摘要:

The Quaternary sediments around the margin of the Bot River's closed estuary have been drilled and a succession up to 52 m thick has been analysed sedimentologically. Four main units have been identified. The basal Unit 1 is a 10 m-thick, angular, quartzose coarse gravelly mud, rich in fragments of rock and vein-quartz, and is mainly encountered in the palaeo-valley under the barrier. It is interpreted as a fluvial basal gravel deposited during the early stages of a Wurm IIa/IIb transgression. Unit 2 is 15 to 30 m thick and is consistently muddy (muddy sand to mud). It is characterized by benthic foraminifera typical of inner-shelf or estuarine environments and is interpreted as a back-barrier lagoonal sediment deposited during the latter stages of the Wurm IIa/IIb transgression. Due to compaction and its subsequent cohesiveness Unit 2 survived re-excavation during the Wurm IIb regression to −130 m, when the mouth of the palaeo-Bot River lay south of False Bay, between the Hangklip Ridge and Betty's Bay Bank. Unit 3 overlies Unit 2 in BOT-103 at Die Keel and is a 12 m-thick shelly, fine to medium sand. Unit 4 is 5 to 15 m thick and is a quartzose, medium sand under the barrier. Farther inland it can be a sandy mud and the unit can be rich in organic matter. Unit 4 was laid down during the Flandrian transgression. Unit 5 is the 15 to 30 m-thick calcareous, quartzose medium sand of the barrier environment that is found on the beach, on the dunes and also on the washover fans that are periodically fed by storm-surges breaching the foredunes. There is evidence of a post-Glacial (5,5 to 2 Ka B.P.) barrier slightly inshore of the present coast and of a Late Pleistocene (125 Ka B.P.) shoreline beside the Lamloch swamps.

ISSN:0035-919X    

DOI:10.1080/00359198509519487

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Bot River estuary can be classified as an end-member stage of a bar-built estuary, occupying a drowned river valley. The modern barrier consists of fairly large back-barrier dunes, hummocky foredunes and a dissipative beach.

ISSN:0035-919X    

DOI:10.1080/00359198509519488

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The bathymetry of the Bot River estuary, water-level records from 1978 to 1983, wind records for a three-week period in August-September 1984, and investigations into the particle-size distribution, mineralogy and chemical composition of sediments in the estuary are reported and discussed.

ISSN:0035-919X    

DOI:10.1080/00359198509519489

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A numerical model for the wind-driven circulation for the Bot River estuary was established. The model was run for various wind-directions and the resulting current patterns are briefly discussed.

ISSN:0035-919X    

DOI:10.1080/00359198509519490

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Historical evidence shows that the Bot River estuarine system has undergone substantial topographical changes during the past century, the most recent being the partial isolation of the Kleinmond from the Bot River estuary, of which it was once apparently a part. Despite these substantial changes, there is no evidence to confirm an early newspaper report that the estuary itself was used as a harbour.

ISSN:0035-919X    

DOI:10.1080/00359198509519491

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

During the flood year of 1981 and in 1983 the Bot River estuary, one of the largest lagoons in the south-western Cape was opened to the sea by three artificial breachings of the sand bar which were aimed at lowering the excessively high water levels in the lagoon and at the re-establishment of estuarine conditions.

ISSN:0035-919X    

DOI:10.1080/00359198509519492

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The physical and chemical properties of the waters of the Bot River estuary have been examined over a period of five years. The parameters measured were: electrical conductivity, pH, alkalinity, temperature, dissolved oxygen, total dissolved salts, sodium, magnesium, calcium, potassium, fluoride, chloride, nitrate, ammonia, sulphate, phosphate and silicate. The physical and chemical properties are mostly affected by artificial openings of and water-levels in the estuary.

ISSN:0035-919X    

DOI:10.1080/00359198509519493

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The primary production of the Bot River estuary, a large closed estuary on the south-western coast of South Africa has been estimated at 11 059 t dry mass y−1. The main contributions to this value come from the submerged aquatic macrophytes (7 987 t dry mass y−1or 72% of total calculated production), reeds (1 503 t dry mass y−1or 14%), benthic diatoms (787 t dry mass y−1or 7%) and phytoplankton (782 t dry mass y-1or 7%). These four categories are believed to contribute over 90% of the primary production during periods of stability when the estuary is closed and full. Much of this production is not directly utilized by herbivores and forms the basis of a bacterial system producing very fine, organically rich material deposited on the estuary bed. Primary production is affected by mouth opening in a number of different ways including changes in volume of water, available surface area for attachment of macrophytes, and loss of macrophytes which are stranded or washed out to sea.

ISSN:0035-919X    

DOI:10.1080/00359198509519494

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of temperature and salinity variations on the suspended bacterial population of the Bot River estuary, a closed estuary, was examined. The population was found to be salt tolerant, and saline water was required for maximal growth rates. Temperatures below 15°C inhibited growth. Bacterial isolates fell into two groups as regards temperature optima, the one having an optimum of 23°C and the other 30°C. The bacterial population in the Bot River estuary is clearly adapted to estuarine conditions.

ISSN:0035-919X    

DOI:10.1080/00359198509519495

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The Bot River estuary is normally closed to the sea and its bacterial population fluctuates seasonally, peaking in late summer. Parameters such as temperature, salinity, organic nutrients and turbidity may directly or indirectly cause these fluctuations. The spatial distribution of this bacterial population differs from that of open estuaries studied elsewhere. However, artificial opening of the estuary results in a distribution pattern similar to that of open estuaries.

ISSN:0035-919X    

DOI:10.1080/00359198509519496

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor