Browsing by Author "Brown, Alec C"

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    Aspects of medical waste disposal in the Cape Peninsula
    (1996) Tolosana, Sandra; Ehrlich, Rodney I; Brown, Alec C
    Hazardous waste management practices at ten medical institutions in Cape Town were studied and tests undertaken to determine concentrations of specific chemicals and radioactivity in liquid effluent outflows, as well as emissions from incinerators. To investigate the sewage outflow for Chemical Oxygen Demand (COD), N, pH and heavy metals, a continuous sampler was installed at two hospitals and a Medical School. Samples were analysed by atomic absorption spectrometry for As, Hg, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and Fe. Mercury levels ranged from l-70μg l⁻¹, exceeding the Environmental Target Quality of 0.04μg l⁻¹, and the South African General Effluent Standard of 20μg l⁻¹ . All other heavy metals were below General Effluent Standard Limits. In addition, a sludge sample from the Athlone Wastewater Plant was tested for Hg, realising 6mg kg⁻¹ on a dry weight basis, which was within Department of Health (DOH) Guidelines of 10 mg kg⁻¹. Samples of incinerator bottom ash analysed for heavy metal content gave Hg concentrations of 1.1-4.0mg kg⁻¹, and Zn concentrations of 5.1-11.0g kg⁻¹. Incinerator ash was also analysed for radio-activity and substantial levels of ¹²⁵I (332-650 bq kg⁻¹ ), and Ga⁶⁷ (9186bq kg⁻¹) recorded, which exceeded the South African limits of 200bq kg⁻¹. In Cape Town, hospital incinerators are old, burn large amounts of plastics and produce toxic emissions. They are all situated in residential or inner-city areas, and even though there is legislation dealing with emissions and chemical waste, these laws are not being enforced. Based on the above results, an investigation was carried out to assess attitudes to and knowledge of hazardous waste in the ten institutions. One thousand questionnaires were administered to staff, and the data from the 80% response rate statistically analysed. Results suggest that there is an urgent need for an holistic approach to toxic waste management, encompassing enforceable legislation coupled with on-going educational programmes and strong support from top management and all levels of staff.
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    Aspects of pollution in False Bay, South Africa (with special reference to subtidal pollution)
    (1992) Rundgren, Carl David; Brown, Alec C
    False Bay is the largest (circa 1000km²) natural, coastal embayment on the South African coastline and is located between latitudes 34°04'S and 34°23'S and longitudes 18°26'E and 18°52'E at the southern tip of Africa, near Cape Town, South Africa. The semi-enclosed nature of the bay makes it unsuitable as a 'sink' for all the contaminated urban stormwater run-off and the greatly increased pollution loads entering the bay. All pollution point sources entering False Bay were identified and described, and some of these selected for detailed study, the emphasis being on the impact of some individual discharges on the subtidal macrofauna. The similar biotic characteristics of three subtidal study sites in the region of the Steenbras Water Treatment Plant discharge indicate that the general turbidity and lower salinity characteristics of eastern False Bay are more likely to be responsible for the impoverished diversity near the outfall rather than the aluminium content of the discharge. Toxicity experiments on the bivalves Choromytilus meridionalis, Mytilus galloprovincialis and Perna perna using alum and ferric sludge indicate that there are no significant short-term sub-lethal toxic effects on the rocky shore bivalves and that decreased salinities in the immediate region of the outfall (as a result of the freshwater stream input) may have a more deleterious effect. A study of eighteen subtidal sites in False Bay indicated that overall densities of subtidal macro plastic debris were low, but that there are some 'hot spots' where densities are relatively high viz., Kalk Bay, Strandfontein, Mnandi, Monwabisi and Gordon's Bay. Colonising of debris by benthic organisms does occur, mostly on white plastic. Most of the debris consisted of plastic packaging from local land-based sources, indicating that it originates from wind-blown litter left by beachgoers. The highest density at the Sunnycove Control Site occurred in January during the peak holiday season. A longer term (three years) study of the subtidal environment in the vicinity of the Marine Oil Refiners outfall pipe indicated that the lack of subtidal macro fauna is more likely due to the harsh environmental conditions (abrasion and smothering) rather than the pollution impact of the outfall. This is confirmed by the abundant, healthy and diverse community on the nearby wreck of the Clan Stuart (1917) which indicates a stable ecosystem. The complexity of False Bay - its unique topography, bathymetry, meteorology make it difficult to attain a true climatic or average circulation. This lack of a consistent conceptual overview of the False Bay physical circulation is a short-coming that needs to be urgently addressed if the dangers of pollution inputs are to be accurately assessed. An overall management policy for False Bay should be urgently formulated and an officially constituted body with legislative power is needed if holistic management of the bay is to be achieved and such a prime recreational asset preserved for future generations. Bibliography: pages 195-225.
