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Article ; Online: Advancing ecosystem accounting in estuaries

Susan Taljaard / Lara van Niekerk / Janine B. Adams / Taryn Riddin

South African Journal of Science, Vol 119, Iss 3/

Swartkops Estuary case study

2023 Volume 4

Abstract: Rapid degradation of ecosystems and loss of ecosystem services have sparked interest in developing approaches to report and integrate such change with socio-economic information systems, such as the System of National Accounts. Here we describe an ... ...

Abstract	Rapid degradation of ecosystems and loss of ecosystem services have sparked interest in developing approaches to report and integrate such change with socio-economic information systems, such as the System of National Accounts. Here we describe an approach and application of ecosystem accounting for individual estuaries, building on approaches previously applied at national and bay levels. Using the Swartkops Estuary as a case study, the focus is on physical accounts for ecosystem extent and condition, as well as accounts for two important ecosystem services (carbon sequestration and recreational use). Pressure accounts are also introduced to demonstrate the value of identifying key areas for management and restoration interventions in response to changes in extent and/or condition accounts. Greater resolution in these account reports, achieved through zoning, provides spatially explicit information on ecosystem assets and their services within an estuary to also inform management decision-making at local level. Further, these accounts can also inform local restoration prioritisation, in support of the UN Decade on Ecosystem Restoration (2021–2030), for example offsetting irreversibly degraded areas in one zone with restoration or maintenance of similar habitats in another. Significance: • This study is the first to apply the ecosystem accounting approach at the individual estuary level. • We provide spatially explicit information on ecosystem assets and their services in support of resource management. • Physical accounts include extent and condition, as well as ecosystem service and pressure accounts. • These accounts inform estuary management and restoration at the local governance level.
Keywords	estuary-level ; extent and condition accounts ; pressure accounts ; physical ecosystem service accounts ; management ; Science ; Q ; Science (General) ; Q1-390 ; Social Sciences ; H ; Social sciences (General) ; H1-99
Subject code	710 ; 551
Language	English
Publishing date	2023-03-01T00:00:00Z
Publisher	Academy of Science of South Africa
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: The state of persistent organic pollutants in South African estuaries

Chijioke Olisah / Janine B. Adams / Gletwyn Rubidge

Ecotoxicology and Environmental Safety, Vol 219, Iss , Pp 112316- (2021)

A review of environmental exposure and sources

2021

Abstract: The long-term health of many South African estuaries is impacted by pollutants entering these systems through industrial and agricultural runoff, sewage outfalls, contaminated storm water drainage, flows from informal settlements, and plastic materials ... ...

Abstract	The long-term health of many South African estuaries is impacted by pollutants entering these systems through industrial and agricultural runoff, sewage outfalls, contaminated storm water drainage, flows from informal settlements, and plastic materials in marine debris. Uncontrolled inputs combined with poor environmental management often result in elevated levels of persistent organic pollutants (POPs) in affected estuaries. Data on POPs research from 1960 to 2020 were analysed in terms of their sources, environmental investigations, and health implications. The outcome showed polychlorinated biphenyls (PCBs) and per- and poly-fluoroalkyl sulphonates (PFASs) to exceed the US EPA health advisory levels for drinking water. Concentration of organochlorine pesticides (OCPs) in water were below the WHO limits, while those in fish tissues from most estuaries were found to be below the US FDA limits. Although environmental compartments in some estuaries (e.g. Rooiels and uMngeni estuaries) seem to be less contaminated relative to other marine systems around the world, many others were polluted and critically modified (e.g. Durban Bay, Swartkops, Sundays, and Buffalo systems). Due to inconsistent monitoring methods coupled with limited data availability, temporal trends were unclear. Of the 290 estuaries in South Africa, 65 were prioritised and recommended for POPs evaluation based on their pollution sources, and a monitoring strategy was defined in terms of sampling. Government policies to curb marine pollution need to be enforced to prevent chronic contamination that leads to water quality deterioration and loss of ecosystem services.
Keywords	Estuarine systems ; Environmental management ; Organochlorine pesticides (OCPs) ; Polychlorinated biphenyls (PCBs) ; Polybrominated diphenyls (PBDEs) ; Polycyclic aromatic hydrocarbon (PAHs) ; Environmental pollution ; TD172-193.5 ; Environmental sciences ; GE1-350
Subject code	333
Language	English
Publishing date	2021-08-01T00:00:00Z
Publisher	Elsevier
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Contributions of Wetland Plants on Metal Accumulation in Sediment

Marelé A. Nel / Gletwyn Rubidge / Janine B. Adams / Lucienne R. D. Human

Sustainability, Vol 14, Iss 3679, p

2022 Volume 3679

Abstract: Wetlands, and especially salt marshes, are well-known sinks of metals, which limit toxic amounts of metals from entering the food chain. This study investigated metal concentrations (Cr, Cu, Fe, Mn, Ni, Pb, Zn) in a highly urbanised estuary, and compared ...

