Recent changes in coral assemblages of a South African coral reef, with recommendations for long-term monitoring

Two-mile reef, Sodwana, South Africa is an unusual coral reef, being situated on a submerged fossilized sand dune and being very southerly (27°54). It is a popular Scuba diving venue receiving about 100000 dives year^–1. The line-intercept transect method, as recommended by the global coral reef monitoring network (GCRMN), was used to determine soft coral, hard coral and other benthos percentage cover. Physical coral damage, disease and bleaching were also recorded. Results were compared with those of B. Riegl (1993 – unpublished PhD thesis) 5 to 7 years earlier. The reef appears to be ecologically and highly dynamic. In the interim, there has been an increase in living benthos cover of 22.3% but also an increase in coral bleaching from 0% in 1993 to 1% in 1998. Physical damage, despite the large number of dives on the reef was minimal (1.52%), although it appears as if coral diseases may be increasing. The 20-m transects recommended by GCRMN are too long for this highly rugose reef with its distinct ridges and gullies. It is recommended that benthos cover, coral damage, bleaching and disease should be monitored annually using 40 5-m transects on the reef ridges and 40 5-m transects on the reef slopes.     

Fish communities in temporarily open/closed estuaries from the warm- and cool-temperate regions of South Africa: A review

The majority of estuaries along the coastline of southern Africa are termed temporarily open/closed estuaries (TOCEs) and are closed off from the sea for varying periods by a sandbar which forms at the mouth. It is therefore important to understand the processes occurring within TOCEs and their importance to fishes in order to make sound management recommendations. Estuaries along the coast of South Africa and their associated fish assemblages are biogeographically distinct and occur in either a subtropical, warm-temperate or cool-temperate zone. There are 125 TOCEs found within the cool-temperate and warm-temperate zones. Most fish species found in TOCEs are the juveniles of marine taxa that breed at sea. Permanently open estuaries generally have a higher diversity of species than TOCEs, but TOCEs still provide important nursery areas for many marine species and numerically often have a higher proportion of estuarine resident species. Important taxa in terms of abundance and biomass in warm-temperate TOCEs include the sparids Rhabdosargus holubi and Lithognathus lithognathus, several mugilid species, estuarine residents (particularly Gilchristella aestuaria and Atherina breviceps) and the freshwater cichlid Oreochromis mossambicus. The diversity of fishes in cool-temperate TOCEs is low when compared with warm-temperate systems and Liza richardsonii tends to dominate catches by number and mass in most systems. Several species recorded in TOCEs show clear longitudinal distribution trends. For example Atherina breviceps is generally more abundant in the lower reaches of estuaries. Mouth state, particularly the frequency, timing and duration of mouth opening plays a key role in determining species richness, composition, diversity and abundance in TOCEs. Mouth state is directly linked to freshwater input. Reduced river inflow leads to prolonged mouth closure and shorter open phases, which inhibits immigration and emigration of marine fish species between estuaries and the sea. Understanding of the effects of various processes occurring within these systems, particularly variation in freshwater input, on the biota of these important systems facilitates the development of informed management recommendations.     

Life-history styles of fishes in South African estuaries

Synopsis Fish utilizing South African estuaries may be divided into two major groups according to the location of their spawning sites. The marine group comprises large species which spawn at sea, enter estuaries mainly as juveniles, and return to the sea prior to attaining sexual maturity. The estuarine group is dominated by small species which have the ability to complete their life cycle within the estuarine environment. They tend to produce relatively few, demersal eggs, or exhibit parental care, which facilitates the retention of eggs and young within the estuary, whereas the marine group release large numbers of small pelagic eggs during spawning and exhibit no parental care. This is contrary to the theory that estuaries (unpredictable environments) should favour altricial life-history styles and the marine inshore zone (a more predictable environment) should favour precocial styles. However, if the total ichthyofauna of South African estuaries is considered, then altricial species predominate. The fact that both altricial and precocial traits are well represented within the overall estuarine fish community suggests that the various taxa have adapted their life-history styles, in different ways, to ensure the utilization of abundant food resources available within these fluctuating systems. A detailed comparison of the life-history styles of the estuarine teleostGilchristella aestuaria and the marine fishMugil cephalus is used to illustrate the contrasting manner in which these two species have succeeded in exploiting South African estuaries.     

