The biological integrity of aquatic ecosystems has become threatened by the effects of high nutrient loads, inorganic and organic chemicals. The effect of these xenobiotics needs to be investigated by the application of biotests in whole effluent toxicity testing and biomarkers in active biomonitoring. Whole effluent toxicity (WET) testing determines the toxicity/effect of whole effluent on aquatic organisms. Sub-lethal effects can be determined by analysing the levels of subcellular/physiological indicators/enzymes in aquatic organisms exposed to in situ conditions. The procedure used for in situ assessments was active biomonitoring (ABM). The aim of this study was to assess the instream health of a known contaminated system (Rietvlei Wetland System, Gauteng, South Africa) using WET and ABM methodologies. Three sites in the Rietvlei Wetland System were selected and sampling was undertaken during high flow (April 2003) and low flow (August 2003) periods. The ABM sampling protocol involved the deployment of aquatic molluscs (Melanoides tuberculata) and fish (Oreochromis mossambicus) for a period of four weeks at the sites. Following the four week exposure period the organisms were transported back to the laboratory and the following biomarkers were assessed: ethoxyresorufin o-deethylase (EROD), acetylcholine esterase (AChE) and metallothione (MT). Water samples were also collected for WET testing during the low flow period, since this was the only period where mortality was observed in the ABM organisms. Standard WET protocols were used to assess the toxicity of the water from the three sites. These protocols were: 96 h Poecilia reticulata lethality test, 48 h Daphnia pulex lethality test and 72 h Selenastrum capricorutum growth inhibition test. In addition the same biomarker analyses that were done on the ABM organisms were carried out on WET exposed D. pulex and P. reticulata. The WET testing and ABM indicated highest toxicity at Sites 1 and 3. Algal growth inhibition test showed highest stimulation of algal growth at Site 2 and inhibition at Site 3. Sites 1 and 2 showed signs of contamination by organophosphates and carbamates due to elevated AChE and reduced EROD. However there were no significant differences in AChE activity between fish tested in the 96h toxicity test and those used in ABM. Very low AChE activity was recorded in D. pulex. Snails also had lower AChE activity when compared to the exposed fish species. Metallothionein content was higher in field-exposed fish than those used in WET, however both assessment protocols indicated that Site 3 was affected the greatest by metals. Snails exhibited higher MT content than fish and D. pulex showed no MT activity. There were no significant differences in MT content between the sites. Acetylcholine esterase appears to be a relevant means of investigating biological effects of many neurotoxic contaminants on aquatic habitats and trophic levels. Metallothionein content is a good indicator of toxicity due to heavy metals for active biomonitoring as well as the WET test. Ethoxyresorufin-O-deethylase is a more difficult biomarker to work with since it shows no differences in activity between control and exposed organisms. The EROD assay does not detect very low levels of EROD induction. Acetylecholinesterase and MT are the recommended biomarker assays for the detection of sublethal responses in the WET laboratory toxicity test. The AChE activities and MT exhibit comparable results in both ABM and WET assessment protocols. In future studies WET testing needs to be complimented with a suite biomarker analyses to determine the type of pollutants in a system and sufficiently describe the pollution status of a system. / Dr. V. Wepener

The biological integrity of aquatic ecosystems has become threatened by the effects of eutrophication, acidification as well as increased organic and inorganic chemical loads. It is necessary to identify the effects of xenobiotics before the onset of death in an exposed organism or deteriorating changes at population level. Biochemical and physiological indicators such as enzymes and stress proteins could be used as a valuable tool for detecting chemical exposure and evaluating their effects on aquatic organisms. The use of selected enzymes in different organs/tissue was evaluated as possible indicators of stress in fish, in their natural environment as well as under controlled laboratory conditions. During the field assessment of enzymes it was found that selected enzymes could be used as indicators of pollution between high flow and low flow seasons when pollution conditions are more concentrated. However, the various enzymes are non-specific indicators of stress and could therefore, be influenced by environmental changes, handling and struggling in the nets. Exposure to sub-lethal and lethal iron concentrations caused significant differences between the levels of enzymes in exposed and control Oreochromis mossambicus, indicating that the use of enzymes under controlled laboratory conditions, toxicity testing is more effective. The demand for sensitive and specific biological assays needed to be satisfied. Heat shock induction after sub-lethal iron exposure was investigated in the reproductive organs/gonads of O. mossambicus. After the refinement of the standard protocol for the assessment of Heat shock protein 70 (HSP 70) it was found that HSP 70 induction are more intense in male individuals than in female individuals. Higher protein concentrations were also found in female reproduction organs possibly due to the presence of vitellogenin. The use of HSP 70 as a diagnostic tool to