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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...

Modern microbialites are useful partial analogues of their ancient counterparts and especially can provide clues on the conditions to which they were once exposed to. One of the conundrums which has been slow to solve is the role that grazing and burrowing metazoans had towards disrupting the Phanerozoic microbial mats that formed microbialites, especially those of the laminar variety, stromatolites. Here we use a modern occurrence where rare active microbialites along the southern African coastline are forming in direct association with a metazoan community. We show that these associations demonstrate clear evidence of burrows and trace marks from the metazoans, reflecting direct occupation of the microbialite matrix by some taxa. Importantly, these permanent burrows appear to form (mostly) without disruption to the microbialite consolidation, but rather are constructed along the same axis of that of the microbialite. Furthermore, stromatolitic layering is also observed in direct association with active metazoans. This provides further evidence for the refugia hypothesis which suggests that under certain conditions metazoans are not necessarily restrictive of microbialite integrity. This is explained by the selective forces acting against the destructive influence of metazoans because of the refugia benefits (oxygen, predation, exposure) that they accrue from this habitat. This calls for a reinterpretation of some palaeontological observations.

The extant stromatolite pools in Port Elizabeth, South Africa, provide a unique ecotone habitat at the interface of fresh groundwater seepage and the marine intertidal zone. Within this transition environment, we investigated the coexistence of two brachyuran species with different habitat preferences, i.e. marine and freshwater by quantifying niche overlap. The aim was to determine whether shifting environmental pressures or variability within the stromatolite pools (i.e. regular state shifts between marine and freshwater conditions) would invoke a dietary response or competitive interaction between these two species that are usually separated by their habitat tolerances. It was hypothesised that there would be little overlap between the two species but that this overlap would be greater in winter compared to summer due to reduced ectothermic activity. Stable isotope niche analysis revealed no dietary overlap between the two species at any site or in either season (summer or winter). Furthermore, isotope signatures suggest that both species feed on resources from their respective microhabitats. Despite the usual tendency of ecotone or edge populations to adopt a generalist diet, both species were able to remain habitat specialists, likely due to their highly mobile nature and access to suitable microhabitats within this dynamic freshwater/marine ecotone. This study is important from an environmental change perspective as it supports the hypothesis that populations occupying transitional environments such as these might be more tolerant of habitat shifts than their counterparts dwelling in more stable localities, and thus these populations are more likely to coexist.

The coleopteran fauna of the Macau SAR in southern China has historically received only limited attention and no updated information has been published since the last substantial works produced in the 1990s. An annotated and illustrated review of the fruit and flower chafers (Scarabaeidae, Cetoniinae) of this region is here presented, in order to provide an account of the current status of the taxonomic diversity and ecology of this important insect group. Eleven species were observed in the SAR during an intense investigation undertaken during the period 2017–2020, with six of these representing new records for Macau and two for the broader region of the Pearl River Delta, also known as the Greater Bay Area. Although this census leads to a substantial increase in the number of species known for the area, it also highlights the threats that the recent escalation in urban development and land-use transformation are posing to a number of species which seem unable to maintain a sustainable population in the region, mainly due to habitat destruction.

Mangrove macrobenthos species are used as ecological indicators as they are sensitive to changes in sediment properties. In this study, the population density of the common mangrove whelk Cerithidea decollata was assessed during different environmental conditions in the St Lucia Estuary, South Africa. Previously, this species was found to persist through both hypersaline and freshwater-dominated conditions. The natural variability in C. decollata populations could provide information on the potential for this widespread species to be used as an ecological indicator in mangroves. We found that snail population density as well as sediment conductivity, moisture content and organic content differed between three mangrove sites that were monitored between 2010 and 2015. The relationship between snail population density and physicochemical characteristics of the sediment was therefore investigated using a mixed-effects model, and sediment conductivity was found to be the best predictor of C. decollata abundance. The resistance of this species to environmental variability could inform on resilience to ecological shifts, which is important when measuring responses associated with climate change.Keywords: abundance, eurytolerant invertebrate, indicator species, mixed-effects model, sediment conductivity, sediment moisture content, sediment organic matter

Modern stromatolites are rare due to several factors that restrict their occurrence, although the conditions promoting their formation are not always well understood. This study performed a comparative analysis of the hydrochemistry of a well-developed peritidal stromatolite pool fed by a freshwater inlet, versus a site with no stromatolite growth, along the Eastern Cape coast of South Africa. Hydrochemical data were modelled with USGS PHREEQC 3.4.0 software to determine the saturation state of water samples at a range of temperature and salinity conditions. The well-developed stromatolite pool always favoured carbonate mineral precipitation, whereas this was not true for the site without stromatolite growth. The chemical potential of the systems indicated that any calcite precipitated was biomediated. Furthermore, as opposed to the site without growth the stromatolite-bearing site was saturated with calcite precursor mineral phases. It was found that nutrients, flow rates, and other physicochemical parameters also influence stromatolite development. The carbonate chemistry of additional freshwater inlets feeding stromatolite-bearing pools and the substrate the inlets emanate from was also investigated. The carbonate content of freshwater inlets along the coast is likely derived from a calcareous source inland from where seeps occur. This study importantly showed that a combination of parameters, viz. physicochemical, hydrochemical, thermodynamical and nutritional, influences the precipitation of carbonate minerals in these peritidal stromatolite-systems.

Proposed hydraulic fracturing in the semi-arid Eastern Cape Karoo region has been a topic of debate over the past few years. Here, we present observations aimed at understanding the dynamics of lower trophic levels, that is the microalgal biomass and species composition in surface waterbodies of this water-scarce region. Thirty-three waterbodies were sampled (13 natural depressions, 9 dams, 11 rivers) during November 2014 (austral spring) and April 2015 (austral autumn). PERMANOVA results indicate that no significant difference was observed for microalgal biomass between waterbody types and sampling events. However, microalgal assemblage data showed a dominance of different algal classes between waterbody types (with depression wetlands and dams dominated by chlorophytes and rivers dominated by diatoms) during both sampling periods and in both biotopes. Some mixing of assemblages (wind- or flow-induced) or exchange between biotopes was found to take place. Several environmental predictors were significantly associated with microalgal assemblage composition according to distance-based Redundancy Analysis (dbRDA) ordinations, most notably, turbidity and light attenuation. Ongoing monitoring initiatives in face of the impending hydraulic fracturing activities should include a comprehensive species-level diversity census, which could further inform management of any impacts associated with this potential disturbance.

