Academic literature on the topic 'Marine algae – South Africa'
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Journal articles on the topic "Marine algae – South Africa"
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Norris, R. E., and M. E. Aken. "Marine benthic algae new to South Africa." South African Journal of Botany 51, no. 1 (February 1985): 55–65. http://dx.doi.org/10.1016/s0254-6299(16)31702-1.
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Norris, R. E. "Some unusual marine red algae (Rhodophyta) from South Africa." Phycologia 30, no. 6 (November 1991): 582–96. http://dx.doi.org/10.2216/i0031-8884-30-6-582.1.
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Adams, Luther A., Gavin W. Maneveldt, Andrew Green, Natasha Karenyi, Denham Parker, Toufiek Samaai, and Sven Kerwath. "Rhodolith Bed Discovered off the South African Coast." Diversity 12, no. 4 (March 27, 2020): 125. http://dx.doi.org/10.3390/d12040125.
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Rhodolith beds have not previously been recorded in South Africa. A multidisciplinary research effort used remote sampling tools to survey the historically unexplored continental shelf off the Eastern Cape coast of South Africa. A rhodolith bed, bearing both living and dead non-geniculate coralline red algae, was discovered in the 30–65 m depth range off the Kei River mouth in the newly proclaimed Amathole Offshore Marine Protected Area. Some of the rhodolith forming coralline algal specimens were identified as belonging to at least three genera based on their morphology and anatomy, namely, Lithophyllum, Lithothamnion and a non-descript genus. Rhodolith mean mass and diameter were 44.85 g ± 34.22 g and 41.28 mm ± 10.67 mm (N = 13), respectively. Remotely operated vehicle (ROV) imagery revealed a suite of epibenthic red macroalgae associated with the rhodolith bed. Taxonomy, vertical structure and distribution of rhodoliths in South Africa require further investigation.
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Afolayan, Anthonia F., John J. Bolton, Carmen A. Lategan, Peter J. Smith, and Denzil R. Beukes. "Fucoxanthin, Tetraprenylated Toluquinone and Toluhydroquinone Metabolites from Sargassum heterophyllum Inhibit the in vitro Growth of the Malaria Parasite Plasmodium falciparum." Zeitschrift für Naturforschung C 63, no. 11-12 (December 1, 2008): 848–52. http://dx.doi.org/10.1515/znc-2008-11-1211.
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Abstract In the course of our search for antimalarial leads from marine algae, four metabolites, sargaquinoic acid, sargahydroquinoic acid, sargaquinal and fucoxanthin, were isolated from the South African alga Sargassum heterophyllum. Fucoxanthin and sargaquinal showed good antiplasmodial activity toward a chloroquine-sensitive strain (D10) of Plasmodium falciparum (IC50 1.5 and 2.0 μm, respectively), while sargaquinoic acid and sargahydroquinoic acid were only moderately active (IC50 12.0 and 15.2 μm, respectively).
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Millar, AJK. "Marine red algae of the Coffs Harbour region, northern New South Wales." Australian Systematic Botany 3, no. 3 (1990): 293. http://dx.doi.org/10.1071/sb9900293.
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The marine benthic red algae of the Coffs Harbour region are described and illustrated in detail. The survey constitutes the first ever detailed descriptive and illustrative mainland regional monograph of any area along the entire eastern Australian seaboard. Collections made intertidally and to depths of 20 m have included 119 species in 74 genera, 26 families, and 8 orders of Rhodophyta, of which 54 (45%) were previously unrecorded from eastern Australia, 22 (18%) are new records for the whole of Australia (16 being new Southern Hemisphere records), 1 (Dictyothumnion) constitutes a new genus, and 16 (13%) are new species in the genera Gracilaria, Curdiea, Botryocladia, Dictyothamnion, Antithamnion, Ceramium, Callithumnion, Anotrichium, Nitophyllum, Phycodrys, Apoglossum, Dasya, Fernandosiphonia, and Herposiphonia. Also included are major Australian revisions of the genera Martensia and Nitophyllum, and six new combinations are proposed (Chondria infestans, Curdiea angustata, Dasya pilosa, Haraldiophyllum sinuosum, Myriogramme pulchellum, and Stenograrnme phyllophoroides). The Coffs Harbour flora, although related to the north-eastern and, to a lesser degree, southern Australian floras, has a number of species previously known only from much more remote localities, such as Japan (6 species), California (4 species), New Zealand (3 species), India (2 species), South America (2 species), the Galapagos Islands (1 species), China (1 species), South Africa (1 species), and the Mediterranean (1 species). Twelve of the 22 species newly recorded for Australia show a definite western Pacific distribution, a region with which the overall Coffs Harbour flora has strong affinities.
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Hiller, Norton, and Robert W. Gess. "Marine algal remains from the Upper Devonian of South Africa." Review of Palaeobotany and Palynology 91, no. 1-4 (March 1996): 143–49. http://dx.doi.org/10.1016/0034-6667(95)00062-3.
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Puckree-Padua, Courtney A., Paul W. Gabrielson, and Gavin W. Maneveldt. "DNA sequencing reveals three new species of Chamberlainium (Corallinales, Rhodophyta) from South Africa, all formerly passing under Spongites yendoi." Botanica Marina 64, no. 1 (January 6, 2021): 19–40. http://dx.doi.org/10.1515/bot-2020-0074.
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Abstract Three new non-geniculate coralline algal species from South Africa are described that were passing under the misapplied name, Spongites yendoi. Based on plastid encoded DNA sequences from psbA and rbcL markers, these species belong in the subfamily Chamberlainoideae. The DNA sequences, supported by the morpho-anatomical character of tetrasporangial conceptacle roof development, placed all three species in the genus Chamberlainium and not Pneophyllum, the only other genus in Chamberlainoideae. In addition to the diagnostic DNA sequences, Chamberlainium capense sp. nov., C. glebosum sp. nov. and Chamberlainium occidentale sp. nov. may be distinguished by a combination of habit, habitat, geographic distribution, and several morpho-anatomical features. Biogeographically all three species are found in the Benguela Marine Province of South Africa, with C. occidentale being the most widespread. Chamberlainium glebosum also has a wide, but disjunct distribution and C. capense is another South African endemic non-geniculate coralline, whose range is restricted to a 43 km stretch of coastline. Thus far, DNA sequences from type specimens of non-geniculate corallines show that only those species whose type localities are from South Africa are correctly applied; all other non-geniculate coralline names are likely misapplied in South Africa.
