Includes bibliographical references. / Runoff and spray-drift-related pesticide input are important sources of non pointsource pesticide pollution in surface waters but few studies have directly compared these routes in a risk assessment scenario. Accordingly a risk assessment approach was instituted to determine differences between runoff and spray-drift based on exposure, effect and mitigation. An exposure assessment using predictive modelling that was validated by fieldbased sampling was used to compare relative pesticide inputs associated with runoff and spray-drift at the catchment level.

Includes abstract. / Includes bibliographical references (p. 119-132). / Cooperative breeding occurs when more than two individuals help to raise offspring that are not their own, and has been the focus of empirical and theoretical research for over forty years. Of central importance to this work are the fitness costs and benefits of helping, and the factors limiting the reproduction of helpers. To understand these, the genetic relationship between individuals must be known. In this thesis, I use genetic and observational data to explore kinship between individuals in groups of wild Southern Pied Babblers Turdoides bicolor.

The present thesis is aimed principally at the population dynamics and biological interactions of Patella species. Most of the work is based on all eleven of the South African species, although volume of work necessitated the omission of the less common species from parts of the work. The research has been centred around the juveniles and adults, although it is realised that larval biology is logically the next field which needs to be explored. The thesis is presented as a series of separate papers, the first in published form and the remainder in manuscript, and is concluded by a resume. A single supporting paper is also included. The entire thesis is based on original work by the candidate, except where acknowledged in the text. The more important conclusions are summarised at the end of each section.

The ungulates include some of the largest land animals and, in consequence, they cannot avoid climatic stress as do small mammals. A great deal of information concerning the physiology of thermoregulation in domestic ungulates is available but relatively little is known about thermoregulation in wild ungulate species. Moreover, in the past, thermoregulation studies were conducted mainly in climatic chambers and consequently the effects of certain important environmental parameters were ignored. The pelages of mammals provide a barrier between the animal and its environment, and the physical characteristics of the pelage can feature prominently in the thermal adaptations of animals to specific climatic zones. Scholander et at. (1950), for example, have demonstrated the value of a thick pelage in arctic mammals. The thick pelage provides good protection against heat loss and thus extends the ambient temperature limits which the animal can tolerate without the need to increase metabolic heat production. Schmidt-Nielsen (1959) has shown that a thick pelage can also be advantageous to an animal in a desert environment. The thick, dorsal fur in the camel provides protection against excessive heat gain from the environment and thereby assists with water conservation. The colour of a mammal's pelage is also involved in the thermal adaptations to specific environmental conditions.

Includes bibliographical references. / An investigation into the decline of blue wildebeest numbers at Etosha National Park was made during the period 1974-1978. Aspects of wildebeest ecology which were investigated were activity patterns, energy and protein budgets, nutrition, nutritional status, disease and parasites, predators and scavengers, and population structure. Activity patterns in the free-ranging population were measured over a period of one year, using marked individuals and by scanning herds. The population spent, on average, 53% of its time resting, 33% grazing, 12% in movement, 1,5% in overt social encounter sand less than 0,5% drinking and suckling. Photoperiod and temperature were the primary correlates of activity/inactivity and a linear relationship existed between increasing temperature and increasing inactivity. The activity data were used to calculate an energy budget for maintenance and activity in the population, while energy demand for growth, gestation, lactation and homeothermy were estimated by formulae based on domestic ruminants. Mean increment over resting metabolic rate for free existence in wildebeest approximated 2,0. This represented a mean annual energy demand of 8,5 gigajoules per wildebeest. Similarly, a protein budget was estimated for the population on a seasonal basis.

Includes bibliographical references (p. 463-490). / In this study, tolerance limits for a number of environmental factors, taken both singly and in combination, have been determined in the laboratory for aquatic nymphs of two mayflies, Baetis harrisoni Barnard 1932 and Choroterpes (Euthraulus) bugandensis (Kimmins 1956). These limits have been examined in the light of available information on the ecology of the nymphs, in order to see to what extent the distribution of each species might be limited by intolerable environmental conditions. Baetis nymphs were found to be dislodged from rocks in the stream flow by current speeds in excess of 0.5-0.6 m/sec actually impinging on the nymphs and estimated 0.1 cm from the substratum surface. Choroterpes nymphs were dislodged by current speeds in excess of 0.3-0.4 m/sec estimated 0.1 cm from the substratum surface. Possible effects of flooding on nymphal populations of each species have been discussed in relation to the behaviour and physical habitat of the nymphs. Baetis nymphs live on rocks exposed to the current and numbers of them are washed away even in moderate floods. Choroterpes nymphs live on the under surfaces of rocks and numbers of them are only washed away by floods sufficiently strong to roll these rocks.

Bibliography: leaves 249-279. / This thesis focusses on two approaches to determining Instream Flow Requirements (IFR) for regulated rivers, specifically in the sub-tropical eastern region of South Afiica using a flow-sensitive fish species, the pennant-tailed catlett 07iloglanis anoterus. In response to the diminishing and altered flow regimes of rivers, and the ecological consequences, a range of methodologies has evolved that attempt to quantify IFRs for rivers. One group of methods that attempts to do this are known as habitat-assessment approaches. They focus specifically on understanding how changes in river flow affect the quantity of physical instream habitat. The most widely used of these is the Instream Flow Incremental Methodology (lAM) and it's associated computer packages, PHABSIM II. More recently, South Africa has also turned its attention of ways to defining IFRs. Given lAM's prominence internationally, it was considered as one potential methodology. Nonetheless, its applicability to local conditions required testing. At the same time, the easterly-flowing rivers were under increasing development pressure, providing a particular immediacy to find appropriate means to define IFRs. Thus, my research was designed to assess the downstream effects of the Injaka Dam on the physical habitat of a flow-sensitive fish species of the Marite River. Specifically, it aimed to test the local applicability of lAM, based on the microhabitat requirements of C anoterus, and to explore an alternative approach if it were found to be unsuitable. Microhabitat is described on the basis of three hydraulic variables: depth, velocity and Channel Index (substratum and cover).

