Department of Biodiversity and Conservation Biology

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https://hdl.handle.net/10566/34

The department of Biodiversity and Conservation Biology is active in the following research areas: jelly fish; education studies; endangered species conservation; landscape ecology and GIS; marine biology; plant ecophysiology; restoration ecology; sustainable livelihoods; taxonomy and systematics; traditional plant use.

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2-phenoxyethanol as anaesthetic in removing and relocating 102 species of fishes representing 30 families from sea world to uShaka Marine World, South Africa
(AOSIS, 2008) Vaughan, D.B.; Penning, M.R.; Christison, K.W.
The South African Association for Marine Biological Research, incorporating Sea World, Oceanographic Research Institute and the Dolphinarium relocated from their old premises of 46 years on Durban’s beach front in March and April 2004 to the new Point Development’s marine theme park, uShaka Marine World in Durban, South Africa. Netting of fishes from the large exhibits could cause physical damage to struggling fishes, increasing the risk of opportunistic secondary bacterial infections (Inoue, dos Santos Neto & Morales 2004) which could not be treated in time for the opening of uShaka Marine World on 30 April 2004.
A cross-over dietary intervention in captive cheetahs (acinonyx jubatus): Investigating the effects of glycine supplementation on blood parameters
(United States: Wiley Subscription Services, Inc, 2024) Kathryn M. van Boom; Tertius A. Kohn
Captive cheetahs are prone to unusual diseases which may be attributed to their high muscle meat, collagen deficient captive diet. Glycine is a simple amino acid that is abundant in collagen rich tissues and has many physiological functions, specifically in collagen synthesis and in the conjugation of detrimental by-products produced during gut bacterial fermentation. Therefore, the aim of this study was to investigate the effect of a 4 week glycine supplementation on the body measurements, haematology and serum blood parameters of 10 captive cheetahs using a randomised controlled cross-over design. This approach has not yet been used to investigate the effect of diet in captive cheetahs. Cheetahs were randomly assigned to a control diet (horse meat only) or a glycine diet (30 g glycine per 1 kg meat) for 4 weeks before being crossed over. Blood was collected at baseline and after each intervention. The glycine diet resulted in a decreased serum albumin, alkaline phosphatase and total calcium concentration and increases in eosinophils and basophils counts compared to the control diet. Body weight also decreased on the glycine diet which may be due to increased β-oxidation and fat loss. This was the first study to investigate the effect of glycine supplementation, which resulted in slight body and blood changes, in captive cheetahs using a cross-over design and this approach should be utilised for future dietary studies.
A framework for optimising opportunistic collaborative syntheses to propel ecological conservation
(Elsevier Ltd, 2024) Sequeira, Ana M.M.; Sherley, Richard B.; Bates, Amanda E.
Ecological data are being opportunistically synthesised at unprecedented scales in response to the global biodiversity and climate crises. Such syntheses are often only possible through large-scale, international, multidisciplinary collaborations and provide important pathways for addressing urgent conservation questions. Although large collaborative data syntheses can lead to high-impact successes, they can also be plagued with difficulties. Challenges include the standardisation of data originally collected for different purposes, integration and interpretation of knowledge sourced across different disciplines and spatio-temporal scales, and management of differing perspectives from contributors with distinct academic and cultural backgrounds. Here, we use the collective expertise of a global team of conservation ecologists and practitioners to highlight common benefits and hurdles that arise with the development of opportunistic collaborative syntheses. We outline a framework of “best practice” for developing such collaborations, encompassing the design, implementation, and deliverable phases. Our framework addresses common challenges, highlighting key actions for successful collaboration and emphasizing the support requirements. We identify funding as a major constraint to sustaining the large, international, multidisciplinary teams required to advance collaborative syntheses in a just, equitable, diverse, and inclusive way. We further advocate for thinking strategically from the outset and highlight the need for reshaping funding agendas to prioritize the structures required to propel global scientific networks. Our framework will advance the science needed for ecological conservation and the sustainable use of global natural resources by supporting proto-groups initiating new syntheses, leaders and participants of ongoing projects, and funders who want to facilitate such collaborations in the future.