monitor cell damage after sub-lethal iron exposure was less effective due to several factors including (1) the selection of the target organ, (2) the different stages of sexual development between individuals, (3) the selection of the exposure toxicant and (4) the presence of another stress protein in female gonads. Most researchers use the Atomic Absorption Spectrophotometry (AAS) method to determine the metal content in fish organs/tissues. During this research it was attempted to find a more time effective, rapid, less hazardous and more economic method to determine metal content in fish organs/tissues. After comparison between the AAS method and Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) microanalyses the AAS method was found to be the most effective method to determine metal content in fish organs/tissues. SEM-EDX microanalyses techniques need more refined sample preparation, calibration and operation skills. / Prof. J.H.J Van Vuren

Philosophiae Doctor - PhD / Results from this study enables a better understanding of groundwater surface water interactions in the TMG, particularly regarding aquatic ecosystems. It has also highlighted the necessity to do proper impact assessments before proceeding with bulk abstraction from this important aquifer. The results also demonstrated the importance of differentiating between real groundwater and non-groundwater discharge contributions to surface hydrology and where these interface areas are located. / South Africa

The trophodynamic implications of reduced freshwater inflow on the zooplankton of eastern Cape estuaries was investigated by a comparison of the community composition and standing stocks, grazing rates and food resources of zooplankton in two systems, the Kariega and the Great Fish estuaries, which are subject to contrasting freshwater inflow. The climate of South Africa is semi-arid, and the low rainfall, coupled with high evaporative loss, result in the region having one of the lowest conversions of rainfall to run-off in the world. In addition, many of the major rivers are extensively impounded, consequently, estuaries often experience prolonged periods of zero or reduced freshwater inflow. The amount of freshwater available for estuarine management in the future is expected to decline as the demand for domestic, agricultural and industrial use increases. The influence of climate, tidal amplitude and wave action are essentially constant, consequently, the individual characteristics of an estuary are determined largely by the indirect influences of catchment size and regulation. Estuaries along the eastern Cape coast range from negative hypersaline systems, to positive systems in which a salinity gradient is well established. The Kariega estuary is a homogeneous marine estuary as a result of minimal freshwater inflow, whereas the Great Fish estuary receives sustained freshwater inflow and is partially-stratified. The quality and quantity of particulate food resources for suspension-feeders depended to a large extent on the allochthonous import of material associated with freshwater inflow. Nutrients, rather than light penetration of the watercolumn are the major factor limiting phytoplankton standing stocks. In the Kariega estuary, phytoplankton standing stocks were low (up to 1.0 μg l⁻¹) and the estuary is classified as oligotrophic. Correlation analyses indicated that lower quality detritus, originating from fringing macrophytes, may contribute substantially to suspended particulate organic material. Phytoplankton food resources were considerably higher in the Great Fish estuary (up to 21.8 μg ⁻¹) which is classified as mesotrophic/eutrophic, and correlation analyses indicated that phytoplankton comprised the dominant fraction of the particulate organic material. Although this suggested that the organic material was of a higher quality, the seston was "masked" by a higher suspended inorganic load. Consequently, the organic fraction comprised between 13 and 22% of total particulate material in the Great Fish estuary, compared with between 20 and 39% in the Kariega estuary. Food resources demonstrated a fairly uniform distribution along the length of the Kariega estuary and exhibited a slight seasonal increase during warmer months. By contrast, the point source influence of freshwater inflow resulted in a spatial gradient of food resources in the Great Fish estuary with higher values recorded towards the upper reaches. There was evidence that higher concentrations of particulate material in the upper reaches are also a consequence of hydrodynamic trapping. There was no marked seasonal pattern in the availability of food resources which were generally elevated in response to sporadic pulses of freshwater inflow. Tidal currents were responsible for elevating suspended food resources by re-suspension of material from the sediments. This effect was probably of greater importance in the Kariega estuary where food resources were generally limiting. In the Kariega estuary, the zooplankton community was dominated by calanoid copepods of the genera Acartia and Pseudodiaptomus. However, in the Great Fish estuary, the community was dominated by the mysid Mesopodopsis siabberi, and the calanoid P. hessei. Community biomass generally reflected the trophic status of the estuary. The mean seasonal biomass recorded in the Kariega estuary was 38 mg m⁻³ compared with 1597 mg m⁻³ in the Great Fish estuary. Greater spatial variability in community biomass was evident in the Great Fish estuary, partly in response to the food resource gradient, but also due to the inability of the mysid shrimps, which dominated the