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Plant invasions have been linked to displacement of native vegetation and altering of fire regimes and might influence vector mosquito populations by altering habitats or nutrient inputs. Whereas wildfire effects on terrestrial ecosystems are relatively well-studied, ash depositions into aquatic ecosystems and effects on semi-aquatic taxa such as mosquitoes have remained overlooked. Here, we investigated mosquito colonization in water treated with ash from native plants [quinine tree (Rauvolfia caffra), Transvaal milk plum (Englerophytum magalismontanum), apple leaf (Philenoptera violacea)] and invasive alien plants [i.e., lantana (Lantana camara), guava (Psidium guajava), red river gum (Eucalyptus camaldulensis)] in containers at two ash concentrations (i.e., 1, 2 g/L). Overall, there was no statistically clear difference in colonization between ash from native and alien species. We recorded colonization by two mosquito genera (Culex spp. and Anopheles spp.), with Culex generally much more abundant than Anopheles. Few differences were identified among the plants, with statistically clear effects of ash type and concentration on larval and pupal stages. High Culex egg and larval abundances were shown in lantana and apple leaf treatments compared to controls, and milkplum versus controls for pupae of both genera. Further research is required to elucidate the influence of nutrient inputs from different ash species on vector mosquito population dynamics.

Background Sound management of protected areas is crucial for biodiversity conservation. In savanna systems, fire is common, yet little is known on the direct and long-term effects of prescribed burns on arthropod abundance, richness, and diversity. Standardised pitfall traps and active searches were used to compare variation in abundance, richness and diversity of arthropods at various experimental burn plots in the Kruger National Park, a protected area in a savanna setting. Results Hymenopterans: Formicidae were the most abundant (76.4%), whilst Coleopterans, Araneae and Orthopterans constituted 18.6, 3 and 1% of the total arthropods collected respectively. Coleopterans were the most diverse group (30.2%) compared to Hymenopterans: Formicidae (24.6), Araneae (24.6) and Orthopterans (4%). Abundance, species richness and diversity of multi-taxa significantly differed between the treatment plots. Abundance and diversity of Formicidae were significantly lower, hence, species richness was significantly higher in annually burnt plots compared to the unburnt control plots. Although the highest number of arthropods was recorded in unburnt plots, species richness and diversity were lowest in these plots compared to those burnt annually and triennially. Conclusions We conclude that late summer burns do not have major ecological impact on arthropods, and it was demonstrated by the abundance and diversity of species recorded at the annually burnt plots. Thus, annual late summer burns can be used as a conservation tool for arthropod inhabiting the protected savanna of Kruger National Park.

Irrigation ponds are increasingly abundant globally, particularly in water-stressed countries with limited natural surface waters, yet knowledge of their ecology is limited. Here, we assessed zoopl...

Wetlands physical and biological processes are fundamental to the distribution and structuring of organic matter in sediments. This study investigated spatial and temporal changes in organic matter sources in sediments within the Nylsvley Wetland, South Africa across two seasons, five sites and three wetland zones and identified pertinent contributors to sediment organic matter. Results showed distributions were uneven throughout the wetlands, with the seasonal zone having slightly high sediment organic matter in the cool-dry season and the permanent zone had high sediment organic matter in the hot-wet season, whereas the temporary zone had low SOM concentrations. Significant differences in nutrient concentrations were observed across wetland zones and seasons for Phosphorous, Potassium, Calcium and Magnesium, with the seasonal zone tending to be the most nutrient-rich in the cool-dry season, and with permanent zone nutrient levels rising substantially in the hot-wet season. Sediment δ13C differed significantly among wetland zones, whereas δ15N was statistically similar. Autochthonous plants were the main sources of organic matter in sediments overall across sites and zones. This study’s findings help to better understand the distribution of organic matter in wetland ecosystems and the role wetland zones play in the seasonal provisioning of allochthonous inputs.

