform with depth, increased wind speed resulted in increased evaporation rate, as expected. However, in the buoyant plume where diluted brine floats over the hypersaline brine, wind speed above a threshold value (∼4 m s−1) caused a sharp decrease in evaporation probably due to mixing of the stratified plume and a consequent increase in the surface water salinity.

Ekman and Eddy Exchange of Freshwater and Oxygen across the Labrador Shelf Break

AbstractTransport of freshwater from the Labrador Shelf into the interior Labrador Sea has the potential to impact deep convection via its influence on the salinity of surface waters. To examine this transport, the authors deployed two underwater gliders on a mission to traverse the continental shelf break multiple times between 5 July and 22 August 2014, the period when Arctic meltwater has historically peaked in transport down the Labrador Shelf. The field campaign yielded a unique dataset of temperature, salinity, and oxygen across the shelf break to a depth of 1000 m at unprecedented spatial resolution. Two mechanisms of cross-shelf transport were examined: Ekman transport and transport due to mesoscale eddies. Ekman transport is quantified using satellite wind stress and near-surface hydrographic properties, and eddy-induced transport is scaled using a parameterized eddy diffusivity and thickness gradients of layers of uniform potential density, as well as the tracer gradients along those isopycnals. Both the Ekman and eddy terms transport high-oxygen and low-salinity water from the shelf to the Labrador Sea during the field campaign. The influence of the eddy-driven oxygen flux from the shelf to the Labrador Sea on oxygen budgets depends strongly on the size of the region over which this eddy flux converges. The deduced offshore transport of freshwater (4 ± 6 mSv; 1 mSv = 103 m3 s−1) from both Ekman and eddy mechanisms, which is likely at a seasonal maximum during this summertime survey, represents about 3% of the annual-mean freshwater flowing through Hudson and Davis Straits but may be an important component of the total freshwater budget of the interior Labrador Sea.

Spatial and Seasonal Standing Crop of Seagrass Communities during Adverse Times in the North-Western Province of the Philippines

Standing crop of seagrass beds and their associated species in Ilocos Sur were studied. It looked into the species classification as to their division, class, order, family, genus, species, and scientific names. Further, the seasonal and spatial standing crop of the species in terms of average number of individuals (N) in every square meter and environmental factors were determined. Differences in spatial and standing crop in the areas were computed, and the relationship of ecological factors was likewisedetermined. This study used descriptive- correlational research design. Surface water temperature, salinity, and pH were monitored every sampling period in each quadrat to determine their influence on the species’ standing crop. Mean, analysis of variance, Scheffe Test and simple bivariate correlation were the statistical tools used. Results showed that ten seagrass species inhabit the four communities of the province. All belong to Division Angiospermae, Class Monocotyledonae, and Order Alismatale. Six (6) belong to Family Cymodoceaceae and four (4) belong to Hydrocharitaceae. These seagrass species belong to the genera Cymodocea, Enhalus, Halodule, Halophila, Thalassia, Thalassodendron and Syringodium. The biomass production of seagrassesin San Esteban, Santiago and San Juan was very high. In all the sites, salinity positively affected the standing crop; temperature had negative effect on it while pH had no effect. Thirty six (36) organisms were found out associated in the seagrass communities. Further monitoring is recommended to have a better assessment of the resource in order to identify factors causing disturbances to the seagrass habitats and to determine appropriate management efforts.

