Ephemeral Pans Research Articles

Drainage reorganization and alluvial architecture of endorheic basins: The Lower Cretaceous record of the Chubut Group in the Golfo San Jorge Basin (Patagonia, Argentina)

The size, shape, and organization of depositional systems in endorheic basins are controlled by the tectonic and climatic history of the sedimentary basin and its boundaries. We evaluate the changes in the alluvial architecture of the Matasiete (Aptian) and Castillo (Albian) formations of the Chubut Group (Cretaceous) in the endorheic Golfo San Jorge Basin (Patagonia, Argentina) analyzing a ∼150 km transect along the San Bernardo Fold Belt, subsurface data, and coeval fluvial successions of the Los Adobes Formation in the nearby Cañadón Asfalto Basin. The Aptian Matasiete Formation represents an externally-sourced, high-accommodation fluvial system with its headwaters in the current Cañadón Asfalto Basin, flowing toward the alkaline lake of the Pozo D-129 Formation through N–S oriented sedimentary corridors of tectonic origin. Low sinuosity, fixed channels with ribbon geometries (mean thickness 7.3 m, W/T ratio 14) are encased in red-colored floodplain fines, whereas stratigraphic intervals rich in resedimented tuffs contain braided rivers with W/T ratio up to 90. Deposition of the overlying Albian Castillo Formation occurred in a W-E elongated basin disconnected from the Cañadón Asfalto Basin, comprising aggradational, volcaniclastic floodplain deposits and smaller-scale fluvial channels of narrow-sheet geometries (mean thickness ∼ 3m, mean W/T ratio 45). The Castillo Formation shows spatial variation in fluvial styles and channel sizes, with intermittent to ephemeral rivers of small scale near the headwaters and seasonal, perennial rivers in downstream positions. Alluvial architecture changes between the Matasiete and Castillo formations reflect changes in the configuration of the basin boundaries, subsequent re-organization of the channel networks, and variable supply of volcaniclastic particles to drainage catchments of different hierarchy that evolved in areas with large variation of the preserved thickness. Comparable geomorphic scenarios in the Okavango Macrobasin show multiple base levels (lacustrine, ephemeral pans), several drainage catchments of variable orientation, scale, and behavior (perennial, intermittent to ephemeral), and exotic rivers adjacent to minor-scale courses.

Impact of artificial waterholes on temporal partitioning in a carnivore guild: a comparison of activity patterns at artificial waterholes to roads and trails.

Temporal partitioning in large carnivores have previously been found to be one of the main factors enabling co-existence. While activity patterns have been investigated separately at artificial waterholes and e.g., game trails, simultaneous comparative analyses of activity patterns at artificial waterholes and game trails have not been attempted. In this study, camera trap data from Maremani Nature Reserve was used to investigate whether temporal partitioning existed in a carnivore guild of four species (spotted hyena, leopard, brown hyena and African wild dog). Specifically, we investigated temporal partitioning at artificial waterholes and on roads and trails an average of 1,412 m away from an artificial waterhole. Activity patterns for the same species at artificial waterholes and roads/game trails were also compared. We found no significant differences in temporal activity between species at artificial waterholes. Temporal partitioning on game trails and roads was only found between spotted hyena (nocturnal) and African wild dog (crepuscular). Between nocturnal species (spotted hyena and leopard) no temporal partitioning was exhibited. Only African wild dog exhibited significantly different activity patterns at waterholes and roads/game trails. This indicates artificial waterholes may be a location for conflict in a carnivore guild. Our study highlights the impact of anthropogenic landscape changes and management decisions on the temporal axis of carnivores. More data on activity patterns at natural water sources such as ephemeral pans are needed to properly assess the effect of artificial waterholes on temporal partitioning in a carnivore guild.

The ephemeral pans of Gras-Holpan: Mokala National Park, Northern Cape, South Africa

