Mean Salinity Research Articles

Assessment of Primary Parameters in Sawa Lake and Their Impact on Productivity

Sawa Lake is one unique enclosed water system situated in southwest Iraq. The current study intends to track the change in water level and analyse the reasons and consequences of the shift in the lake’s physicochemical qualities and primary productivity. Monthly samples were taken from three study sites from February to July 2021. The study found that air and water temperatures increased and decreased at all sites, which were evaluated during the study period. The mean salinity values ranged from 85.92 to 19.67‰, with the highest value (52.20‰) occurring before the drought in February and the lowest value (19.67‰) occurring after the drought in July. The pH level ranged from 7.57 to 8.77. The current study’s nutrient concentration (nitrite, nitrate, and phosphate) was 1.04-19.91, 21.51-251.79, 0.26 - 2.37μg/L, respectively, and there was a reverse correlation between nitrite and nitrate with salinity. The productivity measured by the light and dark bottle method recorded the lowest level (0.25 mg/m3/h) before the drought, and the highest level (3.25 mg/m3/h) was observed after the drought period. Chlorophyll concentration decreased during a drought due to lowered nutrient inputs. These data demonstrate that primary productivity in the lake’s waters is relatively low. And, the drought for the lake occurred as a result of a series of reasons that were strongly influenced by human activities. Traditionally, groundwater is extracted for agricultural purposes in this region. Thus, the rate of groundwater flows into the lake decreases, which negatively affects the physical and chemical parameters and thus affects the productivity of the lake. One of the ways of management is to form a national campaign that adopts exceptional measures to meet the challenges related to groundwater by reformulating and developing water systems, in addition to the proposal to reduce the area of the lake basin industrially to one-third, because the water, even if it returns to flood the lake, does not return to the previous quantities. Thus, when the water quality will be good, it will create the appropriate conditions to increase the productivity of the lake.

Multilayer Feedforward Artificial Neural Network Model to Forecast Florida Bay Salinity with Climate Change

Florida Bay is a large, subtropical estuary whose salinity varies from yearly and seasonal changes in rainfall and freshwater inflows. Water management changes during the 20th century led to a long-term reduction in inflows that increased mean salinity, and the frequency and severity of hypersalinity. Climate change may exacerbate salinity conditions in Florida Bay; however, future salinity conditions have not been adequately evaluated. Here, we employed a Multilayer Feedforward Artificial Neural Network model to develop baseline salinity models for nearshore and offshore sites. Then, we examined the impacts of climate change on salinity using forecasted changes in various input variables under two climate change scenarios, representative concentration pathways (RCP) 4.5 and 8.5. Salinity could rise by 30% and 70% under the RCP4.5 and RCP8.5 forecasts, respectively. Climate change affected nearshore salinity significantly more, which rapidly fluctuated between mesohaline (5 to 18 PSU) and metahaline (40 to 55 PSU) to hypersaline conditions (>55 PSU). Offshore salinities ranged between euhaline (30 to 40 PSU) to metahaline (40 to 55 PSU) conditions. Our study suggests that increased freshwater flow would help maintain suitable estuarine conditions in Florida Bay during climate change, while our novel modeling approach can guide further Everglades restoration efforts.

Diversity of Coastal Phytoplankton in Balayan Bay, Batangas, Philippines

Phytoplankton composition, density, and their relation with 10 abiotic water parameters in six coastal stations [four marine (Anilao, San Luis, Calatagan, and Balayan) and two freshwater (Palanas and Pansipit)] in Balayan Bay, Batangas, Philippines were examined monthly for one year (February 2006–January 2007). A total of 97 taxa of phytoplankton in four phyla were observed. About 85% of these taxa were diatoms (Bacillariophyta). The mean monthly density of phytoplankton ranged from 2,367 (Pansipit Station) to 2,992 units · mL–1 (San Luis Station), with as much as 93% of the total phytoplankton density being made up of diatoms. Cyclotella meneghiniana, a centric diatom, had the highest mean monthly density (143 units · mL–1) in all the stations. Among the six stations, the marine stations generally showed higher phytoplankton density (maximum monthly value = 4,700 units · mL–1, Anilao, in January), species diversity index (maximum monthly value, H’ = 1.402, Balayan, in March), and species richness (maximum monthly value, 29, Balayan, in March) than the freshwater stations. Clear differences were also detected in the physico-chemical characteristics between the freshwater and marine stations. Among the 10 abiotic parameters monitored, mean monthly salinity ranged from 0.92–1.02 psu in freshwater stations and 29.1–32.6 psu in marine stations. Mean monthly water temperatures ranged from 23–33.5 °C and pH ranged from 7.87–8.23. Conductivity in the two freshwater stations ranged from 2,006.17–2,051.92 μS · cm–1 and was 45x of that of the marine stations, which ranged from 44.57–50.48 μS · cm–1. Generally, marine stations showed higher values of total solids, total dissolved solids, and total suspended solids than the freshwater stations. However, marine stations recorded greater water clarity than the freshwater stations (mean monthly depth of Secchi disc ranged from 1.68–3.65 m). Freshwater stations recorded higher mean monthly orthophosphate-P values but generally lower nitrate-N values than the marine stations. These values (1.65–4.31 ppm PO4-P or 0.29–1.41 ppm P; 2.58–5.35 ppm NO3-N or 0.428–1.509 ppm N) are within or near the Philippine standard value of 1.0 ppm for P and N for clean marine water. Changes in some of these abiotic parameters were correlated with changes in the population density of some of the dominant species, to total mean monthly phytoplankton density, species diversity index, and species richness in some of the stations, but no single parameter can explain the biological patterns observed for all stations. No algal bloom was observed during the course of this study, although a potentially harmful dinoflagellate, Ceratium furca, was observed. It was never a dominant alga in any of the stations.

Phytoplankton Community in Relation to Environmental Variables in the Tidal Mangrove Creeks of the Pasur River Estuary, Bangladesh

The Pasur River estuary (PRE) provides vital fishery resources and supports millions of livelihoods in the southwestern coastal region of Bangladesh. Our research focused on phytoplankton community assemblages, alpha diversity indices, and the seasonal succession of major phytoplankton species in relation to physicochemical parameters in the tidal mangrove creeks of the Pasur River estuary. Spatial and temporal variations were assessed by water sampling at 17 stations in the study area from January to December 2019. The mean salinity level in the tidal mangrove creeks of the PRE was significantly (p < 0.05) higher during the dry season than during the wet season. Spatially, no significant variation (p > 0.05) was observed in the dissolved inorganic nitrogen and dissolved inorganic phosphorus between PRE and mangrove creeks, but temporally, the variables varied significantly (p < 0.05). Spatially, no significant variation (p > 0.05) was observed in the alpha diversity of the phytoplankton community but significantly (p < 0.05) varied temporally. Blue-green algae became dominant in the oligohaline conditions during the wet season, while diatoms were dominant during the dry season which severely depleted dissolved silica. In terms of phytoplankton species diversity, our study classifies the study areas as highly diversified zones. Phytoplankton succession from diatoms (dry season) to blue-green algae (wet season) is attributed to the changes in the physicochemical and nutrient parameters depending on seasonal environmental parameter fluctuations. This study illustrated that phytoplankton diversity and density varied with the degrees of habitat and seasonal changes, implying the potential impacts of anthropogenic activities and natural causes on their community structure in tropical estuaries and mangrove creeks.

Evaluation of Factors Affecting Tree and Shrub Bark's Antioxidant Status.

The importance of using the barks of trees and shrubs as powerful natural antioxidants suggests the necessity to evaluate the effect of different environmental factors on bark extracts’ quality. The determination of total antioxidant activity (AOA) and polyphenol content (TP) in the bark of 58 tree and shrub species from 7 regions differing in mean annual temperature, insolation, humidity, salinity level, and altitude was performed. The above stress factors positively affected bark AOA but did not have a statistically significant effect on TP. The bark of trees grown in the seashore proximity was characterized by significantly higher AOA than samples gathered in other areas, similarly to the trees grown at high altitude. The bark antioxidant status of 18 species was described for the first time. New sources of powerful antioxidants were represented by the ornamental shrubs Cornus sanguinea and Cornus alba, which showed the highest AOA (169–171 mg GAE g−1 d.w.). Among the typical halophytes, Calligonum and Tamarix had high AOA (172 and 85 mg GAE g−1 d.w.), while in the bark of tamarisk, an Se accumulator, an Se concentration of about 900 µg kg−1 d.w. was recorded. A significant positive correlation was found between leaves and bark AOA in the Karadag Nature Reserve’s deciduous trees (r = 0.898, p < 0.01). The relationship between bark AOA and TP was highly significant (r = 0.809; p < 0.001) for all samples except the mountainous ones. The results of the present research revealed new opportunities in successive bark utilization.

TIMCOM model datasets for the CMIP6 Ocean Model Intercomparison Project

The participation of the Taiwan Multi-scale Community Ocean Model (TIMCOM) in the Ocean Model Intercomparison Project (OMIP) experiments is introduced here, as part of phase 6 of the Coupled Model Intercomparison Project (CMIP6). Two ocean–sea ice model experiments are compared: (a) OMIP1, forced by the Coordinated Ocean-Ice Reference Experiments Phase II data (1948–2009), and (b) OMIP2, forced by JRA55-do data (1958–2018). The observed annual means and the interannual variability of physical states are reasonably captured in both experiments, but improved mean temperatures and salinities are found in OMIP2. The weaker winds and stronger freshwater discharge in the OMIP2 forcing contribute to some simulated differences between OMIP1 and OMIP2. Many patterns and biases are similar to those found in other modeling efforts, confirming the common systematic biases. However, a few unique features are found in this study, including the recent increase of the Atlantic Meridional Overturning Circulation (AMOC) that has been observed in the last decade and a generally higher Drake Passage transport. The enhanced AMOC can be explained by the recent cooling event over the North Atlantic, which thermally increased the surface density flux. The higher Drake Passage transport compared to observations is possibly linked to a stronger bottom cell of meridional circulation and a smaller Antarctic sea-ice extent.

Widespread declines in water salinity of the endorheic Tibetan Plateau lakes

The Tibetan Plateau (TP) hosts more than one thousand lakes (>1km2) in its endorheic basins. The changing climate in recent decades has led to significant modifications in the endorheic hydrologic system. Most TP lakes experienced dramatically expanding areas, rising water levels, and increasing storage, which inevitably influenced the lake salinity. This study provides a regional-scale investigation of water salinity changes of the TP lakes (for 83 lakes with two-epoch salinity records, among the approximately 160 lakes >50km2) by synthesizing multi-source data around the 1970s and 2010s. Our results reveal lake salinity has considerably declined for most expanding lakes across the endorheic basins. The mean salinity of 62 terminal lakes dropped from 92.76 g l−1 to 42.00 g l−1 during the 1970s–2010s, in contrast to the slight variations (3.42 g l−1 to 1.48 g l−1) of the 21 exorheic or upstream lakes. As a result, many hypersaline lakes have become polysaline or oligosaline lakes, such as Cedo Caka, Norma Co, etc. In particular, some large lakes (e.g., Siling Co, ‘Twin Lakes’, and Ayakkum Lake) also experienced significant drops in water salinity, with the exceptional cases for Nam Co and Qinghai Lake probably due to the relatively low ratios of increased water mass to their net storages. The widespread declining water salinities could greatly influence bacterial richness, diversity, and evenness, and affect the aquatic carbon cycle and utilization in the high-altitude endorheic lakes. More attention should be paid on understanding the saline lake ecosystem evolution and the regional carbon cycle in response to changing water salinity of the TP lakes.

Long-term ecological trajectories of a disturbed Mediterranean coastal lagoon (Biguglia lagoon): Ecosystem-based approach and considering its resilience for conservation?

Coastal lagoons are subjected to ever-increasing direct or indirect anthropic pressures and are inexorably deteriorating with serious issues regarding their resilience. In this paper, we assessed the functioning and evolution of the highly disturbed Biguglia coastal lagoon (Mediterranean Sea, Corsica) through an ecosystem-based approach (EBA), using multiple biotic and abiotic proxies (hydro-climatic context and eutrophication), considering its connectivity to sea and watershed and biological compartments (macrophytes, phytoplankton, and invasive species) and taking into account human influence (management actions and fishing activities). The aim of this work is firstly to provide a comprehensive analysis of its long-term (2000–2021) ecological evolution trajectory and then, based on these results, to anticipate management strategies for supporting its conservation and restoration, and the maintenance of ecosystem services it offers. Results revealed that while the lagoon showed these days a good capacity to recover after disturbance and absorb change, it recently exhibited considerable changes in its phytoplankton community composition, developed an increased susceptibility to biological invasion, and experienced a drastic reduction in fish stocks. The major interannual variations of the mean salinity, strongly dependent on management interventions beyond natural climatic variability, summarized this instability. In the future, the lagoon may no longer be able to cope with even small disturbances, which could then be sufficient to reach a breakpoint and tip the system permanently into undesired/degraded states. We demonstrated that local and punctual management actions are not always beneficial for the entire ecosystem or even detrimental in some instances. Such a retrospective ecosystem-based approach is fundamental for producing the holistic insights required to implement efficient integrated ecosystem management. This further helps enhance lagoon resilience and hence preserve its ecosystem services in the context of increasing global changes. Such lessons are useful anywhere for comparable ecosystems.

Assessment of Water Quality Index in Anzali Lagoon using Multivariate Analysis.

&lt;b&gt;Background and Objective:&lt;/b&gt; Water quality in freshwater bodies is involved with multiple aspects such as physical, chemical and biological processes and their interactions. Due to the vulnerability of water resources, quality control of surface water is one of the key issues in environmental conservation programs. The objectives of the present work were to study the water quality in the Anzali Lagoon and to study the classification of water based on the water quality index in different parts of the Anzali Lagoon. &lt;b&gt;Materials and Methods:&lt;/b&gt; In this study, we sampled water from January to December, 2015 in the Anzali Lagoon. All physicochemical parameters were sampled and determined according to standard methods. &lt;b&gt;Results:&lt;/b&gt; The Water Quality Index results showed the Anzali Lagoon water quality had been "medium" in site 1 and "bad" in sites 2, 3 and 4. The result showed a significant difference between sit 1 and sites 2, 3 and 4 (p<0.05). However, there was no significant difference between sit 2, 3 and 4 (p>0.05). The result showed a clear spatial separation among parts in the Anzali Lagoon. The Eastern part of the Anzali Lagoon showed lower water quality compared to the central and western stations. &lt;b&gt;Conclusion:&lt;/b&gt; This study showed that the level of pollution was different on all of the Anzali Lagoons. The water of the Anzali Lagoon has different quality classes according to the aggregation methods employed. Nutrient loadings from the adjacent agricultural lands combined with high mean salinity values affect all organism conditions. The three primary sources of nutrients, including fertilizers used in agriculture, household waste and livestock waste, reduced the water quality of the Anzali Lagoon.

