Water Quality In Estuaries Research Articles

Ecotoxicology assay for the evaluation of environmental water quality in a tropical urban estuary.

Most studies evaluating the impacts of river pollution in the semi-arid region of Brazil have been geared towards physiochemical analyses, and investigations of the adverse effects of water pollution on associated organisms are scarce. This study aimed to evaluate the water quality in the Poxim river estuary in Aracaju, Sergipe throughout the dry and rainy season by evaluating the survival of the microcrustacean Mysidopsis juniae and physicochemical analyses. The evaluation of physiochemical parameters revealed a decrease in dissolved oxygen content in the rainy season. However, there was a significant reduction in microcrustacean survival in samples during the dry season, when the river flow is reduced and effluents become concentrated. These results suggest that pollutants received and carried by the waters of the Poxim River contribute to the reduction of environmental quality in the estuary, and this impact may vary according to dry and rainy patterns, that are uncertain considering the impacts of climate change on tropical regions.

Assessing and planning future estuarine resource use: A scenario-based regional-scale freshwater allocation approach

Rapid urbanisation and industrial growth in South Africa increases the need for proactive allocation of freshwater resources on a regional scale. A nine-step method is described that sets long-term targets for water resource condition and future use with a focus on estuary water quantity and quality requirements. The approach specifically focuses on the environmental flow allocation to estuaries, nested within a broader, regional (multi-catchment and multi-estuary) water resource landscape. The method differs to most other approaches in that the responses of multiple estuaries to escalating future development in a region are coherently quantified (versus only considering a single estuary in a single catchment). A case study that assessed the health, biodiversity importance and resilience to current and future pressures of 64 estuaries is used to illustrate the method. Projected growth in the study area was integrated into a range of future dam development and wastewater discharge scenarios. The results showed that estuaries around the urban centres were in poor condition, but those in the more rural areas in a more natural state. As a result of their small size, most of the estuaries in the region had little resilience to changes in freshwater quantity and nutrient loading. In contrast, the larger systems, targeted for dam development, only showed sensitivity to water abstraction during low-flow periods when base-flow reduction caused mouth closure and changes in nutrient processes. Broadly, the approach aimed to find a balance between ecological requirements and socio-economic development, which meant that maintaining larger systems in relatively good condition would be at the expense of smaller systems that are already in a poor condition. The approach developed was successful in quantifying the responses of multiple estuaries to escalating future pressures on a regional scale, and could be replicated to assist in managing water resources elsewhere in data-limited environments.

Periphython Epilithic Community Structure in Cikamal Estuary and Cirengganis Estuary, Pananjung Pangandaran, West Java

Nailah S, Rosada KK. 2018. Periphython Epilithic Community Structure in Cikamal Estuary and Cirengganis Estuary,Pananjung Pangandaran, West Java. Pros Sem Nas Masy Biodiv Indon 4: 236-241. Periphyton is one of the biotic communities that canlive well in the waters. Epilithic periphyton is cosmopolitan and allows standardization for spatial or temporal comparisons, therefore itis often used to determine the quality status of a water. The purpose of this research is to know the structure of epilithic periphytoncommunity in Estuary of Cikamal River and Estuary of Cirengganis River Pananjung Pangandaran. The method used is exploration. Ineach study site, samples of periphyton and water were taken. At the time of sampling, physicochemical parameters measured weretemperature, brightness, depth, light intensity, salinity, current velocity, pH, and DO. The results showed that the periphyton in bothestuaries consisted of phytoplankton, zooplankton, and microbenthos. In general, the abundance of phytoplankton is higher compared tothe other two groups. Periphyton in Estuary of Cikamal River found 19 species of phytoplankton, one type of zooplankton, and one typeof microbenthos, while in Estuary of Cirengganis River found 24 types of phytoplankton, nine types of zooplankton, and three types ofmicrobenthos. Periphyton density at Estuary of Cirengganis River is higher than periphyton at Estuary of Cikamal River. The higherdiversity of periphyton species is found in Estuary of Cirengganis River. The periphyton at the Estuary of Cirengganis River has ahigher evenness than the periphyton at the Estuary of Cikamal River. One species that dominates on both estuaries is Navicula sp. Basedon the Sorensen similarity index, both estuaries have a moderate level of community similarity. The water quality of Estuary of CikamalRiver is included into the heavily polluted waters whereas the Estuary of Cirengganis River belongs to the medium contaminated waters.