Lycodonomorphus is a genus of lamprophiid water snake endemic in Africa. Although widespread, abundant and presumably an important component of many aquatic and semi-aquatic food webs, these snakes are poorly understood taxonomically, particularly from a phylogenetic perspective. With only four of the nine species currently sequenced, this study attempts to improve our understanding of the evolutionary relationships within the genus through the phylogenetic placement of one of the most elusive species, Lycodonomorphus obscuriventris. Collected in the Ramsar declared Makuleke Wetlands in northern Kruger National Park (South Africa), the sample used in this study not only yielded the first DNA sequences for the taxon but also represented the most northerly South African record, bridging the gap between the southern and northern populations. The snake was sequenced for three partial mitochondrial genes (16S, Cyt-b, ND4) and one partial nuclear gene (c-mos) and phylogenetically placed, relative to the rest of the genus, using maximum likelihood (ML) and Bayesian inference (BI). Sequence divergences between sister taxa were also estimated using pairwise distance analysis. The concatenated phylogenetic reconstruction yielded similar topological structuring when compared to phylogenies from past articles, with both the ML and BI algorithms recovering strong support for L. obscuriventris as sister to a clade comprising of L. whytii + L. laevissimus + L. rufulus. The phylogenetic placement, albeit based on a single sample, challenges the original placement (morphological) of L. obscuriventris as sub-specific within L. whytii, suggesting that multiple species concepts should be considered when delineating species within this group.Conservation implications: Prior to the discovery of the new record, the global distribution of L. obscuriventris was characterised by two disjunct populations. The new record bridges the distribution gap between these two populations, rendering the distribution continuous. This bodes well for the species as there is likely no barrier to gene flow, thereby buffering the species from localised threats given the more expansive distribution. Furthermore, given that the specimen was sampled from the Kruger National Park, the species is likely to be well-protected as much of its distribution within South Africa seems to fall within protected areas.

Global contamination of freshwater ecosystems by chemical compounds, such as pesticides, may exert high pressure on biologically-driven organic matter decomposition. These pollutants may also impair the quality of organic substrates for colonising invertebrates and reduce primary productivity by decreasing the abundance of phytoplankton. In southern Africa, increasing pesticide usage associated with macadamia plantations, in particular, presents a growing risk to freshwater ecosystems. Here, we examined macadamia (Macadamia integrifolia) leaf litter decomposition following exposure to three pesticides (i.e., Karate Zeon 10 CS (lambda-cyhalothrin), Mulan 20 AS (acetamiprid), Pyrinex 250 CS (chlorpyrifos)) used commonly in macadamia plantations, via an ex-situ microcosm approach. We examined mosquito colonisation of these microcosms as semi-aquatic macroinvertebrates which form a significant component of aquatic communities within standing waters. Macadamia leaf litter tended to decompose faster when exposed to Karate and Pyrinex pesticide treatments. Additionally, chlorophyll-a, conductivity, total dissolved solids, and pH differed among pesticide treatments and controls, with pesticides (Karate Zeon and Mulan) tending to reduce chlorophyll-a concentrations. Overall, pesticide treatments promoted mosquito (i.e., Culex spp.) and pupal abundances. In terms of dominant aquatic mosquito group abundances (i.e., Anopheles spp., Culex spp.), the effect of pesticides differed significantly among pesticide types, with Pyrinex and Mulan treatments having higher mosquito abundances in comparison to Karate Zeon and pesticide-free treatments. These findings collectively demonstrate that common pesticides used in the macadamia plantation may exert pressure on adjacent freshwater communities by shaping leaf-litter decomposition, semi-aquatic macroinvertebrate colonisation dynamics, and chlorophyll-a.

Anthropogenic activities have increasingly subjected freshwater ecosystems globally to various pressures. Increasing land use activities have been highly linked to deteriorating freshwater ecosystems and dwindling biodiversity. For sound management and conservation policies to be implemented, relations between land use, environmental, and biotic components need to be widely documented. To evaluate the impacts of land use on biotic components, this study analyzed the diatom and macroinvertebrate community composition of the Eastern Highlands (Zimbabwe) streams to assess the main spatial diatom and macroinvertebrate community variances and how environmental variables and spatial factors influence community composition. Diatom and macroinvertebrate sampling was done in 16 streams in protected areas (national parks) and impacted sites (timber plantation and communal areas). Water (pH, phosphorus, and ammonium) and sediment (nitrogen, phosphorus, calcium, magnesium, manganese, and zinc) and habitat (substrate embeddedness, and habitat) variables differed significantly with land use. Principal Component Analysis (PCA) showed that the protected area had the best water quality, particularly marked by high pH levels and low phosphorus concentrations among environment types. Heavy metals were high in the communal areas although mercury was higher in the national park. Significant differences were observed in diatom metrics, specifically dominance and evenness, with no significant differences being observed in macroinvertebrate metrics across land uses. Diatoms differed in terms of composition in response to land use. Results provide an important scientific reference for land use optimization and guidance for the formulation of policies to protect freshwater resources in African Highland streams. Management and conservation initiatives in the Eastern Highlands are further recommended as this study detected high levels of mercury in the protected area, implying high levels of illegal mining.

