ISSN:0035-919X    

DOI:10.1080/00359199709520614

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This first paper of the centenary series is not a review paper of a discipline, but rather of a man, the founder of marine scientific endeavour in South Africa, Dr John D.F. Gilchrist FRSSAf. It is written and published as an essay.

ISSN:0035-919X    

DOI:10.1080/00359199709520615

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Investigations on the physical behaviour of the oceans bordering South Africa have gone through a number of distinct historical phases, starting with exploratory work on the Agulhas Current as early as 1778. The first work of a physical nature that derived from South Africa itself was done by John Gilchrist in support of his fisheries investigations. In the period following, before the Second World War, physical research near South Africa was dominated by German endeavours. That work was terminated by the war and not resumed afterwards. The greatest stimulus for South African oceanology came from the International Geophysical Year and the International Indian Ocean Expedition in the 1950s and 1960s. It led to the formation of the South African National Committee for Oceanographic Research, the construction of state-of-the-art research vessels and to a whole new vision on South Africa's ocean environment. The golden years of South African oceanography were the 1970s and early 1980s, with the establishment of the National Research Institute for Oceanology by the Council for Scientific and Industrial Research (CSIR), the blossoming of research at the Sea Fisheries Research Institute, strong national research programmes, including the Benguela Ecology Programme, and a vigorous Antarctic Research Programme. Growth in knowledge and understanding of South African waters increased rapidly, partially as a result of a simultaneous growth in international interest in the region. In the 1980s came the commercialization of the CSIR, the rapid shrinkage in South Africa's research fleet, and restructured funding mechanisms that did not directly encourage participation in international research programmes. This was followed by a new political dispensation in 1994 that has brought about substantially reduced funding for oceanography and also elements of social engineering that have still to show their future effect on oceanographic science in South Africa. The research philosophy of John Gilchrist seems to have been one of basic research of the highest quality, directed at problems that were deemed to be of economic importance. In an attempt to trace his legacy by studying the history of physical oceanography during the past century in South Africa, we find that the influence of his work in the field did not last long, but that the institutions he helped establish have maintained a standing in physical oceanography to this day.

ISSN:0035-919X    

DOI:10.1080/00359199709520616

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In 1895/96. John D. F. Gilchrist was appointed marine biologist to the Cape Colony. During voyages extending as far as Walvis Bay and Maputo, he initiated studies of the marine geology and chemical oceanography of the shelf while mapping substrata for new demersal fishing grounds. The shelf sediments off the East Coast are controlled by wave processes along the inner shelf and by the poleward-flowing Agulhas Current along the outer shelf. In contrast. South Coast sediments of the eastern Agulhas Bank consist of wave-dominated, landward-coarsening modem (Holocene) terrigenous muds to sands on the inner shelf and relict wave-dominated shelly sands on the outer shelf, deposited during Pleistocene lowstands within glacial (hypotbermal) periods. The Agulhas Current also appears to exert a controlling influence over the nutrient chemistry and, hence, primary productivity, on the East and South Coast margins. The surface waters of the Agulhas Current are nutrient-poor and most East Coast areas are consequently considerably less productive than their West Coast counterparts at the same latitude, but the underlying South Indian Central Water (SICW) is nutrient-rich. Recent findings suggest that the Agulhas Current may induce upwelling of nutrient-rich bottom water derived from SICW at sites such as the Natal Bight and off Port Alfred by kinematic upwelling so enhancing the nutrient content of surface waters and increasing the potential for primary production there. A second physical process, which is also thought to be related to interaction of the Agulhas Current and bottom topography, is the dynamic shelf-edge upwelling of SICW onto the shelf along portions of the South Coast where the shelf is wider. It is uncertain whether this is continuous in space or time, but it is possible that the process may, prime bottom waters for wind-induced upwelling in the south-western lee of capes along the South Coast. On the West Coast, the outer-shelf sediment consists of Holocene planktonic-foraminiferal ooze, reflecting the dominating influence of the equatorward-flowing Benguela Current. The middle-shelf sediment often consists of glauconitic sand, whereas the sediment of the inner shelf usually has a landward-coarsening and -thickening wedge of terrigenous muds to sands. Wind-induced upwelling is the dominant West Coast physical process of relevance to the sedimentology and chemistry of the inner shelf and overlying waters. In the southern Benguela this is seasonal, resulting in seasonal variability in the abundance of nutrients and the resultant productivity of surface waters and associated biogeochemical processes, such as the appearance of oxygen-depleted bottom water. There is a northward decrease in the seasonality of these physical and biogeochemical processes along the West Coast, which is reflected in an increase in the reducing nature of the underlying organic-rich sediments between St Helena Bay and Walvis Bay. In the deep-sea environment of the Cape Basin, the clockwise pole-ward flow of both the Antarctic Bottom Water (AABW) and the North Atlantic Deep Water (NADW) is reflected in a major zone of erosion of the sea floor, mantled by abundant ferromanganese nodules, at the foot of the continental rise, which is fed by margin-perpendicular slumps, debris flows and canyon-fed turbidity currents. The currents, driven by Coriolis Force, both swing left (east) into the Agulhas Passage between the Agulhas Bank and the Agulhas Plateau, before parting company in the Transkei Basin, where the AABW is forced eastwards by the northeast-shallowing contours of the Natal Valley. The E-W-orientated Agulhas Drift, a contourite drift, is being deposited on the left (north) side of the AABW. The NADW then heads into the Natal Valley to deposit margin-parallel contourite drifts at the foot of the continental slope as far north as Durban, where the Central Terrace and then the Mozambique Ridge steer the NADW first east and then south back to the mouth of the Natal Valley.