community biomass, to penetrate the lower salinity water of the upper reaches. Zooplankton in the Kariega estuary demonstrated a seasonal pattern of abundance whereas in the Great Fish estuary, community biomass was elevated in response to sporadic pulses of freshwater inflow. Grazing rates, measured in situ using a modified Gliwicz-Haney chamber, indicated that the zooplankton communities were capable of "clearing" substantial proportions of the watercolumn at certain times of the year. The pattern of grazing pressure over a diel cycle was examined in relation to the diel vertical migration movements of the zooplankton. Higher nighttime grazing rates were generally associated with the greater abundance of zooplankton resulting from the movement of zooplankton into the watercolumn after dusk, and their return to the sediments at dawn. Seasonal estimates of diel grazing pressure, extrapolated from daytime and nighttime feeding rates, indicated that the zooplankton "cleared" up to 40% of the watercolumn in a day in the Kariega estuary, and up to 120% d⁻¹ in the Great Fish estuary. However, values of around 25% d⁻¹ in the Kariega estuary, and 50 to 80% d⁻¹ in the Great Fish estuary, were not uncommon. Multiple regression analyses were used in an attempt to explain the influence of environmental factors on the variation in in situ grazing rates. These attempts were largely unsuccessful and the possible reasons, as well as recommended improvements to the methods used, are discussed. Seston concentration in the estuaries was highly variable as a result of the effects of tidal re-suspension and freshwater inflow. Consequently, further laboratory-based experiments were carried out to examine the influence of seston concentration on the filtration rates of the dominant calanoid copepods. Results indicated that some of the unexplained variability in the community filtration rates may be attributed to differences in species-specific response to changes in seston concentration.

<p> In an effort to highlight best practices in the management of wild eastern brook trout, an examination was performed of brook trout management plans and stocking habits for seven randomly selected states within the species native range. Additionally, surveys were distributed to these state&rsquo;s members of Trout Unlimited (TU) in an effort to understand angler motivations, awareness of and attitudes about their state&rsquo;s stocking practices and protection of wild brook trout fisheries. The states selected were within the eastern brook trout&rsquo;s native range and included West Virginia, Tennessee, Pennsylvania, Maine, Vermont, Maryland, and North Carolina. While each state differs in its efforts to either restore or protect existing wild brook trout populations, all seven states continue to stock hatchery-raised brook trout to maintain a viable sport fishery. However, regarding stocking dynamics, each state has unique policies regarding where the stocking occurs in relation to how these efforts potentially impacts wild populations. Survey results indicated that, while the majority of TU members expressed a strong understanding of their states stocking practices, they were still strongly interested in gaining additional information, indicating a need for more transparency regarding stocking habits and practices. Furthermore, survey results indicated that a large percentage of TU members still enjoy fishing for popular, nonnative, sport fish such as bass and brown trout. Additionally, support for policies protecting wild brook trout diminished as opportunities for catching larger fish diminished along with the removal of popular, nonnative sport fish. Overall, results indicated a need for fisheries managers to work more closely with cold-water conservation organizations, such as Trout Unlimited, and their members to assist in the crafting of policies that benefit both the sport fishing industry and wild brook trout populations.</p>

Rising temperatures associated with climate change will alter the fundamental physiological processes of most ectothermic species. Drastic changes in catabolic and anabolic reaction rates exert strong effects on growth, reproduction, and consumption rates that cascade up through all levels of the biological hierarchy. This dissertation determined how climate warming might alter the important relationship between plants and insect herbivores, as mediated through changes in herbivore physiology. Consumption and fitness increased with temperature for almost all consumers. However, all consumers also exhibited a critical temperature, beyond which consumption declined rapidly through metabolism continued to increase. This mismatch in metabolic demands and energy intake reduced consumer fitness at high temperatures. Furthermore, increased metabolic nitrogen demand can induce nitrogen limitation in insect herbivores at high temperatures. These basic physiological changes can modify the way herbivores interact with plants in a number of ways. For example, the Japanese beetle, Popillia japonica, altered its feeding behavior on numerous host plant species, depending on host plant quality. Unfortunately, the effects of temperature on plant-herbivore interactions will be difficult to predict, as there was no predictable relationship between consumption and temperature across numerous plant-herbivore pairs. Finally, rising temperatures disrupt insect herbivore control of plant fitness, thereby altering one of the most important components of plant-herbivore interactions. Thus, climate change will fundamentally change the nature of plant-herbivore interactions in the future.