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Tamele, Isidro, Marisa Silva, and Vitor Vasconcelos. "The Incidence of Marine Toxins and the Associated Seafood Poisoning Episodes in the African Countries of the Indian Ocean and the Red Sea." Toxins 11, no. 1 (January 21, 2019): 58. http://dx.doi.org/10.3390/toxins11010058.
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The occurrence of Harmful Algal Blooms (HABs) and bacteria can be one of the great threats to public health due to their ability to produce marine toxins (MTs). The most reported MTs include paralytic shellfish toxins (PSTs), amnesic shellfish toxins (ASTs), diarrheic shellfish toxins (DSTs), cyclic imines (CIs), ciguatoxins (CTXs), azaspiracids (AZTs), palytoxin (PlTXs), tetrodotoxins (TTXs) and their analogs, some of them leading to fatal outcomes. MTs have been reported in several marine organisms causing human poisoning incidents since these organisms constitute the food basis of coastal human populations. In African countries of the Indian Ocean and the Red Sea, to date, only South Africa has a specific monitoring program for MTs and some other countries count only with respect to centers of seafood poisoning control. Therefore, the aim of this review is to evaluate the occurrence of MTs and associated poisoning episodes as a contribution to public health and monitoring programs as an MT risk assessment tool for this geographic region.
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S.S, Sumayya, Sreelekshmi S.G, and Murugan K. "CULTIVATION AND ECONOMICAL PERSPECTIVES OF GRACILLARIA: MARINE SEAWEED." Kongunadu Research Journal 4, no. 2 (December 30, 2017): 73–79. http://dx.doi.org/10.26524/krj206.
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For decades, seaweed has been of biological, industrial, and pharmaceutical importance. Because of their nutraceutical potential, seaweed has been used as a food throughout Asia. Traditional Chinese medicine used aqueous hot extracts of certain seaweeds in the treatment of cancer. Further, the Japanese and Chinesecultures have used seaweeds to treat goiter and other glandular problems since 300 BC. The Romans used seaweeds in the treatment of wounds, burns, and rashes. The Celts noted that ordinary seaweed contracted as it dried and then expanded with moisture. In Scotland during the 18th century, physicians used dried seaweed stem to successfully drain abdominal wall abscesses. They also inserted seaweed into the cervix in an attempt to treat dysmenorrhea. Many reports outline the use of seaweed to induce abortion. Seaweed was employed intravaginally for ripening of the cervix and was used rectally for strictures. In this juncture, culture and therapeutic potential of Gracilaria was reviewed. Gracilaria is a genus of red algae notable for its economic importance as an agarophyte, as well as its use as a food for humans and various species of shellfish. Various species within the genus are cultivated among Asia, South America, Africa and Oceania. Gracilaria is used as a food in Japanese, Hawaiian, and Filipino cuisine. In Japanese cuisine, it is called ogonori or ogo. In thePhilippines, it is called gulaman and used to make gelatin. In Jamaica, it is known as Irish moss. The moisture content is 12% and protein is 8%. The species are used by local people as salad, preparation of various curries and industrially many by products are synthesized from this sea weed. Medicinally as microbicidal, antiinflammatory, antimetastatic and immuno modulatory potential.
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Lukyanenko, Oleksandr. "GLOBAL MOTIVATIONS AND AQUACULTURE DEVELOPMENT TRENDS." Green, Blue & Digital Economy Journal 1, no. 2 (December 3, 2020): 132–39. http://dx.doi.org/10.30525/2661-5169/2020-2-21.
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The natural and geographical, resource, economic and environmental conditions, global motivations, key trends, specific features of formation and prospects for aquaculture development are researched. It is emphasized that fishing and aquaculture have a special place in solving the global food problem, while significantly affecting the aquatic environment. The interdisciplinary nature of scientific research in the conceptual format of fisheries economics, management of marine ecosystems, aquaculture, green and blue technologies are illustrated. The positioning of fisheries and aquaculture in the format of global problems of mankind and sustainable development in terms of environmentally irresponsible use of bioresources, especially the World Ocean is made, attention is focused on the potentially catastrophic consequences of its pollution, the problem of restoring fish stocks based on climate change is emphasized. The economic, ecological and social expediency of accelerated development of aquaculture, its institutional, functional and organizational-regulatory separation in the structure of global fisheries is substantiated, considering its complexity and inter-sectoral diversification, the author's model of aquaculture is proposed with classification identification of its categories (internal natural, artificial and combined reservoirs and marine, coastal and combined areas), types (with and without feed), species (bony fish, crustaceans, mollusks, other aquatic animals, algae), and consumer products (food, non-food, dual use). The scale, structure and dynamics of aquaculture development have been identified and assessed, and its growing importance in global fisheries has been confirmed. The analysis of the regional structure of aquaculture production by continents is carried out, its distribution by categories and species in Asia, North and South America, Europe, Africa and Oceania is characterized. The special leadership status of China in the global production of aquaculture products is illustrated. It is confirmed that aquaculture is becoming the main source of human fish consumption. The key trends in the development of aquaculture in the European Union have been identified and assessed. The special features of the formation of the relevant market are described. In addition, it has been demonstrated that the scale of aquaculture production only in Norway is comparable to the aggregate indicator of the EU countries. The volumes and structure of aquaculture financing from the budget of the European Maritime and Fisheries Fund are analyzed. Using Spearman's correlation ranks, the peculiarities of aquaculture consumption in terms of volume and price characteristics are studied. The conclusions of the research are substantiated, which confirm the hypothesis of perspective prospects of aquaculture advanced development using the modern innovative technologies and the effective system of its global regulation.
Dissertations / Theses on the topic "Marine algae – South Africa"
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Steyn, Paul-Pierre. "The ecophysiology of Gelidium Pristoides (Turner) Kuetzing : towards commercial cultivation." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1117.