Abstract	Wetlands, and especially salt marshes, are well-known sinks of metals, which limit toxic amounts of metals from entering the food chain. This study investigated metal concentrations (Cr, Cu, Fe, Mn, Ni, Pb, Zn) in a highly urbanised estuary, and compared vegetated rhizosediment ( Salicornia tegetaria , Spartina maritima , and Zostera capensis ) with bare sediment, in a depositional and non-depositional site, in the intertidal zone of the Swartkops Estuary. The samples were collected at two sites along the middle and lower reaches of the estuary and analysed using a Total X-ray Fluorescence (TXRF) spectrometer. It was found that the rhizosediment contained more metals and that metal concentrations in the sediment decreased as follows: S. tegetaria > S. maritima > Z. capensis > bare sediment. Although metal accumulation was similar in bare sediment for the depositional (Site B) and the non-depositional site (Site A), the rhizosediment displayed higher metal accumulation in the depositional site (Site B). However, regardless of site-specific depositional tendencies, rhizosediment displayed higher metal accumulation than bare sediment. These results indicate that vegetated sites and vegetated depositional sites should be the focus of monitoring metals in estuaries around the world.
Keywords	metal pollution ; Swartkops Estuary ; TXRF ; salt marsh ; seagrass ; wetland plants ; Environmental effects of industries and plants ; TD194-195 ; Renewable energy sources ; TJ807-830 ; Environmental sciences ; GE1-350
Subject code	333
Language	English
Publishing date	2022-03-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Conservation implications of herbicides on seagrasses

Johanna W. van Wyk / Janine B. Adams / Sophie von der Heyden

PeerJ, Vol 10, p e

sublethal glyphosate exposure decreases fitness in the endangered Zostera capensis

2022 Volume 14295

Abstract: Worldwide seagrass populations are in decline, calling for urgent measures in their conservation. Glyphosate is the most widely used herbicide globally, leading to increasing concern about its ecological impact, yet little is known about the prevalence ... ...

Abstract	Worldwide seagrass populations are in decline, calling for urgent measures in their conservation. Glyphosate is the most widely used herbicide globally, leading to increasing concern about its ecological impact, yet little is known about the prevalence or impact of glyphosate on seagrasses. In this study, we investigated the effect of sublethal glyphosate exposure on the endangered seagrass, Zostera capensis, to identify effects on growth, photosynthetic pigments and leaf morphology as measures of seagrass fitness. Seagrasses were exposed to a single dose of a commercial glyphosate formulation—ranging between 250 to 2,200 µg/L. After three weeks, the median leaf area decreased by up to 27%, with reductions of up to 31% in above ground biomass (p < 0.05). Photosynthetic pigment concentration showed no significant difference between groups. The observed effects on biomass and leaf area were seen at glyphosate levels below the regulatory limits set for surface water by several countries and may negatively affect the long-term resilience of this ecosystem engineer to additional stressors, such as those associated with climate change and anthropogenic pollution. As such, glyphosates and other herbicides that are washed into estuarine and marine ecosystems, pose a significant threat to the persistence of seagrasses and are important factors to consider in seagrass conservation, management and restoration efforts.
Keywords	Estuarine health ; Herbicide ; Seagrass conservation ; Morphology ; Zostera capensis ; Medicine ; R ; Biology (General) ; QH301-705.5
Subject code	333
Language	English
Publishing date	2022-11-01T00:00:00Z
Publisher	PeerJ Inc.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Salt Marsh Restoration for the Provision of Multiple Ecosystem Services

Janine B. Adams / Jacqueline L. Raw / Taryn Riddin / Johan Wasserman / Lara Van Niekerk

Diversity, Vol 13, Iss 680, p

2021 Volume 680

Abstract: Restoration of salt marsh is urgent, as these ecosystems provide natural coastal protection from sea-level rise impacts, contribute towards climate change mitigation, and provide multiple ecosystem services including supporting livelihoods. This study ... ...

