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An intergrated study of the eziMbokodweni estuary : water and sediment quality, and estuary-nearshore material fluxes.Rambally, Adika. 12 September 2014 (has links)
This study represents an integrated and holistic assessment of the eziMbokodweni Estuary’s water and sediment quality. The estuary was once relatively un-impacted but now flows through a highly anthropogenically-modified catchment, comprising industrial and residential developments (formal and informal), and the eziMbokodweni Wastewater Treatment Works, furthermore the floodplain has been completely transformed to accommodate the Amanzimtoti golf course. Flow from the highly degraded Isipingo River and Estuary is occasionally diverted into the eziMbokodweni and the Southern Sewage Works Outfall, one of the largest deep sea sewage outfalls in the eThekwini Municipality, is located at sea, approximately 1.5 km south of the estuary mouth.
Estuarine health can be studied on various fronts, in this study, the following variables were monitored in the water and sediment columns, seasonally for spring and neap tides: heavy metals, nutrients, bacteria and selected physico-chemical parameters. The results demonstrated that the eziMbokodweni catchment was a major contributor of heavy metals and nutrients to the estuarine system. The quantity of the majority of heavy metals and nutrients transported by the river at the upper estuary exceeded the amount exported to sea at the estuary mouth-nearshore interface, resulting in the estuary accruing large quantities of material seasonality. It was noted that the nearshore waters are enriched, as a variety of heavy metals and nutrients entered the estuary mouth during flood tide episodes.
A range of heavy metals were detected within the sediment profiles obtained from the estuary, with fine to medium grained sediment exhibiting greater heavy metal content, in some cases, multi-fold higher than that detected in medium to coarse grained sediment. Geochemical indices were employed to ascertain the extent to which these metals constituted a pollution threat to the environment. The contamination factor calculated for all sediment layers and sampling sites implied low contamination. The enrichment factor calculated for the majority of heavy metals alluded to natural causes while some heavy metals exhibited significant to extremely high levels of enrichment thus implicating anthropogenic causes as likely sources of these heavy metals. The degree of contamination of the estuary was classified as low. Overall, the heavy metal and nutrient content detected in the sediments were low as compared to the large quantities detected from the budget. This indicates that natural mechanisms exist which facilitate the utilization or removal of these heavy metals and nutrients from the estuary. It is proposed that the most significant manner by which these heavy metals and nutrients are eliminated from the estuary is through episodic flood events that scour and strip fine grained sediment from the estuary bed.
The pH assessment of the estuary revealed that this environment was slightly basic through most of the year with mildly acidic conditions noted during winter. The average Dissolved Oxygen levels were within acceptable levels, with the exception of winter when levels were very close to hypoxic conditions. The average Total Dissolved Solid content indicated that the estuary was compliant with the target water quality range for domestic use on selected seasonal-tidal cycles, and the average Electrical Conductivity levels were compliant with the ideal target water quality range for aquatic ecosystems and domestic use as per the South African water quality guidelines (DWAF, 1996a-e). A salinity gradient was evident in the estuary, as salinity levels decreased with distance from the estuary mouth. The saline nature of the lower estuary provided for the flocculation of material, which was alarming as large quantities of heavy metals and nutrients were detected in the estuary. The lower estuary is therefore susceptible to contamination due to the salinity regime and the dominance of fine grained sediment. The demand for oxygen in the estuary was high during summer, autumn and spring, and within acceptable levels for natural waters during winter. Extremely high levels of Chemical Oxygen Demand were recorded in the estuary which provides prime growth and survival opportunities for bacteria. This correlated with the results from microbiological investigations as high levels of bacteria were noted within the estuary, in both the sediment and water columns. The detected quantities of Total Coliforms, Faecal Coliforms and Escherichia Coliforms exceeded the target water quality thresholds for domestic and full contact recreational use. While at selected sites, the recorded Faecal Coliforms and Escherichia Coliforms levels were deemed compliant for intermediate contact recreational use. However, these sites were not compliant throughout the sampling period. Overall, the upper and mid-estuary exhibited greater counts of bacteria, in both the sediment and water column, than the estuary mouth and was attributed to factors such as flushing, sediment particle size, salinity and the ‘dilution effect’. Furthermore, the sediment of the eziMbokodweni Estuary is serving as a reservoir for bacteria.