Factors associated with the differential distribution of cetaceans linked with deep habitats in the Western Mediterranean Sea

Deep-habitat cetaceans are generally difficult to study, leading to a limited knowledge of their population. This paper assesses the differential distribution patterns of three deep-habitat cetaceans (Sperm whale—Physeter macrocephalus, Risso’s dolphin—Grampus griseus & Cuvier’s beaked whale—Ziphius cavirostris). We used data of 842 opportunistic sightings of cetaceans in the western Mediterranean sea. We inferred environmental and spatio-temporal factors that affect their distribution. Binary logistic regression models were generated to compare the presence of deep-habitat cetaceans with the presence of other cetacean species in the dataset. Then, the favourability function was applied, allowing for comparison between all the models. Sperm whale and Risso’s dolphin presence was differentially favoured by the distance to towns in the eastern part of the western Mediterranean sea. The differential distribution of sperm whale was also influenced by the stability of SST, and that of the Risso’s dolphin by lower mean salinity and higher mean Chlorophyll A concentration. When modelling the three deep-habitat cetaceans (including Cuvier’s beaked whale), the variable distance to towns had a negative influence on the presence of any of them more than it did to other cetaceans, being more favourable far from towns, so this issue should be further investigated.

Fish Diversity in Relation to Salinity Gradient in the Meghna River Estuary, Bangladesh

Variation in salinity is one of the major environmental factors influencing the species diversity of fish in an estuary. Therefore, evaluating the relationship between salinity and species diversity is important. In this study, fish diversity was assessed by fish sampling and visiting local fish markets from February to November 2021. Mean salinity was 10.59 psu (Practical Salinity Unit) and 0.46 psu during the dry and wet seasons, respectively. Harpadon nehereus, Odontamblyopus rubicundus and Pseudapocryptes elongatus species were found as polyhaline (0.06~18.1 psu) species. Anguilla japonica and Arius gagora were abundant in brackish water conditions (0.35~14.2 psu). However, Acanthopagrus latus and Setipinna phasa were found in freshwater conditions (0.06~0.11 psu). The suitability index indicates that commercially important fish species such as Liza parsia, Macrobrachium rosenbergii, Mugil cephalus, Penaeus monodon and Scylla serrata can be used for mariculture during the dry season, and Acanthopagrus latus, Pethia canius and Setipinna phasa during the wet season. Overall, these findings suggest that salinity, water temperature, and chlorophyll-a had a significant (p &lt; 0.05) effect on the fish distribution and assemblage composition in the study area. This finding will be helpful in developing policies for the conservation and management of the aquatic resources in the coastal zone to enrich the blue economy.

Relative RSC tolerance of groundnut

A pot experiment was conducted during summer-2019 to evaluate four varieties of groundnut with four RSC level of irrigation water, A0, A1, A2 and A3 - 0, 2.5, 5.0 and 7.5 meq L-1, respectively, at Department of Agricultural Chemistry and Soil Science. Junagadh Agricultural University, Junagadh. The pod yield of different varieties of groundnut significantly decreased with increasing in the RSC levels of irrigation water. Among the different varieties of groundnut, variety TPG-41 gave highest pod yield (8.41 g pot-1) at RSC level of 0 meq L-1 of irrigation water. The variety TPG-41 recorded highest mean pod yield (7.82 g pot-1), mean salinity index (92.96 %) minimum yield reduction (11.72) at high RSC levels (7.5 meq L-1) and 50 % yield decline at 30.40 meq L-1.

Impact of Riverine Fresh Water on Indian Summer Monsoon: Coupling a Runoff Routing Model to a Global Seasonal Forecast Model