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The ecophysiology of the red alga Gelidium pristoides (Turner) Kuetzing was investigated in an effort to establish a technique for commercial cultivation. The seaweed is of commercial importance in South Africa where it is harvested from the intertidal zone rocky shores along the coast. It is dried and exported abroad for the extraction of agar. Yields and quality could be improved by cultivation in commercial systems. However, attempts at growing the seaweed in experimental systems have all ended in failure. This study aimed to describe the conditions in which the seaweed grows naturally; and investigate its physiological response to selected physical conditions in the laboratory in order to determine suitable conditions for mariculture. Ecological studies showed that G. pristoides grew above the spring low tide water level. The upper limit of the seaweed’s vertical distribution range, as well as its abundance, was largely dependent on wave exposure. The zone normally inhabited by G. pristoides was dominated by coralline turf in sheltered areas, while the abundance of G. pristoides increased towards more exposed rocky shore sites. The seaweed occurred among species such as Pattelid limpets and barnacles, but was usually the dominant macroalga in this zone, with coralline turf and encrusting algae being the only others. Physical conditions in the part of the intertidal zone inhabited by G. pristoides were highly variable. During low tide temperatures could vary by as much as 10°C within the three hours between tidal inundation of the seaweed population, while salinity varied by up to 9 ppt, and light intensity by as much as 800 μmol m-2 s-1. During these exposure periods the seaweed suffered up to 20% moisture loss. Laboratory experiments on the seaweed’s response to these conditions indicated that it was well adapted to such fluctuations. It had a broad salinity (20 and 40 ppt), and temperature tolerance range (18 to 24°C), with an o ptimum of temperature of 21°C for photosynthesis, while there was no difference in the photosynthetic rate of the alga within the 20 to 40 ppt salinity range. The alga had a low saturating irradiance (ca. 45 – 80 μmol m-2 s-1) equipping it well for photosynthesis in turbulent environments, with high light attenuation, but poorly to unattenuated light conditions. Exposure resulted in an initial increase in photosynthetic rate followed by a gradual decrease thereafter. pH drift experiments showed that low seawater pH, and associated increased carbon dioxide availability, resulted in an increase in photosynthetic rate. This response suggests that the seaweed has a high affinity for carbon dioxide, while the reduction in photosynthetic rate in response to bicarbonate use inhibition indicates that it also has the capacity for bicarbonate use. The high affinity of Gelidium pristoides for carbon dioxide as an inorganic carbon source appears to be the primary reason for the low abundance of the alga on sheltered rocky shore areas, and also explains the failure of the alga to grow in tank or open-water mariculture systems. Exposed rocky shores have experience heavy wave action, and the resultant aeration and mixing of nearshore waters increases the availability of carbon dioxide, which is considered a limiting resource. The absence of such mixing and aeration at sheltered site makes this less suitable habitat for G. pristoides. Periodic exposure also makes high levels of atmospheric carbon dioxide available from which the seaweed benefits. The traditional mariculture systems in which attempts have been made to cultivate the seaweed failed to satisfy either of the above conditions.
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Mabande, Edmund Rufaro. "Antimicrobial discovery from South African marine algae." University of the Western Cape, 2018. http://hdl.handle.net/11394/6592.
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>Magister Scientiae - MScAntimicrobials are chemical compounds that destroy or inhibit the growth of microorganisms. The majority of these antimicrobials are actually natural products or natural product derived with key examples being the pioneer antibiotics penicillin and cephalosporin. Antimicrobials are an extremely important class of therapeutic agents; however, the development of drug resistance and slow pace of new antibiotic discovery is one of the major health issues facing the world today. There is therefore a crucial need to discover and develop new antibacterial agents. In this study, the potential of marine algae as a source of new antibiotics was explored. Crude organic extracts and chromatographic fractions obtained from small-scale extraction of 17 different marine algae were used to prepare a pre-fractionated library that would be tested against several disease causing microorganisms. The activity of the pre-fractionated library and purified compounds was determined against a panel of drug resistant microorganisms namely Acinetobacter baumannii ATCCBAA®-1605™, Enterococcus faecalis ATCC® 51299™, Escherichia coli ATCC® 25922™, Staphylococcus aureus subsp. aureus ATCC® 33591™ and Candida albicans ATCC® 24433™. Finally, cytotoxicity tests of 50 selected library extracts and isolated compounds were done against two cell lines namely MCF-7 (breast cancer) and HEK-293 (kidney embryonic). Based on their antimicrobial activity and interesting chemical profiles, the seaweeds Plocamium sp. and Stypopodium multipartitum were selected for further study. Three new and unusual halogenated monoterpenes (4.16, 4.17 and 4.18) were isolated from Plocamium sp., and an unusual meroditerpenoid (5.8) was isolated from Stypopodium multipartitum. The metabolites were purified using preparative (silica gel) chromatography as well as semipreparative normal phase HPLC. The structures of purified compounds were determined from spectroscopic data, including nuclear magnetic resonance (NMR) spectroscopy. A small library of 153 fractions was generated from collections of South African marine algae. Pre-fractionated crude extracts showed excellent antimicrobial activity against all microbes but particularly against Staphylococcus aureus. The compounds were generally active against the Gram positive bacteria and the yeast. In conclusion, three antimicrobial halogenated monoterpenes and an unusual monoterpene were isolated from a Plocamium sp. and Stypopodium multipartitum respectively. Antimicrobial activity of crude fractions was excellent but that of isolated compounds was not as great as anticipated.
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Rufaro, Mabande Edmund. "Antimicrobial discovery from South African marine algae." University of the Western Cape, 2018. http://hdl.handle.net/11394/6529.
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>Magister Scientiae - MScAntimicrobials are chemical compounds that destroy or inhibit the growth of microorganisms. The majority of these antimicrobials are actually natural products or natural product derived with key examples being the pioneer antibiotics penicillin and cephalosporin. Antimicrobials are an extremely important class of therapeutic agents; however, the development of drug resistance and slow pace of new antibiotic discovery is one of the major health issues facing the world today. There is therefore a crucial need to discover and develop new antibacterial agents. In this study, the potential of marine algae as a source of new antibiotics was explored. Crude organic extracts and chromatographic fractions obtained from small-scale extraction of 17 different marine algae were used to prepare a pre-fractionated library that would be tested against several disease causing microorganisms. The activity of the pre-fractionated library and purified compounds was determined against a panel of drug resistant microorganisms namely Acinetobacter baumannii ATCCBAA®-1605™, Enterococcus faecalis ATCC® 51299™, Escherichia coli ATCC® 25922™, Staphylococcus aureus subsp. aureus ATCC® 33591™ and Candida albicans ATCC® 24433™. Finally, cytotoxicity tests of 50 selected library extracts and isolated compounds were done against two cell lines namely MCF-7 (breast cancer) and HEK-293 (kidney embryonic).
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January, Grant Garren. "Bioprospecting for bioactive polysaccharides from marine algae endemic to South Africa." University of the Western Cape, 2016. http://hdl.handle.net/11394/5322.