Artificial neural networks as emulators of process-based models to analyse bathing water quality in estuaries

This study aims to provide a method for developing artificial neural networks in estuaries as emulators of process-based models to analyse bathing water quality and its variability over time and space. The methodology forecasts the concentration of faecal indicator organisms, integrating the accuracy and reliability of field measurements, the spatial and temporal resolution of process-based modelling, and the decrease in computational costs by artificial neural networks whilst preserving the accuracy of results. Thus, the overall approach integrates a coupled hydrodynamic-bacteriological model previously calibrated with field data at the bathing sites into a low-order emulator by using artificial neural networks, which are trained by the process-based model outputs. The application of the method to the Eo Estuary, located on the northwestern coast of Spain, demonstrated that artificial neural networks are viable surrogates of highly nonlinear process-based models and highly variable forcings. The results showed that the process-based model and the neural networks conveniently reproduced the measurements of Escherichia coli (E. coli) concentrations, indicating a slightly better fit for the process-based model (R2 = 0.87) than for the neural networks (R2 = 0.83). This application also highlighted that during the model setup of both predictive tools, the computational time of the process-based approach was 0.78 times lower than that of the artificial neural networks (ANNs) approach due to the additional time spent on ANN development. Conversely, the computational costs of forecasting are considerably reduced by the neural networks compared with the process-based model, with a decrease in hours of 25, 600, 3900, and 31633 times for forecasting 1 h, 1 day, 1 month, and 1 bathing season, respectively. Therefore, the longer the forecasting period, the greater the reduction in computational time by artificial neural networks.

Water Distribution System of Petanu River Estuary for Coastal Area in Bali-Indonesia

Quantity and quality of water is needed along with the increase of population, the increasing change of agricultural land function and tourism development in Bali. This means that the need for domestic and non-domestic water will also increase, thus research on water quality in river estuary, water resources for water and land conservation in Gianyar regency of Bali province is indispensable for sustainability of water supply in terms of water quantity and quality, river area, and water management and land allotment in accordance with existing watershed conditions in Gianyar regency of Bali province in order to reduce land conversion change (Gianyar in figures 2010-2015) and village nomography. Raw Water Distribution (SPAB) in the downstream of Petanu river with SWOT analysis beginning to be managed by indigenous society and based environment. Research method used is quantitative research. This research used primary data in the form of water quality and water quantity data in downstream of Petanu River, population in coastal area of Gianyar Regency, topography data, bathymetry in coastal area of Gianyar Regency, and environmental condition of downstream of Petanu river. The downstream water potential streaming is designed using WATERNET software which is then applied to the Raw Water Flow System in the downstream area of the Petanu river which will be managed by indigenous villagers. The results of this study resulted in water quality at the mouth of the river for odor, color, taste, temperature, turbidity, pH and detergent meet quality standards, while salinity, BOD and COD as well as total coliform does not meet the quality standard, class I. The simulation result from WATERNET shows that the discharge of the river amounted to 20 million m3/year can be utilized for industrial water (hotel) 1,636 rooms, for domestic water 98,181 inhabitant, for 2.33 ha pool water managed by indigenous villagers for the coastal society of Saba Gianyar Regency.