Continued warming, salinification and oxygenation of the Greenland Sea gyre

The Greenland Sea gyre is one of the few areas where the water column is ventilated through open ocean convection. This process brings both anthropogenic carbon and oxygen from the atmosphere and surface ocean into the deep ocean, and also makes the Greenland Sea gyre interesting in a global perspective. In this study, a combination of ship- and float-based observations during the period 1986–2016 are analysed. Previous studies have shown warming and salinification of the upper 2000 m until 2011. The extended data record used here shows that this is continuing until 2016. In addition, oxygen concentrations are increasing over the entire period. The changes in temperature, salinity, and especially oxygen have been more pronounced since the turn of the century. This period has also been characterised by deeper wintertime mixed-layer depths, linking the warming, salinification and oxygenation to strengthened ventilation in the Greenland Sea gyre after 2000. The results also demonstrate that the strengthened ventilation can be tied to advection of warmer and more saline surface water from the North Atlantic through the Faroe-Shetland Channel. This advection has led to more saline surface waters in the Greenland Sea gyre, which is contributing to the deeper wintertime mixed layers.

Time Series Observation on Phytoplankton Dynamics in the Coastal Waters of the World Heritage Site of Indian Sundarban Mangrove Forest, NE Coast of Bay of Bengal

Sea levels on the Indian sub-continent are increasing at the rate of about 2.5 mm/year; the rate of increment is greater in the eastern coast, with an estimated sea level rise of about 3.14 mm/year. This suggests that mean annual sea levels in the Indian sub-continent will be some 15 cm higher in 2060 than what it was during 2000. The Indian Sundarbans in northeast coast of the country, at the apex of the Bay of Bengal is an extremely dynamic deltaic lobe sustaining a wide spectrum of mangrove flora and fauna. It is estimated that sea level in this deltaic lobe has increased by about 15 cm since the 1950s and this has been correlated with changes in the pattern and rates of erosion and accretion in the islands of the Indian Sundarbans. Such geo-physical phenomena may not only pose serious impact on the adjacent aquatic system by way of increasing turbidity, nutrient budget, salinity, pH etc., but the phenomenon has every possibility to shift the biodiversity spectrum of the adjacent land masses (supporting mangrove and mangrove associate species) and aquatic system due to salinization of land, alteration of soil pH, increased erosional activities leading to reduction of water transparency, increased salinity of the water bodies and invasion of the areas with more number of stenohaline species (preferably phytoplankton). The present paper is an attempt to scan the time series observation on phytoplankton dynamics in the coastal waters of Indian Sundarban mangrove forest, NE coast of Bay of Bengal. Twenty four stations have been selected in the present programme at different salinity gradients to evaluate the temporal variations of selective hydrological parameters like surface water temperature, salinity, pH, dissolved oxygen, transparency and nutrient load. Simultaneous data on phytoplankton diversity was also assessed to critically analyze the impact of temporal oscillation of hydrological parameters on the tiny, free floating, drifting, primary producer community. Duncan test applied on the data set of 25 years (1990 to 2015) revealed significant temporal variations of surface water temperature, salinity, pH, transparency, nitrate concentration, phosphate concentration and phytoplankton composition. Since 1990, nine stenohaline phytoplankton species have been recorded in the upstream regions of the deltaic lobe indicating a gradual shifting of aquatic phase towards high salinity. Few environmental variables like dissolved oxygen and silicate did not show variations at significant level. Although the time span is too short to predict potential impact of aquatic climate change on phytoplankton community of the mangrove dominated Indian Sundarbans, but significant temporal variation in the phytoplankton community since 1990 speaks in favour of using these tiny, free floating, drifting, primary producer community as potential bioindicators of aquatic climate change in short term scale.

Risk of seawater intrusion on coastal community of Bentota river basin Sri Lanka

Abstract Land degradation in coastal area is one of the major critical problems affecting the future economic development of Sri Lanka. Eighty percent of land in Bentota river basin has been abandoned and 25km distance along the Bentota river has already been affected by the seawater intrusion. Temporal and spatial variation of physicochemical parameters of selected dug wells, all surface water bodies and soil parameters were measured to detect the magnitude of the salinity due to seawater intrusion during August 2016 to March 2017 by using a systematic sampling method. Surface water, groundwater and soil salinity levels were comparatively very high in the river basin with respect to the WHO standards. With reference to the developed GIS salinity risk assessment weighted overlay model the highly saline, moderately saline, slightly saline and non-saline land extent with respect to the total land extent were 10.16%, 19.47%, 40.18% and 29.79% respectively. The highest economic loss was occurred due to the reduction of agricultural productions in the area (2279ha abandoned) and it was about 3,624,000 USD per year. Therefore, 52% from the total population was economically not active with the reduction of agricultural sector in the area. The total annual economic loss in the coastal community was 7,529,698.50 USD per year and it was directly happened due to the seawater intrusion.