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>Magister Scientiae - MScFucoidan is a marine-derived sulphated polysaccharide with bioactive properties ideal for the food, chemical and pharmaceutical industries. The polysaccharide consists largely of L-fucose, has a highly heterogeneous structure and is of diverse origin. Fucoidan was extracted from Ecklonia maxima, Laminaria pallida and Splachnidium rugosum and the effect of different extraction methods on fucoidan heterogeneity was assessed. Extraction methods employed hot water, hydrochloric acid or calcium chloride salt. Fucoidan yield and purity were determined by various colorimetric assays. Highest fucoidan yield was obtained with the hot water extraction method as seen by highest L-fucose content. Splachnidium rugosum extracts contained ~5 times more L-fucose than Ecklonia maxima and Laminaria pallida extracts. The salt extraction method yielded extracts free of contaminants, however L-fucose content in all extracts was >20 times lower. Acid extraction yielded highest levels of uronic acid contamination and liberated sulphate from the fucoidan polysaccharide. The fucose-to-sulphate ratio for Ecklonia maxima was approximately 1:5, whilst the ratios for Splachnidium rugosum and Laminaria pallida were approximately 1:1 and 1:2, respectively. The acid and salt extraction methods removed all traces of protein contaminants, while the hot water method retained very low levels of protein. The extraction method used to isolate fucoidan was a determining factor in yield and purity. Chemical compositional analyses of hot water extracts were assessed by gas chromatography mass spectroscopy. Splachnidium rugosum and Laminaria pallida extracts consisted largely of L-fucose, while Ecklonia maxima fucoidan was characterized with high glucose abundance. Crude hot water and acid extracts from Splachnidium rugosum tissue were fractionated and purified by (anionic) ion exchange chromatography as bioactivity has been correlated to lower molecular weight forms. In water extracts, ion exchange chromatography resulted in close to 90% decrease in L-fucose, sulphate and uronic acid, while protein content increased by 57%. Similar results were reported for acid extracts; however protein content did not change significantly. These results show that method of extraction may affect the composition of fucoidan post-purification. Hot water extraction is recommended due to higher fucoidan yield, as reflected by L-fucose content, and higher sulphate-to-fucose ratio. High protein content after ion exchange chromatography was however of concern. Since mucilage in Splachnidium rugosum thallus was free of protein, fucoidan was precipitated from mucilage with ethanol. Fucoidan yield of mucilage was >15-fold higher than content in purified hot water extracts with a sulphate-to-fucose ratio of ~1:1. The average molecular weight of native fucoidan in mucilage was estimated at 2367 kDa. The polysaccharide was hydrolysed by gamma-irradiation levels of 10-50 kGy to fractions ranging between 60 and 15.5 kDa. Hot water crude fucoidan extracts from Ecklonia maxima, Laminaria pallida, and Splachnidium rugosum were assessed for anti-oxidant activity by measuring the ability to scavenge free radicals and the capacity to reduce copper ions with 2,2-Diphenyl-1-picrylhydrazyl and Cupric Reducing Anti-oxidant Capacity assays, respectively. Ecklonia maxima crude fucoidan displayed highest anti-oxidant activity and capacity, having the potential to scavenge reactive oxygen species as well as the capacity to reduce copper to less toxic forms in mammalian systems. Splachnidium rugosum showed weakest anti-oxidant activity and lowest reducing capacity. The anti-cancer activity of crude and purified hot water Splachnidium rugosum extracts, as well as non-irradiated (native) and gamma-irradiated fucoidan, and commercially procured fucoidan were assessed for anti-cancer activity against MCF-7 breast cancer cells. Splachnidium rugosum crude and purified fucoidan displayed a half maximal inhibitory concentration of 0.7 mg/mL and 0.029 mg/mL, respectively. Low cytotoxicity of crude and purified Splachnidium rugosum fucoidan against non-cancerous breast epithelial cell line MCF-12A was observed, as seen by half maximal inhibitory concentration values of 2 mg/mL and 0.663 mg/mL, respectively. The cancer specific selectivity of purified Splachnidium rugosum fucoidan was therefore much higher as reflected by 10-fold higher selectivity index than that of crude fucoidan. Native and low molecular weight gamma-irradiated fucoidan also showed bioactive properties including anti-cancer activity as seen by the reduction of cell proliferation in vitro, whereas crude fucoidan showed the ability to scavenge free radicals, and the capacity to reduce copper ions.
National Research Foundation (NRF)
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Mmonwa, Lucas Kolobe. "Phylogeography and epifauna of two intertidal seaweeds on the coast of South Africa." Thesis, Rhodes University, 2009. http://eprints.ru.ac.za/1583/.
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Knott, Michael George. "The natural product chemistry of South African Plocamium species." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1004920.
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The brine shrimp lethality assay was used as a preliminary tool to screen eighteen seaweeds collected from the South African coast. Of the seaweeds tested, the red algae Plocamium corallorhiza and Hypnea rosea, and the green alga Halimeda sp., showed the most potent activity. The chemical investigation of P. corallorhiza resulted in the isolation and structural elucidation of five previously undescribed secondary metabolites, along with three known compounds and four possible artifacts of the extraction process. Standard spectroscopic methods and comparison with known compounds were used to determine the structures of the new metabolites. The new compounds included the linear halogenated monoterpenes 4,8-dibromo-1, 1-dichloro-3,7-dimethyl-2,6-octadiene (99), 4,6-dibromo-l, 1-dichloro-3,7-dimethyl-2,7-octadiene (100), 4,8-dibromo-l, 1,7-trichloro-3,7-dimethyl-2,5-octadiene (101) and 3,4,6,7-tetrachloro-3,7-dimethyl-l-octene (102) and the cyclic monoterpene 5-bromo-5-bromomethyl-I-chlorovinyl-2,4-dichloro-methylcyclohexane (103) while the known compounds were identified as 4-bromo-5-bromomethyl-1chlorovinyl-2,5-dichloro-methylcyclohexane (35), 1,4,8-tribromo-3, 7 -dichloro-3,7-dimethyl-1,5-octadiene (94) and 8-bromo-1,3,4,7-tetrachloro-3,7-dimethyl-1,5-octadiene (96). The four methoxylated compounds (104-107) were presumably formed via a standard substitution reaction between the halogenated monoterpenes 96 and 101 and MeOH, which was used as a component in the extraction solvent. With over 100 000 natural products having been reported, it has become necessary to employ an efficient dereplication strategy to quickly identify known compounds. A simple Gas Chromatography-Mass Spectrometry (GC-MS) method for the efficient physicochemical screening, identification and dereplication of Plocamium metabolites was developed. In this study the crude extracts of P. corallorhiza, P. cornutum and P. maxillosum were screened by GC-MS and the retention times and mass spectral fragmentation patterns of compounds 94, 96, 99 - 107 were used to quickly identify known and new compounds in the crude extracts of P. cornutum and P. maxillosum. This data indicated that compounds 99, 100, 103 were present in both P. corallorhiza and P.cornutum, while compound 102 was found to be present in P. corallorhiza, P. cornutum and P. maxillosum. These studies also indicated that ecotypes and chemotypes are not a significant feature of P. corallorhiza and P. cornutum. Different species of Plocamium (namely: P. corallorhiza, P. cornutum, and P. maxillosum) have very different chemical profiles, and GC may therefore have appreciable taxonomic application in the identification of the different Plocamium spp. which are endemic to South Africa.