Abstract	Restoration of salt marsh is urgent, as these ecosystems provide natural coastal protection from sea-level rise impacts, contribute towards climate change mitigation, and provide multiple ecosystem services including supporting livelihoods. This study identified potential restoration sites for intervention where agricultural and degraded land could be returned to salt marsh at a national scale in South African estuaries. Overall, successful restoration of salt marsh in some estuaries will require addressing additional pressures such as freshwater inflow reduction and deterioration of water quality. Here, we present, a socio-ecological systems framework for salt marsh restoration that links salt marsh state and the well-being of people to guide meaningful and implementable management and restoration interventions. The framework is applied to a case study at the Swartkops Estuary where the primary restoration intervention intends to route stormwater run-off to abandoned salt works to re-create aquatic habitat for waterbirds, enhance carbon storage, and provide nutrient filtration. As the framework is generalized, while still allowing for site-specific pressures to be captured, there is potential for it to be applied at the national scale, with the largest degraded salt marsh areas set as priorities for such an initiative. It is estimated that ~1970 ha of salt marsh can be restored in this way, and this represents a 14% increase in the habitat cover for the country. Innovative approaches to restoring and improving condition are necessary for conserving salt marshes and the benefits they provide to society.
Keywords	socio-ecological system ; salt pan ; estuary ; habitat loss ; degradation ; ecosystem health ; Biology (General) ; QH301-705.5
Subject code	333
Language	English
Publishing date	2021-12-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Rhizosediments of Salicornia tegetaria Indicate Metal Contamination in the Intertidal Estuary Zone

Marelé A. Nel / Gletwyn Rubidge / Janine B. Adams / Lucienne R. D. Human

Frontiers in Environmental Science, Vol

2020 Volume 8

Abstract: Metal pollution is a well-known anthropogenic impact of highly developed estuaries, with dire consequences to the ecosystem. This study investigated the metal concentrations (Al, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in the sediment colonized by Salicornia ... ...

Abstract	Metal pollution is a well-known anthropogenic impact of highly developed estuaries, with dire consequences to the ecosystem. This study investigated the metal concentrations (Al, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in the sediment colonized by Salicornia tegetaria, a dominant salt marsh plant in the lower intertidal zone of the Swartkops Estuary. The samples were collected at five sites along the banks of the middle and lower reaches of the estuary, and analyzed using an Inductively Coupled Plasma –Optical Emission Spectrometer. Metal contamination was determined using established normalized baseline models. It was found that all the sites contained metal enrichment, with the estuary mouth experiencing the least enrichment. Salicornia tegetaria holds a substantial amount of anomalous metals within its rhizosediment—providing a valuable ecosystem service to a highly developed Swartkops Estuary.
Keywords	metal pollution ; Swartkops Estuary ; baseline ; coupled plasma optical emission spectrometer ; salt marsh ; Environmental sciences ; GE1-350
Subject code	670
Language	English
Publishing date	2020-09-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Effective Management of Closed Hypereutrophic Estuaries Requires Catchment-Scale Interventions

Daniel A. Lemley / Stephen J. Lamberth / Warren Manuel / Monique Nunes / Gavin M. Rishworth / Lara van Niekerk / Janine B. Adams

Frontiers in Marine Science, Vol

2021 Volume 8

Abstract: Increased nutrient loading associated with rapid population growth is the leading cause of deteriorating water quality in urbanized estuaries globally. Small estuaries are particularly sensitive to changes when connection with the marine environment is ... ...

