No description available.

Considering South Africa’s richness in aquatic species, very little knowledge exists regarding copepods that are symbiotic on hosts ranging from invertebrates to marine mammals. In order to have any indication of the existing biodiversity of this group of organisms in South African waters, a thorough investigation of all possible hosts needs to be conducted, which in turn will most likely increase the number of recorded symbiotic copepods considerably. The current descriptive study was done in an effort to contribute to a larger study of metazoan parasites of elasmobranch hosts along the KwaZulu-Natal coast of South Africa. A total of 40 (31 Mobula kuhlii; two Mobula eregoodootenkee and seven Manta alfredi) mobulids were examined for infection by symbiotic copepods at the KwaZulu-Natal Sharks Board (KZNSB). More than 90% of all examined hosts were infected with different types of symbiotic siphonostomatoids. Collected copepod specimens were fixed and preserved in 70% ethanol and studied with both the stereo- and light microscopes using the wooden slide technique. Some selected specimens were further studied using Scanning Electron Microscopy (SEM) to elaborate on ill-defined features. A total of 13 different species of the order Siphonostomatoida distributed over five families were identified. The five families include Eudactylinidae (Eudactylina oliveri, Eudactylina diabolophila and Nemesis sp.); Caligidae (Caligus crysophrysi, Pupulina sp. 1, Pupulina sp. 2; Pupulina sp. 3, Unidentified sp. 1, Unidentified sp. 2 and Unidentified sp. 3); Kroyeriidae (Kroeyerina mobulae); Dichelesthiidae (Anthosoma crassum) and Cecropidae (Entepherus laminipes). Two of the 13 species (E. laminipes and A. crassum) are monotypic and were therefore easily identified. Eudactylina oliveri exhibited a prevalence of 75% and 100%; mean intensity of 42 and 130 parasites per host and a mean abundance of 32 and 130 individuals per host while Pupulina sp. 1 exhibited a prevalence of 61.29% and 100%; mean intensity of 41 and 5 individuals per host and a mean abundance of 2 and 5 individuals per host on M. kuhlii and M. eregoodootenkee respectively. Component populations of E. oliveri and Pupulina sp. 1 exhibited an aggregated distribution pattern on their examined hosts. The phylogenetic relationship between nine caligid species (three known Pupulina species, three collected Pupulina species and three Unidentified sp. species as ingroup) with Caligus glandifer as out-group was determined and analysed using a morphological dataset (40 characters) from previous and current descriptions. The ii exhaustive search with PAUP* retained a single most parsimonious tree with a tree length (TL) = 85; consistency index (CI) = 0.7; retention index (RI) = 0.7; homoplasy index (HI) = 0.3 and a rescaled consistency index (RCI) = 0.5. Bootstrap support for the estimated clades was mostly low with values less than 95%. The phylogenetic hypothesis of the 10 caligid species presented in the current study was derived from the phylogenetic analysis of the information for adult females and is therefore not intended to be a definitive theory but should be treated as a testable hypothesis that can be further analysed using more data. The current study provides the first record of C. chrysophrysi, Pupulina sp. 1, Pupulina sp. 2, K. mobulae and E. laminipes on M. kuhlii; E. oliveri, Pupulina sp. 1, Pupulina sp. 2 and Pupulina sp. 3 on M. eregoodootenkee; and E. diabolophila, Nemesis sp., C. chrysophrysi, E laminipes, A. crassum and the three Unidentified species on M. alfredi frequenting the east coast of South Africa and thus contributes to the knowledge of our marine biodiversity. Mobulid hosts were not carefully studied for copepod infection previously and the copepods that were reported from the mobulids were probably found by chance. Therefore future investigation into the symbiotic siphonostomatoids of more mobulid hosts and other host species may result in more reports of symbiotic Copepoda from South African waters. / Thesis (MSc. (Zoology)) -- University of Limpopo, 2013