Includes bibliographical references (p. 104-116). / Ammonia is the major end-product of protein catabolism in abalone, and is excreted into the surrounding water. Build-up of ammonia in abalone aquaculture systems can reach high toxic levels and impact negatively on farming operations. Ammonia levels therefore have to be regulated. Accurate estimates of toxic un-ionized ammonia (FAN) from the total ammonia nitrogen (TAN) measured by photometer test kits is crucial as inaccuracies could result in major losses of abalone on the farms. The accuracy and applicability of two frequently used photometer test kits (the Nesslers method and the Palintest method) were compared. The calculated TAN concentrations were regressed against the prepared standard ammonia concentrations in seawater for both methods. The predicted slope (β = 1) if the methods were 100% accurate was compared to observed slopes using the Nesslers (β=0.8327) and Palintest (β = 0.7507) methods. Both these test kits underestimated the TAN concentrations, but the Nesslers method was more accurate. Nitrites and nitrates are toxic to abalone at much larger concentrations than ammonia and exist at low concentrations in natural systems, therefore the sensitivity of their tests was not as important. Nitrites and nitrates were monitored using the Ferrous sulphate method and the Cadmium reduction method, respectively.

Includes bibliographical references (leaves 139-161). / In their natural environment the diatoms (mixers) are exposed to fluctuations in incident irradiance due to vertical displacements in the water column induced by turbulence whereas the dinoflagellates (migrators and layer-formers) tend to control their vertical positions. In these two groups of phytoplankton physiological acclimation to these fluctuations results in the variation of a number of measurable photosynthetic parameters and variables which can be evaluated in controlled laboratory experiments. The processes can be expressed in time scales from seconds to hours e.g. carbon to chlorophyll ratio changes over several hours. Photoacclimative responses in five species of dinoflagellates (Alexandrium catenella, Protoceratium reticulatum, Prorocentrum micans, Prorocentrum triestinum, Gymnodinium zeta) and three diatom species (Chaetoceros sp., C. capense, C. cf. pendulus) were investigated with respect to parameters of P versus E curves (P*m, α* and Ek) and variability in chemical composition (C and N), photosynthetic capacity, pigment ratios, maximum quantum yield and chlorophyll to carbon ratio. These species were grown at irradiances of 33 (LL), 178 (ML) and 647 μmol quanta . m-2 . s-1 (HL) at a 12:12h day: night length at 17 ºC. The photosynthetic parameters, pigment concentration and Chl a-specific absorption were mostly affected by photoacclimational status. Species-specific differences were observed at the three different light levels in P versus E curves, pigment concentrations, absorption, carbon to chlorophyll a ratios and quantum yield. Photoprotective carotenoids (diadinoxanthin and diatoxanthin) were significantly different relative to Chl a in eight species of dinoflagellates and diatoms.

Bibliography: p. 131-143. / Isolated flight muscle mitochondria of Pachnoda sinuata, Decapotoma lunata, Trichostetha fascicularis, Lepithrix sp. and Camenta innocua prefer the oxidation of proline, pyruvate and α- glycerophosphate, while those of Locusta migratoria prefer the oxidation of palmitoyl-carnitine,pyruvate and α-glycerophosphate. Palmitoyl-carnitine cannot be oxidised directly by P. sinuata flight muscle mitochondria, while proline is oxidised at low rates in locust mitochondria. At low concentrations of proline, the respiration rate during co-oxidation of proline and pyruvate is additive, while at high proline concentrations it is equal to the respiration rates of sole proline oxidation. Flight muscles of P. sinuata and D. lunata were found to have high activities of the enzymes alanine aminotransferase and NAD-dependent malic enzyme which are involved in proline metabolism, while the activities of these enzymes were lower in locust flight muscles. The activity of 3-hydroxyacyl-CoA dehydrogenase, an enzyme used in fatty acid oxidation, is low in the flight muscles of P. sinuata and D. lunata, but high in locust flight muscles. Enzymes involved In carbohydrate breakdown (glyceraldehyde-3-phosphatedehydrogenase, glycogen phosphorylase) were found to have high activities in flight muscles of P. sinuata, D. lunata and L. migratoria. Two methods of tethered flight were investigated. One of these allowed the animals to produce lift. During lift generating flight, proline concentrations in haemolymph and flight muscles of P. sinuata decrease sharply with concomitant increases in alanine concentrations. During recovery after flight, proline concentrations increase while concentrations of alanine decrease. Haemolymph carbohydrate concentrations increase during the first seconds off light but decline consistently thereafter. During a subsequent rest period concentrations again increase. Glycogen concentration in the flight muscles decrease sharply in the first few seconds of flight, gradually declining thereafter. During subsequent recovery, flight muscle glycogen concentrations increase. Lipid haemolymph concentration increase only slightly during flight and rest thereafter. Two distinct metabolic phases were observed during lift generating flight.