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More than half of the world's rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes., (© 2024. The Author(s).)

Protozantaena gigantea sp. nov. is described, based on specimens collected from residual pools in a drying seasonal river in Namaqualand, Northern Cape Province, South Africa. Morphologically, the new species appears to be related to P. labrata Perkins, 1997 from Namibia and P. birdi Bilton, 2022, from the Great Escarpment in the Eastern Cape Province. At up to 2.0 mm in body length, the new species, whilst small, is by far the largest African Protozantaena Perkins, 1997 known to date. The opportunity is also taken to report a new record for P. birdi in the Eastern Cape Drakensberg.

Southern Afrotemperate Forest is concentrated in the southern Cape region of South Africa and whilst it is relatively well known botanically, the fauna, specifically the aquatic invertebrate fauna, is poorly documented. The majority of remaining intact forest habitat is contained within the Garden Route National Park (GRNP), which straddles the provincial boundary between the Western and Eastern Cape. This study undertakes a survey of the water beetle fauna inhabiting the GRNP. The aquatic ecosystems within temperate forests of the region are poorly researched from an ecological and biodiversity perspective, despite being known to harbour endemic invertebrate elements. We collected water beetles and in situ physico-chemical data from a total of 31 waterbodies across the park over two seasons (summer and late winter) in 2017. The waterbodies sampled were mostly small freshwater perennial streams and isolated forest ponds. A total of 61 beetle taxa was recorded (29 Adephaga, 32 Polyphaga) from these waterbodies. The water beetle fauna of these forests appears to be diverse and contains many species endemic to the fynbos-dominated Cape Floristic Region, but very few of the species appear to be forest specialists. This is in contrast to the fynbos heathland habitat of the region, which harbours a high number of water beetle species endemic to this habitat, often with Gondwanan affinity. Our study is the first to document the water beetles of Afrotemperate Forests in the southern Cape region and provides an important baseline for future work on such habitats in the region and in other parts of southern Africa., Competing Interests: No conflict of interest was declared., (Matthew S. Bird, David T. Bilton, Musa C. Mlambo, Renzo Perissinotto.)

Genetic and morphological data have suggested a Gondwanan connection between the three non-marine aquatic gastropod genera Coxiella Smith, 1894, Tomichia Benson, 1851 and Idiopyrgus Pilsbry, 1911. These genera have recently been included in the family Tomichiidae Wenz, 1938, however, further assessment of the validity of this family is warranted. Coxiella is an obligate halophile that occurs in Australian salt lakes while Tomichia occurs in saline and freshwater environments in southern Africa and Idiopyrgus is a freshwater taxon from South America. Despite their novel evolutionary and ecological characteristics, Coxiella, Tomichia and Idiopyrgus are poorly studied, and the lack of a contemporary taxonomic framework restricts our ability to assess the risk of declining habitat quality to these gastropods. We used data from mitochondrial (COI and 16S) and nuclear (28S and 18S) genes in 20 species from all three genera to undertake the most comprehensive phylogenetic test of the Tomichiidae to date. Bayesian and Maximum Likelihood phylogenetic analyses of a concatenated dataset (2974 bp) of all four genes strongly supported a monophyletic Tomichiidae. The COI analysis (n = 307) identified 14 reciprocally monophyletic lineages in Coxiella that comprised eight of the nine currently described species and at least six putative new species. Four distinct genetic clades of species with somewhat distinctive morphologies were found, each of which may constitute a distinct genera. In addition, four species of Tomichia were identified, including three described and one putatively new species. Current species descriptions of Coxiella do not account for the range of morphological variation observed within most described species, and although morphology is reasonably effective at delineating between clades, it is of limited use when trying to separate closely related Coxiella species. The improved understanding of the taxonomy and diversity of Tomichia and especially Coxiella will underpin future studies and conservation planning for these taxa., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2023. Published by Elsevier Inc. All rights reserved.)

Plastic debris is thought to be widespread in freshwater ecosystems globally 1 . However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging 2,3 . Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 μm) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris 4 . Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The Southern African endemic torridincolid water beetle genus Delevea Reichardt, 1976 is revised, based largely on recently collected material from the Republic of South Africa. Significant range extensions are provided for the two previously described species, Delevea bertrandi Reichardt, 1976 and D. namibiensis Endrödy-Younga, 1997, these taxa apparently being endemic to the Fynbos Biome in the Western Cape Province and semi-arid, summer rainfall, areas of the Great Escarpment in Namibia and South Africa, respectively. In addition, two new species, Delevea madiba sp. nov. and D. namaqua sp. nov. are described from winter rainfall areas of Namaqualand in the Northern Cape Province. Both species are currently only known from their type locality and, at up to 2.85 mm in adult body length, D. namaqua sp. nov. is the largest described extant species of the suborder Myxophaga.