Traditionally, it is thought that tropical species diversity and abundance decrease with an increase in latitude, responding to a gradient of drivers related to climate or biotic interactions. To investigate this, potential abiotic (soil, water, and biogeographic parameters) and biotic (brachyuran diversity, gastropod density, tree density, meiofauna density and food availability) drivers of fiddler crabs along the east coast of South Africa (26°S - 34°S) were assessed in multivariate models of fiddler crab presence/absence and abundance. Overall fiddler crab presence/absence was most strongly influenced by biotic variables (i.e. brachyuran diversity, gastropod density, and tree density), while abundance was driven largely by sediment grain size and canopy cover (abiotic variables). Specifically, Austruca occidentalis did not have any strong drivers aside from tree density, both Paraleptuca chlorophthalmus and Tubuca urvillei were influenced strongly by sediment grain size, tree density and crab diversity while Gelasimus hesperiae was influenced by a change in latitude, sediment grain size and meiofauna density. Distribution is not always correlated with latitude or latitudinally-driven variables. Biotic factors seem to play a large role in determining whether or not a species inhabits a specific mangrove habitat while, once established, abiotic factors drive density. This study highlights the complexity of drivers affecting species at their distributional limits, an important assessment considering that these populations would likely demonstrate range shifts in response to climate shifts or changes.

The female of Xiphodontus endroedyi Bartolozzi, 2005 is described for the first time. The new locality record for this species shows that it actually has a wide distribution range across the Cape Floral Region, in the Fynbos Biome. Both larvae and adults were found boring into dead wood at the base of senescent trunks of a variety of Proteaceae species, including the alien invasive Hakea sericea., Fragmenta Entomologica, Vol. 51 No. 2 (2019)

Naturally-occurring pristine estuarine ecosystems are rare in modern environments due to anthropogenic encroachment. There are more than 100 outlets around the South African coast arising from streams flowing from small catchments close to the sea. Eight near natural systems were sampled seasonally over the period of a year to acquire baseline information on water quality and chlorophyll a status across a variety of algal guilds (benthic microalgae, phytoplankton and macroalgal cover). Albeit on a much smaller-scale, these systems represent natural surrogates of larger temporarily open/closed estuaries (TOCEs). Inorganic nutrients (ammonium, total oxidized nitrogen and soluble reactive phosphate), phytoplankton and microphytobenthos chlorophyll a, as well as macroagal percentage cover, were measured using standard methods. Algae showed a seasonal trend, with blooms of both micro- and macro-algae occurring during summer, with a dieback recorded in autumn. During summer, only one system had a phytoplankton peak in chlorophyll a above 20 μg L− 1, while the microphytobenthos concentrations in three of the systems were above 100 mg m− 2. Summer blooms of green filamentous macroalgae occurred in all four micro-outlets and in one micro-estuary. Using a linear mixed-effects modelling approach, significant drivers for algal growth related to temperature, nutrient conditions, light availability and water residence time, all of which are known to stimulate primary production. The results show that enrichment from natural sources display similar responses from primary producers to mesotrophic and/or eutrophic water bodies, with the exception that they revert to a natural state rather than continue into a degraded state as is the case in artificially enriched systems. This importantly demonstrates how larger temporarily/open closed estuaries, most of which are anthropogenically degraded, might have functioned under a former more balanced state. Some of these larger systems now respond to nutrient enrichment by exhibiting permanent cultural eutrophication.

Micro-estuaries and micro-outlets represent small coastal waterbodies that differ in their relative salinity and size, with the former being larger, more saline (mesohaline versus oligohaline), and exchanging with the sea more often than the latter. There are thousands of these waterbodies along the world’s coastline, yet few of these very small systems have been identified and studied. We investigated systematic differences between micro-estuaries and micro-outlets in terms of phytoplankton community composition, including spatio-temporal variation in both community structure and biomass (chlorophyll-a). A multivariate analysis was used to assess differences in environmental variables, biomass and phytoplankton community composition across four seasons and the two waterbody types. A total of 260 (63 families) and 244 (74 families) phytoplankton taxa were identified within the micro-estuaries and micro-outlets, respectively. Nano- and picoplankton were the dominant groups in micro-estuaries, and pico- and microplankton in micro-outlets. Micro-estuaries were rich in phytoplankton taxa representative of marine, estuarine and freshwater conditions, with a successional sequence in dominance evident, from Chlorophyta during winter to Bacillariophyta in spring and Cyanophyta in summer. By contrast, micro-outlets were mostly dominated by freshwater taxa, with Chlorophyta remaining the dominant group across all four seasons. Higher phytoplankton biomass was recorded during the winter when increased nutrients were available following catchment flooding. Seasonal switching in phytoplankton was reflected not only in changing dominance patterns in both habitat types but also in complete replacement of some species in micro-outlets, despite Chlorophyta remaining dominant. Such temporal turnover, which is often accompanied by predictable seasonal changes in environmental conditions, can promote overall species richness by allowing more taxa to coexist in a single environment through temporal niche segregation.

Mangroves occur in South African estuaries at their poleward distribution limits, extending into temperate habitats. In 1963, William Macnae published the first comprehensive assessment of mangrove...

Ciliate epibionts inhabit aquatic systems globally and may exert negative impacts on their hosts. Evidence of the environmental drivers of these epibionts is lacking. This study aimed to test the effects of turbidity on the attachment success of the ciliate Epistylis sp. on the copepod Pseudodiaptomus stuhlmanni in the turbid St Lucia Estuary, South Africa. Epistylis sp. was exposed to P. stuhlmanni individuals for 24 h under six turbidity treatments (range 8–1,500 NTU). The prevalence and density of Epistylis sp. exposed to inorganic silt decreased significantly across the turbidity range in both runs of this experiment. In the natural silt treatments, prevalence increased with turbidity up to 500 and 250 NTU in the first and second experiment, respectively. Beyond these peaks, prevalence decreased. Density peaked at 250 NTU in both experiments. High prevalence and density in the natural silt experiments is directly related to the high organic matter content in this treatment. Association of Epistylis sp. with turbidity may impact negatively P. stuhlmanni, as the longevity of this copepod is negatively related to heavy cover by Epistylis sp. and to turbidity. These findings show that environmental factors may play a key role in modulating epibiotic interactions.

Living coastal stromatolites, layered structures formed by the microbially mediated precipitation of calcium carbonate, are scarce because of grazing and burrowing disruption by metazoans, amongst other reasons. This paper describes Sinelobus stromatoliticus sp. nov., a tanaidacean living within laminated stromatolites along the South African coastline. S. stromatoliticus is the sixth geographically isolated species now recognised within what was once considered to be a single globally cosmopolitan species, S. stanfordi Richardson, 1901. A revised, sex-specific dichotomous key to all the species currently recognised within this genus is provided. Sinelobus stromatoliticus is a prominent and abundant metazoan within the living stromatolite habitats, yet despite being a burrowing and grazing species, stromatolite layering is not hampered by its presence. Future work should determine the relationship between other populations (cf. S. stanfordi) in South Africa (previously identified as Tanais philetaerus Stebbing, 1904) and those of the stromatolite-dwelling S. stromatoliticus. However, given South Africa’s clear biogeographic zonation in other taxa, it is unlikely that this genus that features no pelagic larval stage would be morphologically similar across biogeographic regions.

Modern anthropogenic modifications to aquatic environments, specifically hydrodynamic alterations, play a major role in cyanobacterial bloom potential. In shallow-water ecosystems, salinity is a dr...

Estuarine marine-dependent species, such as Rhabdosargus holubi , depend greatly on structured sheltered environments and important feeding areas provided by estuaries. In this study, we investigate the ecological feeding niches of the estuarine marine-dependent sparid, R. holubi , by using conventional stomach contents and stable isotope methods (δ 13 C and δ 15 N signatures). The study has been carried out in five temperate estuaries in order to understand how fish feed in multiple intertidal vegetated habitats. These habitats included the submerged seagrass, Zostera capensis , and both previously unexplored small intertidal cord grass, Spartina maritima , and the common reed, Phragmites australis . The diet varied amongst habitats, estuaries and fish sizes and data consistently confirmed their omnivorous diet relating to ontogenetic niche shifts. Stomach contents revealed the importance of benthic prey within both the S. maritima and P. australis habitats in the absence of large intertidal vegetation, available during low tides. Similarly, isotopic mixing models showed that R. holubi from these habitats have a greater isotopic niche compared to the Z. capensis habitat, due to their limited availability during the falling tide, suggesting migration between available habitats. Stable isotopes confirmed that R. holubi actively feeds on the epiphytic algae (especially diatoms) covering the leaves and stalks of plant matter, as supported by Bayesian mixing models. These findings add to the current knowledge regarding habitat partitioning in multiple aquatic vegetation types critical to fish ecology and the effective management and conservation of estuaries.

Stromatolites are rare in modern ecosystems due to factors associated with seawater chemistry or biological competition that restrict their formation. Actively calcifying stromatolites, near the Kei Mouth in the Eastern Cape, South Africa, were discovered in the early 2000s. Similar deposits were later described along a 200 km stretch on the south coast of Port Elizabeth. This study aims to describe the environmental setting, the macro- and meso-structures, as well as the evolution of the deposits near Port Elizabeth compared to other similar formations. Results show that the general environmental setting is consistent amongst peritidal stromatolites, including those described in this study. In all instances stromatolite growth occurs on a wave-cut rocky platform in and around rock pools. Growth is maximal within the intertidal to supratidal zone, as a result of freshwater inflow via emerging mineral springs at the base of landward slopes, and the periodic intrusion of seawater via storm surges or wave splash. In comparison with other systems, the South African stromatolite formations exhibit an additional macro-structure (beachrock/conglomerate) and four previously undescribed meso-structures: wrinkled laminar, laminar flat, rhizoliths, and blistered types. The South African stromatolites are also larger and more concentrated than other peritidal stromatolites, which could be due to this area having more suitable growth conditions.

Mangrove gastropods are largely recognised for their roles as benthic deposit feeders that consume macrophyte-derived detritus. However, microalgae may also make a significant contribution towards the diet of these snails. Here we provide the first report on the rates at which microphytobenthos (MPB) is consumed by Terebralia palustris, an Indo-Pacific mangrove gastropod. Although juvenile T. palustris are generally detritivorous, there is increasing evidence that their occurrence on the seaward edge of the mangrove habitat allows them to incorporate a more nutritious food source to their diets in the form of microalgae. Using an experimental approach that incorporated fluorometric techniques, we found that the feeding activity of T. palustris on MPB was not clearly related to diel and tidal cycles at the subtropical location of Kosi Bay, South Africa during two sampling occasions in February and July 2015. However, a faster ingestion rate and higher consumption/digestion efficiency were recorded ...

Metazoans contributed historically to the decline of the microbialites and continue to restrict their formation in most modern environments through grazing and burrowing pressures. Recent evidence suggests that metazoans can coexist with layered microbialites (stromatolites). However, the possible drivers of the invertebrate assemblage directly associated with these unique habitats are not well-understood. This study measured environmental and resource variables within peritidal stromatolites along the South African coastline and related these to the infaunal metazoan community. Clitellates (Naididae and Enchtraeidae), malacostracans (Amphipoda, Isopoda and Tanaidacea), insect larvae (Chironomidae), and polychaetes (Nereididae) were the most abundant groups. The benthic macrofaunal community was most strongly related to salinity, nutrients (dissolved inorganic nitrogen and phosphorus) and macroalgal cover. This suggests that the distribution of some species was restricted by physiological tolerances associated with salinity, while others responded to resource variability within the primary producer community. The absence of an apparent relationship between stromatolite microalgal biomass or composition and the metazoan community occupying the matrix indicates that the invertebrates might be relying on other primary producers as a food resource, such as macroalgae. This suggests that the benthic macrofaunal community may have a limited direct grazing effect on the stromatolite matrix, thereby not hindering the formation of its typical layered fabric.