Application of 1D–2D coupled modeling in water quality assessment: A case study in Ca Mau Peninsula, Vietnam

A few 1D and 2D models are used to simulate and calculate the water level and water quality regarding four state variable (DO, NH4, NO3, and BOD) observations in the main rivers and coastal estuaries on the Ca Mau peninsula. This study calibrates and validates 1D and 2D models during the dry and flood seasons for 2014 and 2015, as well as assesses water quality in coastal estuaries during the dry and flood season of 2016 by using a 2D model. The calibration and validation results of the hydrodynamic 1D and 2D models show that there is a high degree of conformity regarding the phase and amplitude of water level at observing stations with mean absolute error (MAE) ranges from 0.05 m to 0.37 m. The RMSE–observation standard deviation ratio (RSR) vary from 0.12 to 0.64, and the percent bias (PBIAS) is from −8.9% to 3.2%. Calibration and validation of water quality parameter (DO, NH4, NO3, and BOD5 concentration) results have a high correlation coefficient during both the dry and flood season of 2014 and 2015. The standards, originating from the National Technical Regulation on Surface Water quality and on Coastal Water Quality, are used to evaluate pollutant concentrations in estuaries in the study area during the dry and flood seasons of 2016. The water quality parameters contain DO (4.6 mg/l–7.9 mg/l) and BOD (4.6 mg/l–10.7 mg/l) concentrations over the National Technical Regulation on Surface and Coastal Water Quality and the A1 limit with DO (>4 mg/l) and BOD5 (4 mg/l) on surface water quality for domestic water use in the dry and flood seasons. The calculated results will help managers make better plans for aquaculture and aquatic conservation zones in coastal estuaries in the future.

Merkuri (Hg) di Permukaan Perairan Muara Sungai Banyuasin, Sumatera Selatan, Indonesia

The purposes of this study were to determine the water quality, concentration and distribution of Hg in the surface water of Banyuasin river estuary. This research was conducted in June 2016 with 26 sampling stations. Measurement of in situ water quality was done using Conductivity Temperature Depth (CTD) multiparameter profiler while Hg metal was measured using Atomic Absorption Spectroscopy (AAS). The data obtained was interpolated by Inverse Distance Weighted (IDW) and then mapped spatially. The results showed that in general the water quality in Banyuasin river estuary still meets the seawater quality standards for marine biota based on KepMenLH no. 51 in 2004. The concentration of Hg in Banyuasin river estuary ranges from 0.001-0.032 mg/L with a distribution pattern that generally increases towards the ocean. The Hg concentration at the Banyuasin river estuary is on the maximum limit and exceeds the quality standard for marine biota.

Using Bayesian networks to predict risk to estuary water quality and patterns of benthic environmental DNA in Queensland.

Predictive modeling can inform natural resource management by representing stressor-response pathways in a logical way and quantifying the effects on selected endpoints. This study demonstrates a risk assessment model using the Bayesian network relative risk model (BN-RRM) approach to predict water quality and, for the first time, eukaryote environmental DNA (eDNA) data as a measure of benthic community structure. Environmental DNA sampling is a technique for biodiversity measurements that involves extracting DNA from environmental samples, amplicon sequencing a targeted gene, in this case the 18s rDNA gene (which targets eukaryotes), and matching the sequences to organisms. Using a network of probability distributions, the BN-RRM model predicts risk to water quality objectives and the relative richness of benthic taxa groups in the Noosa, Pine, and Logan estuaries in Southeast Queensland (SEQ), Australia. The model predicts Dissloved Oxygen more accurately than the chlorophyll a water quality endpoint and photosynthesizing benthos more accurately than heterotrophs. Results of BN-RRM modeling given current inputs indicate that the water quality and benthic assemblages of the Noosa are relatively homogenous across all sub risk regions, and that the Noosa has a 73%-92% probability of achieving water quality objectives, indicating a low relative risk. Conversely, the Middle Logan, Middle Pine, and Lower Pine regions are much less likely to meet objectives (15%-55% probability), indicating a relatively higher risk to water quality in those regions. The benthic community richness patterns associated with risk in the Noosa are high Diatom relative richness and low Green Algae relative richness. The only benthic pattern consistently associated with the relatively higher risk to water quality is high richness of fungi species. The BN-RRM model provides a basis for future predictions and adaptive management at the direction of resource managers. Integr Environ Assess Manag 2019;15:93-111. © 2018 SETAC.