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. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-021-13185-1.

The physical properties of habitats are crucial determinants of community structure with significant effects on food web dynamics. We examined the effects of rock pool physical properties (e.g. pool size, water depth) and short-term temporal (seasonal) change (e.g. temperature, nutrients) on food web structure at small spatial scales (c. 500 m) on the warm temperate coast of South Africa. Using stable carbon and nitrogen isotope signatures, we characterised food web structure with Layman metrics and quantified food web size, defined as the total area in isotopic space occupied by consumer species. The effects of rock pool physical properties and seasonal changes on species counts and food web structure were evaluated using a Bayesian generalised linear mixed model approach. Substratum type, water depth, pool size, phosphate concentrations, salinity and temperature all influenced overall food web dynamics. A winter reduction of sand cover led to a more heterogeneous substratum and a significant increase in species counts, while consumer niche similarity decreased with increasing pool size in summer. The range of δ15N values, or trophic height, was negatively and positively affected by salinity and phosphate levels, respectively. Overall, the effects of pool physical properties on food web structure were moderated by seasonality.

Biological invasions are one of the top drivers of the ongoing biodiversity crisis. An underestimated consequence of invasions is the enormity of their economic impacts. Knowledge gaps regarding economic costs produced by invasive alien species (IAS) are pervasive, particularly for emerging economies such as India—the fastest growing economy worldwide. To investigate, highlight and bridge this gap, we synthesised data on the economic costs of IAS in India. Specifically, we examine how IAS costs are distributed spatially, environmentally, sectorally, taxonomically, temporally, and across introduction pathways; and discuss how Indian IAS costs vary with socioeconomic indicators. We found that IAS have cost the Indian economy between at least US$ 127.3 billion to 182.6 billion (Indian Rupees ₹ 8.3 trillion to 11.9 trillion) over 1960–2020, and these costs have increased with time. Despite these massive recorded costs, most were not assigned to specific regions, environments, sectors, cost types and causal IAS, and these knowledge gaps are more pronounced in India than in the rest of the world. When costs were specifically assigned, maximum costs were incurred in West, South and North India, by invasive alien insects in semi-aquatic ecosystems; they were incurred mainly by the public and social welfare sector, and were associated with damages and losses rather than management expenses. Our findings indicate that the reported economic costs grossly underestimate the actual costs, especially considering the expected costs given India’s population size, gross domestic product and high numbers of IAS without reported costs. This cost analysis improves our knowledge of the negative economic impacts of biological invasions in India and the burden they can represent for its development. We hope this study motivates policymakers to address socio-ecological issues in India and launch a national biological invasion research programme, especially since economic growth will be accompanied by greater impacts of global change.

Planktonic invasive species cause adverse effects on aquatic biodiversity and ecosystem services. However, these impacts are often underestimated because of unresolved taxonomic issues and limited biogeographic knowledge. Thus, it is pivotal to start a rigorous quantification of impacts undertaken by planktonic invasive species on global economies. We used the InvaCost database, the most up-to-date database of economic cost estimates of biological invasions worldwide, to produce the first critical assessment of the economic dimension of biological invasions caused by planktonic taxa. We found that in period spanning from 1960 to 2021, the cumulative global cost of plankton invasions was US$ 5.8 billion for permanent plankton (holoplankton) of which viruses encompassed nearly 93%. Apart from viruses, we found more costs related to zooplankton (US$ 297 million) than to the other groups summed, including myco- (US$ 73 million), phyto- (43 million), and bacterioplankton (US$ 0.7 million). Strikingly, harmful and potentially toxic cyanobacteria and dinoflagellates are completely absent from the database. Furthermore, the data base showed a decrease in costs over time, which is probably an artifact as a sharp rise of novel planktonic alien species has gained international attention. Also, assessments of the costs of larval meroplanktonic stages of littoral and benthic invasive invertebrates are lacking whereas cumulative global cost of their adults stages is high up to US$ 98 billion billion and increasing. Considering the challenges and perspectives of increasing but unnoticed or neglected impacts by plankton invasions, the assessment of their ecological and economic impacts should be of high priority.