A global systematic review of resource nexus and nature-positive sustainable development: an invitation to a new research agenda
(Taylor and Francis Ltd., 2025) O’Farrell, Patrick John; Makwinja, Yamikani Harry; Kimengsi, Jude Ndzifon
The Resource Nexus concept is acknowledged as a transformative approach to managing resource challenges. Yet, its contribution to nature-positive sustainable development (NPSD) practices remains less understood. This study (i) analyses how resource nexus and NPSD practices have been conceptualised in the literature, (ii) determines the state-of-the-art on the NPSD outcomes that are driven by the Resource Nexus approach, and (iii) identifies methodological development in Resource Nexus and NPSD studies. Search queries were conducted in the Scopus core collection, Web of Science, Google Scholar, and Science Direct, resulting in the inclusion of 117 empirical studies. The study reveals that while Resource Nexus offers a broad lens for engaging with these different environmental resources, its integration with NPSD practices remains underexplored. Firstly, the overall dominance of the water-energy-food (WEF) Nexus (28.2%) was reported, followed by the water-energy-food-climate (WEFC) Nexus (24.8%), and the biota-energy-food-climate (BEFC) Nexus (15.4%). Secondly, most papers reported ecological parameters (61.3%) as the significant NPSD outcomes driven by the Resource Nexus, followed by political (48.7%), and economic (44.4%) outcomes. Only 17% of papers reported socio-cultural outcomes. Finally, quantitative approaches were most commonly used in the literature (56.4%), followed by qualitative approaches (33.3%), while the mixed methods approach (10.3%) remained the least frequently used. Our review highlights the urgent need for a new research agenda focused on (i) a diverse Resource Nexus constellation, (ii) transformative coupled citizen science research that develops actionable strategies to complete the Science-policy-practice cycle, and (iii)innovative research methodologies focusing on multi-level and mixed-method approaches while preserving the diverse values of qualitative and quantitative approaches.
A taxonomic revision of the twelve-scaled species of struthiola (thymelaeaceae: thymelaeoideae): the struthiolamundiig roup
(Elsevier, 2025) Boatwright, James; Makhoba, Thuli; Magee, Anthony Richard
Struthiola L. (Thymelaeaceae: Thymelaeoideae) is a genus of approximately 40 species (Wright, 1915; manning and goldblatt, 2012) largely endemic to South Africa, but with four species in tropical Africa (Peterson, 1958, 1978, 2006). the Greater Cape Floristic Region (GCFR) is the centre of diversity for the genus, as well as for several other related southern African Thymelaeoideae, including Gnidial., Lachnaea l. and Passerina l. Almost all of the South African species of Struthiola are restricted to the GCFR (manning and goldblatt, 2012; Snijman, 2013), with only three of the South African species occurring beyond the region in the grasslands of KwaZulu-Natal (Wright, 1915; hilliard and burtt, 1986; Hilliard, 1993). Struthiola l. was established by Linnaeus (1767) in his Systema Naturae ed. 12 for two species of Thymelaeaceae that were characterised by flowers with just four anthers and petaloid scales (incorrectly described as nectary glands) and subsequently conserved against the earlier name Belvala Adans. (1763) with the conserved type S. erecta l. The genus was last revised more than a century ago by Wright (1915), and as the taxonomy of the southern African species remains poorly understood it has been identified as one of the priority groups for taxonomic revision (Victor et al., 2015; Victor, 2020). Meisner (1857), in his global treatment of Thymelaeaceae, subdivided the genus into three morphological groups based on the number of petaloid scales in the mouth of the hypanthium, viz. four, eight or 12. All subsequent authors have retained these informal subdivisions. The molecular analyses by Makhoba (2024) recovered the species with four scales (the Struthiola striata group) and those with 12 scales (the Struthiola mundii group) as two independent clades nested within the remaining species of the genus, all with eight scales. This confirms the value of the putatively derived scale-numbers of four and 12 in identifying relationships in the genus. The four-scaled S. striata group was recently revised (Makhoba et al., 2019) as a first step towards a comprehensive revision of the genus. As the next step we present a revision of the twelve-scaled species comprising the S. mundii group. Twelve species and three varieties were recognized in the S. mundii group at the onset of this study. Characters such as habit, flower colour, presence or absence of hairs on the hypanthium, hypanthium length, shape of the petaloid scales and the colour of the associated hairs, bracteole length, and presence or absence
Abalone farming in South Africa: an overview with perspectives on kelp resources, abalone feed, potential for on-farm seaweed production and socio-economic importance
(Elsevier, 2006) Troella, M. D.; Robertson-Andersson, Deborah; Anderson, Robert J.; Bolton, John J.; Maneveldt, Gavin; Halling, C.; Probyn, T.