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    Aspects of the sensitivity of juvenile Jasus lalandii and decapod excitable tissue to the water soluble fraction of crude oil
    (1983) Lipschitz, Steven Richard; Brown, Alec C
    1. A flow-through aquarium facility, for testing the toxicity of the water-soluble fraction (WSF) of crude oil is described. 2. The 24 hour median lethal concentration (LC50) of WSF of crude oil for 2 to 3 year old (30 - 45 mm cephalothorax length) juvenile Jasus lalandii ranged from 3,7 to 5,9 mg l⁻¹. 3. Behavioural experiments appear to provide a quick and convenient approach for estimating the relative toxicity of the WSF of crude oil. 4. The major effect of the WSF of crude oil on Jasus heart beat rate was bradycardia. Furthermore, the greater the initial exposure concentration the sooner the heart beat frequency decreased. 5. Exposure of Jasus muscle fibres to the WSF of crude oil resulted in a shift of the resting membrane potential of those fibres in a hyperpolarising direction. Preliminary investigations into the level of excitability of decapod neurons after exposure to the WSF, indicated a rapid increase, followed by a decrease in excitability, to a level below that of unexposed tissue. 6. Recommendations are made as to how the findings of this study could be applied to enhance the sensitivity of toxicity bioassays.
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    Biochemical indicators of the transportation stress of the South Africa abalone (perlemoen), Haliotis midae, Linn.
    (1999) Omolo, Samson Odira; Gade, Gerd; Cook, Peter; Brown, Alec C
    Abalone exposed to air incurred greater metabolic and structural stress in muscle than do abalone at rest. Since foot and shell adductor muscle texture and flavor affect economic values of H Midae, the investigation sought evidence of differences attributable to transport of the commercial South African abalone based on environmental and exercise inducement. Tauropine dehydrogenase from Haliotis. midae muscle exhibits its highest activity 53.85 X 13.56 U g-1 wet weight in shell adductor muscle. The activities of octopine dehyedrogenase, strombine dehydrogenase or alanopine dehydrogenase in adductor muscle were very low. Therefore, tauropine dehydrogenase was isolated from adductor muscles for enzymatic determination oftauropine. Tauropine dehydrogenase was purified 8.5-fold with 47% recovery.
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    A comparison between macrofaunal communities on mixed shores and rocky and sandy shores in False Bay
    (1999) Smith, Cameron Ewart; Brown, Alec C; Branch, George M
    The community structures of three shore types namely: "mixed shores" (those where rocky and sandy-shore habitats are intermixed), pure rocky shores and pure sandy beaches in False Bay, South Africa are compared in this study. Four habitats were identified - pure rock (unaffected by sand), mixed rock (rock affected by sand), mixed sand (sand between emergent rocks) and pure sand (beaches with no emergent rock) - representing a gradation from pure rock to pure sandy beaches. The specific aims of this study were to: (1) Sample quantitatively and describe macrofaunal communities on mixed shores in False Bay; (2) make direct comparisons among both the four types of habitats and three types of shores; and (3) test the hypothesis that sand inundation increases diversity at both habitat (a-diversity) and shore (diversity) level. The biological communities of mixed shores are described in terms of species composition, trophic organisation and zonation. Mixed-shore zonation patterns are different from those previously described for pure rocky shores in the region. The ability of Charomytilus meridiana/is and inability of patellid limpets and various algae, to withstand sand inundation are largely responsible for these differences.
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    The development of continuous automatic biological monitoring systems for water quality control
    (1982) Morgan, William Stephen Gilbert; Brown, Alec C
    During the past decade, South Africa has experienced an unprecendented degree of industrial expansion. Although this has enhanced the material wealth and personal comfort of all the nations' peoples, it has also produced an undesirable consequence - ever increasing pollution of the aquatic environment. Viable systems for continuously monitoring water quality are, therefore, of critical importance for the future management and use of our watersheds. The value of regional monitoring programs using physical and chemical measurements is already well established. The major difficulty with this type of monitoring system, however, arises in the analysis of the data and in making evaluations of a complex ecosystem from the measurements of a few physical parameters such as dissolved oxygen, pH, temperature and conductivity. Further, it is difficult, if not impossible, to predict the biological effects of a complex continuously changing industrial effluent from chemical analyses alone.