Climatic Influences on Southern Makassar Strait Salinity Over the Past Century

AbstractThe Indonesian Throughflow (ITF) is a globally important ocean current that fuels heat and buoyancy fluxes throughout the Indo‐Pacific and is known to covary in strength with the El Niño Southern Oscillation at interannual time scales. A climate system with a less well‐quantified impact on the ITF is the East Asian Winter Monsoon (EAWM), which drives less saline surface waters from the South China Sea (SCS) into the Makassar Strait, obstructing surface ITF flow. We present a subannually resolved record of sea surface salinity (SSS) from 1927 to 2011 based on coral δ18O from the Makassar Strait that reveals variability in the relative contributions of different source waters to the surface waters of the Makassar Strait during the boreal winter monsoon. We find that the EAWM (January–March) strongly influences interannual SSS variability during boreal winter over the twentieth century (r = 0.54, p &lt;&lt; 0.0001), impacting surface water circulation in the SCS and Indonesian Seas.

Drought-induced recharge promotes long-term storage of porewater salinity beneath a prairie wetland

Subsurface storage of sulfate salts allows closed-basin wetlands in the semiarid Prairie Pothole Region (PPR) of North America to maintain moderate surface water salinity (total dissolved solids [TDS] from 1 to 10 g L−1), which provides critical habitat for communities of aquatic biota. However, it is unclear how the salinity of wetland ponds will respond to a recent shift in mid-continental climate to wetter conditions. To understand better the mechanisms that control surface-subsurface salinity exchanges during regional dry-wet climate cycles, we made a detailed geoelectrical study of a closed-basin prairie wetland (P1 in the Cottonwood Lake Study Area, North Dakota) that is currently experiencing record wet conditions. We found saline lenses of sulfate-rich porewater (TDS > 10 g L−1) contained in fine-grained wetland sediments 2–4 m beneath the bathymetric low of the wetland and within the currently ponded area along the shoreline of a prior pond stand (c. 1983). During the most recent drought (1988–1993), the wetland switched from a groundwater discharge to recharge function, allowing salts dissolved in surface runoff to move into wetland sediments beneath the bathymetric low of the basin. However, groundwater levels during this time did not decline to the elevation of the saline lenses, suggesting these features formed during more extended paleo-droughts and are stable in the subsurface on at least centennial timescales. We hypothesize a “drought-induced recharge” mechanism that allows wetland ponds to maintain moderate salinity under semiarid climate. Discharge of drought-derived saline groundwater has the potential to increase the salinity of wetland ponds during wet climate.

Surface Water pCO2 Variations and Sea‐Air CO2 Fluxes During Summer in the Eastern Canadian Arctic

AbstractBased on a 2 year data set, the eastern Canadian Arctic Archipelago and Baffin Bay appear to be a modest summertime sink of atmospheric CO2. We measured surface water CO2 partial pressure (pCO2), salinity, and temperature throughout northern Baffin Bay, Nares Strait, and Lancaster Sound from the CCGS Amundsen during its 2013 and 2014 summer cruises. Surface water pCO2 displayed considerable variability (144–364 μatm) but never exceeded atmospheric concentrations, and average calculated CO2 fluxes in 2013 and 2014 were −12 and −3 mmol C m−2 d−1 (into the ocean), respectively. Ancillary measurements of chlorophyll a reveal low summertime productivity in surface waters. Based on total alkalinity and stable oxygen isotopes (δ18O) data, a strong riverine signal in northern Nares Strait coincided with relatively high surface pCO2, whereas areas of sea‐ice melt occur with low surface pCO2. Further assessments, extending the seasonal observation period, are needed to properly constrain both seasonal and annual CO2 fluxes in this region.

