Wynand Malherbe

Alien freshwater fish parasites from South Africa: diversity, distribution, status and the way forward

The global translocation and introduction of freshwater fish into non-native regions has created the perfect opportunity for the co-introduction of their parasites. In a recent review on non-native freshwater fish introductions in South Africa, 55 fishes were reported as introduced into novel environments in South Africa, with 27 alien and 28 extralimital. However, the parasites potentially co-introduced by these non-native fishes have received much less attention from researchers than the hosts themselves. Thus far, the only attempts at summarising our knowledge on the diversity of introduced freshwater fish parasites in this region dates back to the 1980s when only four parasite species were considered to be alien, with a further eight species as doubtful. Over the last thirty years, more records have been added and this paper aims to provide an up-to-date review of our knowledge on the diversity, distribution, status (co-invasive or co-introduced) and the direction for future studies on introduced freshwater fish parasites in South Africa. Here we consider seven species (four ciliates, and one cestode, copepod and branchiuran respectively) as confirmed co-invaders, and 16 species (one flagelate, four ciliates, one cestode and ten monogeneans) as co-introduced. In addition, six species (three ciliates, two monogeneans and one copepod) previously recorded as invasive are deemed to be of uncertain status, and one ciliate is removed from the list of known invasive parasites from this region. It is further proposed that future research should focus on extralimital co-introductions, especially in the Eastern and Western Cape regions of South Africa where more than half of the fishes present are introduced species. It is also recommended that all new records of introduced parasites and new distribution records of known invasive parasites should include the deposition of voucher specimens in museums and, as far as possible, include molecular confirmation of its identification.

First report of metazoan parasites from the cichlid Pseudocrenilabrus philander and the cyprinid Enteromius paludinosus in a South African Ramsar wetland

Parasites of two small fish species from a Ramsar wetland in South Africa were studied in 2014–2015. The cichlid Pseudocrenilabrus philander (Weber, 1897) was parasitised by the copepod Lernaea cyprinacea Linnaeus, 1758, the monogenean Gyrodactylus thlapi Christison, Shinn & van As, 2005 and four gryporhynchid metacestode (Cyclophyllidea) species: Paradilepis scolecina (Rudolph, 1819), Paradilepis maleki Khalil, 1961, Neogryporhynchus lasiopeius Baer & Bona, 1960 and Valipora campylancristrota (Wedl, 1855). The cyprinid Enteromius paludinosus (syn. Barbus paludinosus) (Peters, 1852) was infected with the monogenean parasites Dogielius intorquens Crafford, Luus-Powell & Avenant-Oldewage, 2012, Dactylogyrus teresae Mashego, 1983, and three Dactylogyrus spp. These results represent several new locality as well as host records and further contribute information on the parasitic diversity in the Barberspan Ramsar wetland.

Distribution of perfluorinated compounds (PFASs) in the aquatic environment of the industrially polluted Vaal River, South Africa

Perfluorinated alkyl substances (PFASs) are highly persistent chemicals, which have a bioaccumulative potential and can be found in wildlife around the world. Although multiple studies have been performed on PFASs pollution of the aquatic environment, little is known on PFASs pollution on the African continent and their possible risks for human health. In the present study, we examined the distribution of 15 PFASs in fish, invertebrates, sediment and water, collected at three sites, representing a gradient of industrial and mining pollution, along the Vaal River, South Africa. Furthermore, possible risks for human health through consumption of contaminated fish were examined. Perfluorooctane sulfonate (PFOS) was the most dominant PFAS measured in biota, whereas perfluoropentanoic acid (PFPeA) was measured in higher concentrations in water. Mean PFAS concentrations in water ranged from <LOQ to 38.5ng/L. PFAS concentrations in water decreased along the gradient and were similar or lower compared to other studies in Europe, Asia and America. PFAS measurements in sediment were <LOQ, with the exception of PFOS at Thabela Thabeng (2.36ng/g dry weight (dw)). Average ∑PFAS concentrations in biota increased along the gradient and ranged from <LOQ to 34.5ng/g wet weight (ww) in invertebrates, <LOQ to 289ng/g ww in liver and <LOQ to 34.0ng/g ww in muscle tissue. Although PFOS concentrations were relatively high compared to literature, concentrations of other PFASs were rather low. A potential risk for humans through consumption of PFAS-contaminated fish was assessed. Tolerable daily intake values (grams of fish that can be eaten daily without risking health effects) were much lower than the average South African fish consumption per day, implying a potential risk for human health through consumption of PFAS contaminated fish. CAPSULE: Concentrations of perfluorinated compounds in water, sediment, fish and invertebrates from the Vaal River were low or intermediate and posed a potential risk for human health through consumption of contaminated fish.