Rivers form an essential component of the earth system, with ~36,000 km3 of riverine freshwater being dumped into the global oceans every year. The role of rivers in controlling the sea-surface salinity and ensuing air-sea interactions in the Bay of Bengal (BoB) is well-known from observational studies; however, attempts to include rivers in coupled models used for seasonal prediction have been limited. This study reports the benefits of river routing in coupled models over prescribing observational river discharge and the impact on the Indian Summer Monsoon (ISM) simulation. Seasonal hindcasts are carried out using a state-of-the-art global coupled ocean-atmosphere-land-sea ice model, Climate Forecast System version 2, coupled to a runoff routing model. It is demonstrated that such a coupling leads to a better representation of the upper ocean stratification in northern BoB, causes mixed layer warming during July-August, and imparts a significant inter-annual variability to the mixed layer heat budget. The rainfall-runoff coupled feedback associated with ISM is captured better, and remote teleconnections with the equatorial Pacific are enhanced. Improved seasonal mean temperature and salinity profiles in the northern BoB lead to the formation of a thicker barrier layer, which is closely tied to the freshwater from rivers. These processes result in an overall enhancement of the ISM rainfall simulation skill, which stems from scale interactions between the sub-seasonal and seasonal variability of ISM. A significant community effort is required to reduce biases in land-surface processes to improve streamflow simulations, along with better parameterization of mixing of river water with the ocean.

Classification of groundwater using multivariate statistical methods: a case study from a part of Haryana, northwestern India.

This article aimed to estimate the local underground water associations, which will, in turn, be applied to discuss the location of each underground water cluster in the flow system. Additionally, this investigation intended to evaluate underground water's aptness from aquifers of the study area for domestic agricultural activities and the prime sources of alteration in the water chemistry. Geographically, the region does not have the privilege of the river (except the Yamuna in the eastern part) running through it and thus, has to rely heavily on groundwater. Therefore, it is necessary to study the groundwater characteristics in this region. This investigation manifested two sub-surface water associations (groups) showing two prime underground water types in the study area: the calcium-magnesium-bicarbonate water-types, groups (clusters) 1 member; and the sodium-bicarbonate-chloride water-types consisting of Group 2 members during post-monsoon and pre-monsoon periods. Group 1 is typical of underground water in recharge regions of the underground water flow system. It is the cleanest underground water type in part except for a few groundwater samples. The highest mean salinity was vested in group 2, the signature of underground waters in discharge regions of the underground water flow system. This investigation observes that three principal elements controlled the hydro-chemistry of underground water in the study area: chemical fertilizers from farms, carbonate mineral weathering, calcite, fluorite, silicate minerals, and exchange of cations in the region. All the underground water groups had high sodium (Na) concentrations and will cause the Na-hazard when applied for agricultural activities. Most samples of groups 1 and 2 were within the class II and I area of Doneen's plot during both periods and were therefore acceptable for agricultural activities in the investigation region.

Effects of environmental factors on the distribution of microbial communities across soils and lake sediments in the Hoh Xil Nature Reserve of the Qinghai-Tibetan Plateau

Comparison of microbial community diversity and composition of terrestrial and aquatic ecosystems in undisturbed regions could expand our understanding on the mechanisms of microbial community assembly and ecosystem responses to environmental change. This study investigated the spatial distribution of bacterial community diversity and composition in the lakeshore soils and lake sediments from one of the best preserved nature reserves, Hoh Xil on the Qinghai-Tibetan Plateau, and explored the corresponding environmental drivers. A total of 36 sediment and soil samples were collected from six alpine lakes and the corresponding shore zones, and their bacterial community structure was identified by high-throughput 16S rRNA gene sequencing. Significant difference (p < 0.05) in diversity and composition of bacterial communities between the soils and sediments was observed. Heterogeneous selection played a dominant role in shaping the spatial variations of bacterial communities between the soils and sediments. Results of canonical correspondence analysis showed that the difference in composition of bacterial communities at OTU level between the soils and sediments was mainly determined by the mean annual temperature, salinity, and contents of total organic carbon and total nitrogen. Structural equation modeling revealed that salinity played a significantly direct role in soil bacterial composition, while mean annual temperature indirectly affected the bacterial composition mainly through changing soil salinity. In contrast, the sediment bacterial composition was directly influenced primarily by the contents of total organic carbon and total nitrogen, while pH also had an important indirect effect on sediment bacterial composition. These results shed light on the distribution patterns of bacterial communities between lakeshore soils and lake sediments in high-altitude permafrost regions, and the major ecological processes and environmental drivers that shaped their bacterial communities, and provide insight into the mechanisms underlying microbial community assembly in such regions.