Estuaries are dynamic on many spatial and temporal scales. Distinguishing effects of unpredictable events from cyclical patterns can be challenging but important to predict the influence of press and pulse drivers in the face of climate change. Diatom assemblages respond rapidly to changing environmental conditions and characterize change on multiple time scales. The goals of this research were to 1) characterize diatom assemblages in the Charlotte Harbor watershed, their relationships with water quality parameters, and how they change in response to climate; and 2) use assemblages in sediment cores to interpret past climate changes and tropical cyclone activity. Diatom assemblages had strong relationships with salinity and nutrient concentrations, and a quantitative tool was developed to reconstruct past values of these parameters. Assemblages were stable between the wet and dry seasons, and were more similar to each other than to assemblages found following a tropical cyclone. Diatom assemblages following the storm showed a decrease in dispersion among sites, a pattern that was consistent on different spatial scales but may depend on hydrological management regimes. Analysis of sediment cores from two southwest Florida estuaries showed that locally-developed diatom inference models can be applied with caution on regional scales. Large-scale climate changes were suggested by environmental reconstructions in both estuaries, but with slightly different temporal pacing. Estimates of salinity and nutrient concentrations suggested that major hydrological patterns changed at approximately 5.5 and 3 kyrs BP. A highly temporally-resolved sediment core from Charlotte Harbor provided evidence for past changes that correspond with known climate records. Diatom assemblages had significant relationships with the three-year average index values of the Atlantic Multidecadal Oscillation and the El Niño Southern Oscillation. Assemblages that predicted low salinity and high total phosphorus also had the lowest dispersion and corresponded with some major storms in the known record, which together may provide a proxy for evidence of severe storms in the paleoecological record.