Gastropods are integral components of mangrove ecosystems as they retain primary carbon by consuming leaf litter. However, alternative primary sources may make a significant contribution toward the diets of primary consumers in subtropical mangroves due to seasonal processes that impact the availability and nutritional quality of the leaf litter. The variability of the dietary niche for the giant mangrove whelk Terebralia palustris was investigated using a stable isotope approach (δ15N and δ13C) in conjunction with gut contents analysis. The size of the isotopic niche for T. palustris was different between November (summer) and July (winter). Isotopic niches were larger in July, indicating higher dietary diversity. There was no overlap between isotopic niches of different-sized T. palustris, which indicates robust resource partitioning and an ontogenetic dietary shift. The C:N ratio of mangrove leaf litter ranged from 59.34 ± 0.9 in November to 201.66 ± 4.5 in July. The high C:N ratio observed in July could be driving the dietary diversification, if T. palustris preferably consumes more nutritious sources such as microphytobenthos. The variability in the diet of T. palustris is important when considering the ecological role of this species, as a link between mangrove primary productivity and higher trophic levels.

The movement of postflexion larvae of marine estuarine-dependent species into estuaries is critical for the survival of fishes reliant on estuaries as nurseries. However, detailed studies focused on environmental variability experienced by postflexion larvae entering a range of estuary types under varying conditions are rare. This study assessed the in situ conditions (temperature, salinity and water clarity) under which the southern African endemic fish Rhabdosargus holubi (Sparidae) recruits into estuaries. Postflexion larvae were sampled in three biogeographic regions (cool temperate, warm temperate and subtropical boundary), which included three estuary types (permanently open estuaries (POEs), temporarily open/closed estuaries and estuarine lake systems) on a seasonal basis, independent of each other. Rhabdosargus holubi larvae were more abundant in spring and summer, in POEs in the warm temperate region. Models predicted that higher larval occurrence in estuaries is a function of lower salinity (e.g. mesohaline zones of 5-17.9 salinity) and lower water clarity (e.g. 0-0.2 Kd, light extinction coefficient), particularly for warm, temperate POEs. This re-emphasizes the importance of freshwater for optimal nursery functioning, which may be compromised by impoundments, abstraction and climate change in water-short countries like South Africa. En las especies de peces dependientes de los estuarios marinos como zonas de cría, el movimiento de las larvas en estadio de postflexión hacia el interior de los estuarios es un proceso crítico para su supervivencia. Sin embargo, son raros los estudios detallados que analicen la variabilidad ambiental experimentada por estas larvas en diversos ambientes estuáricos. Este estudio evaluó las condiciones in situ (temperatura, salinidad y claridad del agua) bajo las que Rhabdosargus holubi (Sparidae), pez endémico de África meridional, recluta en los estuarios. Las larvas en postflexión se muestrearon estacionalmente en tres regiones biogeográficas, independientes entre sí, (templada-fría, templada-cálida y subtropical), que incluían tres tipos de estuarios (POE: estuarios permanentemente abiertos, TOC: estuarios temporalmente abiertos/cerrados y ELS: sistemas de lagos estuarinos). Las larvas de Rhabdosargus holubi fueron más abundantes durante la primavera y el verano, en POEs de la región templada-cálida. Los modelos predijeron que la mayor aparición de larvas en los estuarios es función de una menor salinidad (por ejemplo, zonas mesohalinas de 5-17.9 salinidad) y una menor claridad del agua (por ejemplo con coeficiente de extinción de luz de 0-0.2 Kd), particularmente para POEs templado-cálidos. Esto reafirma la importancia del agua dulce para el funcionamiento óptimo como zona de cría, que puede verse comprometida por los embalses, la extracción de agua y el cambio climático en países con escasez de agua como Sudáfrica.

Living peritidal stromatolites forming at the interface of coastal groundwater seepage and regular marine input are known from only a few locations globally, including South Africa, Western Australia and Northern Ireland. In contrast to modern stromatolites from exclusively fresh or marine waters, which persist due to high calcium carbonate saturation states or hypersaline and erosive conditions (which exclude organisms that might disrupt or out-compete the stromatolite-forming benthic microalgae), the factors supporting stromatolite formation at peritidal locations have not been well-documented. Therefore, the aim of this study was to investigate the fine-scale physico-chemical parameters in terms of pool temperature, salinity and nutrient dynamics at three representative sites along the coastline near Port Elizabeth, South Africa. These parameters were assessed with reference to potential physical, meteorological and ocean drivers using a linear or linear mixed-effects modelling approach. Results demonstrate that nutrient inputs into the pools supporting the majority of stromatolite accretion (barrage pools) are driven by groundwater seepage site-specific properties related to anthropogenic occupation (dissolved inorganic nitrogen; DIN) as well as marine water incursion (dissolved inorganic phosphorus; DIP). Pool temperature is a function of seasonal ambient variability while salinity reflects regular state shifts from fresh to marine conditions, which are related to tidal amplitude and swell height. The regular marine incursions likely promote benthic primary biomass in the phosphorus-limited stromatolite pools, as well as preclude organisms which might otherwise outcompete or disrupt the stromatolite microalgae due to intolerances to extreme (~ 1.5 to ≥ 30) salinity variability.