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    The ecology of three sandy beaches on the West Coast of South Africa
    (1981) Bally, Roderick Peter Alexander; Brown, Alec C; Griffiths, Charles L
    The ecology of three sandy beaches on the west coast of South Africa is examined in this thesis. The first chapter constitutes an introduction to the subject and presents a brief review of studies carried out on beaches in South Africa in order to place this thesis into its proper context. In the second chapter, methods of sampling sandy-beach macrofauna (in particular sampling strategies) are briefly reviewed and discussed. For this study it was decided to adopt a grid sampling strategy, and the value of this strategy was tested. In the third chapter the sedimentological characteristics of the beach were examined in considerable detail in order to determine whether these differed between beaches, between zones and seasons on individual beaches. Characteristic differences were found for all the above categories, and the reasons for these are discussed in detail. Two zonation classificatory schemes for intertidal sandy-beach fauna have been proposed: that of Dahl (1953) and that of Salvat (1964). The zonation of organisms on west coast beaches is described in chapter 4, and the results obtained are discussed in the light of the above zonation schemes. Using cluster analysis, ordination and information statistic techniques, Salvat's zonation scheme was found to best describe the situation on the west coast, and its advantages over Dahl's scheme are discussed. Chapter 5 deals with the biomass and densities of macrofauna and meiofauna on the three beaches studied and discusses these results in relation to season and results obtained on beaches elsewhere. On a very broad basis, it is found that the results from west coast beaches fall within the range of results obtained elsewhere, although they rank among the higher values. The results also show that mean individual mass of organisms is related to beach exposure - the mean mass increases with increasing exposure. The respiratory metabolisms of the three dominant isopod species are examined in chapter 6. Using multivariate analysis, the effects of mass, temperature and activity on respiratory rates were determined for each species. Analysis of the results showed that the activity potential of each species differed, and this was correlated with the degree of exposure of the zone inhabited by each species. Thus the species living at the top of the shore showed a high activity potential while that living at the bottom of the shore had the lowest activity potential. The results and the reason for these differences are discussed and related to the differences in the conditions pertaining in each species' environment. Traditionally, sandy beaches are investigated by means of one or two transects across the beach, and the results extrapolated to the remainder of the beach. The results obtained in chapter 2 show that there is considerable variation in biomass and density values along the beach, but a special study of this was made in chapter 7. This showed that all species in fact have an irregular distribution both along and across the beach. These distribution patches are described for all species on all three beaches in this chapter. In addition, interspecific competition and predator-prey relationships were investigated, to determine whether these had any influence on the distributions of the species concerned. Animal-sediment relationships are investigated in chapter 8 and two major types of relationship are described. The first or gross type occurs where species are excluded from a beach due to unfavourable grain size, or where the intertidal position of all the species is affected by the sediment coarseness. The second type is where species or size-classes within species select particular grades within a particular intertidal zone. Animal-sediment relationships are discussed for each species, although these were not detected in all cases. · In chapter 9 the biogeography of the sandy beach genera occurring on west coast beaches is investigated. It was found that genera generally made up of intertidal species consisted of fewer species, with generally larger distribution ranges, than genera that tended to consist mainly of sub-tidal species. Of the 15 genera investigated in this chapter, almost all had a greater percentage of species occurring tropically than in temperate and arctic and antarctic climatic zones. When these percentages were corrected for coastline length or oceanic area, however, the concentrations of species were found to be highest in temperate zones, in all cases. The reasons for these findings are discussed in the light of Bretsky and Lorenz's (1970) theory pertaining to genetic-adaptive strategies and mass extinctions. Finally, in chapter 10, the results of this thesis are synthesized and placed into the context of existing knowledge on sandy beach ecology. In addition, trends in sandy beach studies are discussed and future fields of research outlined.
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    Physical and biological factors structuring sandy beaches macrofauna communities
    (2000) Nel, Petronella; Brown, Alec C; Griffiths, Charles L; McLachlan, Anton
    Previous sandy beach research described beach macrofaunal communities according to the swash exclusion hypothesis (SEH). This hypothesis stated that more species are present on fine grained, flat dissipative beaches due to a more benign swash climate. It suggested that, as beach morphodynamics change to reflective conditions, which is experienced on coarse, steep beaches, few species can survive; these beaches are therefore characterised by lower macrofaunal diversities, abundance and biomass. Furthermore, little proof has been obtained of biological interactions such as competition or predation, and beaches have been described as physically controlled environments. The aim of this investigation was therefore to redifine the SEH in more specific terms, preferably into a form that is experimentally testable, and to find evidence of biological interactions that could be important enough to modify/explain population or community structures. Furthermore, the study aimed to find experimental procedures to serve as alternatives to the previously correlative type approach.
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    Possible uses of the developmental embryology of the sea urchin Parechinus angulosus for pollution monitoring in the nearshore marine environment
    (1980) Greenwood, Peter John; Brown, Alec C
    The possibility of using the embryological life stages of the common sea urchin Parechinus angulosus for pollution bioassay in the nearshore marine environment. was investigated. Discreet stages of development from freshly spawned gametes. through fertilization. pre-hatch development and post-hatch development to 70 - 80 h pluteus larvae were utilized to determine the effect of a variety of pollutants on subsequent development. Different stages in the developmental ontogeny of the species reflect variable sensitivity to different pollutants. Sensitivity was also shown to be radically modified by variation of temperature, salinity, pollutant type, concentration and exposure period. Generally gametes exposed to stressed conditions prior to fertilization reflected high sensitivity. shown by deviations from the norm in subsequent development. Post-fertilization/pre-hatch development was relatively tolerant of pollutant stress, while post-hatch development showed the greatest sensitivity to abnormal condition. In view of the fact that different stages of development show variable sensitivity to pollutant type, a scheme for routine pollution bioassay is suggested, incorporating all the stages of embryological development.
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    Relation between tolerances and distribution of two species of Ephemeroptera
    (1970) Noble, Robert Graham; Brown, Alec C
    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.
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    Selected molluscs as monitors of metal pollution in coastal marine environments
    (1978) Watling, Helen Ruth; Brown, Alec C
    The potential of bivalve molluscs as monitors of metal pollution in South African coastal marine environments has been investigated using the species Crassostrea gigas, Crassostrea margaritacea, Perna perna and Choromytilus meridionalis. Metal concentrations in these and other species living along an unpolluted coast have been determined by atomic absorption spectrometry following chemical oxidation of the biological tissues. Variations in concentrations within a population may depend upon the size or sex of the individual and on the season during which the sample is collected. Metal accumulation by the four study species has been investigated under controlled laboratory conditions for the elements zinc, cadmium, copper, lead, iron, manganese, nickel, cobalt and chromium. Rates of accumulation differ between species and for each element. Some of the factors affecting cadmium uptake have been studied. Rates of accumulation depend greatly upon the form of the cadmium in solution but are also affected by changes in environmental parameters. The accumulation rates of other elements are probably also affected by these factors, not necessarily in the same way. The solution concentrations tested for these accumulation experiments, and also those tested for their effects on the filtering rates of adults or on the development of larvae, are higher than those normally found in polluted areas. This implies that these species are sufficiently tolerant of the presence of metals in their environment to be able to act as monitoring organisms. However, adult oysters and mussels may react to the presence of metals or to the estuarine environment, where fluctuations in water salinity may occur regularly and where effluents may be discharged into the freshwater stream. The mollusc which has closed its valves for either of these reasons may avoid the pollutant. This reaction obviously affects the ability of molluscs to monitor such pollutant inputs. Theoretically, the four study species cannot be used to monitor metal pollution in coastal marine environments quantitatively, as metal accumulation is influenced by too many environmental variables. However, the results from field sampling surveys can be interpreted with greater confidence when the effects of these variables on metal accumulation are known. In practice, a semi-quantitative measure of metal pollution can be achieved.