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Carter, Anne Margaret. "Studies on the bioactivities of selected Eastern Cape seaweeds." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1004093.
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In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.
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Knott, Michael George. "Isolation, structural characterisation and evaluation of cytotoxic activity of natural products from selected South African marine red algae." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1015460.
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The medicinal chemistry of selected marine algae indigenous to South Africa was investigated. Following the isolation and characterisation of a number of new and known compounds, the associated in vitro cytotoxic profiles of these new compounds was investigated. Plocamium maxillosum yielded two new cyclic polyhalogenated monoterpenes which were characterised as 2E-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.1) and 2Z-chloromethine-4E-chlorovinyl-4-methyl-5-cyclohexen-1-one (2.2) on the basis of one and two dimensional NMR spectroscopic data and MS analysis. These compounds were also found to have good cytotoxic activity against breast cancer cell lines. Although these compounds are based on a regular monoterpene skeleton, they represent an uncommon feature not often seen in cyclic halogenated monoterpenes from marine algae. Plocamium robertiae yielded one new cyclic polyhalogenated monoterpene identified as 4,5- dibromo-5-chloromethyl-1-chlorovinyl-2-chloro-methylcyclohexane (2.6) and one known compound called 2,4-dichloro-1-chlorovinyl-1-methylcyclohexane-5-ene or Plocamene D (2.9). Portieria hornemannii was collected from Port Edward in Natal and yielded three new compounds, namely; 3Z-1,6-dibromo-3-(bromomethylidene)-2,7-dichloro-7-methyloctane (3.1), 1E,3Z-1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.2), 1Z,3Z- 1,6-dibromo-3-(bromomethylidene)-7-chloro-7-methyloct-1-ene (3.3), and one known compound, namely; 3S,6R-6-bromo-3-(bromomethyl)-3,7-dichloro-7-methyloct-1-ene (3.4). Compounds 3.1 and 3.2 showed no cytotoxic activity against breast cancer cells. Another Portieria hornemannii sample was collected from Noordhoek in the Eastern Cape, it yielded one known compound referred to as 3Z-6-bromo-3-(bromomethylidene)-2,7- dichloro-7-methyloct-1-ene (3.5), as well as one new compound called portieric acid A (3.6) or 5-bromo-2-(bromomethylidene)-6-chloro-6-methylheptanoic acid. Portieric acid A showed slight cytotoxic activity and also represents a new class of compound within the genus Portieria. The isolation of secondary metabolites from the South African red alga, Laurencia glomerata, yielded two known compounds; 7-hydroxylaurene (4.9) and cis-neolaurencenyne (4.12), as well as one chamigrane related compound (4.11). Laurencia flexuosa yielded one known compound called 3Z-bromofucin (4.13). Using 1H NMR, GC and molecular systematics, a novel method for identifying different species of Laurencia was also investigated.
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Fakee, Jameel. "The isolation and characterisation of secondary metabolites from selected South African marine red algae (Rhodophyta)." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001472.
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Secondary metabolites from natural sources are fast growing as popular drug leads. The structural novelty and favourable biological activity that these compounds display contribute to their popularity as drugs of the future. Examples of such compounds include the potent anticancer drug paclitaxel isolated from the bark of a yew tree as well as the more commonly known analgesic aspirin which stems from the bark of the willow tree. The biological activities exhibited by these secondary metabolites are vast and range from antimicrobial to anticancer activity to mention but a few. As a result, the isolation of novel compounds from natural sources is on the rise. The South African seaboard is home to a wealth of various marine algal species which produce fascinating secondary metabolites. For example, Portierria hornemanii was shown to produce halomon, a halogenated monoterpene which has displayed promising cytotoxic activity. This study thus focused primarily on pursuing novel compounds from three endemic South African marine algal species which have never been analysed previously from a chemical perspective. These are Plocamium rigidum (Bory de Saint-Vincent), Laurencia natalensis (Kylin) and Delisea flaccida (Suhr) Papenfuss. Four known compounds and one new halogenated monoterpene, (2E,5E,7Z)-8-chloro- 7-(dichloromethyl)-4-hydroxy-3-methylocta-2,5,7-trienal, were isolated from Plocamium rigidum. The breast cancer (MCF-7 cell line) inhibitory activity for these compounds was assessed and it was observed that an increase in the lipophilic nature of the compounds produced more favourable IC50 values. A pre-cursor to bromofucin type compounds, cis-laurencenyne, was isolated from Laurencia natalensis, as well as a new acetoxy chamigrane type compound, 4-bromo- 3,10-dichloro-7-hydroxy-3,7,11,11-tetramethylspiro [6.6] undec-1-yl acetate. Delisea flaccida was seen to contain two known bromofuranone type compounds isolated as an isomeric mixture, 1-[(5Z)-4-bromo-5-(bromomethylidene)-2-oxo-2,5- dihydrofuran-3-yl] butyl acetate and 1-[(5E)-4-bromo-5-(bromomethylidene)-2- oxo-2,5-dihydrofuran-3-yl]butyl acetate. These compounds are famous for their ability to inhibit bacterial biofilm production and they have been isolated before from an Australian Delisea sppAdobe Acrobat 9.53 Paper Capture Plug-in
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Snook, Deborah Jane. "Some aspects of the autecology of Rhizoclonuium riparium (Roth) Harv. with special reference to its growth in the maturation ponds of the Grahamstown sewage works." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1004724.