Hydrography and circulation west of Sardinia in June 2014

Abstract. In the frame of the REP14-MED sea trial in June 2014, the hydrography and circulation west of Sardinia, observed by means of gliders, shipborne CTD (conductivity, temperature, depth) instruments, towed devices, and vessel-mounted ADCPs (acoustic doppler current profilers), are presented and compared with previous knowledge. So far, the circulation is not well-known in this area, and the hydrography is subject to long-term changes. Potential temperature, salinity, and potential density ranges as well as core values of the observed water masses were determined. Modified Atlantic Water (MAW), with potential density anomalies below 28.72 kg m−3, showed a salinity minimum of 37.93 at 50 dbar. Levantine Intermediate Water (LIW), with a salinity maximum of about 38.70 at 400 dbar, was observed within a range of 28.72&lt;σΘ/(kg m−3) &lt; 29.10. MAW and LIW showed slightly higher salinities than previous investigations. During the trial, LIW covered the whole area from the Sardinian shelf to 7°15′ E. Only north of 40° N was it tied to the continental slope. Within the MAW, a cold and saline anticyclonic eddy was observed in the southern trial area. The strongest variability in temperature and salinity appeared around this eddy, and in the southwestern part of the domain, where unusually low saline surface water entered the area towards the end of the experiment. An anticyclonic eddy of Winter Intermediate Water was recorded moving northward at 0.014 m s−1. Geostrophic currents and water mass transports calculated across zonal and meridional transects showed a good agreement with vessel-mounted ADCP measurements. Within the MAW, northward currents were observed over the shelf and offshore, while a southward transport of about 1.5 Sv occurred over the slope. A net northward transport of 0.38 Sv across the southern transect decreased to zero in the north. Within the LIW, northward transports of 0.6 Sv across the southern transects were mainly observed offshore, and decreased to 0.3 Sv in the north where they were primarily located over the slope. This presentation of the REP14-MED observations helps to further understand the long-term evolution of hydrography and circulation in the Western Mediterranean, where considerable changes occurred after the Eastern Mediterranean Transient and the Western Mediterranean Transition.

Assessment of sea water inundation along Daboo creek area in Indus Delta Region, Pakistan

Indus Deltaic Region (IDR) in Pakistan is an erosion vulnerable coast due to the high deep water wave energy. Livelihood of millions of people depends on the fisheries and mangrove forests in IDR. IDR consists of many creeks where Daboo is a major creek located at southeast of the largest city of Pakistan, Karachi. Unfortunately, there has been no detailed study to analyze the damages of sea water intrusion at a large temporal and spatial scale. Therefore, this study is designed to estimate the effects of sea water inundation based on changing sea water surface salinity and sea surface temperature (SST). Sea surface salinity and SST data from two different surveys in Daboo creek during 1986 and 2010 are analyzed to estimate the damages and extent of sea water intrusion. Mean salinity has increased 33.33% whereas mean SST decreased 13.79% from 1987 to 2010. Spatio-temporal analysis of creek area using LANDSAT 5 Thematic mapper (TM) data for the years 1987 and 2010 shows significant amount of erosion at macro scale. Creek area has increased approximately 9.93% (260.86 m2 per year) which is roughly equal to 60 extensive sized shrimp farms. Further Land Use Land Cover (LULC) analyses for years 2001 and 2014 using LANDSAT 7 Enhanced Thematic Mapper Plus (ETM+) has indicated 42.3% decrease in cultivated land. Wet mud flats have spread out at the inner mouth of creek with enormous increase of 123.3%. Significant sea water intrusion has increased the area of barren land by 37.9%. This also resulted in overall decrease of 6.7% in area covered by mangroves. Therefore, this study recorded a significant evidence of sea water intrusion in IDR that has caused serious damages to community living in the area, economical losses. Additionally, it has also changed the environment by reducing creek biological productivity as reported by earlier studies over other regions of the world.