Aquatic invertebrate community structure of selected endorheic wetlands (pans) in South Africa

Shallow wetlands, such as pans, are not well studied in South Africa, even though they perform many important functions, such as providing an important food source for migratory birds and habitat to highly specialized fauna. Aquatic invertebrate diversity, abundance, and water quality in pans were analysed seasonally from 3 provinces in South Africa with contrasting climates. Univariate and multivariate statistics were used to assess similarities in aquatic invertebrate communities and water chemistry among pans. Pans inundated for extended periods had greater aquatic invertebrate diversity, and several of these taxa were not adapted to the temporary environment common to pans. The subtropical region had greater aquatic macroinvertebrate diversity than semiarid regions due to more rainfall per annum in the subtropical region. Water temperature was a major driving factor for diversity, with greater diversity occurring in warmer seasons. High water hardness and salinity were found to drive decreased diversity and encourage the presence of hardy and more tolerant species. Understanding the importance of these aforementioned factors (i.e., pan longevity, temperature, water hardness, and salinity) influencing aquatic invertebrate biodiversity in pans provides a baseline for future studies and impact assessments on these important and understudied systems.

Fish and macroinvertebrate community composition of a floodplain wetland associated with the Harts River, South Africa, in relation to water quality and habitat parameters

The Harts River and its associated floodplain, Northern Cape province, South Africa, are closely associated with the Vaalharts Irrigation Scheme. This floodplain has been poorly studied in the past, with no published aquatic information available. A fish and macroinvertebrate diversity study was undertaken in April 2009 to compare the faunal diversity of the floodplain to that of the Harts River. Numerous taxa found on the floodplain were not present at the river sites. The smaller fish species that prefer lotic habitats were especially abundant in the floodplain compared to the Harts River. Overall, biodiversity of the region in terms of macroinvertebrates increased if the floodplain was taken into account, and therefore the protection of the floodplain through flow regulation and monitoring is essential.

Macroinvertebrate variation in endorheic depression wetlands in North West and Mpumalanga provinces, South Africa

Aquatic macroinvertebrates are rarely used in wetland assessments due to their variation. However, in terms of biodiversity, these invertebrates form an important component of wetland fauna. Spatial and temporal variation of macroinvertebrate assemblages in endorheic depressions (locally referred to as pans ) in Mpumalanga and North West provinces were compared in wet and dry seasons in 2012 and 2013. A total of 29 taxa were identified from both provinces, with similarities in the structure of communities, with the exception of one or two species, in perennial endorheic depressions in both provinces. Macroinvertebrates sampled in Mpumalanga endorheic depressions were similar to those reported in previous studies completed in the area, and most macroinvertebrates sampled in Mpumalanga and North West were known to be commonly found in temporary habitats. Long-term studies are required to understand better the ecological functioning of the pans in the North West province.

A comparison of methods for incubating zooplankton diapausing eggs from sediment of endorheic pans in the Free State, South Africa

Determining the composition of zooplankton in endorheic pans can be challenging, and live sampling of these microcrustaceans does not give a true indication of their species diversity and abundance. The incubation of zooplankton diapausing eggs can assist in determining their diversity and abundance. In this study the efficacy of two incubation methods – isolation and non-isolation – was tested using samples taken in 2013 from five endorheic pans in the Free State province, South Africa. The non-isolation incubation method made use of distilled water in the hatching experiments, whereas the Onbé–Marcus isolation incubation method, using 1:5 v/v ADAM medium/water, was adapted and applied to samples to isolate the diapausing eggs. The isolation method provided hatchlings at a higher rate than that of the non-isolation method, but subsequent removal and identification of the hatchlings was challenging. In particular, the success of the isolation method was putatively related to sediment grain size composition. Some difficulties were also noted in using the non-isolation method in the hatching and growing of anostracans.

The Application of a Macroinvertebrate Indicator in Afrotropical Regions for Pesticide Pollution

Many biotic integrity indices are not able to isolate community effects due to pesticide exposure as the communities also respond to other anthropogenic and natural stressors. A macroinvertebrate trait bioindicator system that is pesticide specific was therefore developed to overcome these challenges. This system, called SPEAR (SPEcies At Risk), was applied in South Africa as an indicator to link known pesticide catchment usage to changes in the macroinvertebrate community, especially when analytical methods are inconclusive. In addition, the SPEARsalinity index within the SPEAR suite of tools was also evaluated for its effectiveness in South Africa. The results indicated that all of the sites have either been exposed to the same pesticide pressure or not been exposed to pesticides as the SPEAR results were similar when compared to the pesticide intensity. The interaction with other factors like nutrients or salinity was likely a factor that confounded the SPEARpesticides indicator.