Biomass and production estimates of a fish community in a small South African estuary

The fish community of the small (17·5 ha) intermittently open East Kleinemonde estuary was sampled between 1994 and 1997 to estimate population size, standing stock, growth and productivity. The estuarine-spawning species were numerically more abundant ( n c . 750 000) but due to their small size contributed only 11·7% to the total biomass. The total annual productivity of all fishes in the estuary ( n c . 890 000), with a standing stock of 28·44 g m ⁻², was calculated at 55·89 g m⁻² year⁻¹. The small sparid Rhabdosargus holubi with a production estimate of 41·35 g m⁻² year⁻¹ accounted for <74% of the total fish production in this estuary.     

Comparative evaluation of Life Cycle Impact assessment methods with a South African case study

Goal and Background  LCIA procedures that have been used in the South Africa manufacturing industry include the CML, Ecopoints, EPS and Eco-indicators 95 and 99 procedures. The aim of this paper is to evaluate and compare the applicability of these European LCIA procedures within the South African context, using a case study. Methods  The five European methods have been evaluated based on the applicability of the respective classification, characterisation, normalization and weighting approaches for the South African situation. Impact categories have been grouped into air, water, land and mined abiotic resources for evaluation purposes. The evaluation and comparison is further based on a cradle-to-gate Screening Life Cycle Assessment (SLCA) case study of the production of dyed two-fold wool yarn in South Africa. Results and Discussion  Where land is considered as a separate category (CML, Eco-indicator 99 and EPS), the case study highlights this inventory constituent as the most important. Similarly, water usage is shown as the second most important in one LCIA procedure (EPS) where it is taken into account. However, the impact assessment modelling for these categories may not be applicable for the variance in South African ecosystems. If land and water is excluded from the interpretation, air emissions, coal usage, ash disposal, pesticides and chrome emissions to water are the important constituents in the South African wool industry. Conclusions  In most cases impact categories and procedures defined in the LCIA methods for air pollution, human health and mined abiotic resources are applicable in South Africa. However, the relevance of the methods is reduced where categories are used that impact ecosystem quality, as ecosystems differ significantly between South Africa and the European continent. The methods are especially limited with respect to water and land resources. Normalisation and weighting procedures may also be difficult to adapt to South African conditions, due to the lack of background information and social, cultural and political differences. Recommendations and Outlook  Further research is underway to develop a framework for a South African LCIA procedure, which will be adapted from the available European procedures. The wool SLCA must be revisited to evaluate and compare the proposed framework with the existing LCIA procedures.     

Ecological integrity assessment of the fish assemblages of the Matigulu/Nyoni and Umvoti estuaries,KwaZulu-Natal,South Africa

The estuarine fish community index (EFCI) and an estuarine fish guild assessment (EFGA) were used in 2004 and 2008 to determine the ecological state and effects of selected ecosystem variables on the Umvoti and Matigulu/Nyoni estuaries. The EFCI indicated that the Matigulu/Nyoni Estuary was in a moderate state and that the Umvoti Estuary was in a poor to very poor state. The EFGA revealed a clear spatial differentiation, based on the estuaries’ fish community structures, that was being driven primarily by the freshwater-dominated state of the Umvoti Estuary and the poor water quality of the Umvoti Estuary. The analysis of estuarine fish assemblage characteristics was shown to contribute towards the management and conservation of these systems.     