Highlights: • Tarebia granifera and Physa acuta densities ranged between 161 and 517 and 15–619 individuals m−2, respectively. • P. acuta moved significantly slower and covered a significantly shorter net distance. • Movement traits associated with exploratory behaviour were similar among species. • Variation in straightness index trait was 1.6-fold greater for P. acuta (CV = 79.9). • Study provides baseline information on alien snail in the Austral subtropical regions. 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.

Size at maturity, sex ratio and maturity stages are key population parameters in fisheries management of exploited stocks because they influence survival of fish populations. The decline in Hydrocy...

As apex predators, marine mammals play a key role in maintaining community structure and functioning in marine ecosystems. Hence, a decline in marine mammal populations may have negative effects on...

1. Land use intensification and climate change are two prominent drivers of variation in biological communities. However, we know very little about how these two potential environmental stressors interact. Here, we use a stable isotope approach to quantify how animal communities respond to urban and agriculture land use, and to latitudinal variation in climate (rainfall and temperature), in 29 streams across South Africa. 2. Community structure was shaped by both land use and climatic factors. The taxonomic diversity of invertebrates was best explained by an independent negative effect of urbanisation, while abundance declined in summer. However, we could not use our variables to predict fish diversity (suggesting that other factors may be more important). 3. Both trophic functional diversity (quantifed using isotopic richness ) and food chain length declined with increasing temperature. Functional redundancy (quantifed using isotopic uniqueness ) in the invertebrate community was high in wet areas, and a synergistic interaction with urbanisation caused the lowest values in dry urban regions. There was an additive effect of agriculture and rainfall on abundance‐weighted vertebrate functional diversity (quantified using isotopic dispersion ), with the former causing a decline in dispersion, with this partially compensated for by high rainfall. 4. In most cases, we found that a single dominant driver (either climate or land use) explained variation between streams. We only found two incidences of combined effects improving the model, one of which was amplified (i.e., the drivers combined to cause an effect larger than the sum of their independent effects), indicating that management should first focus on mitigating the dominant stressor in stream ecosystems for successful restoration efforts. 5. Overall, our study indicates subtle food web responses to multiple drivers of change, only identified by using functional isotope metrics – these are a useful tool for a whole‐systems biology understanding of global change.

Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions. Copepods exhibited destabilising Type II functional responses in all treatments, with female copepods significantly more voracious than males under multiple predator groups. Lovenula raynerae exhibited significantly negative MPEs overall which resulted in prey risk reductions. However, whilst not statistically clear, the magnitude of antagonistic interactions subtly differed among predator-predator compositions and prey densities, with female-female antagonisms generally prevalent at low prey densities, and male-male negative interactions greater under high prey densities. Mixed-sex copepod group predation was predicted by both additive and substitutive models, and additive models generated significantly higher consumption estimates than substitutive equivalents given that their predictions were based on the absence of antagonistic non-trophic interactions. We propose the importance of internal population sex demographics as a further context-dependency which influences the nature of MPEs, with demographic implications requiring investigation across other taxonomic and trophic groups.

Microplastics have become a major environmental concern globally due to their potential impact on ecosystem function. They are known to be ubiquitously present, persistent and bio-accumulative, yet there is a lack of abundance quantifications in freshwater shorelines. Furthermore, there is little understanding of combined effects of seasonality and human population density on the extent of microplastic pollution. In this study, we assessed microplastics in sediment along a subtropical reservoir shoreline across three seasons and seven sites to understand microplastic pollution dynamics along a human population gradient. Multivariable analysis was used to assess relationships among substrate embeddedness, sediment organic matter, human population density and microplastic particle densities and characteristics. Microplastic densities were relatively high during the hot–dry season (mean range 120–6417 particles kg−1 dwt) whilst the hot–wet season had the lowest densities (mean range 5–94 particles kg−1 dwt). Microplastic abundances were positively correlated with population density, demonstrating the direct effects of human activity on microplastic contamination. These results highlight the need to further explore microplastic distribution patterns in freshwater ecosystems in the Southern Hemisphere. Furthermore, our findings suggest particular risk for fauna during low rainfall periods through microplastic concentration effects.

