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Dalu T, Cuthbert RN, Taylor JC, Magoro ML, Weyl OLF, Froneman PW, Wasserman RJ. Benthic diatom-based indices and isotopic biomonitoring of nitrogen pollution in a warm temperate Austral river system. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 748:142452. [PMID: 33113700 DOI: 10.1016/j.scitotenv.2020.142452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 09/13/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Rivers are impacted by pollutants from anthropogenic activities such as urbanisation and agricultural practices. Whilst point source pollution has been widely studied and in some cases remediated, non-point pollutant sources remain pervasive, particularly in developing countries that lack economic and human specialist capacity. Monitoring of pollution levels in many regions is additionally challenged by a lack of robust indicators for nitrogen inputs, however, diatom community indices and analysis of variation in microphytobenthos (MBP) stable isotope analysis variations have potential. The present study investigates variations and utilities in benthic diatom indices and MPB δ15N along different river sections (n = 31) of an austral river between two seasons (wet and dry), testing for relationships with key environmental variables (physical, water and sediment), in the context of N monitoring. One hundred and eighteen diatom taxa belonging to 36 genera were identified, with physical (water flow), water (nitrate, P and total dissolved solids) and sediment (B, Ca, Cr, Na, N, P, SOM, Pb and Zn) variables correlating to one or more of the 12 diatom indices presented. In particular, Biological Diatom Index, Biological Index of Water Quality, Central Economic Community, Index of Artois-Picardie Diatom (IDAP) and Sládeček's Index were strongly explained by sediment variables, whilst Descy's Pollution Index and Schiefele and Schreiner's Index were explained by water and physical variables. Whilst MPB δ15N were within the "no impact" level in the wet and dry seasons at reference (i.e. unpolluted) sites, all sites located in agricultural or urban areas, and downstream of sewage discharges, had a wider range that encompassed increasing organic impacts ("inorganic impacts" to high "organic impacts"). Temperature and turbidity (negative), as well as dissolved oxygen, waterway width and depth (positive), significantly affected MPB δ15N, whilst effects of chemistry variables were less apparent. Overall, we found that MPB δ15N signatures were significantly correlated with Trophic Diatom Index, the Specific Pollution Sensitivity Index and the Artois-Picardie Diatom Index, suggesting the utility of diatoms and MPB δ15N in assessments of aquatic pollution. In turn, MPB δ15N values are strong indicators of N pollution across spatial and seasonal gradients. Thus, the results showed the effects of sediment variables on diatoms to be strong, indicating that sediment rather than water characteristics more strongly structure diatom communities. Thus, sediment variables should be sampled when conducting bioassessment studies.
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Affiliation(s)
- Tatenda Dalu
- Aquatic Systems Research Group, Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa.
| | - Ross N Cuthbert
- South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, 24105 Kiel, Germany
| | - Jonathan C Taylor
- South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; Unit for Environmental Science and Management, North-West University, Potchefstroom 2520, South Africa
| | - Mandla L Magoro
- South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa
| | - Olaf L F Weyl
- DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa
| | - P William Froneman
- Department of Zoology and Entomology, Rhodes University, Makhanda 6140, South Africa
| | - Ryan J Wasserman
- South African Institute for Aquatic Biodiversity, Makhanda 6140, South Africa; Department of Zoology and Entomology, Rhodes University, Makhanda 6140, South Africa
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Protected and un-protected urban wetlands have similar aquatic macroinvertebrate communities: A case study from the Cape Flats Sand Fynbos region of southern Africa. PLoS One 2020; 15:e0233889. [PMID: 32470075 PMCID: PMC7259692 DOI: 10.1371/journal.pone.0233889] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 05/14/2020] [Indexed: 11/19/2022] Open
Abstract
Rapid urbanisation has led to major landscape alterations, affecting aquatic ecosystems’ hydrological and biogeochemical cycles, and biodiversity. Thus, habitat alteration is considered a major driver of aquatic biodiversity loss and related aquatic ecosystem goods and services. This study aimed to investigate and compare aquatic macroinvertebrate richness, diversity and community structure between urban temporary wetlands, located within protected and un-protected areas. The latter were found within an open public space or park with no protection or conservation status, whereas the former were inaccessible to the public and had formal protected, conservation status. We hypothesised that; (1) protected urban wetlands will harbour higher aquatic macroinvertebrate biodiversity (both dry and wet) as compared to un-protected urban wetlands, and (2) that the community composition between the two urban wetlands types will be significantly different. Contrary to our hypothesis, our results revealed no major differences between protected and un-protected urban wetlands, based on the measures investigated (i.e. taxon richness, Shannon-Weiner diversity, Pielou's evenness and community composition) during the dry and wet phase. The only exception was community composition, which revealed significant differences between these urban wetland types. These results suggest that human activities (potential littering and polluting) in the un-protected urban wetlands have not yet resulted in drastic change in macroinvertebrate richness and composition, at least from the dry phase. This suggests a potential for un-protected urban wetlands suffering from minimal human impact to act as important reservoirs of biodiversity and ecosystem services.