A new species of freshwater crab, Potamonautes danielsisp. n., is described from the southern region of the KwaZulu-Natal Province, South Africa. Potamonautes danielsi most closely resembles Potamonautes sidneyi which is re-described here, but can be distinguished by a suite of key morphological characters including carapace shape and width, slim pereopods, inflated propodi of the chelipeds, and the shape and terminal segment length:subterminal segment length ratio of the 1st gonopod. In a previous study (Gouws et al. 2015), a 9.2-11.8 % divergence was found in the mitochondrial COI and 16S genes of the Potamonautes sidneyi clade, allowing for the delineation of a new species. Despite the clear molecular distinction between the two species, it is difficult to separate them based on individual morphological characters, as there is a great deal of overlap even among key features. The new species is found in slow-moving mountain streams and pools at high altitudes between Umhlanga and Mtamvuna, in KwaZulu-Natal.

South African estuarine systems are becoming increasingly altered by anthropogenic and environmental factors, but the consequences of such changes for these systems are still not fully understood. The most common approach for evaluating the ecological status of aquatic systems is studying their associated foodwebs. Due to their high abundance and important ecological role, the larvae of estuarine round herring Gilchristella aestuaria (Gilchrist, 1913) are key candidates for examining the foodweb structure and function of southern African estuaries. The foodwebs and trophic interactions of G. aestuaria larvae in six estuaries in South Africa were compared using larvae sampled in November 2013 and analysed using δ13C and δ15N and Bayesian isotopic mixing models. The main prey type for G. aestuaria larvae in all estuaries was zooplankton. We found a high similarity among the Kariega, Gamtoos, Great Fish and Sundays estuaries in terms of consumers and potential sources for both δ13C and δ15N signatures. Significant differences were found in δ13C values among marine-dominated estuaries, such as the Kromme Estuary, and the more freshwater-dominated systems. In addition, in the Kromme Estuary particulate organic matter was very important in the diet of G. aestuaria larvae. Our results suggest that both food availability and physical environmental parameters strongly affect the diet and condition of G. aestuaria and, consequently, the entire foodweb in the system.Keywords: Bayesian isotopic mixing models, early life history, estuarine ecology, estuarine round herring, fish trophic ecology

Two new species of the southern African genusXiphoscelisBurmeister, 1842 are recognised and described,X. braunsisp. nov.from the Eastern and Western Cape Karoo (South Africa) andX. namibicasp. nov.from the Huns Mountains of southern Namibia and adjacent ranges in South Africa. These were previously overlooked and grouped together withX. schuckardiBurmeister, 1842, but further material and more in-depth analyses have now revealed their clear separation on the basis of key diagnostic features, including clypeal structure, metatibial spur development and aedeagal shape. The densely and coarsely costate elytral structure and the black to brown colour of these species are symplesiomorphies shared with a number of the most primitive genera among the African Cetoniinae. However, these characters also reflect the convergent adaptation to hot and arid conditions they share with several other species occurring in this region. Phylogenetic relationships of the genus with other Cetoniinae are explored using the larval characters highlighted in the description of the 3rdinstar larva ofX. braunsisp. nov.The extraordinary hypertrophy observed in the male metatibial spur of species in this genus, and particularly inX. schuckardi, appears to represent a defence mechanism against potential predators on the ground, apart from playing a role during mating.

Two new species of the southern African genus Xiphoscelis Burmeister, 1842 are recognised and described, X. braunsisp. nov. from the Eastern and Western Cape Karoo (South Africa) and X. namibicasp. nov. from the Huns Mountains of southern Namibia and adjacent ranges in South Africa. These were previously overlooked and grouped together with X. schuckardi Burmeister, 1842, but further material and more in-depth analyses have now revealed their clear separation on the basis of key diagnostic features, including clypeal structure, metatibial spur development and aedeagal shape. The densely and coarsely costate elytral structure and the black to brown colour of these species are symplesiomorphies shared with a number of the most primitive genera among the African Cetoniinae. However, these characters also reflect the convergent adaptation to hot and arid conditions they share with several other species occurring in this region. Phylogenetic relationships of the genus with other Cetoniinae are explored using the larval characters highlighted in the description of the 3rd instar larva of X. braunsisp. nov. The extraordinary hypertrophy observed in the male metatibial spur of species in this genus, and particularly in X. schuckardi, appears to represent a defence mechanism against potential predators on the ground, apart from playing a role during mating.

Estuaries are subject to high environmental variability coupled to tidal salinity shifts. Under restricted freshwater flow and prolonged drought conditions, salinity may exceed natural ranges and thus organisms may experience stressful hypersaline conditions. This study assessed the physiology of a juvenile marine estuarine-dependent species Rhabdosargus holubi (Family: Sparidae) under changing salinity to determine the impact on respiration and survival under shock and acclimatisation exposures. Oxygen consumption was not significantly different in the 2.5 to 45 salinity range and the interaction between temperature and salinity was not significant at the moderate levels tested. This confirmed the strong osmoregulatory capabilities of marine estuarine-dependent R. holubi. However, respiration was impacted at salinities of 55–62.5. The salinity tolerance ranges of R. holubi were expanded beyond those previously observed in the laboratory, to a maximum of 77 when fish were gradually exposed to daily 20% incremental changes. This indicated the ability to adapt to hypersaline conditions that occur gradually in anthropogenically altered estuaries which is an important aspect for management decisions regarding freshwater inputs. The adaptability of Rhabdosargus holubi to hypersaline conditions in estuaries may thereby ensure the maintenance of populations in the short term under certain environmental conditions, such as those currently occurring in a freshwater-scarce South Africa. However, in the long term and at more extreme salinities (> 55), the physiology of R. holubi and similar species may be compromised, thus placing the species at risk.