BACKGROUND: Predation plays a pivotal role in the composition and functioning of ecosystems. Both habitat complexity and predator density are important contexts which may determine the strength of trophic and non‐trophic interactions. In aquatic systems, the efficacy of natural enemies in regulating vector pest species could be modified by such context dependencies. Here, we use a functional response (FR) approach to experimentally quantify conspecific multiple predator effects across a habitat complexity gradient of two notonectids, Anisops sardea and Enithares chinai, towards larvae of the vector mosquito Culex pipiens pipiens. RESULTS: E. chinai exhibited significantly greater consumption rates than A. sardea across habitat complexities, both as individuals and conspecific pairs. Each predator type displayed Type II FRs across experimental treatments, with synergistic multiple predator effects (i.e. prey risk enhancement) displayed in the absence of habitat complexity. Effects of increasing habitat complexity modified multiple predator effects differentially between species given behavioral differences, with habitat complexity causing significant antagonism (i.e. prey risk reduction) with multiple A. sardea compared to E. chinai. CONCLUSION: Habitat complexity effects on multiple predator interactions can manifest differently at the species level, suggesting emergent effects which complicate predictions of natural enemy impact in heterogenous environments. Considerations of density, diversity and habitat effects on efficacies of natural enemies should thus be considered by pest management practitioners to better explain biocontrol efficacies in increasingly diverse environments. © 2020 Society of Chemical Industry

Habitat structure can profoundly influence interaction strengths between predators and prey. Spatio-temporal habitat structure in temporary wetland ecosystems is particularly variable because of fluctuations in water levels and vegetation colonisation dynamics. Demographic characteristics within animal populations may also alter the influence of habitat structure on biotic interactions, but have remained untested. Here, we investigate the influence of vegetation habitat structure on the consumption of larval mosquito prey by the calanoid copepod Lovenula raynerae, a temporary pond specialist. Increased habitat complexity reduced predation, and gravid female copepods were generally more voracious than male copepods in simplified habitats. However, sexes were more similar as habitat complexity increased. Type II functional responses were exhibited by the copepods irrespective of habitat complexity and sex, owing to consistent high prey acquisition at low prey densities. Attack rates by copepods were relatively unaffected by the complexity gradient, whilst handling times lengthened under more complex environments in gravid female copepods. We demonstrate emergent effects of habitat complexity across species demographics, with predation by males more robust to differences in habitat complexity than females. For ecosystems such as temporary ponds where sex-skewed predator ratios develop, our laboratory findings suggest habitat complexity and sex demographics mediate prey risk.

Access to education is a significant determinant in future success, not only for a country but equally for individuals. Higher Education (HE) thus is an integral part of the Sustainable Development Goals and vital in supporting African development. Despite this, there is often a lack of access to HE in many parts of Africa, distance education can subsequently play an important role in increasing access to education by providing materials online. Even though institutions such as the University of South Africa, a provider of Open Distance Learning (ODL), can open access to HE for many marginalised and peripheral communities, we cannot separate access to ODL education from the debate of access to ICTs. Students in urban areas have a significantly different educational experience to students with poor ICT access in urban, peri-urban and rural areas. This paper explores the nature of access to ICT and how this affects students’ ability to access HE.

South Africa has approximately 200 micro-estuaries and micro-outlets along its more than 3 000 km of coastline. Many of these microsystems (i.e. micro-outlets and micro-estuaries) share some charac...

Despite the high abundance of the gobiid fish Glossogobius callidus in many freshwater ecosystems in South Africa, very few studies have assessed the biology and ecology of the species. Here, we in...

The Vhembe Biosphere Reserve, South Africa, contains many wetlands that serve as wildlife habitats and provide vital ecosystem services. Some of the wetlands are continuously being degraded or destroyed by anthropogenic activities causing them to disappear at an alarming rate. Benthic macroinvertebrates are known as good water quality bioindicators and are used to assess aquatic ecosystem health. The current study investigated habitat quality using macroinvertebrate community structure and other biotic variables (i.e. phytoplankton, macrophytes) in relation to environmental variables in the Sambandou wetlands using canonical correspondence analysis (CCA). A total of fifteen macroinvertebrate families were identified over two seasons. The CCA highlighted seven variables, i.e. pH, phosphate concentration, temperature, ammonium, macrophyte cover, conductivity and water depth, which were significant in structuring macroinvertebrate community. Picophytoplankton and microphytoplankton concentrations decreased from winter to summer, whereas nanophytoplankton concentration increased from winter to summer. Thus, the dominance of small-sized phytoplankton indicated nutrient limitation and decreased productivity, whereas winter sites 2 and 3 were dominated by large-celled phytoplankton, highlighting increased productivity. Winter sites were mostly negatively associated with CCA axis 1 and were characterised by high temperature, phosphate and ammonium concentrations, macrophyte cover, pH and conductivity. Summer sites were positively associated with axis 1, being characterised by high water depth and pH levels. The results obtained highlighted that agricultural activities such as cattle grazing and crop farming and sand mining/poaching had a negative effect on macroinvertebrate community structure.