Monitoring bacterial contamination of piped water supply in rural coastal Bangladesh.

Safe drinking water is scarce in southwest coastal Bangladesh because of unavailability of fresh water. Given the high salinity of both groundwater and surface water in this area, harvested rainwater and rain-fed pond water became the main sources of drinking water. Both the government and non-government organizations have recently introduced pipe water supply in the rural coastal areas to ensure safe drinking water. We assessed the bacteriological quality of water at different points along the piped water distribution system (i.e., the source, treatment plant, household taps, street hydrants, and household storage containers) of Mongla municipality under Mongla Upazila in Bagerhat district. Water samples were collected at 2-month interval from May 2014 to March 2015. Median E. coli and total coliform counts at source, treatment plant, household taps, street hydrants, and household storage containers were respectively 225, 4, 7, 7, and 15cfu/100ml and 42,000, 545, 5000, 6150, and 18,800cfu/100ml. Concentrations of both of the indicator bacteria reduced after treatment, although it did not satisfy the WHO drinking water standards. However, re-contamination in distribution systems and household storage containers indicate improper maintenance of distribution system and lack of personal hygiene.

A Framework for Incorporating the Impact of Water Quality on Water Supply Stress: An Example from Louisiana, USA

AbstractWater of poor quality can directly impact the budget of water available for key user groups. Despite this importance, methods for quantifying the impact of water quality on water availability remain elusive. Here, we develop a new framework for incorporating the impact of water quality on water supply by modifying the Water Supply Stress Index (WaSSI). We demonstrate the usefulness of the framework by investigating the impact of high salinity waters on the availability of irrigation water for agriculture in Louisiana. The WaSSI was deconstructed into sectoral components such that the total available water supply could be reduced for a particular demand sector (agricultural irrigation in this example) based on available water quality information. The results for Louisiana highlight substantial impacts on water supply stress for farmers attributable to the landward encroachment of saline surface water and groundwater near the coast. Areas of high salinity near the coast also increased the competition for freshwater resources among the industrial, municipal, and agricultural demand sectors in the vicinities of the municipal areas of Lake Charles, Lafayette, and Baton Rouge, Louisiana. The framework developed here is easily adaptable for other water quality concerns and for other demand sectors, and as such can serve as a useful tool for water managers.

Variability of Indonesian Throughflow and Borneo Runoff During the Last 14 kyr

AbstractWe present a high‐resolution (~20 to 100 years temporal resolution) reconstruction of hydrological changes in the Makassar Strait over the last 14 kyr from Core SO217‐18517 retrieved off the Mahakam Delta (1°32.198′S, 117°33.756′E; 698 m water depth) during the SO217 Makassar‐Java Cruise. Sea surface temperatures, based on Mg/Ca of Globigerinoides ruber and alkenone UK′37, and seawater δ18O reconstructions, based on G. ruber δ18O and Mg/Ca, in combination with sortable silt grain size measurements and X‐ray fluorescence (XRF) core scanner derived elemental data provide evidence for increased precipitation during the Bølling‐Allerød (BA) and early Holocene and for warmer and more saline surface waters and a decrease in the intensity of the Indonesian Throughflow (ITF) during the Younger Dryas (YD). XRF derived Log (Zr/Rb) records, sortable silt data and increased sedimentation rates indicate decreased winnowing, interpreted as a slowdown of the ITF thermocline flow during the YD. We attribute this decline in ITF intensity to slowdown of the Atlantic meridional overturning circulation during the YD. We suggest that changes in Makassar Strait surface hydrology during this interval of Northern Hemisphere cooling and Southern Hemisphere warming were related to a southward displacement of the Intertropical Convergence Zone.