Disaggregation and assessment of estuarine pressures at the country-level to better inform management and resource protection – the South African experience

Niekerk, Lara Van; Taljaard, Susan; Lamberth, Stephen J.; Adams, Janine B.; Weerts, S P; MacKay, CF

doi:10.2989/16085914.2022.2041388

Cited by 16 publications

(52 citation statements)

References 73 publications

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“…During periods of low freshwater inflow, eelgrass beds often become established further upstream as the upper reaches of estuaries become more saline (Adams, 2016). Similarly, increased salinity further upstream would probably also favour macroalgal (Jafta, 2010;Adams, Snow & Veldkornet, 2012;Van Niekerk et al, 2019). This discrepancy could be due to differences in the methods used to map extent or differences in what was defined as submerged vegetation.…”

Section: Resultsmentioning

confidence: 99%

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Claassens

Villiers

Seath

et al. 2021

Aquatic Conservation

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1. The identification and development of locally significant conservation actions require comprehensive and current ecological species information. Logistically this can be difficult, especially when studying rare and cryptic species which are at greater risk of becoming extinct. This study investigated the current distribution and density of the estuarine pipefish Syngnathus watermeyeri, the only Critically Endangered pipefish in the world, and the commonly found longsnout pipefish Syngnathus temminckii.2. Pipefish were surveyed using a seine net in the Kariega, Bushmans, Kasouga and Kleinemonde East and West estuaries, located on the south coast of South Africa, in October 2019, March 2020 and July 2020. The habitat and physico-chemical characteristics of each site were measured to determine whether these factors had an effect on the presence of S. watermeyeri. In addition, available habitat extent within the Bushmans and Kariega estuaries was mapped.3. Pipefish were only detected in two of the five estuaries within the historical range of S. watermeyeri and a total of 59 S. watermeyeri and 45 S. temminckii were found across all three surveys. Zostera capensis and Codium sp. were the dominant submerged vegetation within the Bushmans and Kariega estuaries and the presence of pipefish was positively associated with the availability of vegetation, especially Codium sp. 4. This is the most extensive targeted survey for S. watermeyeri to date, both temporally and spatially, and provides important insights into what threatens this species. This information should be used to inform future IUCN Red List assessments and the development of locally significant conservation actions.

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Section: Resultsmentioning

confidence: 99%

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Claassens

Villiers

Seath

et al. 2021

Aquatic Conservation

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show abstract

“…Six main pressure categories have been identified for South African estuaries, namely: flow modification, land use and development, exploitation of living resources (fishing), pollution (wastewater disposal), inlet manipulation, and biological invasion (plants and fish). 32 To estimate the magnitude of pressure in these accounts, the method of Van Niekerk et al 32 was applied, using various indicators in the EHI as proxies (Table 1).…”

Section: Pressure Accountingmentioning

confidence: 99%

“…Indicators of magnitude and proxies for extent of impact of key pressures in estuaries (adapted from Van Niekerk et al 32 )…”

Section: Tablementioning

confidence: 99%

“…We focused on five of the six key pressure categories identified for South African estuaries, and encountered in the Swartkops, that is: flow modification, land use and development, exploitation of living resources (fishing), pollution (wastewater disposal), and biological invasion (plants and fish). 32 The Swartkops Estuary is a permanently open system and, as yet, mouth manipulation has not emerged as a key pressure and was therefore not included here.…”

Section: Pressure Accountmentioning

confidence: 99%

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Advancing ecosystem accounting in estuaries: Swartkops Estuary case study

et al. 2023

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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.

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“…During low freshwater inflow, the mouth of the Klein Brak closes to the sea and water levels fluctuate in response to freshwater input. The estuary is estimated to be in a moderately to heavily modified state (Van Niekerk et al 2022). Severe reduction in river inflow has resulted in hypersaline conditions and an increase in the frequency and duration of closed mouth conditions.…”

Section: Study Sitesmentioning

confidence: 99%

Investigating transplantation as a mechanism for seagrass restoration in South Africa

Mokumo,

Adams,

von der Heyden

2023

Restoration Ecology

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The extent of seagrasses has declined globally, with restoration through transplantation seen as an important tool for reversing population loss, yet restoration studies for African seagrass species are scarce. This study investigated the use of different planting patterns (straight‐line, compact, and star) and core sizes (11, 18, and 25 cm Ø) in transplanting ecotypes (intertidal and subtidal) in the predominantly open Knysna and temporarily closed Klein Brak estuaries in South Africa. Cores of the endangered seagrass, Zostera capensis, were transplanted in two experimental repeats per ecotype and core size along transects to investigate survival of plants post‐transplant. No significant differences were observed among core sizes, patterns, or ecotypes in the Knysna Estuary, but cores with the compact pattern had better survival rates in the Klein Brak Estuary. Holes left by the smallest cores in donor sites recovered faster through sediment deposition compared to larger holes. Our study demonstrated that seagrass restoration in South Africa is challenging due to limited suitable habitats and strong environmental variability in estuarine ecosystems. It is important that careful consideration, including of genomic diversity and population structure, as well as ecological similarity between donor and recipient populations must be made for each restoration site when assessing its restoration potential. Effective “no‐take bait zones” and upstream catchment management will be important for protecting potential donor meadows.

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Disaggregation and assessment of estuarine pressures at the country-level to better inform management and resource protection – the South African experience

Cited by 16 publications

References 73 publications

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Distribution and density of the Critically Endangered estuarine pipefish across its range – implications for conservation

Advancing ecosystem accounting in estuaries: Swartkops Estuary case study

Investigating transplantation as a mechanism for seagrass restoration in South Africa

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