The South African abalone cultivation industry has developed rapidly and is now the largest producer outside Asia. With a rapid decline in wild abalone fisheries, farming now dominates the abalone export market in South Africa. Kelp (Ecklonia maxima) constitutes the major feed for farmed abalone in South Africa, but this resource is now approaching limits of sustainable harvesting in kelp Concession Areas where abalone farms are concentrated. This paper gives an overview of the development of the South African abalone industry and analyses how abalone farming, natural kelp beds and seaweed harvesting are interlinked. It discusses options and constraints for expanding the abalone industry, focussing especially on abalone feed development to meet this growing demand. Kelp will continue to play an important role as feed and kelp areas previously not utilised may become cost-effective to harvest. There are many benefits from on-farm seaweed production and it will probably be a part of future expansion of the abalone industry. Abalone waste discharges are not at present regarded as a major concern and farming brings important employment opportunities to lower income groups in remote coastal communities and has positive spill-over effects on the seaweed industry and abalone processing industry.
Abalone nutrition – growth performance of Haliotis midae in relation to variable artificial feeds
(University of Western Cape, 2020) Mohamed, Riaaz; Gibbons, Mark J.
Abalone are among the most expensive and sought-after seafood subjects. In South Africa, Haliotis midae is the only commercially significant abalone species and it has become increasingly sold on the global market. The importance of abalone as a mariculture subject has triggered extensive research into maximizing production, with particular emphasis on optimizing growth rates. This study aimed to assess the growth performance of Haliotis midae relative to 1) standard pelleted feed, and 2) kelp-inclusive pelleted feed. I assessed feed stability of the dietary treatments and growth parameters associated with abalone weight gain. Temperature and time of feed submersion were found to significantly affect feed stability. Although there were no significant differences in water stability between feeds, the kelp-inclusive feed produced significantly lower total suspended solids (TSS) than the standard pelleted feed at upper time-temperature combinations.
Abundance and species composition of non-geniculate coralline red algae epiphytic on the South African populations of the rocky shore seagrass Thalassodendron leptocaule M.C. Duarte, Bandeira & Romeiras
(Elsevier, 2013) Browne, Catherine M.; Maneveldt, Gavin; Bolton, John J.; Anderson, Robert J.
Seagrasses support a great diversity of epiphytic organisms and new research has shown that non-geniculate coralline red algae are important occupiers of space on the fronds of seagrasses. Except for a few scant records, there are no detailed published accounts of non-geniculate coralline algae epiphytic on seagrasses in South Africa. The seagrass Thalassodendron leptocaule (previously known as Thalassodendron ciliatum) is unique among southern African seagrasses in that it occurs on exposed rocky outcrops along the Mozambique and north eastern South African coast; most other seagrasses are restricted to sheltered bays and estuaries. Here we present descriptions of three species of non-geniculate coralline red algae which we have identified growing epiphytically on this seagrass in northern KwaZulu-Natal: Hydrolithon farinosum, Pneophyllum amplexifrons and Synarthrophyton patena. Two of the corallines (P. amplexifrons and S. patena) were restricted to the seagrass' stems while the third (H. farinosum) occurred only on the leaves. Of the three coralline epiphytes, P. amplexifrons contributed most to the biomass (average wet weight per plant 0.6±1.18 g); its wet weight, however, varied between habitats. Hydrolithon farinosum and other smaller turf algae amounted to no more than 0.1 g (wet weight) per leaf. Synarthrophyton patena was far more sparsely evident and contributed to less than 0.1 g (wet weight) per stem. Pneophyllum amplexifrons and H. farinosum appear to be pioneer epiphytes and form additional surfaces onto which other seaweed epiphytes attach and grow. Distribution of these epiphytes is explained by the longevity of the stems and leaves of the seagrass.