Abstract	Increased nutrient loading associated with rapid population growth is the leading cause of deteriorating water quality in urbanized estuaries globally. Small estuaries are particularly sensitive to changes when connection with the marine environment is restricted, or lost, because of high water retention. The temporarily closed Hartenbos Estuary (South Africa) is an example of how such pressures can culminate in a severely degraded ecosystem. Wastewater treatment work (WWTW) discharges introduce substantial volumes of freshwater (8,000 m3 d–1) and nutrient loads (38 kg DIN d–1 and 22 kg DIP d–1) into this estuary. This constant inflow has necessitated frequent artificial breaching (inducing alternating states) of the estuary mouth to prevent flooding of low-lying developments and, occasionally, to mitigate against extreme events such as fish kills and sewage spills. This study investigated the efficacy of artificial mouth breaching practices in eliciting responses in selected abiotic and biotic parameters. Microalgal (phytoplankton and benthic diatoms), benthic macrofauna and fish community dynamics were assessed in response to mouth state and water quality conditions using a seasonal monitoring programme. The hypereutrophic nature of the Hartenbos Estuary was highlighted by persistent high-biomass phytoplankton accumulations (>100 μg Chl-a l–1), extreme dissolved oxygen conditions (0.4–20.5 mg O2 l–1) and the predominance of harmful algal bloom (HAB) events comprising Nannochloropsis sp. and Heterosigma akashiwo. Artificial breaching of the mouth facilitated limited tidal exchange and occurred approximately bimonthly once water levels exceeded 1.9 m above mean sea level (MSL). Current pressures and management interventions have culminated in an ecosystem void of natural fluctuations and instead characterised by low diversity and shifts between undesirable states. This is highlighted by the near year-round dominance of only a few opportunistic species/groups tolerant of adverse conditions (e.g., ...
Keywords	eutrophication ; harmful algal blooms ; hypoxia ; mouth management ; nutrient loading ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
Subject code	333
Language	English
Publishing date	2021-06-01T00:00:00Z
Publisher	Frontiers Media S.A.
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Comparative assessment of two agriculturally-influenced estuaries: Similar pressure, different response

Lemley, Daniel A / Janine B. Adams / Susan Taljaard

Marine pollution bulletin. 2017 Apr. 15, v. 117, no. 1-2

2017

Abstract: This study compared the spatio-temporal dynamics in two agriculturally-influenced South African estuaries - Gamtoos and Sundays - to investigate how contrasting hydrological alterations influence physical, chemical and biological responses. With the ... ...

Abstract	This study compared the spatio-temporal dynamics in two agriculturally-influenced South African estuaries - Gamtoos and Sundays - to investigate how contrasting hydrological alterations influence physical, chemical and biological responses. With the Gamtoos Estuary experiencing regular high flow conditions, a key difference between the two systems is the propensity for natural flushing events to occur; a mechanism largely eliminated from the highly-regulated Sundays Catchment. Phytoplankton blooms (>20Chl-aμgl−1) were persistent and seasonal in the Sundays, inducing summer bottom-water hypoxia (<2mgl−1), whilst those in the Gamtoos were episodic and flow-dependent. Of concern in the Sundays Estuary, was the magnitude (>550μgl−1) and recurrent nature of two harmful algal bloom (HAB) species. This study provides the first account of HAB persistence and seasonal hypoxia in a South African estuary, demonstrating the possible consequences of shifting an ecosystem into a new stable state.
Keywords	algal blooms ; anaerobic conditions ; ecosystems ; estuaries ; hydrology ; hypoxia ; summer ; watersheds
Language	English
Dates of publication	2017-0415
Size	p. 136-147.
Publishing place	Elsevier Ltd
Document type	Article
ZDB-ID	2001296-2
ISSN	1879-3363 ; 0025-326X
ISSN (online)	1879-3363
ISSN	0025-326X
DOI	10.1016/j.marpolbul.2017.01.059
Database	NAL-Catalogue (AGRICOLA)

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Article: Unwinding a Tangled Web: a Fine-Scale Approach towards Understanding the Drivers of Harmful Algal Bloom Species in a Eutrophic South African Estuary

Lemley, DanielA / Gavin M. Rishworth / Janine B. Adams

Estuaries and coasts. 2018 July, v. 41, no. 5

2018

Abstract: A permanently eutrophic South African estuary provided an ideal model ecosystem from which to unravel the drivers of recurrent accumulations of harmful algal bloom (HAB) species. Designed to encapsulate broad- to fine-scale variations, seasonal in situ ... ...