Biochemical polymorphisms in South African freshwater fish. Isoenzyme patterns in fish of the families Cyprinidae and Salmonidae

Isoenzyme patterns were studied in local populations of the carp ( Cyprinus carpio ) and the bream ( Sarotherodon mossambicus ) of the Cyprinid family. and in the trout ( Sabno giardneri ) of the family Salmonidae. Homogenates of heart muscle extracts were used in the identification of PGI. NADP-IDH. PGM and 6-PGD.
Polymorphisms found and gene frequencies obtained are discussed separately for each enzyme and species or population.
In the bream, variation was found only at the PGI locus. In the carp only the PGM locus was polymorphic whereas both PGM and IDH showed variation in the trout. The variation at the PGM locus in the trout cannot support the three locus model suggested elsewhere and clearly indicates a single locus for the mo-nomeric enzyme.
The large variety of NADP-IDH types in trout not only illucidates the complexity of this locus but confirms a disomic mode of inheritance. Genetic differences in the trout populations could be related to possible advantages for management purposes.     

A comparison of the macrobenthic faunas of permanently open and temporarily open/closed South African estuaries

Thirteen estuaries in the Eastern Cape Province, South Africa, were broadly categorised according to size and salinity distribution and were assigned to one of the following categories: permanently open estuaries having a strong salinity gradient between mouth and upper estuary, freshwater-deprived permanently open estuaries, medium-sized temporarily open/closed estuaries, and small, temporarily open/closed estuaries. The macrobenthos collected during surveys was then compared in terms of the following parameters: species composition, salinity, sediment mud content, density of macrobenthic animals, Hill's N0 (species richness), and Hill's N1 (diversity). Mud content was found to be the most important environmental variable responsible for biotic patterns found, and sites were consequently assigned to either a sand zone fauna, or a mud zone fauna. Both types of fauna are present in all estuaries sampled, with upper sites of river dominated estuaries having an additional oligohaline fauna, and freshwater-deprived estuaries providing habitat for many marine species. Small, temporarily open/closed estuaries have the highest macrobenthic density, whereas N0 and N1 are highest in freshwater-deprived permanently open systems. River-dominated permanently open estuaries tend to have lower macrobenthic densities, species richness, and diversities compared to estuaries in the other categories. No seasonal differences in these ecological indices were found within any of the estuarine categories.     

Biomass and productivity of fishes in estuaries: a South African case study

Estuaries are well known for their role as nutrient and detrital sinks that stimulate high levels of both primary and secondary production which, in turn, support a large biomass of fishes per unit area. This study reviews available information on coastal fish biomasses (g m^?2 wet mass) and productivity (g m^?2 wet mass year^?1) in order to place South African data on these topics into a global perspective. Using biogeographic fish productivity estimates, together with estuarine water area, the approximate annual teleost production in South African estuaries was calculated at 585, 1706 and 13 904 t in the cool temperate, warm temperate and subtropical regions, respectively. Total annual fish production in estuaries on the subcontinent is conservatively estimated at 16 195 t, but this figure is likely to fluctuate widely, depending on recruitment success and annual environmental conditions pertaining to these systems. Approximately 2000 t of fish are estimated to be harvested by fishing activities in South African estuaries each year, which represents c. 12% of annual fish production. Although this figure may appear sustainable, the reality is that there are a few heavily targeted estuary‐associated marine species at the top of the food chain that are being overexploited by both anglers and subsistence fishermen. Natural mortalities due to piscivorous fish and bird predation has been estimated at c. 3% of total fish biomass per month in the East Kleinemonde Estuary, but this figure will vary considerably depending on bird abundance and foraging patterns along the coast. In contrast to catches made by the fishermen, piscivorous fishes and birds are targeting mainly juvenile marine fish and small estuarine resident species that are very abundant and generally low down in the food web.     

Fish sampling in the marine-dominated Kariega Estuary,South Africa,using a demersal otter trawl: day/night effects

Very few demersal fish assemblage studies using otter trawls in estuaries have been done in South Africa and none of these have tested for the effects of diel period. This study aimed to test whether diel period affects otter trawl catches in the clear, permanently open Kariega Estuary in terms of both species composition and abundance. Fish were sampled by day and night from 30 October to 1 November 2007 at 15 sites using an otter trawl. More species were collected at night, when there were higher catch rates for all key species, with the exception of Rhabdosargus holubi, which was more abundant during the day. Overall assemblages collected by day and by night were similar, with six species accounting for over 90% of the catch in both day and night samples. Both day and night samples reflected differences related to region, with the highest mean CPUE during day and night sampling being recorded in the head region.     

Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplain

During the flood season of 1992–1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species.     

Preliminary indications of climate-induced change in a warm-temperate South African estuarine fish community

The fishes of the warm-temperate East Kleinemonde Estuary (South Africa) have been sampled bi-annually, in summer and winter, using seine and gillnets since December 1995 and a total of 19 families, represented by 38 species were recorded between December 1995 and July 2006. Indicative of a warming trend, six new species of tropical fishes ( Valamugil cunnesius, Valamugil robustus, Liza alata, Liza macrolepis, Glossogobius giuris and Terapon jarbua ) were recorded in the catches from 1999 onwards, with V. cunnesius and L. macrolepis recorded in catches almost every year after 2002. Mean annual sea-surface temperatures recorded along the adjacent coast have been increasing during the past decade and this may have facilitated the southward extension of tropical marine fishes into the warm-temperate biogeographic zone.     

A comparative ecology of estuaries in Nigeria

A bar-built estuary, a drowned river valley and two river delta estuaries were compared and contrasted to elucidate the impact of some abiotic factors, notably climate, salinity, and oxygen on the distribution of the aquatic fauna and flora.Salinity was recognizable as the key factor responsible for the population dynamics in these habitats. The mangrove community is characteristically zoned, but development and distribution of the trees is restricted in view of coastal geomorphic and hydrological processes to the western banks of the estuaries.The preponderance of marine fish species in estuaries was confirmed, although the wide salinity tolerance of some prolific-breeding Cichlidae from freshwater was noted. Forty-eight species of bony fishes were recorded in Lagos Lagoon, the Escravos, and Qua Ibo estuaries and classified by salinity tolerance into stenohaline and euryhaline marine species (66%), and freshwater species (34%). The same estuarine ichthyofauna were split into trophic groups: piscivores (46%), zooplankton feeders (10%), meiobenthos feeders (27%), and macrobenthos feeders (17%).     

Fishes as indicators of environmental and ecological changes within estuaries: a review of progress and some suggestions for the future

Estuarine habitats, and the fish assemblages associated with them, are potentially impacted upon by many anthropogenic influences which can have a direct influence on the food resources, distribution, diversity, breeding, abundance, growth, survival and behaviour of both resident and migrant fish species. The direct and indirect coupling between ichthyofaunal communities and human impacts on estuaries reinforces the choice of this taxonomic group as a biological indicator that can assist in the formulation of environmental and ecological quality objectives, and in the setting of environmental and ecological quality standards for these systems. This review examines the rationale and value of selecting fishes as bio-indicators of human induced changes within estuaries, using examples from both the northern and southern hemispheres. The monitoring of estuarine 'health' using fish studies at the individual and community level is discussed, with an emphasis on the potential use of estuarine fishes and their monitoring and surveillance in national and international management programmes. In illustrating the above concept, examples are presented of the way in which fishes are threatened by anthropogenic impacts and of the way in which teleosts can contribute to a monitoring of estuarine ecosystem health.     

Waders in winter: long-term changes of migratory bird assemblages facing climate change

Effects of climate change on species occupying distinct areas during their life cycle are still unclear. Moreover, although effects of climate change have widely been studied at the species level, less is known about community responses. Here, we test whether and how the composition of wader (Charadrii) assemblages, breeding in high latitude and wintering from Europe to Africa, is affected by climate change over 33 years. We calculated the temporal trend in the community temperature index (CTI), which measures the balance between cold and hot dwellers present in species assemblages. We found a steep increase in the CTI, which reflects a profound change in assemblage composition in response to recent climate change. This study provides, to our knowledge, the first evidence of a strong community response of migratory species to climate change in their wintering areas.     