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Korotkevich AY, Potapov AM, Tiunov AV, Kuznetsova NA. Collapse of trophic‐niche structure in belowground communities under anthropogenic disturbance. Ecosphere 2018. [DOI: 10.1002/ecs2.2528] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Anastasiya Yu. Korotkevich
- Institute of Biology and Chemistry Moscow State Pedagogical University Kibalchicha Street 6k3 129164 Moscow Russia
| | - Anton M. Potapov
- A.N. Severtsov Institute of Ecology and Evolution Russian Academy of Sciences Leninsky Prospect 33 119071 Moscow Russia
- J.F. Blumenbach Institute of Zoology and Anthropology University of Göttingen Untere Karspüle 2 37073 Goettingen Germany
| | - Alexei V. Tiunov
- A.N. Severtsov Institute of Ecology and Evolution Russian Academy of Sciences Leninsky Prospect 33 119071 Moscow Russia
| | - Natalia A. Kuznetsova
- Institute of Biology and Chemistry Moscow State Pedagogical University Kibalchicha Street 6k3 129164 Moscow Russia
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Cuthbert RN, Dalu T, Wasserman RJ, Dick JTA, Mofu L, Callaghan A, Weyl OLF. Intermediate predator naïveté and sex-skewed vulnerability predict the impact of an invasive higher predator. Sci Rep 2018; 8:14282. [PMID: 30250163 PMCID: PMC6155278 DOI: 10.1038/s41598-018-32728-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 09/14/2018] [Indexed: 12/03/2022] Open
Abstract
The spread of invasive species continues to reduce biodiversity across all regions and habitat types globally. However, invader impact prediction can be nebulous, and approaches often fail to integrate coupled direct and indirect invader effects. Here, we examine the ecological impacts of an invasive higher predator on lower trophic groups, further developing methodologies to more holistically quantify invader impact. We employ functional response (FR, resource use under different densities) and prey switching experiments to examine the trait- and density-mediated impacts of the invasive mosquitofish Gambusia affinis on an endemic intermediate predator Lovenula raynerae (Copepoda). Lovenula raynerae effectively consumed larval mosquitoes, but was naïve to mosquitofish cues, with attack rates and handling times of the intermediate predator unaffected by mosquitofish cue-treated water. Mosquitofish did not switch between male and female prey, consistently displaying a strong preference for female copepods. We thus demonstrate a lack of risk-reduction activity in the presence of invasive fish by L. raynerae and, in turn, high susceptibility of such intermediate trophic groups to invader impact. Further, we show that mosquitofish demonstrate sex-skewed predator selectivity towards intermediate predators of mosquito larvae, which may affect predator population demographics and, perversely, increase disease vector proliferations. We advocate the utility of FRs and prey switching combined to holistically quantify invasive species impact potential on native organisms at multiple trophic levels.
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Affiliation(s)
- Ross N Cuthbert
- Institute for Global Food Security, School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK. .,DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa. .,Ecology and Evolutionary Biology, School of Biological Sciences, University of Reading, Harborne Building, Reading, RG6 6AS, England, UK.
| | - Tatenda Dalu
- Department of Ecology and Resource Management, University of Venda, Thohoyandou, 0950, South Africa.,South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa
| | - Ryan J Wasserman
- Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, P. Bag 16, Palapye, Botswana.,South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa
| | - Jaimie T A Dick
- Institute for Global Food Security, School of Biological Sciences, Medical Biology Centre, Queen's University Belfast, Belfast, BT9 7BL, Northern Ireland, UK
| | - Lubabalo Mofu
- South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa
| | - Amanda Callaghan
- Ecology and Evolutionary Biology, School of Biological Sciences, University of Reading, Harborne Building, Reading, RG6 6AS, England, UK
| | - Olaf L F Weyl
- DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, 6140, South Africa
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Wasserman RJ, Weston M, Weyl OLF, Froneman PW, Welch RJ, Vink TJF, Dalu T. Sacrificial males: the potential role of copulation and predation in contributing to copepod sex-skewed ratios. OIKOS 2018. [DOI: 10.1111/oik.04832] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Ryan J. Wasserman
- School of Science, Monash Univ. Malaysia; Jalan Lagoon Selatan, 47500 Bandar Sunway Selangor Darul Ehsan Malaysia
- South African Inst. for Aquatic Biodiversity (SAIAB); Grahamstown South Africa
| | - Mark Weston
- Zoology and Entomology; Rhodes Univ.; Grahamstown South Africa
- Dept of Biological Sciences; Univ. of Cape Town; Rondebosch, Cape Town South Africa
| | - Olaf L. F. Weyl
- DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology; South African Inst. for Aquatic Biodiversity (SAIAB); Grahamstown South Africa
| | | | - Rebecca J. Welch
- Dept of Zoology and Entomology; Univ. of the Free State; Qwaqwa, Phuthaditjhaba South Africa
| | - Tim J. F. Vink
- Dept of Botany; Coastal and Marine Research Unit, Nelson Mandela Metropolitan Univ.; Port Elizabeth South Africa
| | - Tatenda Dalu
- South African Inst. for Aquatic Biodiversity (SAIAB); Grahamstown South Africa
- Dept of Ecology and Resource Management; Univ. of Venda, Thohoyandou; Limpopo South Africa
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