A number of options have been proposed to improve the degraded state of the eziMbokodweni Estuary and are ultimately aimed at curbing the anthropogenic input of these contaminants. The insight gained from this study provides the database from which more integrated and holistic estuarine management strategies can stem, that are applicable not just to the eziMbokodweni Estuary but estuaries in general. / M.Sc. University of KwaZulu-Natal, Durban 2013.
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Ecosystem functioning of selected estuaries on the east coast of South Africa.Cisneros, Kelly Ortega. 15 September 2014 (has links)
River inflow is one of the most important factors influencing the density and biomass of estuarine biotic communities. The aim of this study was to obtain an understanding of the ecosystem functioning of selected estuaries on the east coast of South Africa and to represent their dynamics through ecosystem models. The responses of water column nutrients, plankton density and biomass to inlet phase changes for 16 temporarily open/closed estuaries (TOCEs) in South Africa were first determined. This analysis demonstrated that inlet phase and the duration of mouth closure were the most important factors determining plankton density and biomass of the analysed TOCEs. Estimates of planktonic standing stocks for four of these estuaries revealed that stocks can be from 26 to 10 000 times higher during the closed compared to the open phase. Also, slightly higher variability of planktonic density and biomass was recorded during the closed phase of TOCEs. The second major thrust of this study was to analyse the variability and temporal stability of planktonic and macrobenthic invertebrate density and biomass in two KwaZulu-Natal estuaries over a dry/wet cycle. The results suggest that “stable” variability and species synchronization could be the mechanisms whereby the estuarine biota of these systems compensate for environmental changes and attain a degree of environmental homeostasis. The third major thrust involved an assessment of the spatio-temporal variations in the elemental composition and stoichiometry of suspended and sediment detritus, zooplankton and macrobenthic taxa from two estuaries over a dry/wet cycle. Significant seasonal variations in the elemental composition of detritus, zooplankton and macrobenthic species were found, with the variations in the elemental content of sediment and suspended detritus being related to the seasonal changes in river inflow, while the among-taxa variability was mainly explained by feeding mode. Finally, static seasonal carbon and nitrogen ecosystem network models were developed for the East Kleinemonde, Mlalazi and Mpenjati estuaries to investigate their nutrient dynamics and ecosystem functioning. The results indicated that the East Kleinemonde and Mpenjati estuaries were mainly dependent on primary producers during the dry season, especially the high standing stocks of phytoplankton and microphytobenthos. Similarly, the dependency on detritus was higher during the wet season due to the high riverine imports during this season. Consequently, higher detritivory was recorded in all three study systems during the wet season. Cycling of nitrogen was higher than of carbon on a seasonal basis, with higher recycling of nitrogen during the dry season implying a lower availability of this element due to reduced freshwater inflow and nutrient input during the low rainfall period. System indices indicated that the organization of these systems was higher during the dry season, while the overheads on imports and exports peaked during the wet season. The ecosystem models analysed here provide an initial insight into the overall carbon and nitrogen dynamics of estuaries on the east coast of South Africa. / M.Sc. University of KwaZulu-Natal, Durban 2013.
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The influence of turbidity on fish distribution in Natal estuaries.Cyrus, Digby Paul. January 1984 (has links)
Studies In other parts of the world have proved that
turbidity affects aquatic life and work In Australia and
North America has shown that the distribution of some fish
species may be determined by the level of turbidity present.
This, coupled with the fact that: (i) Natal estuaries are
important as nursery areas for the juveniles of many marine
fish species, (ii) the estuaries exhibit a wide range of
turbidities and (iii) little was known of the effects of
turbidity on the fish populations in estuaries, led to this
study being undertaken.
Turbidity and its effects on fish distribution In
Natal estuaries was investigated from January 1980 to June
1983. Lake St. Lucia, which is predominantly turbid but also
has clear water areas, was the main study area. Six other
estuarine systems sampled were chosen to cover a wide range
of estuarine types and turbidities. Field sampling was
undertaken to determine which species were present under
different turbidities, simultaneously physical factors which
were potentially affecting fish distribution were also
monitored. In addition to this, laboratory equipment which
enabled a turbidity gradient to be established In a choice
chamber tank was used to test the turbidity preferences of 10
common estuarine species for which field data were available.
These tests allowed the elimination of all physical factors
except turbidity.