An integrated appraisement of multiple faecal indicator bacteria and sterols in the detection of sewage contamination in subtropical tidal creeks.

The quality of water bodies has been regulated by national environmental agencies and based on faecal indicator bacteria, such as thermotolerant coliforms Escherichia coli and Enterococcus sp. Additionally, faecal sterols (mainly coprostanol) have been used to corroborate sewage discharge in marine environments. In this study, faecal material input was evaluated in two sampling campaigns in transects of two tidal creeks using bacterial and chemical indicators to both compare and establish the water quality in a South Atlantic subtropical estuary. The Itiberê tidal creek (S1) was classified as "contaminated" by faecal material, while the Peças tidal creek (S2) presented variable water quality according to the sampling period and sewage indicators considered in this evaluation. Then, the integrated application of chemical and bacterial indicators was applied for tidal creeks with different sewage contamination levels and under distinct environmental conditions and confirmed that Enterococcus sp. and coprostanol are the most suitable for estuarine environments.

The Impact of Landscape Characteristics on Groundwater Dissolved Organic Nitrogen: Insights From Machine Learning Methods and Sensitivity Analysis

AbstractThe effect of groundwater nutrient inputs on river and estuary water quality and the potential impacts of urbanization on groundwater are central concerns in many coastal areas. It has been previously identified that dissolved organic nitrogen (DON) can be the dominant form of total dissolved nitrogen (TDN) in some aquifers. However, there is a paucity of evidence about the sources and flow paths of DON, relative to inorganic nitrogen in groundwater. DON and dissolved organic carbon/DON were first compared against different landscape variables in this study, and no significant relationships were found. However, the relationships became statistically significant when shallow samples (sampling depth < 10 m) were separated from deep samples. A random forest model and sensitivity analysis were then applied to further our understanding of the ecohydrological drivers and seasonal patterns that shape DON variability. The random forest algorithm was built to classify 171 groundwater wellbores into three classes (low: <0.5 mg/L; medium: 0.5–2.5 mg/L; and high: >2.5 mg/L) which achieved 72% classification accuracy using landscape characteristics, hydrological conditions, and temporal information. The results indicated that the effects of landscapes on sandy shallow groundwater DON were controlled both by certain landscape characteristics and depth to groundwater. A conceptual model of groundwater DON is therefore proposed where the balance of exposure and processing time scales from the surface to groundwater is the critical control on the preservation of landscape signatures; we expect that this conceptual model would be applicable for other sandy, shallow groundwater areas.

Spatio-temporal dynamics of inherent optical properties in oligotrophic northern Gulf of Mexico estuaries

Coastal and estuarine ecosystems provide numerous economic and environmental benefits to society. However, increasing anthropogenic activities and developmental pressure may stress these areas and hamper their ecosystem services. Satellite remote sensing could be used as a tool for monitoring water quality parameters, including inherent optical properties (IOP) in coastal regions. Spatio-temporal information on IOP variability will help in understanding the dynamics of the water quality of estuaries. The objective of this research was to develop a novel hybrid model by combining and parameterizing existing quasi analytical and semi-analytical algorithms to estimate IOPs in four oligotrophic northern Gulf of Mexico Florida estuaries. The hybrid model was applied to above surface remote sensing reflectance data representing the Medium Resolution Imaging Spectrometer (MERIS) and Sentinel-3's Ocean and Land Colour Instrument (OCLI) bands. The hybrid model produced a root means squared error (RMSE) of 0.32 m−1 (13.95% NRMSE) for total absorption (at), 0.21 m−1 (7.61% NRMSE) for detritus-gelbstoff absorption (adg), and 0.09 m−1 (22.77% NRMSE) for phytoplankton pigment absorption (aphi). Results showed that absorption by detritus and gelbstoff (adg) dominates the water in these estuaries. Monthly IOP variability in 2010 revealed that compared to other estuaries, magnitudes of IOPs was the highest in Pensacola Bay and therefore the highest attenuation. Findings also indicated that river discharge and precipitation predominantly govern the IOP variations in all four estuaries, showing an increase in IOP values following the high flow period. The hybrid model improved IOP retrieval in these low chlorophyll-a (Chl-a) estuaries where the existing spectral decomposition models did not perform satisfactorily.