Ephemeral pans are transient natural habitats with harsh conditions found in semi-arid regions. These pans endure high evaporation rates, extreme temperatures and an overflow of water. Pans are characterised by dry land becoming submerged in water temporarily (flood-like) followed by a prolonged period absent of water (drought-like). Ephemeral pans are unique habitats that are essentially transient habitats from a freshwater system to increased salinity and eventually a dry landscape. Biodiversity associated with these pans must adapt to the transient environmental conditions. Unique adaptations of the biota for these habitats allow them to withstand extreme conditions. The objective of this study was to (1) identify changes in the water quality over time in the pans, to (2) identify succession of macro-invertebrates and (3) identify the water quality parameters of pans as drivers of macro-invertebrate assemblages. A total of five pans were measured in the Northern Cape province of South Africa located on the Savanna and Nama-Karoo biomes within a 4500 ha area. The measurements taken included water quality variables (pH, salinity, total dissolved solids [TDS]), taxon diversity and richness of macro-invertebrates and aquatic birdlife. Evaporation rate between the pans varied with time. There was a difference in the macro-invertebrate taxon richness between the pans. Macro-invertebrate taxon succession was observed over time and some macro-invertebrates showed confinement to pans of a particular biome. It was found that pH was significantly the most contributing factor to the taxon richness and diversity of the macro-invertebrates recorded, while the salinity and TDS increased with time as water evaporated.Conservation implications: The shrimps (fairy, clam and tadpole) were unique to the Nama-Karoo pans. It was found that pH (p 0.05) was the most contributing factor to the taxon richness and diversity of the macro-invertebrates recorded, and salinity and TDS increased with time as water evaporated.

Description of a new species of Potamonautes MacLeay, 1838, from the iSimangaliso Wetland Park, South Africa.

A new species of freshwater crab, Potamonautes isimangaliso sp. n., is described from the western shores of False Bay, Hluhluwe, within the iSimangaliso Wetland Park, South Africa. While bearing a superficial resemblance to Potamonautes lividus, the new species has been found to be genetically distinct, diverging from the former by 7.4–7.8% in mtDNA. Potamonautes isimangaliso most closely resembles Potamonautes lividus, but is distinguished by a unique suite of carapace characters, colouration, and size. The new species also lives in close association with oxygen-poor, fresh ephemeral pans, while the habitat of Potamonautes lividus is well above the surface water line of the closest water body. An updated identification key for the Potamonautes species of South Africa is provided.

Restoring breeding habitat for Giant Bullfrogs (Pyxicephalus adspersus) in South Africa

Habitat fragmentation and transformation arising from urbanisation are leading causes of frog population declines. Artificial wetlands are sometimes used in remediation to minimise biodiversity loss in urban landscapes, but little is known about the specific habitat requirements of frog species for breeding. The aim of our study was to identify pan characteristics that promote Giant Bullfrog (Pyxicephalus adspersus) breeding success, in order to improve artificial wetland design. African Bullfrogs breed in ephemeral pans and are currently listed by the International Union for Conservation of Nature (IUCN) regionally as ‘Near Threatened’. Most suitable bullfrog habitat has been transformed in the highly urbanised province of Gauteng, South Africa. We conducted this study in the Total Petroport N14 Biodiversity Reserve (Gauteng Province), which is an artificial wetland complex created in 2006 specifically for the conservation of bullfrog populations. Tadpole numbers and froglet recruitment were compared to the physical characteristics and water quality of 12 pans over two breeding seasons. Total dissolved solids (TDS) in pan water were weakly correlated with tadpole number. Survival to metamorphosis was significantly higher in pans which had been lined and as a result had longer hydroperiod. Frog recruitment, however, was not related to any of the measured physical characteristics of the pans. Thus, bullfrogs appear to be non-selective in their choice of breeding sites, and breeding success appears to largely depend on stochastic events, such as drying of pans. Confounding factors such as proximity to human activity may also impact breeding success. We conclude that a wide variety of artificial pans can adequately ameliorate negative impacts of land transformation on bullfrog recruitment.

A breeding island for Lesser Flamingos Phoeniconaias minor at Kamfers Dam, Kimberley, South Africa

Kamfers Dam is a 500-ha perennial wetland located just north of Kimberley, South Africa. This wetland was previously an ephemeral pan, but is now permanently inundated as it receives most of Kimberley’s effluent water. It also receives storm-water run-off from Kimberley and from a c.160 km2 large catchment. Kamfers Dam probably supports the largest permanent population of Lesser Flamingos Phoeniconaias minor in southern Africa, with sometimes >80,000 individuals present.

