Thesis (M.A.)--Stellenbosch University, 1988. / ENGLISH ABSTRACT: The Benguela upwelling system off southern and south western Africa is a zone of strong and extensive upwelling. Owing to the greater fIsh numbers found along the front between the upwelling and South East Atlantic Ocean the frontal zone is a key element in the ecology of the upwelling area. This discourse focuses on the perturbations of this front. The major data source used was the daily Meteosat satellite imagery for the years 1978, 1979 and 1982 to 1985 in the visible and infrared wavebands. These data enable the investigation of cross frontal activity for the entire Benguela Upwelling System at various spatial and temporal scales. NOAA satellite infrared imagery was also used. At the macroscale two upwelling zones are described. The fIrst is the upwelling core along the coast which exhibits well-developed and persistent upwelling. Offshore of this is an area in where the more transient fllament activity predominates. This outer zone is one of constant change and presents highly variable frontal boundary locations. As far as the persistent upwelling is concerned, the northern boundary closely approximates that suggested by Shannon (1985) of l7oS. Cape Agulhas was the effective southern boundary of any regular upwelling. The mean offshore extent of the outer upwelling is 270 kilometres off Liideritz and 45 kilometres off Cape Town. An analysis of the seasonal location of the front shows that the greatest upwelling extent at both Liideritz and Cape Town is observed in winter. Although the winter upwelling extent is the greater of the two seasons, the summer frontal location at Cape Town, in turn, exhibits remarkable stability. The upwelling off Liideritz, on the other hand, is prone to almost constant frontal location fluctuations. . Most of the variation occurs as a result of the growth and decay of fllaments. Filaments were seen along the entire upwelling zone from Cape Agulhas to Cape Frio. On average, the fllament sector was 270 kilometres wide off Liideritz. Between Cape Point and Cape' Agulhas the southwards extent of the upwelling rarely exceeded 40 kilometres, while the maximum fllament off Cape Point was about 200 kilometres. A fllament at Cape Point generally extends about 40 kilometres westwards and the upwelling zone off Walker Bay stretches about 20 kilometres southwards, onto the Agulhas Bank. Along the coast between Cape Agulhas and Cape Point the fllaments rapidly react to changes in the wind speed and direction. Mesoscale weather systems are therefore important factors in determining fllament activity there. This also true to some extent at Liideritz. The berg wind can induce rapid fllament growth off Liideritz. Despite an upwelling positive wind direction it is the wind speed that determines whether upwelling will develop at Cape Town at all. At Liideritz the wind speeds appear to determine the cross frontal temperature gradient. The greater the wind speed, the steeper the temperature gradient. Cross frontal temperature gradient of between 0.020C and .006oC per kilometre were calculated for Liideritz, which compares well with readings in the Californian upwelling zone (Koblinsky et al. 1984). In the way fllaments extend the length of the frontal zone greatly and the manner in which these cold water streams react to the changing winds, they are complex upwelling frontal features of great variability and importance in the Benguela upwelling system. / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MTech (Oceanography))Cape Peninsula University of Technology, 2010 / The current dynamics along the Tsitsikamma coast is described from a combination of acoustic current measurements. satellite-tracked surface drifters and underwater temperature recordings made between November 2006 and March 2008. The Tsitsikamma coast is largely a Marine Protected Area (MPA) that protects a rich marine biodiversity. The nearshore currents are important in the dispersal of eggs and larvae of many marine species. including the paralarvae of the commercially caught chokka squid. LoNgo reynaudii. Changes in the environment, including the currents. can affect the successful recruitment of chokka squid, and can bring about large annual fluctuations in biomass that creates economic uncertainty in the squid fishery. Results confirm the existence of a predominantly alongshore current off the Tsitsikamma coast. At Middelbank eastward flow was slightly dominant, with a percentage occurrence of 58% vs. 41% westward flow near the surface. The percentage eastward flow decreased with depth, with 41% vs. 58% westward flow near the seabed. At Thyspunt westward and eastward flow occurred at near equal percentages. but westward flow was slightly dominant throughout the water column. The alongshore current was strongest near the surface during eastward flow (maximum = 141 crn.s1: average = 27 crn.s '). while westward surface currents were weaker (maximum velocity = 78 cm.s1: average = 19 crn.s1). Current speed generally decreased with depth and opposing surface and bottom currents, associated with a thermal stratified water column, were occasionally recorded. The nearshore flow regime was characterised by frequent barotropic alongshore reversals that occurred year round. An increase in strong eastward episodes, and opposing surface and bottom currents during spring and summer months have implications for the dispersal of squid paralarvae during the summer and winter spawning seasons. In summer, the combination of strong eastward pulses in the current and upwelling at the capes favoured dispersal onto the midshelf of the Agulhas Bank. In winter, alongshore oscillations without the offshore displacement associated with upwelling. restricted offshore dispersal which caused surface particles to be retained inshore. Drifter trajectories show that both the eastward and westward nearshore current can link the inshore spawning grounds with the nursery grounds, offshore on the central Agulhas Bank; and that passive, neutrally buoyant material in the surface layer can reach the vicinity of the cold ridge in as little as eight days. The wind-driven processes of upwelling and coastal trapped waves (CTWs). and the influence of the greater shelf circulation are discussed as possible driving forces of variability in the currents off the Tsitsikamma coast. The occurrence of coastal trapped waves during thermal stratification appears to drive the jet-like, eastward pulses in the current. and results suggest that the propagation of CTWs may regulate and even enhance upwelling and downwelling along the Tsitsikamma coast.