Causes, Assessment, and Treatment of Nutrient (N and P) Pollution in Rivers, Estuaries, and Coastal Waters

As a consequence of industrialization, urbanization, and population growth in the past decades, high nutrient concentrations from point and non-point sources in aquatic systems have caused major problems to the water quality in rivers, estuaries, and coastal waters. Although the nutrient pollution due to land use change cannot be ignored, the combined sewer overflows and discharging sites have been important point sources of nutrient pollution. Integrated hydrodynamic, chemical, and biological models developed in recent years, which simulate the nutrient transportation from both point and non-point sources, are useful tools to assist in identifying the transport and fate of nutrients from both point and non-point sources. In this paper, water quality data from published literature were reviewed and analyzed to evaluate nutrient (N and P) pollution in aquatic systems. An integrated monitoring and management plan should be continuously developed in the future to monitor and regulate nutrient discharges from point and non-point sources.

Characteristics of saltwater intrusion during high and low waters along Sungai Kilim, Langkawi Kedah

Salinity distribution is one of the physical indices that is important to determine water resources management and quality in estuaries. There are many other driven parameters in determining salt intrusion such as tides, river discharge, and river geometry. This paper studies the salinity distribution using the tide driven parameters during high and low waters. The objectives of this study are to obtain the salinity and pH values at different tidal impact of low and high waters in determining one of the physical indices along Kilim River, Langkawi. There were ten different stations with 500 m of interval along the study area starting from the Kilim River Jetty towards the river mouth. The salinity was obtained from six different depths with the reading of pH values and temperature as supporting details of the observation made along the Kilim River, Langkawi. The depth at each station varied from 0.5 to 3.0 m with 0.5 m of interval. Based on the results obtained from this study, the salinity during high water was highly stratified compared to those of low water. The salinity characteristic is important to further research on the impact of sea level rise at the estuaries. The salinity distribution pattern may contribute to the different species of vegetation along the Kilim River, Langkawi. Therefore, this study will help in contributing the mangrove migration for future research.

A preliminary study of marine water quality status using principal component analysis at three selected mangrove estuaries in East Coast Peninsular Malaysia

This research presents marine water quality status in three different mangrove estuaries. The objective of this study is to evaluate the surface water quality of three estuaries in east coast Peninsular Malaysia. The parameters measured were Dissolved Oxygen (DO), pH, Biochemical Oxygen Demand (BOD), total dissolved solid (TDS), ammonium (NH4-N), turbidity (TUR), total suspended solid (TSS) and coliform. Monthly sampling was performed during the dry season, from June 2016 until September 2016. Data were analysed using principal component analysis (PCA). PCA yielded two PCs where VF1 forms strong factor loadings for pH, NH4-N, SAL, and TDS signifying saltwater intrusion in mangrove area. VF2 designed strong factors of BOD, TUR and Coliform and strong negative loading of DO indicating anthropogenic pollutions in the area. This study output will be a baseline setting for future studies in mangrove estuary marine water quality. Mangrove marine water samples of future monitoring studies in mangrove estuary will benefit by enabling understanding of pollution loading and coastal water quality. It is essential to plan a workable water quality modelling as powerful tool to simulate marine water quality and forecast future consequences to facilitate mangrove biodiversity conservation.

Characteristics of Nitrogen Variation and Its Response to Rainfall:A Case Study in Wuxi Port at Taihu Lake Basin