Most environmental studies concerning the environmental health of the Swan- Canning River system have focussed on nutrient inputs from both rural and urban catchments that are the cause of algal blooms. On occasions these algal blooms have resulted in fish deaths attributed to oxygen starvation. Relatively few studies have examined whether non-nutrient contamination is affecting the health of the riverine environment. Those studies that have, have concentrated on measuring the levels of heavy metals, organochlorines, organophosphates, and hydrocarbons in the sediments and water of the river system, and in the flesh of the biota. However, chemical analysis often fails to detect chemicals of concern due to high laboratory detection limits. In addition, analysis of the body burden of contaminants within biota does not necessarily convey if exposure is inducing adverse effects at the individual or ecosystem levels. The use of biochemical markers as a tool for the assessment of the health of the Swan-Canning River system was examined under a collaborative research project with the Waters and Rivers Commission, established in response to the recognition of the paucity of information from chemical analyses. The present study focussed on the estuarine portion of the Swan-Canning River system, using the black bream (Acanthopagrus butcheri), an estuarine dependent fish species, as a biomonitoring tool. Prior to the commencement of this study it had been determined that the black bream was a suitable fish species for use as a biomonitoring tool when using mixed function oxygenase (MFO) activity induction under laboratory conditions. / Biopsies taken from feral black bream collected from eight sites during the period 2000 to 2002 from the estuary confirmed that the use of MFO induction in this fish species as a biomarker of exposure to organic contaminants is a reliable biomarker. Fish gender was a confounding factor in the interpretation of MFO induction when using the enzyme ethoxyresorufin-O-deethylase (EROD) as EROD activity was suppressed in both pre- and post-spawning female black bream. No such suppression was identified when using the MFO enzyme ethoxycoumarin-O-deethylase (ECOD). However, due to differences in the pattern and intensity of the induction of EROD and ECOD activities it was concluded that ECOD activity was not a substitute for EROD activity to detect certain chemical as ECOD activity represents a different cytochrome P450 pattern to EROD activity. No spatial, seasonal or interannual differences in the level of the enzyme sorbitol dehydrogenase (SDH) in the blood of the black bream were measured indicating that the interpretation of MFO activity induction was not compromised by hepatocellular damage. This study has shown that the black bream in the Swan-Canning Estuary are exposed to, and are metabolising polycyclic aromatic hydrocarbons (PAHs), notwithstanding that the chemical analysis of the contaminant load of these substances in the estuarine waters is consistently below laboratory detection limits. In addition, biomarker responses such as ECOD activity indicate that various other organic pollutants are present and are being metabolised by the black bream. / The measurement of biliary metabolites clearly show that, under winter conditions, the comprehensive drainage system of the Swan Coastal Plain contributes PAHs from pyrogenic sources such as burnt fuels into the estuary although the onset and intensity of rainfall events notably impacts on the volume of stormwater inflow. During the summer months, when freshwater flow is minimal, petrogenic sources of PAHs are dominant. Metabolic enzyme analysis points to the black bream being challenged in their aerobic capacities during summer, and that gill tissue was the most suitable tissue to evaluate the aerobic and anaerobic capacity of this fish species. Furthermore, there was a significant negative correlation between stress protein (hsp70) expression and DNA integrity in field-collected fish suggesting that the black bream within the estuary are highly stressed. No gradient of response in biomarker levels was identified in the Swan-Canning Estuary under either winter or summer conditions indicating there are multiple sources of inputs of potential pollutants along the length of the estuary. Stormwater and road runoff are the primary source of pollutant input into the estuary in the winter months, while summer biomarker levels, particularly PAH, appear to reflect the high usage of the estuary for recreational purposes and runoff from poorly irrigated parks and gardens. Significant rainfall events at any time of the year have the potential to adversely impact the biota of the estuary, particularly when these events result in a flush of water from the drains following long dry periods. / The study shows that the black bream is a suitable fish species to use under field conditions to detect the presence of bioavailable non-nutrient contamination within the Swan-Canning Estuary. A suite of biomarkers in black bream have been tested seasonally and annually but only a small number of biomarkers have proven suitable for routine monitoring of the health of the Swan-Canning Estuary. This treatise concludes with several recommendations for further investigations into biomarkers of fish health for the purpose of increasing our understanding on the sources and type of contamination entering the estuary, and potential effects on the aquatic biota of the Swan-Canning River system. These recommendations include, but are not limited to: (1) the need to determine baseline levels for the different biomarkers investigated in this study, (2) the examination of the Moore River or the Warren River estuaries as potential reference sites for biomarker studies in the Swan- Canning Estuary, (3) the advantage of identifying a second estuarine-dependent indigenous fish as a biomonitoring tool, (4) the requirement for a targeted study aimed at clarifying the relationship between major drain discharges, biomarker levels and impacts on river biota, and (5) a study of estuarine waters utilising SPMDs be undertaken in tandem with biomarker analysis of field captured fish would be beneficial.

This thesis revealed Australian lakes to be richer in chironomid (Diptera: Insecta) species than was previously recognised. A methodology for the collection of chironomid exuviae from lakes was developed using a 12-month study of exuviae from a single lake, Lake McKenzie, Jervis Bay. The method is a rapid and effective way to produce an inventory of species living within a lake. In addition, a distinct biogeographical pattern was detected for chironomid species from a survey of chironomids from southern and eastern Australian freshwater lakes. Geographical location of the lake was more influential on the distribution of chironomid species than was the type of lake. The majority of lake dwelling chironomid species in this investigation were restricted to lakes within one of four geographic lake regions; Tasmania, south-eastern Australian mainland, Fraser Island or tropical north Queensland. A temporal investigation of chironomid exuviae was conducted on a pair of small upland Blue Mountain waterways. Abundance and species richness of exuviae exhibited diurnal patterns. A chemical and macro-invertebrate survey of zinc and sewage organic waste discharges to upland streams in the Blue Mountains detected marked ecological impairment. Macro-invertebrate families responded in different ways to the two different types of waste discharge. According to the family-level results, chironomid larvae responded negatively (reduced abundance) to the zinc pollution and positively (increased abundance) to the sewage pollution. Another major finding from this thesis was that chironomid species assemblages, in the streams surveyed, were strongly impaired by zinc-contaminated mine drainage and sewage effluent. This differed to the family-level larval results. This thesis provided the first Australian evidence that many chironomid species are intolerant of heavy-metal pollution. This research also revealed further evidence that many chironomids species are intolerant of sewage pollution. / Doctor of Philosophy (PhD)

