Research

RECENT PROJECTS

An ecological survey of Cahora Bassa reservoir, Mozambique, with emphasis on the phytoplankton, water and sediment quality dynamics. Environmental management of the Cahora Bassa reservoir and its surrounding areas is one element of Hidroeléctrica De Cahora Bassa (HCB) mandate. In recent years, there has been significant development of algae and green coloration in some parts of the reservoir, in particular near the dam and Zumbo, Messenguezi and Carinde sub-basin, at the reservoir’s principal inlet. This has raised concerns about possible changes in the ecological status of the lake’s waters. For this reason, it was decided to engage a specialist to carry out studies to assess the aquatic ecology of the Cahora Bassa reservoir. Team: Dr Tatenda Dalu (Project Leader), Prof Tamuka Nhiwatiwa, Mr Farai Dondofema. Funders: Hidroeléctrica De Cahora Bassa. (2018–2020)

The trophic functioning of aquatic food webs in the grassland river-floodplain of Nylsvlei Ramsar Wetland Site. Most studies on subsidies between aquatic-floodplain-terrestrial ecosystems are geographically biased towards the Northern hemisphere and therefore, there is a need for holistic investigations across different climatic zones. The main aim/objective of this project is to quantify the extent to which terrestrial resources maintain floodplain food webs and how this is influenced by wooded, grassland and/or human activities. The project envisages a study of biodiversity and ecosystem dynamics of the major South African Wetland system, favouring a multidisciplinary approach gathering past and new relevant data series from biology, ecology and biogeochemistry. One of the key themes is to unravel the contribution of various terrestrial resources in sustaining productivity in the major river network. Data from other studies has implicated the importance of the role of methane (CH4) inputs and CH4 oxidation under strong river-floodplain interactions. However, river-floodplain interactions are currently under threat given the various human-mediated floodplain alterations. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Prof Olaf LF Weyl, Mrs Florence M Murungweni, Prof Michelle Jackson, Prof Steven Bouillon. Funders: University of Venda Niche Funding, NRF Thuthuka. (2018–2020)

Potamonautids conservation: impacts, opportunities and challenges related to community sustainable livelihoods. Human population growth threatens the integrity of 0.8% of the Earth’s freshwater ecosystems globally, through reduction of its ability to support biodiversity and provide ecosystem services. We aim to assess direct or indirect community livelihoods impacts on preservation of crab species Potamonautes spp., and attempt to identify opportunities and constrains to conservation of crabs within the pre-existing livelihoods of the community households. We hope this will lead to better formulation and implementation of conservation strategies through provision of recommendation strategies that provide long lasting conservation action plans. Local communities’ involvement will be key for success of any crab conservation activities. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Dr Jonathan D Tonkin , Mrs Mwazvita TB Dalu (Co-Project Leader), Prof Tamuka Nhiwatiwa, Mr Gregory Dowo. Funders: Rufford Foundation. (2017–2020)

Assessing the effect of rotenone concentration as a biological control tool for common carp Cyprinus carpio and bluegill Lepomis macrochir in Western Cape reservoirs. Fish invasions are a major threat to imperilled South African fishes and other aquatic fauna. Many introduced fishes are, however, also valuable in inland fisheries which are important contributors to food security, livelihoods and the economy. To facilitate management of alien species, South Africa has promulgated the National Environmental Biodiversity Act (NEM:BA): Alien Species Regulations and the NEMBA: Alien Invasive Species Lists. These legislative instruments recognise the need to balance biodiversity impacts with economic benefits and allow for the use of non-native fishes in areas that are of low conservation concern because they are already invaded. It is, however, recognised that in some areas, and particularly those of high conservation priority (e.g., protected areas, the Freshwater Ecosystem Priority Area “fish sanctuaries”), the removal of non-native fish is necessary to restore natural processes. From a river rehabilitation perspective, eradicating non-native fish using piscicides such as rotenone, allows for the rehabilitation of several kilometres of river. While non-native fish removal by rotenone has been demonstrated to be an effective management tool, its collateral effects on non-target aquatic organisms is a cause for concern. Developing National Policy on the use of rotenone for river and dam rehabilitation, therefore, requires knowledge on the potential impacts of rotenone treatments in South Africa. Team: Dr Tatenda Dalu (Research Specialist), Dr Ryan J Wasserman, Prof Olaf LF Weyl, Dr Terence Bellingan, Dr Martinne Jordan, Dr Ettiene Slabbert, Dr Sean Marr. Funders: Water Research Commission. (2017–2018)