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During 1982 benthic and floating filamentous algal mats appeared in the maturation ponds of the Grahamstown Sewage Disposal Works. These mats clogged the ponds and reduced the efficiency by which the effluent was purified. As they continued to be a problem despite numerous efforts to remove them, this study was initiated to investigate the alga, establish why it was successful in the pond environment, and how its growth could be controlled. The physico-chemical environment of a representative maturation pond was characterised while laboratory studies were conducted to investigate the growth, photosynthetic and respiratory characteristics in the alga. The alga was identified as Rhizoclonium riparium (Roth) Harv. although its morphological variability was greater than that reported in the literature. Growth and photosynthetic studies indicated that the alga favoured temperatures between 20 and 30⁰C and relatively high light intensity (700μE.m⁻².s⁻¹) and that it was highly productive. In addition, the alga exhibited photoadaptive ability, although it seemed to be sensitive to photoinhibition. Its success in the maturation pond was attributed to the favourable physico-chemical environment, particularly the high transparency of the effluent which allowed the penetration of PAR to the pond floor and to the alga's ability to adapt to the change in environment when it floated from the pond floor to its surface. Although the algal mats contribute to the oxidation of the effuent within the maturation pond, they are generally detrimental to the system because they shade the water column and inhibit wind-induced mixing. Recommendations on methods of controlling of the mats are presented.KMBT_363
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Books on the topic "Marine algae – South Africa"
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Norris, Richard E. The marine red algae of Natal, South Africa: Order Gelidiales (Rhodophyta). Edited by Leistner O. A. Pretoria, South Africa: National Botanical Institute, 1992.
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International Seaweed Symposium (17th 2001 Cape Town, South Africa). Seventeenth International Seaweed Symposium: Proceedings of the XXVIIth International Seaweed Symposium, Cape Town, South Africa, 28 January - 2 February 2001. Oxford: Oxford University Press, 2003.
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Vuuren, Sanet Janse Van. Easy identification of the most common freshwater algae: A guide for the identification of microscopic algae in South African freshwaters. Pretoria, South Africa: Resource Quality Services (RQS), 2006.
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Mitchell, Adams Nancy, and Fox Jeffrey M, eds. Marine algae of the northern South Island: A list of species. Wellington, New Zealand: National Museum of New Zealand, 1992.
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Levanets, Anatoliy. Non-marine algae of Africa: A bibliography (1799-2010). Potchefstroom: The Platinum Press, 2010.
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Price, J. H. Seaweeds of the western coast of tropical Africa and adjacent islands: A critical assessment, IV Rhodophyta (Florideae) 2 Genera G. London: British Museum (Natural History), 1988.
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Price, James H. Seaweeds of the western coast of tropical Africa and adjacent islands: A critical assessment, iv, Rhodophyta (Floridae). 1. Genera A - F. London: British Museum (Natural History), 1986.
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M, John D., ed. The marine algae and coastal environment of tropical West Africa. 2nd ed. Berlin: J. Cramer, 1987.
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Benson-Evans, Kathryn. A guide to the freshwater brackish and marine algae of South Wales, UK. Cardiff: BioLine, 1996.
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W, Lawson George, and Ameka Gabriel K, eds. The marine macroalgae of the tropical West Africa sub-region. Berlin: J. Cramer, 2003.
Find full textBook chapters on the topic "Marine algae – South Africa"
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Vosloo, Mathys C., and Martin G. J. Hendricks. "Marine and Estuarine Nematodes in South Africa." In Nematology in South Africa: A View from the 21st Century, 495–519. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-44210-5_24.
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Griffiths, Charles, Tamara Robinson, and Angela Mead. "The Alien and Cryptogenic Marine Crustaceans of South Africa." In In the Wrong Place - Alien Marine Crustaceans: Distribution, Biology and Impacts, 269–82. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-0591-3_8.
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Millar, Alan J. K. "Marine benthic algae of North East Herald Cay, Coral Sea, South Pacific." In Sixteenth International Seaweed Symposium, 65–74. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4449-0_8.
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Samaai, T., K. Sink, S. Kirkman, L. Atkinson, W. Florence, S. Kerwath, D. Parker, and D. Yemane. "The Marine Animal Forests of South Africa: Importance for Bioregionalization and Marine Spatial Planning." In Perspectives on the Marine Animal Forests of the World, 17–61. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-57054-5_2.
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Phelp, David, Marius Rossouw, Andrew Mather, and Godfrey Vella. "Storm Damage and Rehabilitation of Coastal Structures on the East Coast of South Africa." In Coasts, marine structures and breakwaters: Adapting to change, 1: 464–475. London: Thomas Telford Ltd, 2010. http://dx.doi.org/10.1680/cmsb.41301.0041.
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Davies-Coleman, Mike T. "Secondary Metabolites from the Marine Gastropod Molluscs of Antarctica, Southern Africa and South America." In Molluscs, 133–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/978-3-540-30880-5_6.
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Sowman, Merle. "Governability Challenges Facing Small-Scale Fishers Living Adjacent to Marine Protected Areas in South Africa." In MARE Publication Series, 359–77. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17034-3_19.
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Gaines, Susan M., Geoffrey Eglinton, and Jürgen Rullkötter. "Molecular Informants: A Changing Perspective of Organic Chemistry." In Echoes of Life. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195176193.003.0007.
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Lodged in the earth’s outermost layer, ephemeral scratch on a mineral skin, life plays cards with a handful of elements—builds molecular extravaganzas of carbon and hydrogen, oxygen, nitrogen, sulfur, or precious phosphorus, and forms the pieces to the parts that, assembled, define it. When the game is over, the cards reshuffled, the parts dismantled—membranes ruptured, shells dissolved, bones ground to dust—a few of those organic molecules remain in the sediments and rocks, bearing witness to the distant moments of their creation. Imagine the most humble bit of life, a microscopic alga basking in the sun-graced surface of the sea. Think of the tiny animal that grazes on the alga, dismantling its parts, using the pieces and discarding the difficult-to-digest fats and sturdy membrane lipids in tiny pellet-like feces that sink slowly into the dark waters of the deep sea—a thousand meters, two, three, maybe more. Imagine the bacteria that cling to the pellets as they settle onto the seafloor, zealous recyclers of organic molecules, using some and transforming others, leaving them stripped down or broken but still recognizable among the generic mineral bits of shell and clay that accumulate, particle by particle, year by year, layer by layer. Dig down, dig back, through meters and kilometers of sediments, through millennia and epochs, and you’ll find them yet, those molecular relics, testaments to that tiny, light-loving bit of bygone life. What do those molecules know, what do they have to say? Might they remember their maker’s name and environment, how that tiny alga lived and died? Was it rich or poor, food plentiful or scarce, the water warm or cold? Perhaps there was a current from the south, or cold nutrient-rich waters upwelling from the deep. Maybe there was a drought in Africa and dry winds blew nutrient-laden dust over the Atlantic, the continent’s misfortune a literal windfall for marine algae. Perhaps a meteor fell that year and the light went out of the sky, the temperature dropped suddenly, and the world died in a blink.
