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Munyai LF, Mugwedi L, Wasserman RJ, Dondofema F, Riddell E, Keates C, Dalu T. Water and sediment chemistry drivers of chlorophyll-a dynamics within a Ramsar declared floodplain pan wetland system. Environ Sci Pollut Res Int 2024; 31:28549-28563. [PMID: 38561533 DOI: 10.1007/s11356-024-33052-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 03/19/2024] [Indexed: 04/04/2024]
Abstract
Floodplain pans are hydrologically dynamic in nature and characterised by variables such as chlorophyll-a (chl-a), water, and sediment chemistry over their hydroperiods. The present study investigated the spatio-temporal variations in water and sediment physico-chemical, and chlorophyll-a concentration characteristics of six floodplain pans found in the Ramsar declared Makuleke wetlands, Kruger National Park, South Africa. The water and sediment physico-chemical variable values were generally elevated during the high-water period, whereas chlorophyll-a concentrations varied across pans and hydroperiod. Benthic chl-a concentration significantly varied across pans with concentrations ranging from 161 to 1036.2 mg m2. The two-way ANOVA showed significant differences in benthic chl-a concentration among hydroperiods, and no significant differences were observed in pelagic chl-a across pans and hydroperiods. Generally, pelagic and benthic chl-a concentration increased as water and sediment chemistry variables increased. Furthermore, three sediment variables, i.e. pH, calcium, and magnesium, and water conductivity were found to be significant in structuring benthic chlorophyll-a dynamics in pans. However, none of the sediment and water variables had a significant effect on pelagic chl-a. Hydroperiod had a significant effect on influencing chl-a concentration, with high and low water level periods being characterised by low and high chl-a concentration, respectively. The n-MDS results showed strong overlaps in chl-a biomass among the Makuleke floodplain pans across hydroperiods. The increasing chl-a concentration in these floodplain pans due to potential bioturbation effects as a result of large mammals could potentially lead to eutrophication, which in turn could affect the system's primary productivity and aquatic biota. Therefore, it is important to establish a continuous monitoring programme on these pans to inform sound management decisions.
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Affiliation(s)
- Linton F Munyai
- School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa.
- Aquatic Systems Research Group, Department of Geography and Environmental Science, University of Venda, Thohoyandou, 0950, South Africa.
| | - Lutendo Mugwedi
- Aquatic Systems Research Group, Department of Geography and Environmental Science, University of Venda, Thohoyandou, 0950, South Africa
| | - Ryan J Wasserman
- Department of Zoology and Entomology, Rhodes University, Makhanda, 6140, South Africa
- South African Institute for Aquatic Biodiversity, Makhanda, 6140, South Africa
| | - Farai Dondofema
- Aquatic Systems Research Group, Department of Geography and Environmental Science, University of Venda, Thohoyandou, 0950, South Africa
| | - Eddie Riddell
- Regional Integration Unit, Conservation Management, SANParks, Kruger National Park, Skukuza, 1350, South Africa
- Centre for Water Resources Research, University of KwaZulu-Natal, Pietermaritzburg, 3209, South Africa
| | - Chad Keates
- South African Institute for Aquatic Biodiversity, Makhanda, 6140, South Africa
| | - Tatenda Dalu
- School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa
- South African Institute for Aquatic Biodiversity, Makhanda, 6140, South Africa
- Stellenbosch Institute for Advanced Study, Wallenberg Research Centre at Stellenbosch University, Stellenbosch, 7600, South Africa
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Mpakairi KS, Muthivhi FF, Dondofema F, Munyai LF, Dalu T. Chlorophyll-a unveiled: unlocking reservoir insights through remote sensing in a subtropical reservoir. Environ Monit Assess 2024; 196:401. [PMID: 38538854 PMCID: PMC10973079 DOI: 10.1007/s10661-024-12554-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 03/16/2024] [Indexed: 04/09/2024]
Abstract