Records of pan (floodplain wetland) sedimentation as an approach for post-hoc investigation of the hydrological impacts of dam impoundment: The Pongolo river, KwaZulu-Natal

River impoundment by dams has far-reaching consequences for downstream floodplains in terms of hydrology, water quality, geomorphology, ecology and ecosystem services. With the imperative of economic development, there is the danger that potential environmental impacts are not assessed adequately or monitored appropriately. Here, an investigation of sediment composition of two pans (floodplain wetlands) in the Pongolo River floodplain, KwaZulu-Natal, downstream of the Pongolapoort dam constructed in 1974, is considered as a method for post-hoc assessment of the impacts on river hydrology, sediment supply and water quality. Bumbe and Sokhunti pans have contrasting hydrological regimes in terms of their connection to the main Pongolo channel – Bumbe is a shallow ephemeral pan and Sokhunti is a deep, perennial water body. The results of X-ray fluorescence (XRF) geochemical analysis of their sediment records over a depth of >1 m show that whilst the two pans exhibit similar sediment composition and variability in their lower part, Bumbe pan exhibits a shift toward increased fine-grained mineral supply and associated nutrient influx at a depth of c. 45 cm whilst Sokhunti pan is characterised by increased biogenic productivity at a depth of c. 26 cm due to enhanced nutrient status. The underlying cause is interpreted as a shift in hydrology to a ‘post-dam’ flow regime of reduced flood frequencies with more regular baseline flows which reduce the average flow velocity. In addition, Sokhunti shows a greater sensitivity to soil influx during flood events due to the nature of its ‘background’ of autochthonous biogenic sedimentation. The timing of the overall shift in sediment composition and the dates of the mineral inwash events are not well defined, but the potential for these wetlands as sensitive recorders of dam-induced changes in floodplain hydrology, especially those with a similar setting to Sokhunti pan, is clearly demonstrated.

Occurrence and abundance of waterbirds at an ephemeral pan in the Northern Cape Province, South Africa

Bi-monthly counts of waterbirds were made between March and September 2003 at an ephemeral pan in the Northern Cape Province following the first substantial inundation since 1988. Bi-annual counts between 1991 and 2003 indicated that the pan infrequently supported waterbirds, with waterfowl and small waders generally being the dominant species. During the bimonthly counts, a total of 50 waterbird species was recorded, with the most dominant species, both in terms of numbers and duration of presence, being Black-winged Stilt Himantopus himantopus (max. 378), Cape Shoveller Anas smithii (max. 260) and South African Shelduck Tadorna cana (max. 200). Most other waterfowl and wader species were regular but in lower numbers. Species groups that occurred in limited numbers or for short periods include primarily herons, grebes, flamingos, ibises and storks. Species abundance and richness reached a peak one month after the pan was inundated, followed by a gradual decline over the ensuing two months.

Vegetation ecology of the pans (playas) of Soetdoring Nature Reserve, Free State Province

A comparison of the vegetation of two pans (playas) inside Soetdoring Nature Reserve, a freshwater and a brackish pan, is presented. These ephemeral pan communities are also compared to the vegetation of the hot spring and two permanently inundated earth dams inside the brackish pan's basin. The vegetation of the freshwater communities differs significantly from that of the brackish pan itself. The freshwater pan was classified as a Mixed Grass Pan and the brackish pan as an Open Diplachne Pan. The Mixed Grass Pan is characterised by a Cynodon transvaalensis – Gnaphalium declinatum community, associated with the following sub- communities: Selago dinteri – Cynodon transvaalensis , Panicum schinzii – Cynodon transvaalensis and Portulaca oleracea – Cynodon dactylon subcommunity. Cynodon transvaalensis is the dominant species in this pan. The Open Diplachne Pan is characterised by a Diplachne fusca – Eragrostis bicolor community with a Diplachne fusca subcommunity and an Eragrostis bicolor – Diplachne fusca subcommunity associated with it. Diplachne fusca is dominant in the pan basin. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed five distinct plant communities for the pan basins and freshwater areas inside the basin collectively. This information is important since very few published analyses are available for pans in the Free State Province, as well as in South Africa as a whole.

Sexual segregation in habitat use by elephants in Chobe National Park, Botswana

AbstractWe report on a study conducted on free‐ranging African elephants in the woodlands of northern Botswana. We compared bull groups and family units with regard to (1) their patterns of habitat use and (2) their ranging distances from perennial water sources. During the dry season, adult males frequented more habitat types than family units, whereas family units used a wider diversity of habitats than bulls during the wet season. Bulls roamed widely (>10 km) from perennial drinking water in the dry season, when family units congregated within 3.5 km of the rivers. During the wet season, when ephemeral pans were abundant, all elephant groups were found at intermediate distances (5 km) from the rivers. The spacing of elephants in the dry season is consistent with sexual segregation but we reject the hypothesis that this is an outcome of indirect competition for food, because our concurrent studies on elephant feeding ecology found no evidence for intraspecific competition. Instead, we propose that most adult male elephants space themselves to avoid conflict with musth bulls and roam widely in the dry season between discretely distributed feeding ‘hotspots’. The small proportion of males that are in musth remain close to family units to maximize mating opportunities, and family units are unable to range far from water in the dry season. This is due to (1) comparatively high rates of water turn‐over among juveniles and lactating cows and (2) the reduced mobility of neonates.