ISSN:0035-919X    

DOI:10.1080/00359199709520617

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A review of biological oceanographic research in South Africa since the time of John Gilchrist is presented, with emphasis on recent activities. The progress from descriptive studies to community ecology, then to quantitative dynamics, modelling and applications to fisheries oceanography is described. The interlinking between physical and biological processes in this complex region, leading to enhanced fish production, provides the impetus for future biological oceanographic research in South Africa.

ISSN:0035-919X    

DOI:10.1080/00359199709520618

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This review traces the development of South African coastal fisheries from prehistory to the present. Three phases are identified—a low-intensity prehistoric phase, in which attention was focused on easily accessed intertidal species, a period of rapidly increasing commercialisation and technological development, covering most of the present century, and a newly emerging phase of increasing species and product diversification. The effects of exploitation on both the target stocks themselves, and their associated communities, are examined. The population densities and size distributions of many target species have been radically impacted by human exploitation and such effects are generally well documented. The effects of exploitation on community dynamics are far less well appreciated, but they can be equally dramatic and may carry major economic implications. For example, rock lobster, sea urchins, abalone and kelp are linked by a complex web of biological interactions. Options for improving the management strategies applicable to coastal marine resources are discussed, including the need for management at the level of ecosystems rather than species, the revision of regulations to accommodate biological and social realities, and the feasibility of novel approaches such as the encouragement of co-operatives, co-management and coastal zonation of different types of harvesting.

ISSN:0035-919X    

DOI:10.1080/00359199709520619

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

South Africa's offshore living marine resources are commercially the most valuable of its renewable marine resources. They are herein defined as the demersal, pelagic and squid fisheries. Reviews are given of the fisheries and the focus research has taken since Gilchrist's days, with accent on the present situation and understanding. Progress has not always been smooth, but many of the developments in research on offshore living resources have placed South Africa at the forefront of fisheries management. Looking to the future, options are explored and likely scenarios generated. Certain is the fact that management of the offshore living marine resources has been and will continue to be exciting and, to some extent, even controversial.