Effective water resources management and monitoring are essential amid increasing challenges posed by population growth, industrialization, urbanization, and climate change. Earth observation techniques offer promising opportunities to enhance water resources management and support informed decision-making. This study utilizes Landsat-8 OLI and Sentinel-2 MSI satellite data to estimate chlorophyl-a (chl-a) concentrations in the Nandoni reservoir, Thohoyandou, South Africa. The study estimated chl-a concentrations using random forest models with spectral bands only, spectral indices only (blue difference absorption (BDA), fluorescence line height in the violet region (FLH_violet), and normalized difference chlorophyll index (NDCI)), and combined spectral bands and spectral indices. The results showed that the models using spectral bands from both Landsat-8 OLI and Sentinel-2 MSI performed comparably. The model using Sentinel-2 MSI had a higher accuracy of estimating chl-a when spectral bands alone were used. Sentinel-2 MSI's additional red-edge spectral bands provided a notable advantage in capturing subtle variations in chl-a concentrations. Lastly, the -chl-a concentration was higher at the edges of the Nandoni reservoir and closer to the reservoir wall. The findings of this study are crucial for improving the management of water reservoirs, enabling proactive decision-making, and supporting sustainable water resource management practices. Ultimately, this research contributes to the broader understanding of the application of earth observation techniques for water resources management, providing valuable information for policymakers and water authorities.
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Affiliation(s)
- Kudzai S Mpakairi
- Department of Earth Sciences, Institute of Water Studies, University of the Western Cape, Bellville, 7535, South Africa.
- School of Wildlife Conservation, African Leadership University, Kigali, Rwanda.
| | - Faith F Muthivhi
- Department of Geography and Environmental Sciences, University of Venda, Thohoyandou, 0950, South Africa
| | - Farai Dondofema
- Department of Geography and Environmental Sciences, University of Venda, Thohoyandou, 0950, South Africa
| | - Linton F Munyai
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa
| | - Tatenda Dalu
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa
- South African Institute for Aquatic Biodiversity, Makhanda, 6140, South Africa
- Stellenbosch Institute for Advanced Study, Wallenberg Research Centre at Stellenbosch University, Stellenbosch, 7600, South Africa
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Mashamba R, Cuthbert RN, Dondofema F, Munyai LF, Wu N, Dalu T. Spatiotemporal variation in macroplastic abundances along a subtropical Austral river system. Environ Monit Assess 2024; 196:273. [PMID: 38363433 DOI: 10.1007/s10661-024-12409-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 01/29/2024] [Indexed: 02/17/2024]
Abstract
Plastic pollution is a ubiquitous problem that poses a threat to society and the environment. The issue is especially pervasive in the aquatic environment, where large amounts of plastic debris accumulate from numerous anthropogenic pathways. Relatively little is known about the extent of macroplastics in African subtropical Austral rivers, where management strategies are lacking. This study quantifies and compares the variation in macroplastic abundances along the Mvudi River, South Africa, over four sites and four seasons. We observed a non-significant difference in macroplastic abundance and variation across sites and seasons, with pollution therefore widespread across these contexts. However, the diversity of plastic debris (i.e. γ-diversity value) decreased generally along sites, with most macroplastic items being collected during winter, and fewer macroplastic during autumn. We observed high abundances of macroplastic debris on the shoreline compared to the mainstream, with high proportional abundances of plastic bags and film (> 57.8%) macroplastic physical type across all sites and seasons. We also observed a high proportional abundance of the polymer polypropylene (> 25.3%) across seasons. The information derived from this study serves as the baseline for understanding seasonal variations in plastic debris and their driving factors on this and other subtropical Austral rivers.
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Affiliation(s)
- Ronald Mashamba
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa
| | - Ross N Cuthbert
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, Belfast, BT9 5DL, UK
| | - Farai Dondofema
- Department of Geography and Environmental Sciences, University of Venda, Thohoyandou, 0950, South Africa
| | - Linton F Munyai
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa
| | - Naicheng Wu
- Department of Geography and Spatial Information Techniques, Ningbo University, Ningbo, 315211, China
| | - Tatenda Dalu
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa.
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Makherana F, Cuthbert RN, Monaco CJ, Dondofema F, Wasserman RJ, Chauke GM, Munyai LF, Dalu T. Informing spread predictions of two alien snails using movement traits. Sci Total Environ 2022; 811:152364. [PMID: 34919923 DOI: 10.1016/j.scitotenv.2021.152364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/05/2021] [Accepted: 12/09/2021] [Indexed: 06/14/2023]
Abstract
Invasive alien species are a growing global problem, and aquatic ecosystems have been regarded as particularly vulnerable. Biological invasions can alter ecosystem functioning, threaten native biodiversity and burden the global economy. Understanding alien species ability to disperse via locomotion following arrival to new environments is critical for prediction of spread rates. Here, we quantified in-field densities and compared movement traits between two widespread invasive alien snails, Tarebia granifera and Physa acuta. We measured the: (i) net distance and velocity to determine dispersal potential; and (ii) turning angles (both absolute and relative) and straightness index as proxies for exploratory behaviour. Tarebia granifera exhibited a significantly greater velocity and covered a significantly larger net distance (i.e., greater spread rate) than Physa acuta. In-field densities were marked for both species (T. granifera: mean 351 individuals m-2; P. acuta: mean 235 individuals m-2), but differed spatially. The exploratory behavior (i.e., mean or absolute turning angles and straightness index) did not differ significantly between the two alien species; both species showed a slight tendency to turn counterclockwise. The present study suggests a more rapid capacity to self-disperse in T. granifera than P. acuta, which could facilitate rapid spread within and between aquatic systems. Thus, this current study highlights the often-overlooked role of animal behaviour in promoting invasion; this autecological information can help inform predictive models for the spread of alien snails within freshwater ecosystems.
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Affiliation(s)
- Fhatuwani Makherana
- Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa
| | - Ross N Cuthbert
- GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, 24105 Kiel, Germany; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa
| | - Cristián J Monaco
- IFREMER, IRD, Institute Louis-Malardé, University of the Polynésie française, EIO, 98725 Taravao, Tahiti, French Polynesia
| | - Farai Dondofema
- Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa
| | - Ryan J Wasserman
- Department of Zoology and Entomology, Rhodes University, Makhanda 6140, South Africa; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa
| | - Glencia M Chauke
- Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa
| | - Linton F Munyai
- Aquatic Systems Research Group, Department of Geography and Environmental Sciences, University of Venda, Thohoyandou 0950, South Africa
| | - Tatenda Dalu
- South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit 1200, South Africa; Wissenshaftskolleg zu Berlin Institute for Advanced Study, Berlin 14193, Germany.
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Dalu T, Banda T, Mutshekwa T, Munyai LF, Cuthbert RN. Effects of urbanisation and a wastewater treatment plant on microplastic densities along a subtropical river system. Environ Sci Pollut Res Int 2021; 28:36102-36111. [PMID: 33686602 PMCID: PMC8277625 DOI: 10.1007/s11356-021-13185-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 02/22/2021] [Indexed: 04/13/2023]
Abstract
Global freshwaters are increasingly threatened by pollutants emanating from human activities around watersheds. Microplastic pollution is an increasing problem for rivers worldwide, potentially threatening ecological integrity, ecosystem services and human health. We present quantifications and characterisations of sediment microplastic pollution in a subtropical river system in southern Africa, and relate distributions to wastewater treatment works, abiotic variables and urban environments. We additionally apply several diversity indices to decipher how microplastic types differ across the river system seasonally. Over two thousand microplastic particles were found across five sites and three seasons in the river system, comprising microbeads of various colours and microfibres. Microplastic concentrations were highest and most diverse in the hot-wet (mean range 76.0 ± 10.0-285.5 ± 44.5 microplastic kg-1) season as compared to the cool-dry (16.5 ± 4.5-27.0 ± 5.0 microplastic kg-1) and hot-dry (13.0 ± 4.0-29.0 ± 10.0 microplastic kg-1) seasons, and were mostly dominated by microfibres. However, no clear patterns were found in relation to wastewater treatment operations spatially, or in relation to abiotic variables in the river system. This study therefore finds a diverse range of microplastic types widely distributed in the river system that differ across seasons. Our results provide important, novel insights into plastic pollution in an understudied area of the Global South, and point to extensive pollution from sources outside of wastewater treatment works.