This study investigated the response of macrophytes to physico-chemical factors in seven South African estuaries and showed that dominant salt marsh species that occur in different estuaries respond to the same environmental factors. The most important variables influencing distribution were elevation, water level, sediment- and groundwater electrical conductivity and depth to the water table. In permanently open estuaries (Kromme and Olifants) transect surveys identified three distinct vegetation zones i.e. submerged macrophytes, intertidal salt marsh and supratidal salt marsh. In the Kromme Estuary intertidal salt marsh (81.2 ha) covered extensive areas, whereas supratidal (143 ha) and floodplain (797.1 ha) salt marsh were dominant in the Olifants Estuary. Transect surveys identified four distinct vegetation zones (submerged macrophytes, intertidal salt marsh, supratidal salt marsh and reeds and sedges) in the temporarily open/closed estuaries (Mngazi, Great Brak, East Kleinemonde and Seekoei estuaries), although all zones did not occur in all of the estuaries sampled. In the Mngazi Estuary reeds and sedges (1.09 ha) covered extensive areas (no submerged or salt marsh vegetation was present), whereas salt marsh (Great Brak 24.45 ha, East Kleinemonde 17.44 ha and Seekoei 12.9 ha) vegetation was dominant in the other estuaries. Despite the geographic differences, environmental factors influencing macrophyte distribution were similar in all estuaries. Canonical Correspondence Analysis showed that vegetation distribution was significantly affected by elevation, groundwater and sediment electrical conductivity and depth to groundwater. Supratidal species were associated with a greater depth to groundwater (1.2 ± 0.04 m; n = 153) compared to intertidal species (0.5 ± 0.01 m; n = 361). Correlation analysis showed that water level and rainfall were correlated with groundwater electrical conductivity in the lower and upper intertidal zones for all the estuaries sampled. These data indicate the influence of the estuary channel on the physico-chemical conditions of the salt marsh. Low rainfall (16 ± 3.3 mm per annum) in the Olifants Estuary (30-100 mS cm-1) and lack of freshwater flooding in the Kromme Estuary (42-115 mS cm-1) have resulted in high sediment electrical conductivity by comparison with the other estuaries sampled. In the Orange River Estuary approximately 70 ha of salt marsh have been lost through the building of a causeway and flood control levees. Even though salt marsh vegetation can tolerate hypersaline sediments by using the less saline water table, the groundwater at the Orange River Estuary was too saline (avg. of 90.3 ± 6.55 mS cm-1, n = 38) to be of use to the dominant floodplain species, Sarcocornia pillansii. Freshwater inflow to estuaries is important in maintaining longitudinal salinity gradients and reducing hypersaline conditions. In the Olifants Estuary and the Orange River Estuary where supratidal salt marsh is dominant, freshwater inflow is important in raising the water level and maintaining the depth to groundwater and salinity. Lack of freshwater inflow to the Kromme Estuary has highlighted the importance of rainfall in maintaining sediment salinity within acceptable ranges for the salt marsh. Macrophytes are relatively good indicators of physico-chemical factors in estuaries. From an understanding of the response of specific species to environmental variables, ecological water requirements can be set and sensitive areas can be rehabilitated.

Studies on morphological variation are important as it can depict the relationship with environmental factors clearly and convey an understanding of the manner, mechanism and factors influencing plant adaptation and evolution. Although many studies have been conducted on South African salt marsh plant physiology and phytosociology there are at present very few morphological studies on estuarine plants. The aim of this study was to compare the morphological variation of estuarine macrophytes in three different estuary types in the warm temperate biogeographic zone of South Africa and to compare characters used in the taxonomic descriptions of species with those measured in the field. Permanently open estuaries investigated were Ngqusi (WC), Kowie (KW) and Swartkops (SW) estuaries. The Knysna Estuary (KN) was the estuarine bay investigated and the temporarily open/ closed estuaries (TOCEs) were the East Kleinemonde (EK) and Great Brak (GB) estuaries. Macrophytes were morphologically different across different estuary types. This suggests that there were different factors operating between these estuary types that would directly influence the morphology of species. The variation of plant height with different estuary types can be attributed to the fact that smaller salt marshes also have smaller habitat ranges compared to larger ones. The variation in morphological characteristics such as plant height can also be attributed to biogeographical range. Most morphological characteristics measured in the field fall within previously published ranges, and so these characters are useful in delimiting species. There were significant relationships between phenotypic variables and multivariate environmental variables. The most important of these variables were soil electrical conductivity, soil organic content and soil water content. Specifically, plant height increased with water content and decreased with salinity, flower stalk length had strong significant positive correlations with moisture content, organic content and pH while there were strong significant correlations with redox potential and electrical conductivity. Salt marshes are considered ideal for studying variation of species due to the