Spinicaudatan clam shrimp are a widespread and diverse group of branchiopod crustaceans, yet few mitochondrial genomes have been published for this taxonomic group. Here, we present the mitogenome ...

Highlights: • Baetidae, Corixidae, Coenogrionidae, Dytiscidae and Physidae were the most abundant families. • Functional feeding group ratios indicated that all sites were strongly autotrophic. • Environmental variables and fish had an influence on macroinvertebrate community. • Different macroinvertebrate taxa respond differently to seasonal changes. Abstract: Wetlands in the Global South are under increasing pressure due to multiple stressors associated with global change. Water and sediment quality assessments, as well as biomonitoring using macroinvertebrates communities, are fundamental tools for informing wetland condition and management strategies. Here, we examine water and sediment parameters affecting aquatic macroinvertebrates in Nlyslvey Wetland, Limpopo Province, South Africa. Water quality, sediments, fish and macroinvertebrate community data were collected across three seasons (hot-dry, hot-wet, cool-dry) from five sites. Baetidae, Corixidae, Coenogrionidae, Dytiscidae and Physidae were the most abundant and dominant families, with functional feeding group (FFG) ratios indicating that all sites were strongly autotrophic, had high predator-prey ratios, few shredders and had a stable substrate across seasons. Fish abundances increased significantly towards the cool-dry season. Based on redundancy analysis, P, Ca, pH, Cu and Na were strongly positively associated with macroinvertebrates, including Physidae, Corixidae, Planorbidae, Ostracoda, Potamonautidae and Hydropyschidae; turbidity and sulphur were associated with Dytiscidae, Oligochaetae, Libellulidae, Gerridae and Dixidae, and fish abundance, Fe, oxygen reduction potential and total dissolved solids were negatively associated with Baetidae, Belostomatidae, Hydrophilidae and Leptoceridae. Therefore, these variables accounted for large levels of variation in macroinvertebrate families, with the cool-dry season clearly distinguished from the hot-wet and hot-dry seasons according to functional feeding groups. Being a protected area, this information could provide a useful baseline for further studies into wetlands in the region subject to greater anthropogenic stresses, as well as future studies in this Ramsar site under global changes. Further studies are required to assess the importance of environmental factors influencing the richness and distribution of macroinvertebrate communities in wetlands under growing anthropogenic pressures.

Wildfires are natural or anthropogenic phenomena increasing at alarming rates globally due to land-use alterations, droughts, climatic warming, hunting and biological invasions. Whereas wildfire effects on terrestrial ecosystems are marked and relatively well-studied, ash depositions into aquatic ecosystems have often remained overlooked but have the potential to significantly impact bottom-up processes. This study assessed ash-water-phytoplankton biomass dynamics using six plant species [i.e., three natives (apple leaf Philenoptera violacea, Transvaal milk plum Englerophytum magalismontanum, quinine tree Rauvolfia caffra) and three aliens (lantana Lantana camara, gum Eucalyptus camaldulensis, guava Psidium guajava)] based on a six-week mesocosm experiment with different ash concentrations (1 and 2 g L-1). We assessed concentrations of chemical elements, i.e., N, P, K, Ca, Mg, Na, Mn, Fe, Cu, Zn and B from ash collected, and we have observed significant differences among the species. High concentrations of P, K, Mn, Fe, Cu, Zn and B were recorded from Transvaal milk plum ash and low concentrations of P, K, Ca, Mg, Cu and Zn were recorded from apple leaf. An increase in phytoplankton biomass (using chlorophyll-a concentration as a proxy) for all treatments i.e., 1 and 2 g L-1 for all plant species ash was observed a week after, followed by decreases in the following weeks, with the exception of 2 g L-1 for lantana, gum and control. Silicate concentrations (i.e., used as a proxy for diatom abundance) showed increasing patterns among all ash treatments, with exception of controls. However, no clear patterns were observed between native and alien plant ash on both chl-a and silicate concentrations. We found that ash has notable effects on water chemistry, particularly nitrate, which increased throughout the weeks, whereas, pH and conductivity were high at low ash concentrations. The impacts of ash on water chemistry, chl-a and silicate concentrations vary with individual species and the amount of ash deposited into the system.