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Affiliation(s)
- Tatenda Dalu
- Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, 1200, South Africa.
| | - Thabiso Banda
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou, 0950, South Africa
| | - Thendo Mutshekwa
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou, 0950, South Africa
| | - Linton F Munyai
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou, 0950, South Africa
| | - Ross N Cuthbert
- GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, 24105, Kiel, Germany.
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Netshiongolwe NR, Cuthbert RN, Maenetje MM, Chari LD, Motitsoe SN, Wasserman RJ, Munyai LF, Dalu T. Quantifying Metal Contamination and Potential Uptake by Phragmites australis Adans. (Poaceae) Along a Subtropical River System. Plants (Basel) 2020; 9:plants9070846. [PMID: 32635545 PMCID: PMC7412227 DOI: 10.3390/plants9070846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/25/2020] [Accepted: 06/30/2020] [Indexed: 11/16/2022]
Abstract
Metal pollution is pervasive across terrestrial and aquatic ecosystems owing to anthropogenic activities. Sediments can accrue high concentrations of metals and act as secondary sources, and thus may be valuable indicators of metal contamination across spatiotemporal scales. In aquatic systems, the extent of metal pollution may be further mediated by transference among sediments and living organisms, with plant metal contaminants potentially predictive of underlying sediment concentrations. The present study thus quantifies the extent of metal pollutants (Na, K, Ca, Mg, Cu, Zn, Mn, B, Fe) across multiple study sites and seasons (cool-dry, hot-wet, hot-dry) in a subtropical river system. Furthermore, uptake by a key macrophyte species, Phragmites australis, was examined and correlated with sediment pollution levels among different plant parts. Overall, sediment pollution load indices differed seasonally, being significantly highest during the cool-dry season irrespective of sampling location, suggesting that periods with reduced water flows can exacerbate metal pollution levels in riverine sediments. Also, metal concentrations were highest in upstream wetland sites, indicating a capacity for metal sink effects in these areas. Overall, macrophytes contained high concentrations of select metals, however composition and concentrations differed across plant parts, with roots containing particularly high concentrations of Fe and B. Correlations between sediment and macrophyte concentrations were mostly non-significant, whilst stem Mn and Fe concentrations correlated significantly negatively and positively to sediment concentrations, respectively. The present study identifies key spatiotemporal differences in multiple metal contaminants in an understudied subtropical aquatic system that align with hydrological regime differences. Whilst macrophytes were not found to be major accumulators, or predictors, of metal contaminants in this study, they may collectively play a central role in concentration regulation in aquatic systems.
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Affiliation(s)
- Ndivhuwo R. Netshiongolwe
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; (N.R.N.); (M.M.M.); (L.F.M.)
| | - Ross N. Cuthbert
- GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, 24105 Kiel, Germany;
| | - Mokgale M. Maenetje
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; (N.R.N.); (M.M.M.); (L.F.M.)
| | - Lenin D. Chari
- Centre for Biological Control, Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa; (L.D.C.); (S.N.M.)
| | - Samuel N. Motitsoe
- Centre for Biological Control, Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa; (L.D.C.); (S.N.M.)
- Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa;
| | - Ryan J. Wasserman
- Department of Zoology and Entomology, Rhodes University, Grahamstown 6140, South Africa;
- Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, Palapye Private Bag 16, Botswana
| | - Linton F. Munyai
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; (N.R.N.); (M.M.M.); (L.F.M.)
| | - Tatenda Dalu
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; (N.R.N.); (M.M.M.); (L.F.M.)
- Correspondence:
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