Salinity as a Determinant Structuring Microbial Communities in Coastal Lakes.

The response of bacterioplankton structure to salinity level in coastal lakes (n = 9) along the southern Baltic Sea coastline was studied. In terms of mean salinity levels (0.2–5.2 PSU), the lakes represented freshwater, transitional, and brackish types. Results showed that salinity determines the spatial and seasonal distribution patterns of microorganisms in costal lakes. Increased salinity contributed to a significant decline in total bacterial numbers (TBN). The TBN was lowest in brackish lakes in autumn (4 × 106 cells/mL) and highest in freshwater lakes in summer (7.11 × 106 cells/mL). The groups of Proteobacteria are appropriate bioindicators in any classifications of coastal ecosystems, particularly at low-haline stress. Alpha- and Gamma- subclasses of Proteobacteria are identifiers for brackish habitats, while Betaproteobacteria, due to their intolerance to haline stress, prefer freshwater habitats. Counts of euryhaline Actinobacteria, the dominant group of bacterioplankton (31.8%), decreased significantly with increased salinity. Actinobacteria and Deltaproteobacteria were identifiers of transitional lakes. Cytophaga-Flavobacteria showed affinity with freshwater ecosystems, but this relation was not statistically significant (p > 0.05). The bacteria groups correlated with other physico-chemical parameters of water, such as oxygenation (Actinobacteria) or organic carbon (Betaproteobacteria, Deltaproteobacteria). The impact of hydrological connectivity and salt-water interference on the microbiota structure and biogeochemistry of coastal waters should be considered in the assessment of the ecological status of coastal lakes.

Groundwater Quality Assessment of Ikorodu Local Government Area of Lagos State in Nigeria

An assessment of the quality of groundwater in Ikorodu Local Government Area (LGA) was carried out in September 2020 (Late wet season). A total number of 29 samples were collected from different selected locations of the study area. The samples were collected from private and government bore holes. The pH, Total dissolved solids (TDS), Salinity, Turbidity, Hardness, Biochemical oxygen demand (BOD), Chemical oxygen demand (COD), Phosphate, Nitrate, Sulphate, and Total bacterial count (TBC) were determined according to American Public Health Association (APHA) standard techniques. The results showed that the mean pH, TDS, Salinity, Turbidity, Hardness, BOD, COD, Phosphate, Nitrate, Sulphate, and TBC in the water samples were 7.0 ±0.59, 176.0 ±132.2mg/L, 0.14 ±0.11g/kg, 0.32 ±0.05 NTU, 59.58 ±34.89mg/L, 11.59 ±3.41mg/L, 14.90 ±4.18mg/L, 0.97 ±0.46mg/L, 2.62 ±1.27mg/L, 9.44 ±5.94mg/L, and 4.92 ±2.94 x 102 cfu/mL, respectively. The calculated Water quality index (WQI) of the different sampling points showed the least WQI was 50.3 and the highest WQI was 66.9. Overall, the WQI indicated “Poor” quality of groundwater in the Ikorodu Local Government Area of Lagos State.

Effects of Temperature and Salinity on Surface Currents in the Equatorial Pacific

AbstractSurface currents in the equatorial Pacific play a key role in determining thermohaline structures in the upper ocean, thus acting to modulate the tropical Pacific mean state and interannual variability. In turn, the thermohaline structure and its variability can also affect surface currents by changing ocean density and pressure gradients. Currently, the thermohaline effects on the surface currents have not been well understood, especially for the salinity role. In this study, the thermohaline effects on surface currents in the equatorial Pacific are systematically evaluated based on an analytical scheme, which is used to calculate surface currents in producing the Ocean Surface Current Analysis Real‐time (OSCAR) product. Several calculations are performed with the original OSCAR‐based scheme and an improved scheme including the salinity effect. It is demonstrated that the thermohaline effects are generally dominated by the temperature role, but the salinity effect plays a non‐negligible role near the dateline and in the far eastern Pacific. The thermohaline effects are quantified and highlighted on seasonal and interannual time scales. For annual mean surface currents, temperature and salinity effects work together to weaken zonal currents north of the equator, with their reduced amplitude by about half. Seasonally, the thermohaline effects are dominant in spring due to the weakened wind effect. Interannually, the salinity effect explains up to 25% of the total variance in the far eastern equatorial Pacific. This study highlights the substantial contributions of thermohaline anomalies to surface current variabilities, in which salinity can play an important contributing role.