ISSN:0035-919X    

DOI:10.1080/00359199709520620

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

South Africa's marine ecosystems have a wide variety of top predators, including both cartilaginous and teleost fish, 15 breeding seabirds and many more that are migratory to the region, seals, whales and smaller cetaceans. Land-breeding seabirds and seals were readily accessible to early colonists, and together with the obvious larger whales, were among the earliest marine resources to be exploited intensively. A number of species had been reduced to low levels by the start of the 20th century. Early research had two main objectives, in the case of exploited species investigation of factors influencing yields, and in the case of non-utilized species, such as many of the region's fish, the documentation of species. The landing of whale carcases at mainland whaling stations provided opportunity to investigate the biology of larger whales. As fisheries on the prey of top predators developed, some of the predators were regarded as competitors of fishermen. Research then aimed to quantify the competition, and included investigation of population size, diet and consumption, and species interactions in an ecosystem context. As fisheries expanded, some prey stocks collapsed and some seabirds decreased in abundance. This prompted research into the use of seabirds as indicators of the state of fish resources. In KwaZulu-Natal, attacks by sharks on man led to research aimed at reducing the incidence of attacks and the introduction of shark nets, which, due to their non-selectivity, had an influence on several species. Direct exploitation, depletion of prey resources, and incidental mortality, such as in the shark-net fishery, led to deterioration in the conservation status of several of South Africa's top predators, notably some sparids, seabirds and cetaceans. Consequently, much recent research has addressed issues of conservation concern, with the aim of securing sound management of predator populations. Issues of continuing concern include scarcity of food, incidental mortality and oiling and other forms of pollution. Top predators are expected to earn considerable revenue through ecotourism and recreational pursuits, and this is likely to become a focus of future research. Because of the migratory nature of many top predators, it is foreseen that their management will become multinational and it is expected that the funding basis for research will broaden to include non-governmental agencies. The advancement of technology will lead to automation of some monitoring studies and increased understanding of at-sea behaviour. The discovery during the celebrations of 100 years of marine science in South Africa of a fifteenth species of seabird breeding in the country suggests that the era of exploration and documentation has not yet closed.

ISSN:0035-919X    

DOI:10.1080/00359199709520621

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The history and development of South Africa has been linked strongly to the sea over the past 500 years, since the first visits by the early Portuguese navigators in the late 15th and early 16th centuries. The earliest coastal development was associated with the construction of ports and harbours, and the country now has six commercial ports equipped with modem facilities, as well as a number of smaller ports used mainly by the fishing fleets. Construction of some of these has presented particular challenges, because of the littoral drift and its impact on adjacent beaches. Since the 1950s. a series of excellent facilities and amenities, including tidal pools and small craft marinas, has been developed for recreation, and the management of effluent has been managed through the construction of Ocean outfalls. On the South African west coast, and extending into Namibia, there are rich coastal and offshore marine diamond deposits, and innovative approaches have been developed to allow their mining. For all of these developments, up-to-date, accurate environmental information has been a key input, and appropriate measuring networks and data-management techniques and facilities have been developed to allow the use of the information. Worldwide there has been a growing awareness of environmental issues. In 1992, one of the world's largest international environmental meetings took place in Rio De Janeiro. There, coastal states were urged to commit themselves to integrated and sustainable development of coastal areas, so giving impetus to the already growing international trend towards integrated coastal zone management (ICZM). People are adopting and demanding an integrated and holistic approach in the coastal area. South Africa was until recently excluded from the international community. Perhaps the most significant development in ICZM in South Africa is the participatory policy-formulation programme launched in the mid 1990s that will address the shortcomings currently experienced. Indeed, South Africa is poised on the brink of major advances in the field of ICZM. It is predicted that the country will become a major force in the advancement of all spheres of ICZM in both East Africa and the whole African continent. Historically, coastal engineering proceeded with little regard for the environment, in many cases with devastating effects, from environmental, economic and social points of view. As the years went by, and information became more freely available, there was a growing awareness that the environment had to form part of the calculations, formulae and debate of coastal engineers and other interest groups operating in the coastal area. Therefore, over the past 30 years, marine and environmental scientists and coastal engineers in South Africa developed methodologies that allowed a holistic approach to the technological support for judicious development of the coastal and marine resources of South Africa. The path of increasing collaboration was initially fraught with conflict between engineers and environmentally orientated coastal managers. Recently, the two viewpoints have increasingly converged, and at present it would appear that a new breed of professional, coastal development scientists, consisting of coastal engineers and coastal, marine and environmental scientists, will be playing a key role in the sustainable development of our coastal resources.

ISSN:0035-919X    

DOI:10.1080/00359199709520622

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0035-919X    

DOI:10.1080/00359199709520623

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor