Towards the classification of eutrophic condition in estuaries

Lemley, Daniel A.; Adams, Janine B.; Taljaard, Susan; Strydom, Nadine A.

doi:10.1016/j.ecss.2015.07.033

Cited by 78 publications

(39 citation statements)

References 51 publications

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“…Limiting nutrients for microalgal primary production in estuaries (Davis & Koop, 2006; Thomas et al, 2005) can be supplemented by a consistent supply of nutrients by point sources such as WWTW flows. Estuaries exhibit system‐specific responses to eutrophic processes, dependent on the volume of water in the estuary, the status of the estuary mouth, the volume of water inflow to the estuary and the nutrient and organic matter composition in the inflowing waters (Cloern, 2001; Lemley et al, 2015; Nixon, 2009). These interconnections mean that systems that exhibit high levels of nutrient loading will not always exhibit processes characteristic of eutrophication, if freshwater flow volumes are high enough (Eyre, 1998).…”

Section: Discussionmentioning

confidence: 99%

“…Freshwater inflow therefore directly influences residence time and nutrient loading (Howarth & Marino, 2006; Wolanski & Elliott, 2015), which in turn regulates primary production dynamics (Anandraj, Perissinotto, & Nozais, 2007; Eyre, 1998; Howarth & Marino, 2006). A decrease in magnitude of riverine flows may result in lengthened flushing times, decreased magnitude of riverine flows and dilution of nutrient concentrations (De Villiers & Thiart, 2007) and increased mouth closure (Allanson & Winter, 1999; Schumann et al, 1999; Wolanski & Elliott, 2015), thereby influencing the rate at which the process of eutrophication occurs (Ferreira et al, 2011; Lemley, Adams, Taljaard, & Strydom, 2015). For instance, the addition of wastewater flows to two South African TOCEs resulted in eutrophic levels of chlorophyll‐a (Thomas, Perissinotto, & Kibirige, 2005).…”

Section: Introductionmentioning

confidence: 99%

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The importance of climatic variability and human influence in driving aspects of temporarily open‐closed estuaries

Brooker

Scharler

2020

Ecohydrology

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Freshwater availability is a major topic in scientific literature and the public domain.Estuaries are complex and dynamic ecosystems that depend on freshwater inflow from their catchments and exchange with the marine environment. Catchment forcings are subject to shifts in frequency and intensity due to regional hydrological variability over time. Human manipulation of freshwater regimes may further alter this beyond natural variability through flow abstraction and additional inputs in the form of wastewater. To elucidate the effect of climate variability and human activities, we conducted a time series investigation on hydrological drivers into a small South African estuary (uMdloti), representative of temporarily open-closed estuaries. Subsequently, we investigated the ability of the hydrological variables to drive physical parameters and microalgae in the estuary. Freshwater abstraction caused a disconnect between rainfall and river flow, and increased lag times during dry spells, peaking at 115 days. Annual seasonal peaks in rainfall were not represented in river flow due to the dam. Wastewater discharges equate to 4% of the mean annual runoff from the catchment, which has reduced from a natural runoff of 85.8 to 71.9 Mm −3 year −1 . Due to this and damming of catchment flows, wastewater discharging into the estuary was the most important driver of water quality in the system, resulting in increased nutrient and decreased dissolved oxygen concentrations, whereas river flow was an important driver at high flow volumes. An understanding of interaction effects between climatic variability and catchment flow manipulation is vitally important to estuarine management and their ecological viability. K E Y W O R D S climatic variability, estuarine water quality, freshwater abstraction, hydrological drivers, intermittently open-closed lagoons, temporarily open-closed estuaries, wastewater treatment works

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The importance of climatic variability and human influence in driving aspects of temporarily open‐closed estuaries

Brooker

Scharler

2020

Ecohydrology

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“…The discharge exceeds design capacity at the Kelvin Jones, Despatch and KwaNobuhle WWTWs (75 ML•d −1 , 77 ML•d −1 and 79 ML•d −1 respectively; DWA, 2009). Increased stratification, water retention and high nutrient loads favour phytoplankton blooms (Lemley et al, 2015), thus encouraging eutrophic conditions that are now persistent in the estuary.…”

Section: Discussionmentioning

confidence: 99%

“…Eutrophication in South Africa appears to be increasing with persistent phytoplankton blooms being reported in a number of other estuaries (Snow et al, 2000;Kotsedi et al, 2012;Kaselowski and Adams, 2013;Lemley et al, 2018). By applying the pelagic component of a eutrophic condition index, proposed by Lemley et al (2015), the eutrophic condition of the Swartkops Estuary could be assessed (Table 1). Except for dissolved oxygen levels, all the parameters (DIN, DIP and phytoplankton biomass) were classified as being in an overall 'Poor' or 'Very Poor' state, thus indicating the eutrophic or hypertrophic nature of the system.…”