Indian Ocean Subtropical Underwater and the Interannual Variability in Its Annual Subduction Rate Associated with the Southern Annular Mode

Abstract In this study, the Indian Ocean Subtropical Underwater (IOSTUW) was investigated as a subsurface salinity maximum using Argo floats (2000–20) for the first time. It has mean salinity, potential temperature, and potential density values of 35.54 ± 0.29 psu, 17.91° ± 1.66°C, and 25.56 ± 0.35 kg m−3, respectively, and mainly extends between 10° and 30°S along the isopycnal surface in the subtropical south Indian Ocean. The annual subduction rate of the IOSTUW during the period of 2004–19 was investigated based on a gridded Argo dataset. The results revealed a mean value of 4.39 Sv (1 Sv ≡ 106 m3 s−1) with an interannual variability that is closely related to the southern annular mode (SAM). The variation in the annual subduction rate of the IOSTUW is dominated by the lateral induction term, which largely depends on the winter mixed layer depth (MLD) in the sea surface salinity (SSS) maximum region. The anomalies of winter MLD are primarily determined by SAM-related air–sea heat flux and zonal wind anomalies through modulation of the buoyancy. As a result, the annual subduction rate of the IOSTUW generally increased when the SAM index showed negative anomalies and decreased when the SAM index showed positive anomalies. Exceptional cases occurred when the wind anomaly within the SSS maximum region was weak or was dominated by its meridional component. Significance Statement The Indian Ocean Subtropical Underwater (IOSTUW) is characterized as a subsurface salinity maximum in the subtropical south Indian Ocean, and it has potential contribution to regional sea level change and interoceanic salinity exchange. The purpose of this work is to give a more precise description of the IOSTUW and to better understand the formation process of this water mass. Our results shine new light on hydrological characteristics of the IOSTUW based on an observational dataset collected during the past two decades. In addition, the formation of the IOSTUW was found to be closely related to the leading mode of variability in the atmospheric circulation of the Southern Hemisphere though air–sea heat flux and surface wind anomaly.

Observed poleward freshwater transport since 1970.

Warming-induced global water cycle changes pose a significant challenge to global ecosystems and human society. However, quantifying historical water cycle change is difficult owing to a dearth of direct observations, particularly over the ocean, where 77% and 85% of global precipitation and evaporation occur, respectively1-3. Air-sea fluxes of freshwater imprint on ocean salinity such that mean salinity is lowest in the warmest and coldest parts of the ocean, and is highest at intermediate temperatures4. Here we track salinity trends in the warm, salty fraction of the ocean, and quantify the observed net poleward transport of freshwater in the Earth system from 1970 to 2014. Over this period, poleward freshwater transport from warm to cold ocean regions has occurred at a rate of 34-62 milli-sverdrups (mSv = 103 m3 s-1), a rate that is not replicated in the current generation of climate models (the Climate Model Intercomparison Project Phase 6 (CMIP6)). In CMIP6 models, surface freshwater flux intensification in warm ocean regions leads to an approximately equivalent change in ocean freshwater content, with little impact from ocean mixing and circulation. Should this partition of processes hold for the real world, the implication is that the historical surface flux amplification is weaker (0.3-4.6%) in CMIP6 compared with observations (3.0-7.4%). These results establish a historical constraint on poleward freshwater transport that will assist in addressing biases in climate models.