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de Necker L, van Rooyen D, Gerber R, Brendonck L, Wepener V, Smit NJ. Effects of river regulation on aquatic invertebrate community composition: A comparative analysis in two southern African rivers. Ecol Evol 2024; 14:e10963. [PMID: 38327690 PMCID: PMC10847884 DOI: 10.1002/ece3.10963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 12/02/2023] [Accepted: 12/04/2023] [Indexed: 02/09/2024] Open
Abstract
While natural floods play a crucial role in shaping the composition of aquatic communities, the most rivers worldwide are regulated or dammed for anthropogenic purposes, resulting in alterations to the biological and chemical composition of these ecosystems. Studies have demonstrated various negative effects of river regulation on aquatic invertebrate communities globally. However, there is a scarcity of research in Africa, despite its vulnerability to anthropogenic impacts. This study aimed to compare aquatic invertebrate communities in the Phongolo River, an impacted regulated river, and the Usuthu River, a less impacted unregulated river, in South Africa. It further aimed to ascertain whether Lake Nyamithi, a naturally saline lake receiving water from both of the aforementioned systems, exhibited a stronger similarity to one of the two rivers in terms of its aquatic invertebrate composition. Aquatic invertebrate and water samples were collected from 2012 to 2018 over several surveys. The Usuthu River demonstrated a diverse and sensitive aquatic invertebrate community, emphasising its high conservation value. The Phongolo River demonstrated effects of anthropogenic impact, with taxa more resilient to changes in water quality and flow compared to the Usuthu River. Mismanagement and excessive water use may lead to the loss of any remaining sensitive aquatic invertebrate communities in this river. The presence of invasive molluscan in the Phongolo River and Lake Nyamithi also poses a threat to the native aquatic invertebrate communities. These invasive species are currently absent from the Usuthu River although other invasive species, such as the Australian redclaw crayfish, are found in both river systems. Lake Nyamithi displayed a unique aquatic invertebrate community, distinct from both rivers and their floodplains. This study provides important baseline information on the Usuthu River's aquatic invertebrates and emphasises the need to maintain adequate water flow in rivers and floodplains to protect biodiversity and sensitive species.
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Affiliation(s)
- Lizaan de Necker
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
- South African Institute for Aquatic Biodiversity (NRF‐SAIAB)MakhandaSouth Africa
| | - Divan van Rooyen
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
| | - Ruan Gerber
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
| | - Luc Brendonck
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
- Animal Ecology, Global Change and Sustainable Development, Department of BiologyUniversity of LeuvenLeuvenBelgium
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
| | - Nico J. Smit
- Water Research Group, Unit for Environmental Sciences and ManagementNorth‐West UniversityPotchefstroomSouth Africa
- South African Institute for Aquatic Biodiversity (NRF‐SAIAB)MakhandaSouth Africa
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Gerber R, de Necker L, van Vuren JHJ, Ikenaka Y, Nakayama SMM, Ishizuka M, Wepener V, Smit NJ. A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus). JOURNAL OF FISH BIOLOGY 2023; 103:1129-1143. [PMID: 37498144 DOI: 10.1111/jfb.15516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 07/19/2023] [Accepted: 07/26/2023] [Indexed: 07/28/2023]
Abstract
Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.
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Grants
- 127549 Department of Science and Innovation Professional Development Programme
- 22KK0163 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 17KK0009 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 18KK028708 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 17K2003807 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 18H0413208 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 20K20633 Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan
- 105979 National Research Foundation of South Africa
- 85505 National Research Foundation of South Africa
- 105122 National Research Foundation of South Africa
- K5-1922 Water Research Commission of South Africa
- K5-2185 Water Research Commission of South Africa
- JPMJSA1501 JST/JICA SATREPS (Science and Technology Research Partnership for Sustainable Development
- JPMJAS2001 aXis (Accelerating Social Implementation for SDGs Achievement
- PJ36210002 JST AJ-CORE
- JSPS CORE to CORE program
- Hokkaido University SOUSEI Tokutei Research
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Affiliation(s)
- Ruan Gerber
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Lizaan de Necker
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- South African Institute for Aquatic Biodiversity (NRF-SAIAB), Makhanda, South Africa
| | - Johan H J van Vuren
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Yoshinori Ikenaka
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
- Translational Research Unit, Veterinary Teaching hospital, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan
- One Health Research Center, Hokkaido University, Sapporo, Japan
| | - Shouta M M Nakayama
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Mayumi Ishizuka
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Nico J Smit
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- South African Institute for Aquatic Biodiversity (NRF-SAIAB), Makhanda, South Africa
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Mofu L, Dalu T, Wasserman RJ, Woodford DJ, Weyl OLF. Trophic ecology of co-occurring fishes in the Sundays River Valley irrigation ponds, assessed using stable isotope and gut content analyses. JOURNAL OF FISH BIOLOGY 2023; 102:1191-1205. [PMID: 36856200 DOI: 10.1111/jfb.15360] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 02/17/2023] [Indexed: 05/13/2023]
Abstract
The analysis of food web structures has increased the understanding of the dynamics of organisms belonging to different trophic levels. In this study, the diet of two native species, Glossogobius callidus and Gilchristella aestuaria, was assessed in the presence of two non-native species, Oreochromis mossambicus and Gambusia affinis, in irrigation ponds, Eastern Cape Province, South Africa. The proportion of dietary items consumed and assimilated by the four fish species were inferred from gut contents and carbon and nitrogen stable isotope analysis. Stable isotope analysis revealed that both G. affinis and O. mossambicus had a larger isotopic niche size than G. callidus and G. aestuaria. Although G. callidus fed on benthic resources and G. aestuaria fed on phytoplankton, gut content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, whereas G. aestuaria fed mainly on plankton resources. Considerable niche overlap corroborates the view that resource competition is a major factor shaping the composition of the four fish species. This study highlighted the low diversity of the food web within the Sundays River Valley irrigation ponds, where food items are shared by all the small-bodied fishes.
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Affiliation(s)
- Lubabalo Mofu
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
- DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Makhanda, South Africa
- Centre for Invasion Biology, South African Institute for Aquatic Biodiversity (SAIAB), Makhanda, South Africa
| | - Tatenda Dalu
- School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, South Africa
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
| | - Ryan J Wasserman
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
- Department of Zoology and Entomology, Rhodes University, Makhanda, South Africa
| | - Darragh J Woodford
- South African Institute for Aquatic Biodiversity, Makhanda, South Africa
- Centre for Invasion Biology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Olaf L F Weyl
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa
- DSI/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Makhanda, South Africa
- Centre for Invasion Biology, South African Institute for Aquatic Biodiversity (SAIAB), Makhanda, South Africa
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de Necker L, Brendonck L, Gerber R, Lemmens P, Soto DX, Ikenaka Y, Ishizuka M, Wepener V, Smit NJ. Drought altered trophic dynamics of an important natural saline lake: A stable isotope approach. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 834:155338. [PMID: 35452726 DOI: 10.1016/j.scitotenv.2022.155338] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/07/2022] [Accepted: 04/13/2022] [Indexed: 06/14/2023]
Abstract
Climate change and associated droughts threaten the ecology and resilience of natural saline lakes globally. There is a distinct lack of research regarding their ecological response to climatic events in the Global South. This region is predicted to experience climatic events such as El Niño-Southern Oscillation (ENSO) more often and with greater severity with the potential to alter the structure and functioning of aquatic ecosystems significantly. From 2015 to 2016 South Africa experienced one of the most severe country-wide droughts as a result of a strong ENSO event. Our study aimed to investigate the effect of this supra-seasonal drought on the trophic structure of fish communities in a naturally saline shallow lake of a Ramsar wetland using stable isotope techniques. Fishes and potential basal sources were collected from the lake, during predrought conditions in 2010 and after severe drought (recovery phase; 2017). The δ13C and δ15N values of food web elements were determined and analysed using Bayesian mixing models and Bayesian Laymen metrics to establish the proportional contribution of C3 and C4 basal sources to the fish (consumer) diets, and examine the fish community in terms of isotopic niche and trophic structure, respectively. Fish consumers relied predominantly on C3 basal sources in the predrought and shifted to greater reliance on C4 basal sources, decreased isotopic niche space use and a reduction in trophic length in the recovery phase. Drought altered the type and abundance of the basal sources available by limiting sources to those that are more drought-tolerant, reducing the trophic pathways of the food web with no significant alterations in the fish community. These results demonstrate the resilience and biological plasticity of Lake Nyamithi and its aquatic fauna, highlighting the importance of freshwater inflow to saline lakes with alterations thereof posing a significant threat to their continued functioning.
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Affiliation(s)
- Lizaan de Necker
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa; South African Institute for Aquatic Biodiversity (NRF-SAIAB), Makhanda 6139, South Africa.
| | - Luc Brendonck
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa; Animal Ecology, Global Change and Sustainable Development, Department of Biology, University of Leuven, 32 Charles Deberiotstraat, Leuven 3000, Belgium.
| | - Ruan Gerber
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
| | - Pieter Lemmens
- Laboratory of Aquatic Ecology, Evolution and Conservation, KU Leuven, Ch. Deberiotstraat 32, 3000 Leuven, Belgium; Leibniz Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
| | - David X Soto
- Department of Nuclear Sciences and Applications, Division of Physical and Chemical Sciences, Isotope Hydrology Section, International Atomic Energy Agency, Vienna, Austria.
| | - Yoshinori Ikenaka
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa; Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan; Translational Research Unit, Veterinary Teaching Hospital, Faculty of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan; One Health Research Center, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan.
| | - Mayumi Ishizuka
- Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Kita 18, Nishi 9, Kita-ku, Sapporo 060-0818, Japan.
| | - Victor Wepener
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa.
| | - Nico J Smit
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa.
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Hadfield KA. The North-West University (NWU) Zoology centennial special issue. AFRICAN ZOOLOGY 2020. [DOI: 10.1080/15627020.2020.1755595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Kerry A Hadfield
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
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