Of the physical parameters monitored In the field,
turbidity, temperature and food availability In the benthos,
were determined as being important In affecting fish
distribution within estauries. However, comparison of fish
distribution data for twenty species, with these factors
showed that turbidity was exerting the major influence. It
was also found that fish species occurred In one of five
groups, inhabiting either clear, 'clear to partially turbid',
intermediate or turbid waters or they were indifferrent to
turbidity. Laboratory results for eight of ten species tested
showed significant aoreement with the field data. The results of this study have shown that turbidity is
the most important factor determining the distribution of
juvenile marine fish In estuaries and that the greatest
number of species are present in , waters which are not clear.
The attraction to and presence in such systems appears to be
related to the fact that turbid estuaries 'provide protection
from fish and bird predators while also acting to reduce
intraspecific predation. Of factors attracting juvenile fish
into estuaries, turbidity is probably the single most
important acting in this respect. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1984.
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The trophic ecology and macrofauna of Kahana Estuary, OahuTimbol, Amadeo Sembrano January 1972 (has links)
Typescript. / Bibliography: leaves [208]-221. / xix,, 221 leaves illus., maps, tables 28 cm
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Seasonal variations in tidal dynamics, water quality and sediments in the Alsea EstuaryMcKenzie, David Roller 18 October 1974 (has links)
During 1973 data was collected to analyze the seasonal variations of the tidal dynamics, water quality and sediments of the Alsea
Estuary. A summary of historical information with a list of all
known alterations to the estuary was made. A complete physical
description, including the geographical setting and mixing classification of the estuary, was done.
Times of high and low water and tidal ranges at three locations
were measured. Tide measurements made at Waldport indicated that the
published tide predictions for that location were reliable. At a
location upstream of the estuary embayment noticeable damping of the
tidal wave amplitude was detected during periods of high river flow
and high tidal range. High water lag times were found to decrease
during periods of high river flow, but low water lag times were
unaffected by river flow. The tide motion was found to be a damped,
partially standing wave, which altered its behavior according to the
volume of water in the estuary.
The high and low tide water quality parameters of salinity,
temperature, dissolved oxygen, turbidity and pH were measured at 10
to 18 locations during each season to determine any seasonal changes
in them. The parameters at a given location were found to be a function of river flow and tidal range.
Winter and summer sediment samples were analyzed for grain size
distribution, volatile solids and porosity. The sediments from the
main channel exhibited characteristics of a high velocity regime and
those of the north channel, a low velocity regime. / Graduation date: 1975
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A mtDNA study of aspects of the recent evolutionary history and phylogeographic structure of selected teleosts in coastal environments of south-western Australiarhoddell@central.murdoch.edu.au, Richard James Hoddell January 2003 (has links)
At present, there is a general lack of information regarding the spatial genetic
architecture and genetic diversity of estuarine and coastal freshwater fish in
Australia or about the interacting intrinsic, extrinsic and historical influences
responsible for sculpting these patterns. This thesis represented the first
investigation of the phylogeographic structure and recent evolutionary histories
of teleost fishes from the coastal and estuarine environments of south-western
Australia, using the resolution afforded by mtDNA sequence data. Available
evidence indicated that, to different degrees, these species have limited
potential for dispersal amongst local assemblages from different water bodies.
As this theoretically reduces the confounding effects of recent gene flow on
extant genetic structure, these fishes were well suited to studying the
influences of historical factors. Historical influences were expected to be
particularly profound, given that these coastal environments underwent
massive modifications during Late Quaternary eustatic fluctuations.
The thesis consists of four major components, which explored different
aspects of interspecific and intraspecific phylogeny and p hylogeograp hy of
three teleost species, based on mtDNA control region and cytochrome b
fragments. First, the relationship between the endemic, 'strictly estuarine'
Leptatherina wallacei (Atherinidae) and the more widespread, 'estuarine &
marine' 6. presbyteroides was examined, with a view to establishing whether
6. wallacei represents a monophyletic or polyphyletic lineage and whether this
species was derived recently (i.e. in Holocene estuaries). Second, the
phylogeographic structure and genetic diversity of L. wallacei were investigated and compared with data from L. presbyteroides, with a view to
using this information to interpret the recent evolutionary histories of each
congener. Third, the divergence between assemblages of L. wallacei
inhabiting two isolated coastal lakes was used to estimate a maximal
substitution rate for the control region, which was then used to infer general
time frames for the divergence between the two Leptatherina species and
between the major phylogeographic partitions within each species. Fourth,
investigations were initiated into phylogeographic patterns and levels of
genetic diversity within and among assemblages of Pseudogobius olorum
(Gobiidae) from several coastal lakes and an estuary.