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"Chapter Eleven. Exploitation Of Marine Resources." In South Africa and the Law of the Sea, 281–336. Brill | Nijhoff, 2011. http://dx.doi.org/10.1163/ej.9789004210059.i-534.58.
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"Chapter Thirteen. Protection Of The Marine Environment." In South Africa and the Law of the Sea, 351–406. Brill | Nijhoff, 2011. http://dx.doi.org/10.1163/ej.9789004210059.i-534.66.
Full textConference papers on the topic "Marine algae – South Africa"
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L’Arvor, E., T. Maya, and P. Lattes. "Seismic Survey Challenges offshore South Africa." In Second EAGE Marine Acquisition Workshop. European Association of Geoscientists & Engineers, 2020. http://dx.doi.org/10.3997/2214-4609.202034010.
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Luyt, Catherine Diane. "CALIBRATION OF BIFIDOBACTERIAL INDICATORS FOR MICROBIAL WATER QUALITY MONITORING IN SOUTH AFRICA." In 13th SGEM GeoConference on WATER RESOURCES. FOREST, MARINE AND OCEAN ECOSYSTEMS. Stef92 Technology, 2013. http://dx.doi.org/10.5593/sgem2013/bc3/s12.006.
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Tandlich, Roman. "WEATHER FORECASTING AND ITS LEGAL FRAMEWORK FOR DISASTER MANAGEMENT IN SOUTH AFRICA." In 13th SGEM GeoConference on WATER RESOURCES. FOREST, MARINE AND OCEAN ECOSYSTEMS. Stef92 Technology, 2013. http://dx.doi.org/10.5593/sgem2013/bc3/s12.060.
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Parr, Kayla S., Thomas J. Algeo, and Andrey Bekker. "CONTROLS ON TRACE METAL ENRICHMENT IN EARLY PROTEROZOIC MARINE SEDIMENTS OF BRAZIL AND SOUTH AFRICA." In 50th Annual GSA North-Central Section Meeting. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016nc-275607.
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Sims, P. F., L. F. Jackson, D. W. Japp, and A. Dehrmann. "Conflicts in Marine Resource Utilisation on the Agulhas Bank, South Africa: The Interaction Between the Fishing Industry and the Offshore Oil and Gas Industries." In SPE International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production. Society of Petroleum Engineers, 1998. http://dx.doi.org/10.2118/46882-ms.
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Onuoha, K. Mosto, and Chidozie I. Dim. "Prospects and Challenges of Developing Unconventional Petroleum Resources in the Anambra Inland Basin of Nigeria." In SPE/AAPG Africa Energy and Technology Conference. SPE, 2016. http://dx.doi.org/10.2118/afrc-2571791-ms.
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ABSTRACT The boom in the development of unconventional petroleum resources, particularly shale gas in the United States of America during the last decade has had far reaching implications for energy markets across the world and particularly for Nigeria, a country that traditionally has been Africa’s leading crude oil producer and exporter. The Cretaceous Anambra Basin is currently the only inland basin in Nigeria where the existence of commercial quantities of oil and gas has been proven (outside the Tertiary Niger Delta Basin). The possibility of similarly finding commercially viable resources of unconventional petroleum resources in the basin appears quite attractive on the basis of the existence of seepages of shale oil and presence of coal-bed methane in some of the coal seams of the Mamu Formation (Lower Coal Measures) in the basin. This paper presents the results of our preliminary assessment of the shale oil and gas resources of the Anambra Basin. Our main objective is to locate the zones of very high quality plays within the basin, focusing on their depositional environments (whether marine or non-marine), areal extent of the target shale formations, gross shale intervals, total organic content, and thermal maturity. Data on the total organic content (TOC %, by weight) and thermal maturity of shales from different wells in the basin show that many of the shales have high TOCs (i.e greater than 2%) comparable to known shale gas and shale oil plays globally. Shale oil seepages are known to occur around Lokpanta in south-eastern Nigeria, but there is a general predominance of gas-prone facies in our inland basins indicating good prospects for finding unconventional petroleum in this and other Nigerian inland sedimentary basins. The main challenge to the exploration of unconventional resources in Nigeria today has to do with the absence of the enabling laws and regulatory framework governing their exploration and subsequent exploitation. The revised Petroleum Industry Bill (PIB) currently under consideration in the National Assembly is expected to introduce drastic and lasting changes in the way the petroleum industry business is conducted in the country, but all the provisions of the draft law pertain mainly to conventional oil and gas resources.
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Trümpy, Daniel, Jan Witte, Immanuel Weber, and João P. Da Ponte Souza. "Source Rocks of Somalia – A Regional Assessment." In SPE/AAPG Africa Energy and Technology Conference. SPE, 2016. http://dx.doi.org/10.2118/afrc-2582343-ms.
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ABSTRACT In total, some 60 wells have been drilled onshore and less than 10 offshore Somalia*, none of which in deep water. Several prospective basins remain undrilled, such as the offshore Jubba and Mid Somali High basins and the onshore Odewayne basin. In view of the gas discoveries offshore Mozambique and Tanzania, and also of encouraging results offshore Kenya (sub-commercial oil discovery Sunbird-1) and in Madagascar, the Somalian offshore and onshore basins were re-evaluated. As to the Somali onshore basins, the extension of the Yemeni Jurassic and Cretaceous rifts into Somalia highlights their prospectivity. Seeps abound (Odewayne and Nogal basins) and some wells encountered good shows. Late Jurassic and Upper Cretaceous marine shales are source rock candidates. Gas in the area of Mogadishu may be associated with the Early Triassic Bokh Fm. source rock. Seeps in western Somalia are rare, and may result either from long-distance migration out of the Calub Graben or from locally mature Lower Cretaceous or Upper Jurassic. We establish an inventory of proven and possible source rock occurences in Somalia by integrating publicly available data on slicks and seeps, geological and gravity maps, literature data, well data and geological information from adjoining basins. Our data indicate that in the Somali part of the Gulf of Aden, high heat-flow may critically affect the Late Jurassic source rock. However, Late Cretaceous or even Eocene sources may be locally oil-mature. The presence of source rocks on the Somali Indian Ocean margin remains presently speculative. Abundance of slicks in the area south of Mogadishu may not relate to hydrocarbons. Of more interest are reported isolated slicks further to the north, in deeper waters of the Mogadishu and Mid-Somalia High Basins. These slicks may be related to Lower/Mid-Jurassic, Late Jurassic, Late Cretaceous or Eocene sources. Analysis of onshore seeps in northern Somalia (Nogal, Daroor, Odewayne basins), integrated with seismic data, will allow to determine the origin of these oils and an assessment of the size of prospective kitchen areas. In the offshore, 3D-Basin-modelling will be required to determine which areas are prospective for gas or, especially, for oil.