Microbial mats were the dominant habitat type in shallow marine environments between the Palaeoarchean and Phanerozoic. Many of these (termed ‘microbialites’) calcified as they grew but such lithified mats are rare along modern coasts for reasons such as unsuitable water chemistry, destructive metazoan influences and competition with other reef-builders such as corals or macroalgae. Nonetheless, extant microbialites occur in unique coastal ecosystems such as the Exuma Cays, Bahamas or Lake Clifton and Hamelin Pool, Australia, where limitations such as calcium carbonate availability or destructive bioturbation are diminished. Along the coast of South Africa, extensive distributions of living microbialites (including layered stromatolites) have been discovered and described since the early 2000s. Unlike the Bahamian and Australian ecosystems, the South African microbialites form exclusively in the supratidal coastal zone at the convergence of emergent groundwater seepage. Similar systems were documented subsequently in southwestern Australia, Northern Ireland and the Scottish Hebrides, as recently as 2018, revealing that supratidal microbialites have a global distribution. This review uses the best-studied formations to contextualise formative drivers and processes of these supratidal ecosystems and highlight their geological, ecological and societal relevance. Dynamic interchanges between salinity states both exclude many destructive metazoans and competitors and provides optimal nutrient conditions for benthic microbial and microalgal growth. The outflowing groundwater seeps are alkaline and rich in calcium carbonate, which reflects local catchment geological processes. These habitats support a diverse microbial community dominated by Cyanobacteria as well as some metazoan species previously unknown to science, or unknown for the region. Several taxa (from invertebrates to fish) utilise this environment as refugia. Supratidal microbialites are important coastal features because of the organisms they support and the ecological processes that they facilitate, such as habitat connectivity. Culturally and socially, the value of these habitats is increasingly being appreciated, for example as traditional freshwater supply points or as an unrealised geotourism opportunity. This review also frames new information about threats, opportunities for future research and conservation trajectories for these unique geobiological habitats.

Shallow coastal lakes are under increasing pressure from climate change. Low rainfall and reduced run-off contributed to an unprecedented drought in Lake St. Lucia since 2002. Physico-chemical variables and microalgal biomass are analysed, tracking the transition from drought (2009) to wet conditions (2014). Despite low water levels and habitat loss due to desiccation, microalgal biomass remained high mainly due to cyanobacterial contribution. The system exhibited distinct spatio-temporal patterns in terms of salinity, water level, DIN, microalgal biomass and class composition associated with the drought, transition and wet climatic phases. Regime shifts were detected, coinciding with the end of the drought and the beginning of the wet phase. The St. Lucia ecosystem responds rapidly to changes in climatic phases while sustaining microalgal stocks; it may therefore be relatively resilient to extreme drought events.

Recently-discovered peritidal stromatolite ecosystems in South Africa form at the interface of freshwater seeps and the ocean intertidal zone, sharing several similarities with both tidal pool and estuarine ecosystems. While the overall ecology of tidal rock pools has been well studied, the dynamics of the phytoplankton assemblage have been comparatively neglected. In addition, there are no studies to date which describe the dynamics of phytoplankton within a habitat associated with stromatolites. The aim of this study was to investigate the coarse-scale phytoplankton community composition of a series of peritidal pools associated with living stromatolites, using a spectral fluorescence analysis tool, in relation to source-specific drivers related to both freshwater and marine forces. Three sites were sampled monthly from January to December 2014. Physico-chemical, biotic and meteorological parameters were recorded to assess some of the factors which might influence the phytoplankton size-fractionation and community composition using a generalised linear modelling approach. Results indicate that fresh or marine pool state, temporal differences associated with season, macronutrients (N and P), and benthic microalgal biomass are important drivers of the phytoplankton assemblages. Specifically, a transition from fresh to marine pool conditions resulted in an increased abundance of smaller phytoplankton size fractions and a shift from Chlorophyta and Cyanophyta to Bacillariophyta and Cryptophyta. Overall, the community was dominated by Chlorophyta and Bacillariophyta. There was consistency between the drivers and composition of the phytoplankton community compared to those from the few other comparable published studies. Furthermore, this study demonstrates a system which is dominated by benthic rather than pelagic microalgae in terms of biomass, thereby supporting the persistence of actively accreting stromatolites.

Bivalves feed on a combination of phytoplankton and zooplankton and have the potential to impact considerably the planktonic biomass, especially when they occur in high densities, such as in oyster and mussel beds. The brackwater mussel Brachidontes virgiliae is numerically dominant during wet phases within Africa’s largest estuarine lake, St Lucia, in the iSimangaliso Wetland Park on the east coast of South Africa. The ingestion rates and potential grazing impact of this small mussel (maximum shell length = 2.5 cm) were estimated for both the wet and dry seasons using an in situ gut fluorescence technique. Ingestion rates were higher during the wet season (5.78 μg pigment ind.–1 d–1) than during the dry season (4.44 μg pigment ind.–1 d–1). This might be explained by the increased water temperature and food availability during the wet season. Because of the patchy distribution of mussel populations, there could be higher localised grazing impact near mussel aggregations. Results showed a potential grazing impact of up to 20 times the available phytoplankton biomass at specific sites. These high grazing impacts have the potential to deplete phytoplankton stocks in the lake, especially during wet phases in the northern reaches, where mussel densities are highest. This needs to be factored into ecological models of Lake St Lucia, because the system might function differently during increased flood events.Keywords: bivalves, diel variations, estuarine lake, population feeding impact, suspension-feeding

Fiddler crabs (Uca spp.) undergo the zoeal stage of development in open-ocean waters, where they experience stable salinity levels, low turbidity and reduced predation. The St Lucia estuarine system has undergone many geomorphological changes, both natural and anthropogenic, and the estuary mouth has been closed since the early 2000s. Despite recent attempts to improve marine connectivity, it remains limited, occurring primarily on the flood tide through channels connected to the adjacent Mfolozi River. Larval export from the St Lucia Estuary is therefore almost non-existent. A laboratory study was undertaken to examine the silt and salinity tolerance of Uca annulipes first stage zoeae, to investigate whether survival in the closed-estuary conditions would be possible. Salinity tolerance was narrow, with zoeae displaying 100% mortality at salinities 35 after five days. Zoeae were widely tolerant to silt loading and did not display a significant decrease in survival over a range of 0–1 000 NTU. A ...