Based on monitoring data of the water quality in the Wuxi port estuary of Taihu Lake from 2010 to 2015, we studied the temporal variation characteristics of nitrogen and its response to rainfall in Wuxi port. The results showed that the pollution level in Wuxi port is serious, with an average annual total nitrogen (TN) concentration of (4.41-5.92 mg·L-1), worse than the water environment quality grade Ⅴ standard (2 mg·L-1). The ammonia nitrogen (NH4+-N) concentration was 1.09-1.72 mg·L-1. The concentrations of TN and NH4+-N showed obvious seasonal variations, with the concentration of TN and NH4+-N in summer and autumn higher than in spring and winter. The concentration of TN in 2015, 2012, and 2011 was 5.92, 5.82, and 5.47 mg·L-1, respectively, which was significantly higher than in 2013 and 2014. The concentration of NH4+-N in 2011 (1.72 mg·L-1) was higher than in 2013 and 2015. With the increase of rainfall intensity, the TN concentration showed an increase after the first downward trend and then a decrease, while the NH4+-N concentration increased first and then decreased. In addition, the nitrogen concentration in the non-flood season was higher than in the flood season.

Local implementation of a national program: The National Estuary Program response following the Deepwater Horizon oil spill in the Gulf of Mexico

The US Environmental Protection Agency's National Estuary Program (NEP) was established in 1987 under the Clean Water Act to improve the water quality and ecological integrity of estuaries of national importance. There are twenty-eight individual local programs in the NEP, covering watersheds in eighteen coastal states and Puerto Rico. Each is charged with bringing together citizens, scientists, businesses and government officials to collaboratively solve environmental problems and promote healthy, vibrant communities. Decisions are based on sound science and actions are implemented using adaptive management strategies. With expertise and comprehensive local networks, each local NEP is able to serve as a foundation for addressing emerging environmental problems, including hazardous events, such as oil spills and hurricanes. An example is the unique role that the NEPs along the Gulf of Mexico played during the Deepwater Horizon oil spill. Immediately following the spill, while federal and state agencies and oil industry experts worked to contain the spill, local communities were faced with conflicting and confusing information about the activities. The NEPs provided credible and continuously-updated information to local communities; led major outreach efforts in their communities concerning the event; and served as conduits for scientific information and data to local, state and federal agency scientists and officials. Gulf NEPs continued to facilitate community involvement and provide long-term assistance to the state and federal recovery efforts along the Gulf, and are now coordinating community-based restoration efforts to assist in the long-term recovery of the resources and communities along the Gulf coast.

Marsh persistence under sea-level rise is controlled by multiple, geologically variable stressors

ABSTRACTIntroduction: Marshes contribute to habitat and water quality in estuaries and coastal bays. Their importance to continued ecosystem functioning has led to concerns about their persistence.Outcomes: Concurrent with sea-level rise, marshes are eroding and appear to be disappearing through ponding in their interior; in addition, in many places, they are being replaced with shoreline stabilization structures. We examined the changes in marsh extent over the past 40 years within a subestuary of Chesapeake Bay, the largest estuary in the United States, to better understand the effects of sea-level rise and human pressure on marsh coverage.Discussion: Approximately 30 years ago, an inventory of York River estuary marshes documented the historic extent of marshes. Marshes were resurveyed in 2010 to examine shifts in tidal marsh extent and distribution. Marsh change varied spatially along the estuary, with watershed changes between a 32% loss and an 11% gain in marsh area. Loss of marsh was apparent in high energy sections of the estuary while there was marsh gain in the upper/riverine section of the estuary and where forested hummocks on marsh islands have become inundated. Marshes showed little change in the small tributary creeks, except in the creeks dominated by fringing marshes and high shoreline development.Conclusions: Differential resilience to sea-level rise and spatial variations in erosion, sediment supply, and human development have resulted in spatially variable changes in specific marsh extents and are predicted to lead to a redistribution of marshes along the estuarine gradient, with consequences for their unique communities.

Natural forcings on a transformed territory overshoot thresholds of primary productivity in the Guadalquivir estuary

A three year-long quasi continuum sampling dataset on the Guadalquivir estuary water quality was used to assess the role of light availability on its biological production. We found that inorganic nutrients within the estuary are very high (with mean values for inorganic nitrogen and phosphorous of 285 and 2.4μM respectively) while phytoplankton biomass remains low most of the time (with a mean value of 2.6mg/m3). A strong relationship between phytoplankton biomass and water turbidity was found indicating that, indeed, light availability is the major constraint of primary production in this system. Most of the time this limitation of primary production is not associated to enhanced turbidity connected to fresh water inputs. Instead, our data indicate that, independently of freshwater inputs, the photosynthesis is restricted by tidal forcings enhancing turbidity in an estuary that has been highly modified. Our results match with classical theories on the functioning of well-mixed, estuarine ecosystems as well as with recent modeling exercises. We also discuss the potential impacts of this particular characteristic of some estuarine systems for their management and regulatory control.