Waterbird diversity, densities, communities and seasonality in the Kalahari Basin, Botswana

Surveys in all major wetlands in Botswana (52,127 birds of 104 species on 10,672 ha of water and along 1782 km of shoreline) showed that waterbird diversity (from rarefaction) and densities were highest at small ephemeral endorheic pans. Oligotrophic waters in the Okavango Delta had similar diversity, but 10 times lower density. Large saline pans and highly eutrophic sewage ponds supported high densities, but the lowest diversity. Man-made dams were intermediate. The Chobe floodplains and mesotrophic backwaters in the Okavango were the only important dry season refuges found; many waterbirds leave the country during dry periods. Ephemeral pans constitute the most important wetland system for birds in the Kalahari Basin.

What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia

Simmons, R.E., Barnard, P.E. & Jamieson, I.G. 1998. What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia. Ostrich 70 (2): 145–148 The ability of wetland birds to rapidly find and exploit ephemeral pans is well known in and lands, but the episodic nature of such events means that the methods employed are poorly understood. Birds may: (i) wander randomly until wetlands are found; (ii) predict rainfronts and rainfall using changes in pressure gradients as cues; or (iii) follow rainfronts directly and descend onto pans as they fill. Observations from isolated pans in Namibia during the first rains indicate that wetland birds follow rainfronts, and descend onto pans as they fill. In one 30 ha pan, 37 birds of 5 species had arrived one day after filling and in another 50 ha pan over 300 birds of 13 species were attracted within 3 days of filling. Wetland birds, like migratory raptors, therefore, follow rainfronts, andMaywander locally thereafter. How species such as grebes and flamingos that exploit these pans for later breeding and intercontinental movements (respectively) time their flights to coincide with fully flooded pans remains unknown.

Long‐term effects of daily grazing orbits on nutrient availability in Sahelian West Africa: 2. Effects of a phosphorus gradient on spatial patterns of annual grassland production

Abstract. This paper reports on an investigation of the effect of a livestock‐generated gradient in phosphorus‐availability on spatial patterns of annual rangeland production around pastoral watering points in the Sahelian region of West Africa. The study was conducted along a major transhumance corridor used for at least the past century by herds managed by agropastoralists of the Inland Niger Delta of Mali. Eighteen sites on sandy substrate were established at varying distances from: (1) a more persistent pan from which livestock disperse to graze primarily during the early dry season (D1); and (2) a line of ephemeral pans from which livestock disperse to graze during the rainy season (D2). Data on the species composition, standing herbaceous mass, and annual herbaceous cover were collected at these sites over the 2 years following a significant drought. These vegetative parameters show considerable interannual variation in their spatial pattern. As reported elsewhere (companion paper), chemical analyses of soil and plant samples collected at these sites show a significant negative correlation between phosphorus availability and D2. This is consistent with livestock‐mediated nutrient transfer from outlying zones toward rainy‐season pans. The effect of this phosphorus gradient on annual rangeland production was analysed using a regression modelling approach. Two vegetative production parameters, vegetated surface fraction (VSF) and herbaceous above‐ground standing mass of vegetated surface (VAGM), were regressed in a two‐and three‐step process on the following factors: (1) background soil and rainfall data; (2) forb fraction of herbaceous production (for VAGM only), followed by: (3) D1 and D2. These analyses find that while the phosphorus‐availability gradient had a significant effect on spatial patterns of herbaceous production during the year immediately following the drought, it had little effect in the subsequent year's production. This difference is explained by the increased importance of nitrogen in limiting herbaceous production during the second year, resulting from its different rainfall history.

Seasonal changes in the invertebrate community of small shallow ephemeral pans at Bain's Vlei, South Africa

Changes in invertebrate population numbers and composition were monitored in six small shallow ephemeral pans during four consecutive inundations of spring, summer and autumn 1988/1989. The community was generally characterized by crustaceans and was invaded by insect larvae in summer. Community changes and succession were prominent in spring but less so in summer and autumn. Large pans supported more species than small pans. During longer inundation there was less difference between the initial and the final population composition than during shorter inundation, although the total population density did not increase significantly. This indicated that population composition stabilized as inundation lengthened. Population changes of six representative taxa were not correlated to changes in the physical and chemical characteristics of the water.