Phylogenetic analyses indicated that the two Leptatherina species were
characterised by exclusive and reciprocally-monophyletic lineages of
haplotypes from both mtDNA regions, supporting the monophyletic origins of
L. wallacei. Both 6. wallacei and 6. presbyteroides exhibited high levels of
genetic diversity and extensive overall subdivision (e.g. Qsr = 0.691 & 0.644
respectively for control region data). There was a profound phylogeographic
break in both species between all conspecific assemblages from the lower
west coast (LWC phylogroup) and all those from the south coast (SC
phylogroup), which suggested the influences of shared extrinsic and/or
historical factors. There was limited genetic structuring within the two major
phylogroups of either Leptatherina species, apparently reflecting recent
connectivity amongst local assemblages, with subsequent fragmentation and
insufficient time for lineage sorting. However, two major phylogeographic
breaks distinguished monophyletic control region phylogroups of L. wallacei from the isolated coastal Lake Clifton and Lake Walyungup, consistent with
their independent evolution following lacustrine entrapment during the
Holocene.
The divergence between these two isolated lacustrine assemblages of
Leptatherina wallaceiformed the basis for an estimate of the maximal
substitution rate of the control region. While these data were unable to
provide a precise estimate of the actual rate of molecular evolution, all the
evidence suggested that it was proceeding very rapidly. The maximal rate
estimate of 172.3% lineage-' MY-' was among the fastest ever reported.
Based on this rate, the two Leptatherina species diverged at least 1 SKya, thus
rejecting a Holocene origin for L. wallacei. The divergence between the LWC
and SC phylogroups of L. wallacei has been ongoing for at least GKya, while
the equivalent divergence in L. presbyteroides has been ongoing for at least
11 Kya. As the time frames of these divergences were consistent with periods
of massive environmental modifications associated with the end-Pleistocene
fall in sea level and the HMT, it was likely that these factors have played
important roles in sculpting the species' divergence and intra-specific genetic
structure. Although useful in temporally scaling genetic divergences within
and between the two Leptatherina species, wider application of this rate
estimate to questions regarding other taxa was limited. For example, evident
rate heterogeneity between the genera precluded its use with even the
relatively closely-related atherinid Atherinosoma elongafa.
Phylogeographic analyses identified high levels of genetic diversity and
extensive genetic subdivision (e.g. st = 0.652 for control region) amongst an
estuarine and several lacustrine assemblages of Pseudogobius olorum,
although phylogeographic structure was shallower than in either Leptatherina
species. There was increased divergence between three assemblages from
the lower west coast and two from the south coast, consistent with the
profound break evident in the Leptatherina. One lacustrine assemblage
appeared to represent a distinct lineage and a preliminary maximal rate
estimate (~61.4% lineage-1 MY-1) was calculated based on the minimum
divergence of this assemblage from its nearest conspecifics. Although slower
than the rate calculated for L. wallacei, this was still high for teleost fishes.
Overall, this study indicated that historical environmental factors, especially
those related to Quaternary eustatic changes, have played important roles in
sculpting the phylogeography and evolution of three teleost species from
south-western Australia. Moreover, as these species have differential
dependencies on estuarine environments (is. 'strictly estuarine' vs 'estuarine
& marine') and represented two different taxonomic groups (i.e. Atherinoidei &
Gobioidei), historical environmental factors may have exerted similar
influences on other coastal species in the region.
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Home range dynamics of spotted grunter, pomadasys commersonnii, in a South African intermittently open estuary /O'Connell, Bronwyn Anne. January 2008 (has links)
Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2008.
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Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa /Allan, Elizabeth Louise. January 2007 (has links)
Thesis (M.Sc. (Zoology & Entomology)) - Rhodes University, 2008.
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An assessment of suspended sediment in Weeks Bay Reserve, Baldwin County, Alabama, using geospatial modeling and field sampling methodsThomason, Jamie Cindi, January 2008 (has links)
Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.
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Parameter estimation in tidally influenced numerical models determination of an appropriate objective function /Tate, Jennifer N. January 2008 (has links)
Thesis (M.S.)--Mississippi State University. Department of Civil and Environmental Engineering. / Title from title screen. Includes bibliographical references.
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