Section: Discussionmentioning

confidence: 99%

Deterioration in the water quality of an urbanised estuary with recommendations for improvement

Adams

Pretorius

Snow

2019

WSA

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Water quality characteristics of the heavily urbanised and industrialised Swartkops River and Estuary in the Eastern Cape have been the focus of several studies since the 1970s. Overloaded and poorly maintained wastewater treatment works (WWTWs), polluted stormwater runoff and solid waste have all contributed to the deterioration in the water quality of the river and estuary. The objective of this study was to determine the current water quality status of the Swartkops Estuary, by investigating spatial and temporal variability in physico-chemical parameters and phytoplankton biomass and where possiblerelate this to historical water quality data. The present study found evidence suggesting that water is not flushed as efficiently from the upper reaches of the estuary as was previously recorded. Reduced vertical mixing results in strong stratification and persistent eutrophic conditions with phytoplankton blooms (> 20 μg chl a·L−1), extending from the middle reaches to the tidal head of the estuary. The Motherwell Canal was and still is a major source of nitrogen (particularly ammonium) to the estuary, but the Swartkops River is the primary source of phosphorus with excessive inputs from the cumulative effectof three WWTWs upstream. An analysis of historical water quality data in the Swartkops Estuary (1995 to 2013) shows that all recorded dissolved inorganic phosphorus measurements were classified as hypertrophic (> 0.1 mg P·L−1), whereas 41% of dissolved inorganic nitrogen measurements were either mesotrophic or eutrophic. If nutrient removal methods at the three WWTWs were improved and urban runoff into the Motherwell Canal better managed, it is likely that persistent phytoplankton blooms and health risks associated with eutrophication could be reduced.

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“…Si un cuerpo de agua no presenta ningún estrés antropogénico, el índice reportará un valor bajo, lo que significa que el ecosistema tiene pocos nutrientes, sedimentos o contaminantes de diferente tipo [25][26][27]. El índice de estado trófico adoptado para lagos tropicales, es una modificación del índice de Carlson [28] realizada por Toledo et al [29], que alteró las expresiones originales para adecuarlas a los ambientes tropicales [30].…”

Section: íNdice De Estado Trófico Calculado Con El Disco De Secchi (Iunclassified

Evaluación espacio-temporal del estado trófico de un lago de grandes dimensiones usando imágenes MOD09GA

Eraso

Trindade

2017

Cien.Ing.Neogranadina

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<p>Aunque la relación empírica entre imágenes satelitales y datos recolectados en campo del disco de Secchi ha sido demostrada por estudios previos en cuerpos de agua continentales, la creación de líneas base para el monitoreo espacio-temporal que permita identificar la estacionalidad del Índice de Estado Trófico calculado con el Disco de Secchi (IET-DS) ha sido poco explorado en el monitoreo de grandes lagos. Para realizar un ejemplo práctico de la dinámica espacio-estacional trófica en el embalse de Porto Primavera (Estado de São Paulo - Brasil) a partir de mayo de 2000 hasta abril de 2015, se utilizaron imágenes generadas por el sensor <em>MODIS-Terra</em>, e igualmente, dos trabajos de campo fueron realizados para obtener valores del Disco de Secchi (DS). Estos valores se usaron para ajustar y validar un modelo de correlación entre los valores de reflectancia de la banda centrada en los 645nm y el DS. Los resultados indicaron que el modelo tiene un alto coeficiente de determinación (R2 = 0,80) y un moderado error asociado a las estimaciones (RMSE = 0,47m). El análisis de la variación estacional del (IET-DS) muestra el siguiente patrón: la transparencia del lago es afectada por las estaciones seca y lluviosa. El valor promedio de las estaciones de muestreo localizadas en el lago lo clasifican como oligotrófico, las regiones próximas a la desembocadura del río Pardo, presentan una clasificación eutrófica durante gran parte del año; en las temporadas de verano y otoño esta condición se extiende a casi toda la región norte del lago.</p>

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Towards the classification of eutrophic condition in estuaries

Cited by 78 publications

References 51 publications

The importance of climatic variability and human influence in driving aspects of temporarily open‐closed estuaries

The importance of climatic variability and human influence in driving aspects of temporarily open‐closed estuaries

Deterioration in the water quality of an urbanised estuary with recommendations for improvement

Evaluación espacio-temporal del estado trófico de un lago de grandes dimensiones usando imágenes MOD09GA

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