Acoustic cues to development of African penguins (Spheniscus Demersus) begging calls
(John Wiley and Sons Inc, 2024) Zanoli Anna; Ludynia Katrin; Tenneriello Chiara
Avian begging calls mediate parent–offspring conflict and direct parental care to genetically related progeny. We found that the fundamental frequency of begging calls of African Penguins Spheniscus demersus decreases as the penguins age and gain mass, before reaching a lower plateau when the chick reaches about 1 kg. Our results suggest that the food solicitation signals of this species may inform parents of the offspring’s body mass. Our results may also lead to the development of non-invasive tools for facilitating censusing chick growth in wild colonies.
Acoustic observations of jellyfish in the Namibian Benguela
(Inter-Research, 2001) Brierley, Andrew S.; Axelson, Bjorn Erik; Buecher, Emmanuelle; Sparks, Conrad A.J.; Boyer, Helen; Gibbons, Mark J.
Multi-frequency acoustic data (18, 38 and 120 kHz) were collected in conjunction with pelagic trawl sampling for gelatinous macrozooplankton during a cruise to the Namibian Benguela in September 1999. Sampling focused specifically on the scyphozoan Chrysaora hysoscella and the hydrozoan Aequorea aequorea, both of which occur in large numbers, are probably of major ecological importance, and physically hamper pelagic fishing and diamond extraction activities. C. hysoscella was detected predominantly at an inshore station and A. aequorea was found in greatest abundance further offshore in deeper water. Echo-sounder observations were linked directly to net catches, and relationships between catch density (number of individuals m–3) and nautical area scattering coefficients (sA) at each frequency were determined for both species in order to estimate target strength (TS) using the comparison method. TS for C. hysoscella (mean umbrella diameter 26.8 cm) was –51.5 dB at 18 kHz, –46.6 dB at 38 kHz and –50.1 dB at 120 kHz; for A. aequorea (mean central umbrella diameter 7.4 cm) TS was –68.1 dB at 18 kHz, –66.3 dB at 38 kHz and –68.5 dB at 120 kHz. These TS values compared favourably with previously published estimates for related species. Jellyfish were caught at high numerical densities (maxima 3 C. hysoscella per 100 m3, 168 A. aequorea per 100 m3). These high densities, combined with the not unsubstantial TS at frequencies used for fisheries surveys, imply that jellyfish could potentially bias acoustic estimates of fish abundance. We suggest a simple multifrequency approach that could be used to discriminate between echoes from jellyfish and some commercially important pelagic fish in the northern Benguela ecosystem.
Acoustic signalling in bladder grasshoppers (orthoptera: pneumoridae)
(University of the Western Cape, 2022) Lagaa, Sasya; Couldridge, Vanessa
Sound plays a vital communicative role in many Orthopteran insect species. Acoustic signals are often used during courtship behaviour and mate location. The Pneumoridae, commonly referred to as bladder grasshoppers, are a family of insects native to southern and eastern Africa. They are highly adapted for long-distance sound communication, with the males emitting very loud advertisement calls that are typically distinctive to each species. However, relatively few previous studies have examined sound communication within the entire family, and little is known about interspecific variation in signals and how this relates to evolutionary history. The aim of this study was to compare acoustic signal characteristics, as well as the morphology of the sound-producing structures, across multiple species in order to better understand morphological constraints on sound production.
Adequacy of existing protected areas in conserving biodiversity at global and regional levels in relation to socio-economic conditions
(University of the Western Cape, 2005) Gaika, Lindiwe; Knight, Richard; Faculty of Science
At a meeting of worl leaders at the United Nations Conference on Environment and Development in Rio de Janeiro in 1992, it was recognized that because of the tremendous increase in the size of the global populations (which now is estimated to exceed six billion), there were concerns that global biodiversity was at risk if insufficient land were not put aside for conservation within formal Protected Areas. The primary aim of this study was to compare investment in Protected Areas in relation to socio-economic conditions at global and regional levels.
African rangelands and pastoralism in a changing continent: Perspectives and opportunities
(Taylor and Francis Group, 2023) Samuels, M Igshaan; Egeru, Anthony; Mugabe, Prisca
Eighty-five years ago, Africa was described as a land of promise because it provided an immense opportunity for maximum return in the minimum time (Olaniyan 2000). It was treated this way because it was considered more for its deposits of natural wealth and less for its potential for settlement or as a destination market for goods and services produced in Europe and elsewhere (Le Clair 1937). For over 50 years, this narrative held ground but in the last 20 years, perception has shifted with Africa becoming a destination market and a growth opportunity creator, whilst holding ground as a resource provider (Sy 2016).