Predation is a critical ecological process that directly and indirectly mediates population stabilities, as well as ecosystem structure and function. The strength of interactions between predators and prey may be mediated by multiple density dependences concerning numbers of predators and prey. In temporary wetland ecosystems in particular, fluctuating water volumes may alter predation rates through differing search space and prey encounter rates. Using a functional response approach, we examined the influence of predator and prey densities on interaction strengths of the temporary pond specialist copepod Lovenula raynerae preying on cladoceran prey, Daphnia pulex, under contrasting water volumes. Further, using a population dynamic modeling approach, we quantified multiple predator effects across differences in prey density and water volume. Predators exhibited type II functional responses under both water volumes, with significant antagonistic multiple predator effects (i.e., antagonisms) exhibited overall. The strengths of antagonistic interactions were, however, enhanced under reduced water volumes and at intermediate prey densities. These findings indicate important biotic and abiotic contexts that mediate predator–prey dynamics, whereby multiple predator effects are contingent on both prey density and search area characteristics. In particular, reduced search areas (i.e., water volumes) under intermediate prey densities could enhance antagonisms by heightening predator–predator interference effects., Predator and prey densities are variable spatiotemporally across all habitat types globally. Our results indicate that predatory interaction strengths differ depending on densities of both predator and prey participants, with antagonistic multiple predator effects enhanced at intermediate prey densities. Future habitat changes resulting from anthropogenic activity that alter communities could have marked implications for trophic dynamics.

Clam shrimps (Spinicaudata) are a widespread and diverse crustacean group that frequent temporary aquatic habitats, but few complete mitochondrial genomes have been published for this group. Here, ...

Diatoms are siliceous micro-algae and have been used with increasing frequency as bioindicators in aquatic ecosystems. Typically, European diatom indices have been modified and augmented with data on taxa endemic to and commonly found in other parts of the world. In order to further test the application of diatom indices, water quality and diatom sampling were performed in the Bloukrans River system, Eastern Cape Province of South Africa. Nine sites with contrasting water quality were sampled along the length of the river in February, May and July 2018. Multivariate statistical analysis (Canonical Correspondence Analysis) was employed to elucidate spatiotemporal differences in diatom community structure. Canonical correspondence analysis indicated that differences in diatom community assemblages were best explained by dissolved oxygen, temperature, nitrate, conductivity and phosphate. Diatom-based indices incorporated in OMNIDIA software were also applied to assess the integrity of the water quality as indicated by diatom communities. Several foreign indices (e.g. the trophic diatom index (TDI), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. The SADI demonstrated that the Bloukrans River was impacted and had significant correlations with water quality variables (p

Developing predictive methods to forecast the impacts of existing and emerging invasive species is of critical importance to biodiversity conservation. However, invader impacts are context-dependent, making reliable and robust predictions challenging. In particular, it is unclear how temporal variabilities in relation to temperature regime shifts influence invader ecological impacts. In the present study, we quantify the functional responses of three coexisting freshwater fishes: the native freshwater River Goby Glossogobiuscallidus, and the non-native Mozambique Tilapia Oreochromismossambicus and Western Mosquitofish Gambusiaaffinis, under two temperature treatments using chironomid larvae as prey. This was used along with fish abundance data to determine temporal differences in ecological impacts of each fish species between seasons (i.e. at two corresponding temperatures). All three fish species exhibited potentially population-destabilizing Type II functional responses. Their maximum feeding rates were consistently higher in the warm temperature treatment, whereas attack rates tended to be reduced. Non-native Mozambique Tilapia had the highest maximum feeding rate under both temperature treatments (18 °C and 25 °C), followed by the non-native Western Mosquitofish and lastly the native River Goby, suggesting greater per capita impacts on native prey by non-native fishes. The predatory fish abundances differed significantly according to season, with native River Goby and non-native Mozambique Tilapia generally more abundant than non-native Western Mosquitofish. By multiplying functional response maximum feeding rates with abundances of each fish species across the seasonal gradient, the relative impact potential of non-native Mozambique Tilapia was consistently higher compared to that of native gobies. Western Mosquitofish impacts were less apparent, owing to their low abundances. We demonstrate how seasonal temperature fluctuations affect the relative impact capacities of introduced species and the utility of consumer functional response and the relative impact potential metric in impact forecasting.