Changes of Benthic Macroinvertebrates in Thi Vai River and Cai Mep Estuaries Under Polluted Conditions with Industrial Wastewater

Abstract The pollution on the Thi Vai River has been spreading out rapidly over the two lasted decades caused by the wastewater from the industrial parks in the left bank of Thi Vai River and Cai Mep Estuaries. The evaluation of the benthic macroinvertebrate changes was very necessary to identify the consequences of the industrial wastewater on water quality and aquatic ecosystem of Thi Vai River and Cai Mep Estuaries. In this study, the variables of benthic macroinvertebrates and water quality were investigated in Thi Vai River and Cai Mep Estuaries, Southern Vietnam. The monitoring data of benthic macroinvertebrates and water quality parameters covered the period from 1989 to 2015 at 6 sampling sites in Thi Vai River and Cai Mep Estuaries. The basic water quality parameters were also tested including pH, dissolved oxygen (DO), total nitrogen, and total phosphorus. The biodiversity indices of benthic macroinvertebrates were applied for water quality assessment. The results showed that pH ranged from 6.4 – 7.6 during the monitoring. The DO concentrations were in between 0.20 - 6.70 mg/L. The concentrations of total nitrogen and total phosphorous ranged from 0.03 - 5.70 mg/L 0.024 - 1.380 mg/L respectively. Macroinvertebrate community in the study area consisted of 36 species of polychaeta, gastropoda, bivalvia, and crustacea, of which, species of polychaeta were dominant in species number. The benthic macroinvertebartes density ranged from 0 - 2.746 individuals/m−1 with the main dominant species of Neanthes caudata, Prionospio malmgreni, Paraprionospio pinnata, Trichochaeta carica, Maldane sarsi, Capitella capitata, Terebellides stroemi, Euditylia polymorpha, Grandidierella lignorum, Apseudes vietnamensis. The biodiversity index values during the monitoring characterized for aquatic environmental conditions of mesotrophic to polytrophic. Besides, species richness positively correlated with DO, total nitrogen, and total phosphorus. The results confirmed the advantage of using benthic macroinvertebrates and their indices for water quality assessment.

A screening model for assessing water quality in small, dynamic estuaries

Despite mounting evidence of the harm associated with excessive nutrient loading to estuaries, tools to translate this body of knowledge into sound environmental management and planning practices in data-poor environments are lacking. In this paper, a design science approach is adopted to develop a screening (box) model for the water quality assessment of South African estuaries. The key design principles are first distilled from literature on the nutrient dynamics and hydro-morphological functioning of small, dynamic, bar-blocked estuaries. The proportional volume contribution of land-based flows (river inflows, diffuse inflows from the peri-catchment, point source discharges) is determined, a water quality class is allocated to each of the inflows, and the overall water quality class for the land-based inflows to an estuary is determined. Taking the percentage mouth closure and the perched nature of the estuaries into account, a WQ Similarity rating is allocated. This similarity rating reflects the degree of similarity of the water quality in the estuary to the reference (natural) water quality. The entire water quality assessment uses readily available information such as land-cover data, legal limits for disposal and water quality monitoring data where they exist, making it suitable for a data-poor environment. The screening model is calibrated and validated on a selection of South African estuaries for which official health condition assessments exist. Results are promising, and the screening model is deemed appropriate for assessing the water quality of individual estuaries and for comparing the sensitivity of multiple estuaries to changes in the volume and nutrient loading of land-based inflows. As such, the screening model can be employed at a regional or national scale for strategic assessments of water quality in small, dynamic estuaries.