The South African coastline is just over 3000 km in length yet it covers three major biogeographic regions, namely subtropical, warm temperate and cool temperate. In this review we examine published information to assess the possible role of climate change in driving distributional changes of a wide variety of organisms around the subcontinent. In particular we focus on harmful algal blooms, seaweeds, eelgrass, mangroves, salt marsh plants, foraminiferans, stromatolites, corals, squid, zooplankton, zoobenthos, fish, birds, crocodiles and hippopotamus, but also refer to biota such as pathogens, coralline algae, jellyfish and otters. The role of pioneers or propagules as indicators of an incipient range expansion are discussed, with mangroves, zoobenthos, fishes and birds providing the best examples of actual and imminent distributional changes. The contraction of the warm temperate biogeographic region, arising from the intrusion of cool upwelled waters along the Western Cape shores, and increasingly warm Agulhas Current waters penetrating along the eastern parts of the subcontinent, are highlighted. The above features provide an ideal setting for the monitoring of biotic drivers and responses to global climate change over different spatial and temporal scales, and have direct relevance to similar studies being conducted elsewhere in the world. We conclude that, although this review focuses mainly on the impact of global climate change on South African coastal biodiversity, other anthropogenic drivers of change such as introduced alien invasive species may act synergistically with climate change, thereby compounding both short and long-term changes in the distribution and abundance of indigenous species.

By using permanently resident zooplankton, we assessed the ecological level (i.e. community and or population) that provides more in-depth indication of the stress related to salinity and temperature fluctuations in temperate estuaries. In the semi-arid warm temperate South Africa, the Gamtoos estuary experiences a full salinity gradient maintained by irregular but relatively frequent freshwater pulses, whereas the Kromme estuary is euhaline throughout its extent and receives only occasional freshwater inputs when the storage reservoir six km upstream overtops. Changes in the species evenness index of Pielou and the abundances of estuarine resident zooplankton species were modelled against salinity and temperature variations of respective estuaries. In the Gamtoos estuary, response of individual populations provided more in-depth information regarding zooplankton variability. However the most abundant resident zooplankton i.e. Acartia longipatella a copepod was not the best predictor of the salinity and temperature fluctuations. Conversely, the Kromme estuary study provided insights into the potential vulnerability of the resident estuarine zooplankton community to cold. Further, the population level study exposed responses of specific species against salinity changes. We discuss the pros and cons of designing ecological indicators of abiotic stress based on specific species, targeted to specific ecological level, and needs of considering the frequency and magnitude of fresh water inflow in an estuary. A suggestion is to use specific taxonomic group(s) (e.g. Copepods) to better understand the abiotic stress factors of specific set of estuaries (e.g. freshwater rich/starved) until a ‘one size fits all’ indicator is found for temperate estuaries.

Three females and one male specimen of a previously unconfirmed species of horsehair worms (Nematomorpha) from South Africa are described using Scanning Electron Microscopy. The females correspond to the description of Chordodes ferox Camerano, 1897, a species previously described from the Democratic Republic of the Congo (Congo-Kinshasa) and an adjacent, not further specified region of the Republic of Congo (Congo-Brazzaville). Characteristic is the presence of enlarged and elevated simple areoles around the base of a thorn areole, in combination with further cuticular characters. This is the latest of a total of six species of horsehair worms reported from South Africa so far. Two species of praying mantids, Polyspilota aeruginosa (Goeze, 1778) and Sphodromantis gastrica Stål, 1858, have been identified as hosts of Chordodes ferox, while its distribution range in the region and the period of adult emergence from the host remain largely unknown.

Extant marine stromatolites act as partial analogues of their Achaean counterparts, but are rare due to depleted ocean calcium carbonate levels and suppression by eukaryotic organisms. Unique, peritidal tufa stromatolites at the interface between marine and freshwater inputs were discovered in South Africa in the past decade. Our aim was to investigate the benthic microalgal community (green algae, diatoms and cyanobacteria) of these stromatolites to assess succession and dominance patterns using real-time, in situ measurements of algal concentrations and composition. These biological measurements were modelled using generalized linear modelling (GLM) multivariate statistics against water physical and chemical parameters measured at regular monthly intervals, from January to December 2014. Salinity peaked and temperature dipped in winter, with both correlated to microalgal community change (GLM: P < 0.01). Diatoms and cyanobacteria, which construct the stromatolites, were consistently the dominant groups within the algal community, with minimal green algae present throughout the year. Importantly, this demonstrates a unique, relatively stable microalgal stromatolite community as opposed to those of other marine stromatolites, which likely require seasonal and stochastic disturbance to persist. This has implications in terms of interpreting community succession and differential layering in modern and fossilized stromatolites respectively.

Lake St Lucia is among the most important shallow ecosystems globally and Africa's largest estuarine lake. It has long been regarded as a resilient system, oscillating through periods of hypersalinity and freshwater conditions, depending on the prevailing climate. The alteration of the system's catchment involving the diversion of the Mfolozi River away from Lake St Lucia, however, challenged the resilience of the system, particularly during the most recent drought (2002–2011), sacrificing much of its biodiversity. This study reports on the transition of the St Lucia zooplankton community from a dry hypersaline state to a new wet phase. Sampling was undertaken during routine quarterly surveys at five representative stations along the lake system from February 2011 to November 2013. A total of 54 taxa were recorded during the study period. The zooplankton community was numerically dominated by the calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the cyclopoid copepod Oithona brevicornis . While the mysid Mesopodopsis africana was still present in the system during the wet phase, it was not found in the swarming densities that were recorded during the previous dry phase, possibly due to increased predation pressure, competition with other taxa and or the reconnection with the Mfolozi River via a beach spillway. The increase in zooplankton species richness recorded during the present study shows that the system has undergone a transition to wet state, with the zooplankton community structure reflecting that recorded during the past. It is likely, though, that only a full restoration of natural mouth functioning will result in further diversity increases.