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    Sex in southern african spirostreptida millipedes : mechanisms of sperm competition and cryptic female choice
    (1997) Barnett, Mandy; Telford, Steven; Nicolson, Sue W; Brown, Alec C
    Spirostreptida millipedes comprise three families, the Harpagophoridae, Spirostreptidae and Odontopygidae. They are polygynandrous. Males transfer sperm via species-specific accessory genitalia called gonopods, that comprise three components, two of which, the emote and telopodite, are involved in processes of sperm transfer. The emotes function to translocate ejaculates from the penes to the vulvae, where they are stored. A delay between insemination and fertilisation provides an arena for syn- and postcopulatory sexual competition. These operate at the gametic level via sperm competition and cryptic female choice. By combining studies of genital form and function with single and double mating experiments, this study elucidates these processes in some southern African Spirostreptida millipedes.
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    Studies on the biological extraction of plant macronutrients from sewage effluents
    (1968) Hemens, Julian Guy; Brown, Alec C
    Eutrophication of water supplies has necessitated the development of methods to prevent discharge of excessive quantities of nitrogen and phosphorus. Operation of a generally applicable process for removing these elements from sewage effluents has not yet been reported. The investigations described here were carried out to determine the feasibility of using the nutritional requirements of controlled ecological systems for this purpose. The results are presented as an alternative approach to the chemical methods that have received consideration.
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    Studies on the osmotic and ionic regulation of the striped dogfish Poroderma africanum (Gmelin)
    (1974) Haywood, Geoffrey Philip; Brown, Alec C
    This thesis presents ideas, techniques, results and conclusions from a 3-year research project regarding the osmotic and ionic regulation of the South African striped dogfish Poroderma africanum (Gmelin). The experiments where devised early in 1971 but due to the time required for personally constructing equipment and facilities and for modifying and equipping the laboratory and aquaria with the necessary apparatus, actual experimentation and subsequent obtaining of results was not possible before November 1971. The main theme of the research was the investigation of the major body fluids and their relationship to external conditions, in a local elasmobranch species. The topic has been extensively examined in some overseas countries hut so far very little physiological work on the osmoregulation of marine elasmobranchs has been carried out in the South African region. The species chosen was also considered interesting in view of its common occurrence around the Cape (at the time of commencement of the work) and the fact that it seemed to be relatively limited in its distribution around the African coast, although in appearance it resembles the Scyliorhinid dogfishes widely distributed around overseas coasts.
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    Studies related to the artificial spawning and culture of the Abalone, Haliotis midae linne, 1785
    (1996) Henry, Neil Richard; Brown, Alec C; Branch, George M
    The successful aquaculture of the abalone Haliotis midae requires a multi-disciplinary approach. Experiments were designed to provide insight into various aspects of abalone biology and seawater system design. A comparative evaluation of a closed and open seawater system for an H. midae hatchery was performed. Monthly seawater temperatures and nitrite levels were higher in the closed system. The salinity of the closed system seawater varied more than that of the open system. The pH of seawater in the closed system varied between 7.7 and 8.2. This was lower than the 7.9 to 8.35 pH range of the open system seawater. An open system is thus clearly preferable to a closed system. Haliotis midae reproductive condition can be assessed visually by examining the shape and colour of the broodstock gonads. Spawning experiments showed that abalone should be starved for at least 24 hours prior to spawning induction. Haliotis midae can be induced to spawn by treatment with hydrogen peroxide when exposed to seawater at a pH of between 9.0 and 9.9 (males and females) Spawning can reliably be induced by using final hydrogen peroxide concentrations in the range of 7 to 25 mM for male and female H. midae. Gravid broodstock should be exposed to hydrogen peroxide for 100 to 300 minutes during spawning induction. There was no significant impact observed for prior conditioning of the brood-stock to the spawning tanks, lunar phase and timing of spawning induction relative to sunset. Haliotis midae larval toxicity to chlorine, copper and ammonia was investigated. The LT50 to a chlorine concentration of 0.06 mg/l was 170 minutes. For copper the LT50 of larvae exposed to 0.12 mg/l was 53 minutes. The LT50 of ammonia at 5 mg/l was 600 minutes. A brief synopsis of the major findings is presented in the last chapter. Some discussion on the future prospects of the abalone industry is also provided.