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Weiss, Carlos V. C., Omar Castellanos, Bárbara Ondiviela, José A. Juanes, and Raúl Guanche Garcia. "Development of a Tool to Identify Potential Zones for Offshore Aquaculture: A Global Case Study for Greater Amberjack." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77870.
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This paper presents an innovative tool to recognize potential zones for the development of offshore aquaculture activities from an expanded spatial perspective. The methodology — developed in the framework of the TEN-SHORES project (Development of new technologies in oceanic aquaculture RTC-2014-2485-5) — aims to identify optimal conditions for the growth of fish species and for cage resistance. The first step is based on the Delphi method and consists of the selection of variables according to their relevance to fish species and to the cage location. The selected variables were acquired from reanalysis models and remote sensing data (time series of 20–30 years). In the second step, an evaluation system was developed to estimate the percentage of time (on a 0-1 scale) that the selected variables remain in optimum conditions, for the fish and the cage, in the whole data series (grid of 0.25°). Suitability maps were generated according to the conditions for the fish species growth and to house a generic cage. The integration of these maps allows for the identification of potential zones (>0.7) for farming the Greater amberjack (Seriola dumerili), highlighting unexploited offshore zones in South and North America, Oceania and in the Africa continent. The developed tool can be applied to large-scale studies of different aquaculture species, as well as to other types of marine uses.
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Lang, Donogh W., Paul Bohan, Victor Gomes, Germain Venero, and Hugues Corrignan. "Advances in Riser Management Technology Enabling Improved Efficiency for Deepwater and Harsh Environment Drilling." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96261.
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Abstract Despite the abrupt fall in crude oil prices since 2014, operators continue to explore for, and develop, oil and gas resources in some of the most challenging offshore environments. Exploration and development drilling is currently ongoing or planned in locations such as West of Shetland, offshore Eastern Canada, along Ireland’s Atlantic margin, in the South Atlantic Ocean and offshore South Africa. All these locations are characterized by the challenges of deepwater, powerful ocean currents and high seas. With the lower oil price environment, carrying out drilling operations at these locations both safely and economically requires the adoption of new digital technologies and associated processes that maximize efficiency and reduce the cost of well programs. A significant aspect of this relates to planning and execution of operations involving the marine drilling riser, which can be a major contributor to non-productive time in deepwater and harsh environment locations. This paper describes a holistic approach to addressing this challenge, which covers every phase of riser operations for the drilling program, from pre-operations global riser analysis through to post-operations assessment. The paper focuses on the technology that enables this holistic solution, with emphasis on the state-of-the-art riser management technology that is deployed on the drilling vessel. This uses an advanced finite element model of the riser, BOP stack, wellhead, conductor, casing and soil interaction as well as a detailed model of the riser tensioning system. The same model is used in both the pre-operations global drilling riser analysis phase and the operational drilling phase to ensure consistency. Incorporation of the model provides the capability to perform forecast analysis on-board the rig, allowing offshore personnel to simulate a range of operations hours and days in advance using forecast metocean conditions, thereby assessing the feasibility of critical well construction operations before they commence. Capabilities for real-time monitoring of ongoing operations, fusing sensor data with the riser model, are also described. These provide calculation of live watch circles and operating envelopes for connected-mode operations, in addition to tracking of riser joint, wellhead, conductor and casing fatigue from both wave and VIV excitation. Additionally, calibration of soil models — often a critical input to wellhead fatigue analyses — can be performed. Application of the technology is illustrated by means of a case study describing deployment on a record-breaking well in a harsh environment location. This demonstrated significant cost savings while simultaneously increasing safety and improving integrity assurance.
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Williams, Dara, and Feargal Kenny. "Calculation of VIV Fatigue of Multi-Pipe Systems." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61089.
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In various regions of the world offshore oil and gas production and exploration is met with the challenges of operating in extreme currents. These extreme current loads increase the risk of vortex induced vibration (VIV) of the riser system and the associated fatigue damage induced by these vibrations. Regions of particular concern are the Gulf of Mexico where strong loop currents occur, East Africa where the Benguela current dominates and regions offshore South America where strong eddy currents can occur. In order to ensure robust riser design for these regions it is necessary to perform detailed evaluations of the expected VIV response of the global riser system. The assessment of VIV response of steel riser systems is commonplace in the industry and there are well established industry practices in relation to this. In addition there are a number of commercially available VIV analysis tools. Whilst commercially available VIV analysis tools have proved effective in the analysis of long slender structures such as risers there are also a number of limitations in the level of complexity of the model that can be achieved. The analysis approach utilized by these models is based on simplified geometries and linearization of complex non-linear interactions. As a result of these simplifications these analysis tools are not suited to the analysis of non-linear multi-pipe models. Many offshore riser configurations consist of one or more pipe or casing strings enclosed by an outer pipe which is exposed to the environment. In a scenario where VIV of the outer pipe occurs then there will also be a corresponding deflection and curvature transmitted to the inner pipe(s). The displacements and associated stresses of the inner pipe(s) are largely dictated by the response of the outer pipe. Thus for multi-pipe configurations where the inner pipe is not constrained by cement or centralisers (e.g. landing string inside marine riser) the issue arises as to how to calculate the fatigue of the inner strings due to VIV oscillation of the outer string. At the time of writing no standard industry approach exists to address this issue and therefore this paper will outline and demonstrate a proposed approach to address this issue. The objective of this paper is to outline a novel analysis approach for the calculation of inner string fatigue resulting from VIV of the outer pipe. This proposed methodology combines the benefit of simplified VIV analysis tools with more detailed non-linear global finite element modelling techniques to enable a more comprehensive and accurate assessment of fatigue life of the complete system. The benefits and effectiveness of the proposed method are demonstrated through the analysis of a series of case studies which include landing string fatigue and riser fatigue for deep water applications.