Abstract	A permanently eutrophic South African estuary provided an ideal model ecosystem from which to unravel the drivers of recurrent accumulations of harmful algal bloom (HAB) species. Designed to encapsulate broad- to fine-scale variations, seasonal in situ bihourly monitoring of abiotic and phytoplankton components took place at a fixed location over a 24-h period on four sampling occasions. Four known HAB species were recorded at bloom concentrations (> 20 μg Chl-a L−1) during the study, including Heterosigma akashiwo, Heterocapsa rotundata, Mesodinium rubrum, and Karenia cf. mikimotoi. Model results identified temperature as a key driver, with distinct community shifts between winter (~H. rotundata and M. rubrum) and spring/summer (~H. akashiwo and K. cf. mikimotoi) conditions. Evidence of niche overlap between all four HAB taxa was highlighted by their predilection for elevated nitrate levels, a vertically stratified water column and mesohaline (ca. 10) surface waters. As such, internal biotic processes such as plasticity of diel vertical migration patterns, reliance of M. rubrum on suitable ‘prey’ resources, and the suppressive pressure of H. akashiwo on co-occurring taxa-explained phytoplankton community dynamics beyond the influence of physico-chemical variability. These findings provide novel insight regarding the ecology of HAB taxa and how they have adapted to thrive in anthropogenically manipulated environments.
Keywords	algal blooms ; chlorophyll ; ecosystems ; estuaries ; eutrophication ; Heterocapsa ; Karenia ; Mesodinium ; migratory behavior ; models ; monitoring ; nitrates ; phytoplankton ; plasticity ; spring ; summer ; surface water ; temperature ; winter
Language	English
Dates of publication	2018-07
Size	p. 1356-1369.
Publishing place	Springer US
Document type	Article
ZDB-ID	2229170-2
ISSN	1559-2731 ; 1559-2723
ISSN (online)	1559-2731
ISSN	1559-2723
DOI	10.1007/s12237-018-0380-0
Database	NAL-Catalogue (AGRICOLA)

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Article: Testing the efficacy of an estuarine eutrophic condition index: Does it account for shifts in flow conditions?

Lemley, Daniel A / Janine B. Adams / Nadine A. Strydom

Ecological indicators. 2017 Mar., v. 74

2017

Abstract: Eutrophication of estuaries via anthropogenic nutrient enrichment is an issue being addressed extensively on a global scale, however it remains a topic that garners further attention due to its complexity. The aim of this study was to test the efficacy ... ...

Abstract	Eutrophication of estuaries via anthropogenic nutrient enrichment is an issue being addressed extensively on a global scale, however it remains a topic that garners further attention due to its complexity. The aim of this study was to test the efficacy of a recently proposed eutrophic condition index in five permanently open estuaries, subsequent to flow variations. Further, in order to elucidate their potential role in augmenting eutrophic conditions, the influence of vegetated habitats on associated microalgal communities was investigated. The study took place in the summer of 2014 and 2015. On each sampling occasion, all of the proposed ‘state’ indicators (nutrients, oxygen and microalgal communities) were assessed and supplemented with a heuristic ‘pressure’ component (flow conditions). Overall, the proposed index was shown to be sensitive to environmental perturbations providing shifts in classification ratings illustrating the dilution (Swartkops Estuary) or augmenting (Kromme, Gamtoos, and Kariega estuaries) effect of freshwater pulse events. Additionally, the sensitivity of selected epiphyte and microphytobenthos (MPB) parameters to water quality variations was verified, thus supporting their inclusion as indicators in the proposed index. Regarding the role of microhabitats in promoting microalgal growth, it was found that MPB biomass was higher (5–290%) and benthic diatom diversity generally lower (5–50%) in vegetated compared to unvegetated habitats – an important consideration when applying the index. The habitat complexity and stabilisation provided by estuarine macrophytes (Phragmites australis and Zostera capensis) supported notable autotroph colonisation. This highlights their importance in structuring trophic pathways, whilst also potentially providing a corridor for the intensification of eutrophic symptoms in estuaries. Overall, this study provides an important step towards the verification of a proposed assessment methodology which may serve to provide a baseline from which the eutrophic status of estuaries can be monitored – particularly in countries where such assessment frameworks are lacking.
Keywords	Bacillariophyceae ; biomass ; epiphytes ; estuaries ; eutrophication ; freshwater ; macrophytes ; microalgae ; microhabitats ; nutrients ; oxygen ; Phragmites australis ; summer ; water quality ; Zostera
Language	English
Dates of publication	2017-03
Size	p. 357-370.
Publishing place	Elsevier Ltd
Document type	Article
ZDB-ID	2036774-0
ISSN	1872-7034 ; 1470-160X
ISSN (online)	1872-7034
ISSN	1470-160X
DOI	10.1016/j.ecolind.2016.11.034
Database	NAL-Catalogue (AGRICOLA)

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