The fish and tadpole assemblages inhabiting micro-estuaries and micro-outlets along a warm-temperate section of the Eastern Cape coast were investigated over four seasons between 2015 and 2016. The specific aim of this study was to elucidate whether nekton assemblages in coastal microsystems are similar to those found in larger estuarine systems on the same coastline, and whether the presence or absence of tadpoles can indicate a difference between the two microsystem types. Oligohaline and/or freshwater conditions prevailed in micro-outlets for much of the sampling period, while micro-estuaries were mostly mesohaline. Nekton communities in micro-outlets were dominated by tadpoles (Xenopus laevis), with juvenile Pseudomyxus capensis sometimes present, while Oreochromis mossambicus, Gilchristella aestuaria, P. capensis and Mugil cephalus were the most common fish species in micro-estuaries which had an almost complete absence of tadpoles. The micro-estuaries had a low estuarine function when compared to temporarily open/closed estuaries, while the micro-outlets had very limited estuarine characteristics and an almost complete absence of fishes. Due to their restricted periods of stability and small size, micro-estuaries served as only intermediate nursery areas for small numbers of 0+ marine fish which, after less than a year, need to migrate to nearby larger estuarine systems that can provide the full range of nursery habitats for subsequent growth and development. The limited numbers of estuarine resident fishes (e.g. G. aestuaria) and freshwater fish species (e.g. O. mossambicus) confirm the marginal habitat and food availability in these microsystems for fishes that are normally abundant in other types of Eastern Cape estuaries and rivers. The results of this study confirm that there are clear distinctions between the nekton of the two microsystem types, thus making fish and tadpole assemblages a viable tool for differentiating between micro-estuaries and micro-outlets in this province.

Animal-mediated trophic resource transfers are important determinants of ecosystem functioning but are influenced by anthropogenic activities. In Africa, hippo defecation can influence aquatic processes at multiple scales, yet little is known about this phenomenon, with repercussions for estuarine benthic ecosystems being a particularly important knowledge gap. Here, we use in situ experiments to test responses of benthic meiofauna to dung loading in the St Lucia Estuary, which is Africa's largest estuarine ecosystem and home to one of South Africa's largest hippo populations. Findings indicate that high dung-loading levels negligibly affect meiofaunal community structure, with few community and individual metrics responding significantly. Richness and diversity displayed differential responses at the two experimental sites, with increasing trends occurring at the first site following dung addition but with a reversal at the second site. Similar findings were recorded for abundances of juvenile Assiminea cf. capensis (gastropod) and sizes of Nemata. In relation to prior findings for macrofauna from the same experiment, meiofaunal responses appeared weak and spatially idiosyncratic. We conclude that meiofauna are more robust and opportunistic than macrofauna in responding to dung-loading and suggest that high input rates may shift benthic communities from larger macrofaunal groups to smaller meiofaunal assemblages. We advocate that understanding traits of recipient assemblages that determine their susceptibility to hippo dung is necessary to develop a predictive understanding of this phenomenon. This would be especially important in protected areas that experience freshwater deprivation and support large and expanding hippo populations.

Natural sources of freshwater are a limiting feature to the distribution of terrestrial species that rely on regular hydration, especially in coastal environments. Early modern humans would similarly be restricted by water supply and likely would have congregated or settled in close proximity to permanent water bodies such as beyond the estuarine extent of large rivers. However, along the modern south coast of southern Africa, for example, distances between freshwater from rivers can exceed what would be convenient daily walking limits. In the absence of alternative water supply, or a means of water storage, these distances would preclude human settlement beyond river borders. Recent discovery of living peritidal stromatolites forming along the southern South African coastline suggests a potential alternative water source. These unique ecosystems form only at locations where groundwater rich in calcium carbonate meets periodic marine intrusion along the coastal margin. Calcium carbonate is precipitated by cyanobacteria and sediment is trapped by diatoms, primarily, to form layered deposits that preserve into the fossil record. Critical to the formation and growth of these stromatolites is a fresh, uninterrupted supply of groundwater. During their growth, the peritidal stromatolites accumulate and retain this freshwater through the formation of rimstone dams and barrage pools at the seaward margin of neocoastal geological outcrops. Recognising the presence of permanent water sources other than rivers for early humans is challenging; however, these stromatolites provide a clear signature of an alternative water resource. Here we review the modern prevalence of peritidal stromatolites in this region, of which approximately 540 are known along a 200 km stretch of South Africa's southern coastline featuring only 11 estuaries. This is linked to features (cf. rimstone dams and barrage pools) resembling peritidal stromatolites in the adjacent Palaeo-Agulhas Plain landscape using multibeam echosounder and side-scan sonar data and contextualised as a possible water resource for early modern humans.

This study forms the first basic assessment of microphytobenthos (MPB) dynamics in micro-estuaries and micro-outlets in southern Africa. It examines MPB community responses to environmental variables and further investigates MPB composition qualitatively across different micro-estuaries and micro-outlets over four seasons in a warm temperate region of the subcontinent. Combinations of multivariate analyses were used to explore similarities and differences in MPB communities between systems. Human-induced catchment changes between microsystems ranged from no alteration (rating 0; mostly micro-outlets) to extreme modification (rating 5; mostly micro-estuaries). Two hundred and sixty-seven MPB taxa were identified within all the microsystems, with 247 and 230 MPB taxa being observed in the micro-estuaries and micro-outlets, respectively. The MPB communities differed slightly in terms of microsystem types and seasons, but no significant differences were observed. Multivariate analyses (i.e. Boosted Regression Trees, Canonical Correspondence Analysis) showed that water column variables were significant and important in structuring MPB communities, with soluble reactive phosphorus, sediment pH, turbidity, ammonium and temperature being documented as key drivers. The MPB community composition clearly reflected the influence of catchment anthropogenic activities on species composition and structure. Moderately modified catchments resulted in MPB community structure variation among water bodies in relationship to land use and salinity gradients. The study found that; (i) by virtue of their size, microsystems and their catchments are likely to be particularly vulnerable to anthropogenic pressures when compared to systems of larger size; (ii) a typical impacted state may reflect reduced environmental heterogeneity which, compared to larger systems, may be achieved over much shorter time periods (following a particular event) or under much less intensive impacts; and (iii) the response in terms of MPB structure may predictably reflect a concomitant change from a complex community dynamic (structure and spatio-temporal attributes) to one that approaches a homogeneous structure (poor spatial zonation, strong taxonomic dominance, low species diversity).