Assessing the effect of common carp Cyprinus carpio and organic pollution on the trophic ecology of aquatic ecosystems. Alien fishes are well established in South Africa and most rivers contain several alien fishes (Ellender & Weyl 2014). Most widespread are species used for aquaculture (e.g., Nile tilapia Oreochromis niloticus) and for the enhancement of fisheries (e.g. black bass species (Micropterus spp.), trout (Onchorhychus mykiss and Salmo trutta) and common carp (Cyprinus carpio)). These species are considered conflict species because they benefit society but also cause environmental harm (Ellender et al., 2014; Zengeya et al., 2017). As a result, their management is often complicated by the different value sets of stakeholders (see Woodford et al., 2017). In South Africa, this has already resulted in considerable conflicts in the development of AIS management strategies for trout and Nile tilapia (Weyl OLF pers. comm.) and, as the Department of Agriculture Fisheries and Forestry starts implementing its new Inland Fisheries Policy (a Draft has already been circulated) is likely to complicate management of black bass and common carp populations. To develop proactive management approaches will require understanding the drivers of invasions and the extent of their impacts on South African environments. Unfortunately, these are poorly researched for many of the conflict species and particularly for common carp where no studies have assessed for impacts in South Africa. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Prof Olaf LF Weyl, Dr Michelle Jackson. Funders: South African Institute for Aquatic Biodiversity. (2017)

Ecological and functional response studies of ephemeral/temporary ecosystems assessed using field and laboratory studies. Biological control can assist in the management of disease vector mosquitoes. However, we urgently require the identification of novel and effective agents to aid population management strategies. Previously, predatory biocontrol of disease vector mosquito species has focused extensively on cyclopoid copepods, but prey size refuge effects have been identified as a hindrance to their predatory efficacy. Calanoid copepods have yet to be examined in the context of mosquito control, despite their high prevalence, diversity and distribution. Here, we apply functional responses (FRs; resource use as a function of resource density) to examine predation efficiencies of a recently described ephemeral pond specialist species, the freshwater calanoid copepod Lovenula raynerae Suárez-Morales, Wasserman & Dalu 2015, using different size classes of larvae of the disease vector complex Culex pipiens as prey. Lovenula raynerae effectively consumed C. pipiens larvae across their ontogeny. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Mr Ross N Cuthbert (Co-Project Leader), Prof Olaf LF Weyl, Prof Jaimie TA Dick, Prof Amanda Callaghan, Prof William P Froneman. Funders: Rhodes University, National Research Foundation, South African Institute for Aquatic Biodiversity, Water Research Foundation. (2014–2017)

Newly discovered biggest known African freshwater copepod, Lovenula rayneri Saurez, Wasserman, Dalu 2015

PREVIOUS PROJECTS

Assessing the plankton dynamics in the Sunday River valley irrigation reservoirs. Team: Dr Tatenda Dalu (Researcher), Dr Ryan J Wasserman, Prof Olaf LF Weyl, Prof Jaimie TA Dick, Dr Darragh Woodford, Mr Ross N Cuthbert. Funders: South African Institute for Aquatic Biodiversity. (2016–2017)
Grahamstown water quality assessment project. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Prof Olaf LF Weyl, Prof William P Froneman, Dr Jonathan D Tonkin, Dr Tongayi Mwedzi, Dr Holly A Nel. Funders: Rhodes University, South African Institute for Aquatic Biodiversity. (2016)
Eastern Cape micro-inlet/micro-estuary research. Team: Dr Tatenda Dalu (Research specialist), Prof Alan K Whitfield, Prof Janine B Adams, Prof Renzo Perissinotto, Dr Lucienne Human, Mr Mandla Magoro, Dr Shuan D Deyzel Mrs Lyndall Naidoo. Funders: South African Institute for Aquatic Biodiversity, National Research Foundation. (2015–2016)
An assessment of the effect of rotenone concentrations on selected non-target aquatic fauna. Team: Dr Tatenda Dalu (Research specialist), Dr Ryan J Wasserman, Prof Olaf LF Weyl, Dr Martinne Jordan, Dr Ettiene Slabbert. Funders: Water Research Commission, DST-NRF Centre of Excellence in Invasion Biology. (2015)
Functional response studies of invasive species, Micropterus salmoides, Pseudocrenalabus philander, Tilapia spermanii and Lepomis macrochirus. Team: Dr Tatenda Dalu (Researcher), Dr Mhairi E Alexander, Dr Ryan J Wasserman, Prof Olaf LF Weyl, Prof Jaimie TA Dick. Funders: National Research Foundation, DST-NRF Centre of Excellence in Invasion Biology. (2015)
Ecological and functional response studies of small aquatic ecosystems assessed using both field and laboratory studies in the Eastern Cape, South Africa. Team: Dr Tatenda Dalu (Co-Project Leader), Dr Ryan J Wasserman (Co-Project Leader), Dr Eduardo Suarez-Morales, Prof Olaf LF Weyl, Mr Ross N Cuthbert, Prof Jaimie TA Dick, Prof William P Froneman, Prof Amanda Callaghan. Funders: National Research Foundation, Rhodes University. (2014–2017)
Ecological assessment of the recently discovered Potamonautes mutareensis sp. nov. in the Eastern Highlands of Zimbabwe, with implications to conservation. Team: Dr Tatenda Dalu (Project Leader), Dr Ryan J Wasserman, Dr Jonathan D Tonkin, Dr Timothy Dube, Dr Mhairi E Alexander, Mrs Mwazvita TB Dalu, Mr Samuel N Motitsoe, Prof William P Froneman. Funders: Idea Wild, Rufford Foundation. (2014–2015)
Impact of introduced crayfish Cherax quadricarinatus on Lake Kariba littoral zone ecosystem inferred using stable isotope approach. Team: Dr Tatenda Dalu (Researcher), Prof Tamuka Nhiwatiwa, Mr Lightone Marufu, Dr Crispen Phiri, Prof Lindah Mhlanga, Prof Maxwell Barson. Funders: University of Zimbabwe, Zimbabwe Research Council. (2014–2015)
Connectivity through allochthony: Reciprocal links between adjacent and terrestrial ecosystems in South Africa. Team: Dr Tatenda Dalu (Research specialist), Prof William P Froneman, Prof Martin Villet, Prof Nicole Richoux, Prof Alan K Whitfield, Prof Dan Parker, Dr Lenin Chari, Dr Leandro Bergamino, Dr Jeff W Hean, Dr Sydney Moyo, Prof Adrian Craig. Funders: National Research Foundation, Rhodes University, Water Research Commission. (2012–2014)
An applied ecological assessment of the drivers in decline, distribution and conservation of five endangered frog species in the Eastern Highlands (Zimbabwe). Team: Dr Tatenda Dalu (Co-Project Leader), Mr Edwin M Tambara (Co-Project Leader), Dr Lenin D Chari. Funders: Rufford Foundation. (2012–2013)
Limnological study of Malilangwe reservoir in the south-eastern lowveld of Zimbabwe. Team: Dr Tatenda Dalu (Project Leader), Dr Bruce W Clegg, Prof Tamuka Nhiwatiwa. Funders: Malilangwe Trust, DAAD. (2011–2012)
T he impact of environmental pollution on potable water quality . Team: Dr Tatenda Dalu (Researcher), Prof Maxwell Barson, Prof Tamuka Nhiwatiwa. Funders: Ministry of Health and Child Welfare (Zimbabwe), VLIR-UOS, University of Zimbabwe, World Health Organisation. (2007–2008)

Sunday River irrigation ponds

Water hyacinth Echihornia crassipes and water fern Azolla sp.

Kaysers Beach rocky shore, Eastern Cape

Lajuma River

Most of my research is supported by the following funding bodies as research grants, scholarships and fellowships either as individual grants or through research collaborators funds