Thesis (MTech (Oceanography))--Cape Peninsula University of Technology, 2009 / A collaborative study between Marine and Coastal Management (MCM) and the Oceanographic Research Institute (ORI) was initiated in March 2001 to investigate the physical oceanography of Sodwana Bay, South Africa, and the affects on coral communities resident to the area. A bottom-mounted Acoustic Doppler Current Profiler (ADCP) and three Underwater Temperature Recorders (UTR) were deployed to complement the long-term monitoring UTR deployed on Nine-Mile Reef (NMR) in 1994. The study was terminated after 30 months, whereby all instruments were removed except for the long-term monitoring UTR.

Ph.D. / The investigations reported here conducted during 1990-1994 had the following objectives: Selection of representative localities in impoundments and rivers in wetlands affected by radionuclide- and metal-containing effluents and seepage water from mines and metal-processing industries. To determine the occurrence and concentration of radionuclides and selected metals in mine- and industry-polluted waters and sediments in catchments of the Blesbokspruit, the Klip River and the Crocodile River systems. To establish radionuclide and metal concentrations in some semi-aquatic and aquatic weeds in these mine- and industry-polluted waters with observations on the ability of some plants to accumulate certain metals in their roots and/or shoots. To evaluate some benthic macro-invertebrate organisms as possible indicators of radionuclide and metal pollution in the affected streams. To determine the radionuclide and metal concentrations in selected vegetable crops irrigated with mine- and industry-polluted water. The localities where the investigation took place were mainly in wetland regions on the East and West Rand. Water of polluted streams traverse expansive wetlands containing floating, emergent and submerged aquatic vegetation. These plants play an important role in the recovery from pollution of the affected waters. Pollutants are also available to and accumulated by other aquatic organisms such as crabs, fish and birds. In addition, the same water is often used for the irrigation of vegetable crops, thereby creating potential pathways through which these pollutants may be consumed by humans. All the above objectives have largely been met in as such that potential sources of pollution were identified and pollutants detected in the abiotic (water and sediments) environment. These pollutants were also found in wetland biota as well as agricultural crops irrigated with contaminated water. Potential pathways for the transfer of these pollutants were identified and dose assessment modelling was conducted.

This thesis investigates the variability occurring in the secondary metabolites produced by three South African marine molluscs. Chapter Two discusses the isolation and spectroscopic structure elucidation of the metabolites isolated from two Siphonaria species. The re-investigation of Siphonaria capensis yielded siphonarienfuranone (2.2) as the only common polypropionate isolated from both the 1998 and 2009 collections of S. capensis from the same areas suggesting possible seasonal or genetic variation in polypropionate production. The sterol cholest-7-en-3,5,7- triol (2.33) was also isolated form the 2009 collection of S. capensis and this is the first time this compound has been isolated from a Siphonaria species. The second species, Siphonaria oculus is closely related to S. capensis and the investigation into the former’s secondary metaboliteproduction revealed 2.2 as a major metabolite suggesting an inter-species overlap in polypropionate production. Three new polypropionate metabolites, 2.35, 2.36 and 2.37 were also isolated from S. oculus. An unsuccessful attempt was made to establish the absolute configuration of 2.37 using the modified Mosher’s method and the limited amount of 2.37 available prevented any further attempts at resolving the absolute configuration of this compound. The 1H NMR analysis of the defensive mucus collected directly from S. oculus revealed the presence of the acyclic polypropionate 2.37 as a minor metabolite. The absence of characteristic signals for the furanone containing compounds 2.2, 2.35 and 2.36, might suggest that these compounds cyclise from a hypothetical acyclic precursor (2.38) during standard work up of bulk acetone extracts of Siphonaria species. Chapter Three discusses the re-isolation and spectroscopic structure elucidation of the metabolites isolated from the nudibranch, Leminda millecra. Three known natural products, millecrone A (3.1), 8-hydroxycalamenene (3.6) and cubebenone (3.8) were re-isolated from our 2010 collection of L. millecra, as well as the new minor metabolite 8-acetoxycalamenene (3.16). The cytotoxic prenylated toluquinones and toluhydroquinones (3.9-3.15) initially isolated from the 1998 collection of L. millecra were not found in the 2010 collection supporting the hypothesis that these compounds may be of fungal origin. L. millecra clearly shows variability in the compounds sequestered by this species with millecrone A (3.1) being the only common metabolite in the three investigations of L. millecra to date. An unsuccessful attempt was made to establish the absolute configuration of 3.1, 3.6 and 3.8 through initial LAH reduction of the ketone moiety contained in 3.1 and 3.8 and esterification of the resultant diastereomeric alcohol mixtures and the phenol functionality in 3.6 with (1S)-camphanic chloride. Crystallisation of the (S)- camphanate esters of 3.6 and 3.8 for X-ray analysis were unsuccessful, while the unexpected conjugate addition of a hydride in 3.1 resulted in complex diastereomeric mixtures which could not be separated by HPLC.