Life cycles and challenges for fish species that breed in South African estuaries

The literature currently recognizes four guilds of estuarine resident fish species, namely solely estuarine, estuarine and marine, estuarine and freshwater, and estuarine migrant. In this review the life cycles of actual representatives from these four guilds are assessed to determine whether the current definitions, which have never been formally tested, are appropriate to fish species resident in South African estuaries. Detailed information and diagrammatic life cycles are provided for the selected species covered by this review. A potential new estuarine resident guild category is also identified, namely, those taxa that are primarily estuarine but also have subpopulations recorded in both adjacent marine and freshwater habitats. The full range of reproductive characteristics employed by estuary resident species is examined, ranging from live bearers, pouch and nest brooders, to a suite of oviparous taxa that attach their ova to estuarine rocks, shells, and submerged vegetation, all of which assists with larval retention within the estuarine environment. The small size and early reproductive maturity of most estuarine resident species is highlighted, with reduced vulnerability to predation in shallow, sheltered, often turbid estuary waters offering considerable protection during spawning events when compared to the open ocean. In addition, these small fish would not have to move considerable distances at any stage of their life cycle, since egg, larval, juvenile, and adult stages all occur in the same place. The existence of contingent subpopulations within many estuarine resident species is noted, physico-chemical stresses on these species are highlighted, and the eurytopic nature of these small fish taxa emphasized.     

Desire Work: Producing Heterosexuality in South African Pentecostal Gay Men

Gay men in Cape Town, South Africa joined a Pentecostal ministry in an attempt to produce what they understood as ‘natural’ heterosexual attraction. In this article, I explore how these gay men try to form new selves through what I call ‘desire work’, or physical and emotional micropractices and discipline. Desire is not ‘natural’, but it is produced through a multitude of engagements with cultural norms, public life, political economies, and social forces. New selves are built through concerted bodily changes and comportment [Mahmood, Saba. 2005. Politics of Piety: The Islamic Revival and the Feminist Subject. Princeton, NJ: Princeton University Press], and although gay Pentecostal men shared this process, their success was limited. I understand desire work as a response to a larger context in which many Pentecostals are disaffected with the post-apartheid government and withdraw from politics as a result. Their fears of the uncertainties of democracy pushed them to engage in optimistic fantasies of heterosexual lives, which were not often realised [Berlant, Lauren Gail. 2011. Cruel Optimism. Durham, NC: Duke University Press].     

Using stable isotope analysis to study the diet of Gilchristella aestuaria larvae: preliminary insights into the foodwebs of six South African estuaries

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.     

'Fish in hot water": the challenges facing fish and fisheries research in tropical estuaries

Tropical estuarine areas comprise small systems of a few km, larger estuaries, coastal lakes of hundreds of km 2 and vast shallow coastal waters that are contiguous with estuaries and have similar reduced salinities. Many of the world's great estuaries are in the tropics, e.g. the Amazon, Orinoco, Congo, Zambezi, Niger, Ganges and Mekong. The distribution of tropical and subtropical estuaries approximately follows that of mangroves. Like estuaries everywhere, they are a focus of human activity and are among the most exploited of ecosystems. In few other places do the activities of fishers, industrialists, shippers, farmers, conservationists, sports enthusiasts and biologists overlap to such an extent. Quite apart from the possible eects of all these activities, the fishes of subtropical and tropical estuaries already face one of the most rigorous of aquatic environments; but despite this, species diversity and productivity are high. Only in tropical estuaries are animals from such a wide range of taxa so closely associated, annelid worms, prawns, crocodiles, birds, ' hippos ', dolphins and of course fishes, all may form part of the overall community, often with functional ecological links. Unfortunately, the diculties of working in these often inhospitable environments, has meant that biologists have favoured projects in more appealing areas, such as coral reefs. While it is still true that most estuarine research is conducted in industrialized developed countries, nearly all of which are in cold or temperate regions, there has been a recent upsurge in tropical estuarine fish research. This is being driven by two imperatives, food security and the conservation and maintenance of biodiversity. Both these problems require knowledge of the ecology of tropical estuarine fishes, particularly their relationships with the environment and the extent to which they are dependent on estuaries or adjacent habitats for survival.