An ambusher’s arsenal: chemical crypsis in the puff adder (Bitis arietans)
(The Royal Society, 2015) Miller, Ashadee Kay; Maritz, Bryan; McKay, Shannon; Glaudas, Xavier; Alexander, Graham J.
Ambush foragers use a hunting strategy that places them at risk of predation by both visual and olfaction-oriented predators. Resulting selective pressures have driven the evolution of impressive visual crypsis in many ambushing species, and may have led to the development of chemical crypsis. However, unlike for visual crypsis, few studies have attempted to demonstrate chemical crypsis. Field observations of puff adders (Bitis arietans) going undetected by several scent-orientated predator and prey species led us to investigate chemical crypsis in this ambushing species. We trained dogs (Canis familiaris) and meerkats (Suricata suricatta) to test whether a canid and a herpestid predator could detect B. arietans using olfaction. We also tested for chemical crypsis in five species of active foraging snakes, predicted to be easily detectable. Dogs and meerkats unambiguously indicated active foraging species, but failed to correctly indicate puff adder, confirming that B. arietans employs chemical crypsis. This is the first demonstration of chemical crypsis anti-predatory behaviour, though the phenomenon may be widespread among ambushers, especially those that experience high mortality rates owing to predation. Our study provides additional evidence for the existence of an ongoing chemically mediated arms race between predator and prey species.
Amphibian monitoring in Kakamega Forest, Kenya
(2007) Wairimu, Vincent Muchai; Channing, A.; Veith, M.
Since the late 1970 there has been increased concern of amphibian decline and extinction. Several causes for the worldwide declines have been suggested and include ultraviolet radiation, predation, pollution, climate change, diseases and habitat modification. To counter this, more research on the subject has been encouraged of which long term monitoring has been suggested as a research method. The study was conducted in Kakamega Forest in Kenya, which is the country's remnant of the once vast Guineo-Congolian forest. A rectangular transect whose sides measured 600 m in total was established and transect walks were carried out every two weeks for two consecutive days between 2002 and 2006. 24 species were targeted in the study and were sampled through VES and AES and data recorded in a GPS and later downloaded. In this study I examined the influence of rainfall, temperature, habitat and moon phases on the activity of frogs in Kakamega Forest. I also determined under which weather conditions sampling was more efficient. When monitoring was carried out by two observers I tested whether their data were similar. Data were analysed using non-parametric methods (Kruskal-wallis and Tukey test), species abundances analysed using EstimateS..Out of the 24 targeted species only 14 were recorded, with a total of 535 specimens being counted mostly at night. Most frogs in Kakamega Forest were more active in temperatures between 20 and 25oC. There was not much variation and there was no frog activity when the temperature was extremely high. There was rainfall throughout the year and there was no significant differences in the number of frogs counted in rainfall above 200 mm or below 200 mm. There was no significant difference in the number of specimens found in the different vegetation segments in the forest. More amphibians were caught under cloudy, rainy and clear conditions at night than under any weather condition during the day. During the day, more amphibians were caught during cloudy conditions than when it rained or when there was no cloud cover. There was no difference in catch among night conditions and there was no difference between clear and rainy days In Kakamega Forest, night is the best time to sample amphibians. In terms of weather it is best to sample when it is cloudy both during the day and at night. There were no differences in sampling abilities between two observers tested under similar weather conditions.
An acoustic, genetic and morphological review of the genus Bullacris (Orthoptera; Pneumoridae)
(University of the Western Cape, 2017) Gordon, Mikhaila Leigh; Couldridge, Vanessa
Bladder grasshoppers (Orthoptera: Pneumoridae) are nocturnal African herbivores that are endemic to the coastal regions of southern Africa. They rely heavily on sound communication for mate location and have a unique body structure, with an inflated abdomen seen only in males that aids in sound production. They have a continuous distribution that extends along the coast of South Africa from Namibia, into the eastern regions of Mozambique and beyond, as far as Uganda. Bullacris is the largest genus within the Pneumoridae family. Members of this genus are mostly found within South Africa and inhabit different vegetation biomes, namely the Succulent- Karoo, Fynbos and Savannah biomes. There are currently seven described species within the genus, based solely on morphological differences. However, these morphological differences are not well defined for all species pairs, leading to some degree of uncertainty in species delineation.