explicit environmental gradients and plants occurring in salt marshes are halophytes that exhibit a range of morphological traits that allows for growth and reproduction under the stressful and extreme conditions. Considering recent climate change predictions and the consequent effects on South African estuaries this study provides significant information with regard to the response of species to a changing environment. The study was also aimed at updating the existing botanical database for South African estuaries in terms of species occurrence in South African estuaries, taxonomic name changes of existing species, new species, common names and habitats. Species diversity indices were also calculated for different estuaries, estuary types and biogeographic zones and diagnostic descriptions of the dominant salt marsh species were developed. The objective of this was that these data should provide baseline information for determining habitat richness and plant species diversity of South African estuaries which in turn should be used in determining priority estuaries for conservation and management. The identification key, developed using the DELTA software, would also aid researchers, managers and laymen in identifying salt marsh species. Results showed that the total number of macrophyte species, including intraspecific taxa and macroalgae, was 242 in 53 estuaries that were updated . There was an increase in the number of taxa recorded in the database primarily due to 1) research focus and full taxonomic surveys on larger estuaries and the big research projects has led to the identification of more species, 2) the addition of species that are not characteristically known as estuarine species, 3) the addition of 50 macroalgal taxa and 4) minor changes due to taxonomic revisions of species and the addition of newly described species. The Shannon diversity index showed that greater species diversity was found in the Berg (Groot) Estuary (4.220) and the Uilkraals Estuary (4.025). The cool temperate bioregion was the most diverse in the number of taxa (58) with the highest Shannon index (4.736). Permanently open estuaries were the most diverse in the number of unique taxa (56) with the highest Shannon index (4.867). Estuarine managers need to be aware of the species diversity in different estuarine types as well as the associated impacts on them. Conservation planning must therefore include species. Diagnostic features of INTKEY indicated that all 57 taxa were distinguishable from each other. Contrary to expectations plant height and not floral morphology was the best diagnostic characteristic. Ecological information such as the estuarine habitat, where different life forms occur, was important in delimiting species.

Accumulation and toxicity of cadmium, lead and thallium in duckweed (Lemna minor L.) The toxicity and accumulation of lead, cadmium and thallium in the aquatic plant Lemna minor was investigated, using a modification of the Organisation for Economic Co-operation and Development (OECD) standard growth inhibition test. Plants were cultured in modified Swedish Institute Standard (SIS) at pH 6.5±0.5 under 85 µmol m-2 S-1 at 25°C and exposed to a wide range of lead, cadmium, and thallium concentrations from environmentally realistic to very high concentrations (0.001, 0.01,0.1, 1, 10, 100, 1000 and 10 000 µmol L-1) for seven days. Various physico-biochemical endpoints were measured after seven days of exposure. The concentrations of dissolved lead, cadmium, and thallium remaining in the residual solutions, and accumulation of lead, cadmium and thallium in fronds and roots were assessed using Inductively Couple Plasma – Mass Spectroscopy (ICP-MS). Over the exposure duration, lead, cadmium, and thallium concentrations in solution decreased rapidly and chlorosis was observed in fronds exposed to the three highest lead, cadmium, and thallium concentrations. After seven days of exposure, there were significant decreases in the relative growth rate (RGR), relative frond area (RFA), pigment content (chlorophyll a, b and total carotenoid) and activity of photosystem II (Fv/Fm) at concentrations of 0.1, 1, 10, 100, 1000 and 10 000 µmol L-1Pb, 10, 100, 1000 and 10 000 µmol L-1cd, 0.01,0.1, 1, 10, 100, 1000 and 10 000 µmol L-1TI. However, our results suggested that root elongation based on relative growth rate of L. minor will be an optimal and relevant endpoint in compare to other endpoints. As expected, results demonstrated that root elongation was concluded that root length was most predictive of a dose response model compared to the rest of growth endpoints and physiological and biochemical endpoints when assessing toxicity of lead, cadmium and thallium using L. minor. Toxicity testing for the floating macrophytes should include root elongation measurement which alone will be sufficient to meet sensitivity and variability requirements for toxicity testing. Cellular concentrations of lead, cadmium, and thallium were higher in roots than fronds, whereas more lead, cadmium, and thallium was adsorbed to the extracellular matrix of fronds than roots. The bio - concentration factor (BCF; i.e. lead concentration in plant tissue at day seven relative to residual lead concentration in the growth medium at day seven) indicates that L. minor is a good accumulator of lead, cadmium, and thallium particularly at lower concentration, but the physiological data shows that these metals toxic at concentrations that can be encountered in wastewater treatment facilities. The translocation factor (TF) value was found to be less than 1. Though, lead, cadmium and Thallium was mostly stored in roots, only minor amounts of lead, cadmium and thallium were trans located to fronds.