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus-building Delphi technique. Our 14 priority topics fell into five broad themes (autecology, population dynamics, global stressors, global diversity, and ecosystem services) and included understanding diets throughout mussel life history; identifying the drivers of population declines; defining metrics for quantifying mussel health; assessing the role of predators, parasites, and disease; informed guidance on the risks and opportunities for captive breeding and translocations; the loss of mussel-fish co-evolutionary relationships; assessing the effects of increasing surface water changes; understanding the effects of sand and aggregate mining; understanding the effects of drug pollution and other emerging contaminants such as nanomaterials; appreciating the threats and opportunities arising from river restoration; conserving understudied hotspots by building local capacity through the principles of decolonization; identifying appropriate taxonomic units for conservation; improved quantification of the ecosystem services provided by mussels; and understanding how many mussels are enough to provide these services. Solutions for addressing the topics ranged from ecological studies to technological advances and socio-political engagement. Prioritization of our topics can help to drive a proactive approach to the conservation of this declining group which provides a multitude of important ecosystem services., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Climate change is rapidly driving global biodiversity declines. How wetland macroinvertebrate assemblages are responding is unclear, a concern given their vital function in these ecosystems. Using a data set from 769 minimally impacted depressional wetlands across the globe (467 temporary and 302 permanent), we evaluated how temperature and precipitation (average, range, variability) affects the richness and beta diversity of 144 macroinvertebrate families. To test the effects of climatic predictors on macroinvertebrate diversity, we fitted generalized additive mixed-effects models (GAMM) for family richness and generalized dissimilarity models (GDMs) for total beta diversity. We found non-linear relationships between family richness, beta diversity, and climate. Maximum temperature was the main climatic driver of wetland macroinvertebrate richness and beta diversity, but precipitation seasonality was also important. Assemblage responses to climatic variables also depended on wetland water permanency. Permanent wetlands from warmer regions had higher family richness than temporary wetlands. Interestingly, wetlands in cooler and dry-warm regions had the lowest taxonomic richness, but both kinds of wetlands supported unique assemblages. Our study suggests that climate change will have multiple effects on wetlands and their macroinvertebrate diversity, mostly via increases in maximum temperature, but also through changes in patterns of precipitation. The most vulnerable wetlands to climate change are likely those located in warm-dry regions, where entire macroinvertebrate assemblages would be extirpated. Montane and high-latitude wetlands (i.e., cooler regions) are also vulnerable to climate change, but we do not expect entire extirpations at the family level., Competing Interests: Declaration of competing interest We have no conflicts of interest to disclose., (Copyright © 2022 Elsevier B.V. All rights reserved.)

One newly described species of Chironomidae, Polypedilum (Pentapedilum) cranstoni sp. nov., was discovered in ephemeral rock pools from the Maloti-Drakensberg mountains in South Africa. Desiccation-resistant larvae were obtained from bottom sediments of rock pools that had been dry for the previous several months. After rehydration, ex situ adults emerged and were collected. The morphology and diagnostic characters of the new species (male and female adults) are described here together with an analysis based on their COI gene sequence.

The ephemeral waterbodies of southern Africa are regarded a global hotspot for large Branchiopod diversity. Although the distributions and systematics of Anostraca and Notostraca have been fairly well defined, clam shrimps have received much less attention. So far, 18 clam shrimp species are known from the sub-region, but none of the available published literature defines their distribution in South Africa. Furthermore, most of the recent studies were concentrated in the mesic provinces, while very little information is available from the Northern Cape, where most ephemeral waterbodies in the country occur. This study reviews the distribution of clam shrimps in South Africa by reviewing published distribution records and contributing novel data from surveys in the Northern Cape. We found that 13 of the 18 species from the sub-region occur in South Africa, of which four are restricted to their respective provinces. We further clarify the current state of endemism patterns in South Africa and provide novel findings from the Northern Cape, including three new range extensions. The Northern Cape hosts the highest species richness, with nine species, followed by the Eastern Cape, where seven species have been recorded so far. Most other provinces have low species richness and endemism, while no species records have been published from the Limpopo province yet. Surveys over large geographical scales are important, and more research is needed on clam shrimp systematics in South Africa.

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., Competing Interests: The authors have declared that no competing interests exist.

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events., (© 2019 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.)

Mesoceration explanatum sp. nov. and M. piketbergense sp. nov. are described from the Piketberg range in the Western Cape Province, South Africa, bringing the total number of known species in the genus to 55, all of which are endemic to South Africa. M. explanatum sp. nov. is a member of the truncatum group, whilst M piketbergense sp. nov. belongs to the endroedyi group and is apparently closely related to M. concessum Perkins Balfour-Browne, 1994 and M. tabulare Perkins, 2008, both of which are endemic to the Cape Peninsula. The two new species were both relatively abundant in the Piketberg, and may be narrowly endemic to this inselberg-like mountain range.

Numerous specimens of a freshwater shrimp with small eggs belonging to the Caridina nilotica complex collected in the South Western Indian Ocean were studied and compared with recent and old collection specimens genetically (16S mitochondrial analysis for recent and type specimens) and morphologically. The results revealed that, in the Indian Ocean, what has been identified by several authors under various species names of the complex C. nilotica, was in fact C. natalensis De Man, 1908. This valid species is re-described and compared with closely related species, often confused with it in this area: C. brachydactyla De Man, 1908, C. brevidactyla Roux, 1920, C. gracilipes De Man, 1892 and C. longirostris H. Milne Edwards, 1837.