An analysis of the fire regime and its effects on post-fire recovery in Namaqualand Granite Renosterveld vegetation
(University of the Western Cape, 2017) Simons, Megan Brigette; Knight, Richard
Namaqualand Granite Renosterveld (NGR) is a fire-prone shrubland largely confined to the Kamiesberg Uplands. More than 20% has been transformed by agricultural activities such as grazing and dryland cropping. The history of fires of Namaqualand Granite Renosterveld was assessed over a period from 2000 - 2015. Furthermore, this study aimed to assess the effects of fire and grazing on the dynamics of Elytropappus rhinocerotis and the post-fire vegetation recovery. Satellite imagery, field observations and combination of field sampling techniques were used to compile a comprehensive fire database and to collect data on vegetation parameters. The Kamiesberg Uplands has a human-induced fire regime with a fire frequency of 4.2 years, which appears to be shorter for NGR compared to other Renosterveld - types. The majority of the fires were in summer and early autumn which is the ecologically accepted season with high fire intensities. Fire Danger Index ratings for summer burns were in the dangerous and very dangerous categories. In terms of cover, the distances between E. rhinocerotis individuals were significantly more on the burnt than on the unburnt sites. The density of unpalatable species on the burnt sites is also strongly associated with E. rhinocerotis. Elytropappus rhinocerotis appears to facilitate a role as a nurse-plant for various species in renosterveld. The local biotic and abiotic conditions, allows E. rhinocerotis to maintain its abundance, thus displaying niche construction by a single species.
An Investigation of Benthic Epifauna to Support Classification and Mapping of Outer Shelf Ecosystems in KwaZulu-Natal
(University of the Western Cape, 2017) Makwela, Mapula Salome; Smit, AJ
Ecosystem classification and mapping are foundational steps for effective ecosystem-based marine spatial planning, marine ecosystem assessment and integrated ocean management. The aims of this study were to interrogate and refine existing ecosystem classification and maps using quantitative data for epifaunal communities and to investigate the potential physical drivers which may contribute most to the distribution patterns of these ecosystem types. A total of 27 sites between Pennington and Ballito on the east coast of South Africa, including unconsolidated sediment, mixed and reefs habitat types, in the 48 to 85m depth range, was examined. Epifauna data were quantified from seabed imagery collected by remotely-operated vehicle covering more than 13 130 epifaunal individuals counted representing over 170 morphospecies from five taxa. Multivariate analyses of data from 17 sites surveyed in southern KwaZulu-Natal (KZN) revealed that epifauna at unconsolidated sediment sites were significantly different to that occurring on either mixed or reef substrates and epifauna occurring on mixed substrates were also significantly different to those occurring on reefs. Epifauna at mixed sites were more similar to epifaunal assemblages at reef sites than epifauna at unconsolidated sediment sites.
An analysis of primary and secondary production in lake Kariba in a changing climate
(University of Western Cape, 2011) Ndebele-Murisa, Mzime R.; Musil, Charles; Raitt, Lincoln
Analysis of temperature, rainfall and evaporation records over a 44-year period spanning the years 1964 to 2008 indicates changes in the climate around Lake Kariba. Mean annual temperatures have increased by approximately 1.5oC, and pan evaporation rates by about 25%, with rainfall having declined by an average of 27.1 mm since 1964 at an average rate of 6.3 mm per decade. At the same time, lake water temperatures, evaporation rates, and water loss from the lake have increased, which have adversely affected lake water levels, nutrient and thermal dynamics. The most prominent influence of the changing climate on Lake Kariba has been a reduction in the lake water levels, averaging 9.5 m over the past two decades. These are associated with increased warming, reduced rainfall and diminished water and therefore nutrient inflow into the lake. The warmer climate has increased temperatures in the upper layers of lake water, the epilimnion, by an overall average of 1.9°C between 1965 and 2009. The warmer epilimnion has led to a more stable thermocline in the lake, and its upward migration from a previously reported 20 m depth to the current 2 to 5 m depth reported in the lake’s Sanyati Basin. A consequence of the more stable thermocline has been the trapping of greater amounts of nutrients in the deep, cold bottom waters of the lake, the hypolimnion, and this coupled with a shorter mixing (turnover) period is leading to reduced nutrient availability within the epilimnion. This is evident from a measured 50% reduction in nitrogen levels within the epilimnion, with phosphorus