Inter‐specific interactions are key factors in the structuring and functioning of ecological communities. Therefore, it is necessary to assess species interactions, such as predator–prey dynamics and competitive exclusion, within the context of continuing global species introductions. The aim of the present study was to assess ecological impacts and competitive exclusion dynamics involving co‐occurring introduced and native fish species, using the multiple predator functional response (FR) approach. We use comparative FR analysis (resource uptake as a function of resource density) to assess inter‐specific interactions between the invasive western mosquitofish Gambusia affinis and the native freshwater river goby Glossogobius callidus towards chironomid larvae. The FR was derived for each fish species as individuals and when in heterospecific pairings. Data from single individuals were used to predict the expected FR of individuals when in heterospecific multiple predator combinations. Expected FRs were then compared to the observed FRs of each predator in combination trials, enumerated using prey items in their gut contents. Both fish species displayed Type II FRs, however, in single fish trials, invasive mosquitofish had significantly higher FRs (curve asymptotes; i.e. shorter handling times and higher maximum feeding rates) than native river gobies. Heterospecific mosquitofish‐river goby combinations revealed that the FR of the river goby was reduced (i.e. longer handling times and lower maximum feeding rates) by the presence of mosquitofish, whereas this combination greatly enhanced mosquitofish FR magnitudes (i.e. shorter handling times and higher maximum feeding rates). The heterospecific treatments resulted in neutral impacts on prey and there were clear inter‐species interference in favour of the non‐native mosquitofish. This study demonstrates how multiple predators can alter the shape of individual FRs, with neutral effects on prey but superior invader competitive ability. This has implications for predicting the naturalisation success of invasive predators, as predatory and competitive interactions with native predators and prey may facilitate rather than impede establishment.

The quantification of microplastics in environmental samples often requires an observer to determine whether a particle is plastic or non-plastic, prior to further verification procedures. This implies that inconspicuous microplastics with a low natural detection may be underestimated. The present study aimed at assessing this underestimation, looking at how colour (white, green and blue), size (large; ~1000 μm and small

Environmental and biological features of Austral subtropical pan types were assessed, along with the drivers of chlorophyll-a (chl-a) concentrations. Chl-a biomass varied considerably across seasons and endorheic pans had elevated chl-a concentrations compared to floodplain pans. The major driver of chl-a concentration based on generalised linear/non-linear models (GLZ) was total phosphorous and total suspended solids for all pan types and seasons combined. These results are discussed within the context of secondary productivity, aquatic ecosystem heterogeneity and endorheic pan conservation.

Anthropogenic disturbances within or near aquatic ecosystems often contribute to eutrophication events. Cyanobacteria are a key group responsible for environmental problems associated with eutrophication processes. Interest is growing in estimating the threat of cyanobacteria in tropical Africa, however, there is still a lack of understanding regarding temporal drivers of cyanobacteria dynamics in natural aquatic ecosystems given the paucity of relevant fundamental research in this area. To better understand cyanobacteria dynamics, potential drivers of cyanobacteria dynamics were investigated in a model tropical reservoir system, whereby phytoplankton communities and water quality parameters were sampled during the tropical hot-wet, cool-dry and hot-dry seasons. Fifteen cyanobacteria taxa were recorded over the study period. Microcystis spp. and Cylindrospermopsis spp., known cyanotoxins producers, were the most prevalent bloom-forming taxa found in the study, with overall Cyanobacteria relative abundances being greatest during the cool-dry season. This was likely driven by decreased river inflows and increased reservoir mixing during the cool-dry period. Combinations of macrophyte cover, dissolved oxygen levels, water transparency, reactive phosphorus, water depth and chemical oxygen demand were found to significantly affect cyanobacteria community structure. The study highlights that under climate change forecasts (for much of tropical arid Africa), potentially harmful and problematic algal species may proliferate. Management options, therefore, need to be explored to maintain water quality and potable availability to mitigate against indirect harmful effects of environmental changes on ecosystems and human communities that utilise their services.