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    Toxicological consequences of pesticidal use in the Republic of South Africa
    (1986) Fourie, H O; Brown, Alec C; Watermeyer, G S
    Chemicals used in agricultural activities, could possibly be the most potent group of compounds used on a regular basis by employees representing a significant fraction of the unskilled, economically active, labour market of a country. Certainly, such a statement will hold true for South Africa and probably for most Third World and developing states. All chemical compounds contain the inherent property of being toxic and/or hazardous. However, pesticides are chemicals intentionally used to kill. They are therefore not avoidable and in contrast to other chemicals are used only because of their ability to kill. As in most other countries in the world, poisoning in the Republic of South Africa is to be expected due to the use of pesticides. In the handling of pesticides, statistics show South Africa to be vulnerable to an appreciable number of deaths and poisoning cases. There could be a number of reasons for this phenomenon, two of them probably being ignorance and negligence on the part of officers in charge of handling pesticides, and perhaps the most important, the exploitation of unskilled labour in applying and handling pesticides. It is believed that the South African agricultural industry represents both the First and Third World and should thus be ideally suited for investigating: (1) acute intoxication due to chemicals used in the agricultural industry. It was found that the annual consumption of pesticides in the Republic of South Africa results in a dose of approximately 250 mg/m² which compares very favourably with consumption rates of developed countries. An analysis of the products registered indicates a total of 1 211 products containing 359 different active ingredients. The three chemical groups responsible for 73% of the poisoning cases (organophosphates 55%, carbamates 14%, organochlorines 4%) are with the exception of pyrethroids, also the chemicals most frequently formulated. Products containing these three chemical groups constitute only 41% of all formulated products, but are responsible for 73% of all intoxications. It is concluded that the poisoning rate by pesticides is appreciably higher than officially notified, and that the fatality rate could be two orders of magnitude higher than developed countries. A compendium - the first of its kind in South Africa for use by hospitals and clinical practitioners and containing trade names, chemical classification, active ingredients, toxicology, symptomatology and proposed treatment procedures for each product, is presented as an appendix. (2) chronic exposure to residues of agricultural products in the diet of South Africans is investigated. Food intake data was calculated from 24-hour dietary recall studies. Residues of only 4 compounds were present in 33 composite, ready-to-eat foods, consisting of 5 538 foodstuffs sampled over a period of one-year country wide, and representing 142 different food items categorised into 11 food groups. The residues found were well within acceptable levels and compare very favourably with those found in the diets of developed countries. It has to be concluded that possible chronic exposure due to agricultural chemical contaminants, to the white population at least, does not exist, and emphasises a sound regulatory policy towards the use of these chemicals in South Africa. (3) a hypothesis of this study that it is not possible that neither the inherent toxicities of pesticidal compounds, nor a paucity of knowledge about the toxicological, chemical and physical properties of these compounds could be mainly responsible for the numerous intoxications recorded annually. An epidemiological 400 case study (descriptive design), investigated the contribution by occupational, environmental, cultural and socio-economic variables to poisoning. The numerous effects by these variables are described and amongst many others, it is concluded that the recommendations of the World Health Organization to classify pesticides by hazard, is confusing to illiterate and semi-educated users and should not be recommended to developing countries.
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    Water quality requirements for first-feeding in marine fish larvae of the Cape of Good Hope, with description of developmental stages
    (1979) Brownell, Charles L; Brown, Alec C; Field, John G; Champion, Harold
    The tolerance of marine fish larvae to NH₃, NO₂⁻, NO₃⁻, H⁺, OH⁻, O₂, and CO₂ was investigated using the decrease in first-feeding incidence following a 24-h exposure as the criterion of response. Ten species, all hatched from pelagic eggs collected at sea, were used in the studies: two soleids (Heteromycteris, Synaptura), a cynoglossid (Trulla), a gadid (Gaidropsarus), a congiopodid (Congiopodus), four sparids (Diplodus, Lithognathus, Pachymetopon, and an unidentified species), and a centracanthid (Pterosmaris). Concentrations that inhibited first-feeding are compared to 24-h LC 50's for the same species, and to concentrations that are known to induce lethal and sublethal responses in other teleost species. Judging from their effect on first-feeding, un-ionized ammonia, elevated pH, and reduced oxygen concentration are considered to be potential hazards in the rearing tank. NO₂⁻, NO₃⁻, H⁺, and free CO₂ are nontoxic at levels likely to be encountered in practical fish culture. There are only minor inter-specific differences in calculated 24-h first-feeding EC 50's (concentration that reduces first-feeding incidence by 50%), which suggests general applicability of the results to a wide variety of first-feeding marine fish larvae. Data are presented on the age at first-feeding and point-of-no-return. The suitability of assorted micro-particles (including the rotifer, Proales, and Pine pollen) as experimental foods is discussed.