levels displaying a much smaller net decline due to localised sources of pollution inflows into the lake. These changes in lake thermal dynamics and density stratification have reduced the volume of the lake epilimnion by ~50%, which includes the well mixed, oxygenated euphotic zone leading to more acidic waters (lower pH) and increased water ionic concentrations (conductivity), and decreased dissolved oxygen levels, which have resulted in a 95% reduction in phytoplankton biomass and a 57% decline in primary production rates since the 1980s. The reduced nitrogen levels especially have contributed to a proliferation of nitrogen-fixing Cyanophyceae, the dominant Cylindrospermopsis raciborskii comprising up to 66% of the total phytoplankton biomass and 45.6% of the measured total phytoplankton cellular concentrations. Also, shifts in seasonal dominance of different phytoplankton groups have been observed in the lake during turnover, the Cyanophyceae having increased in dominance from 60% of the total phytoplankton biomass in the early 1980’s to the current 75%. In contrast, the Bacillariophyceae have declined substantially, from 18% of the total phytoplankton biomass in the early 1980’s to the current 1.7%. The diminished phytoplankton biomass of more palatable phytoplankton, and the proliferation of smaller, less palatable phytoplankton taxa, has resulted in reduced zooplankton biomass and species richness and altered zooplankton species composition. Concentrations of large Cladocera and Copepoda especially have declined substantially in the lake by up to 93.3% since the mid 1970s, with small Rotifera currently comprising 64% of the total zooplankton biomass. The reductions in zooplankton biomass correspond with recorded decreases in catches per unit effort for the sardine Limnothrissa miodon (Kapenta), which have been steadily declining in the lake since 1986.
Analysis of three wetland medicinal plants: Centella asiatica, Cyperus longus and Typha capensis found in the Western Cape Province of South Africa.
(University of the Western Cape, 2017) Saibu, Olusola Surajudeen; Smit, A.J.; Mabusela, W.T.
South Africa is recognised worldwide for its rich diversity of plants, many of which have been used in ethno-medicine. However, the use of wetland plant species in ethno-medicine required further investigations. This research is aimed at investigating three wetland medicinal, plant species, Centella asiatica, Cyperus longus and Typha capensis based on their geographical, seasonal, mineral nutrient (Fe, Mn, Ca, Mg, K and Na) and secondary metabolite characteristics. Samples of each species were collected from Grabouw, Kelderhoff, Kenilworth, Pringle Bay, University of the Western Cape (UWC) and Worcester within the Western Cape Province of South Africa. Specimen and soil collections were carried out during autumn, spring, summer and winter of 2014. Both plant and soil samples were acid digested and mineral nutrient concentrations in the samples were analysed using an atomic absorption spectrometer (AAS). Secondary metabolites were determined using analytical TLC on normal phase Merck-Silva gel coated aluminium plates as well as by using HPLC separation from crude extracts of C. asiatica, C. longus and T. capensis using LC-MS hardware from Agilent. The elemental analysis of soil samples showed that Ca, K, Mg, Mn and Zn concentrations were predominantly low. Soil mineral concentrations increased progressively from inland (Worcester) towards the coastland in the south (Pringle Bay). Calcium and sodium concentrations, in particular, were higher in soil samples obtained from Grabouw (inland south) and decreased northward towards Worcester. Comparatively, plant mineral concentrations were generally higher than soil concentrations. The high concentration of some of these essential elements, in selected plants is an indication that these plant species could be a good source of essential elements. High concentrations of phytochemicals were found in Centella asiatica during winter, while Cyperus longus and Typha capensis exhibited high concentrations during autumn indicating variation in respect of season. Consequently, harvesting of the studied plants should be done at the season with a relatively high phytochemical concentration. Studies are needed to investigate the extent of pesticide or herbicide contamination in wetland plants to protect the health of users. The LC-MS analyses of the three study species showed that seasonal variation affects metabolite constituents and moreover that these metabolite constituents differ from one locality to another. The seasonal variation of the elements in the studied medicinal plants justified the importance of harvesting seasons in the optimal utilization of the studied plants for medicinal purpose. s, for C. asiatica, anti-bacterial treatments for C. longus and fertility enhancement and birth control for T. capensis.

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