Abstract not available

Nototodarus sloanii is an important component of the Southern Ocean fauna, and the basis of a large commercial fishery. Despite this, much is unknown about the biology of this species. This study examines some aspects of the biology of N. sloanii. Stomach contents analysis identified no significant differences in diet between male and female squid. Sixteen putative species, including 12 identifiable teleosts, 2 crustaceans, and 2 cephalopods were identified in the diet of this species. The euphausid, Nyctiphanes australis was the most important prey item, Lanternfish, Lampanyctodes hectoris, and Pearlside, Maurolicus muelleri, were of secondary importance. Squid were aged using counts of statolith micro-increments and back-calculation from the date of capture showed that hatching occurred between August and February, with a peak in the austral winter/spring and another smaller peak in the austral summer. Growth rate for male squid differed depending on whether squid were hatched in the winter/spring or summer. Growth rates were more variable in the winter/spring-hatched individuals, and they attained larger size than summer-hatched squid. This was not the case for female squid. Mean age for immature winter/spring-hatched squid was significantly higher than for summer-hatched squid, although there was no significant difference in mean mantle length or body mass. No significant differences between mean age, mantle length, or body mass for same-gender mature squid, regardless of hatch season, were apparent. However, mature female squid hatched in the winter/spring season were significantly longer (ML) than mature male squid hatched in winter/spring. No squid was found to be older than 211 days. All squid had started to mature by 91-120 days old and all were fully mature at 180 days. Validation experiments run on juvenile squid using calcein markers were inconclusive, however the increments in the statoliths were very similar to those found in other validated species of ommastrephid squid, thus for the purposes of this study they were assumed to be of daily periodicity. Gladius increments identify a gender difference in growth rate, with female squid having a shorter initial slow growth phase than male squid. Gonadosomatic indices (GSIs) were calculated for male and female squid. These were low (7.12%�0.3% for females and 1.9%�0.2% for males) suggesting that these squid are intermittent spawners. This is further supported by a histological examination, which found germinal cells of different stages present in the same gonad. Lack of mature individuals in this study means that these results are suggestive rather than definitive; more examination of the reproductive process of this squid is required. Histological examination was also used to validate the Lipinski maturity scale for use with this species, while some misidentification occurred the scale is useful to place squid into the broad categories of immature, maturing, or mature. New maturity scales were created for N. sloanii utilising these broad categories. Finer-scale identification is not possible using this scale, as maturation appears to be a continuous process. Morphometric measurements were taken from both hard and soft tissues and were analysed using non-metric multidimensional scaling and analysis of similarity. Divisions were only apparent in the hard structure measurements. They did not appear to be age, dietary or reproductive differences.

South Australian mangroves consist of only one single species Avicennia marina (Fosk.) Vierh.var australasica (Walp) Moldenke, 1960. They are distributed discontinuously within St. Vincent Gulf and Spencer Gulf and provide significant valuable habitat both in economical and ecological terms. The Fisheries Act 1971-1982 protected the existence of mangroves and the Harbour Act 1936-1981 controlled removal of mangrove areas in coastal development. To date very few ecological studies have been conducted in the South Australian mangroves, particularly on the infaunal organisms that have an important role in maintaining the ecological dynamic within the estuaries systems. As this is the first study on infaunal mangrove communities in the inverse estuaries of South Australia, there was no prior data for ecological comparison. The study was conducted at three mangroves location (Garden Island, Middle Beach and Saint Kilda) close to Adelaide in May 2000 and 2001. Overall the study has reported that the infaunal mangrove assemblages of South Australian mangroves were comparable to other temperate mangroves. The infaunal communities were characterised by lower diversity and abundance compared to the tropical or subtropical mangroves. The infaunal zonation related to the tidal gradient and habitat variation was detected. Most infauna organisms occupied the surface layers and substantially decreased towards the deeper layers. The study also suggested that sediment structure of mangrove systems were complex and infaunal communities responded differently to the change of environmental conditions both in small scale and larger scale. Thus, assessing the infaunal communities structure in mangrove systems should be based on ecological characteristics rather than geographical positions. The examination of dominant polychaetes families showed that different species have different responses to the environmental cues within mangrove systems. The study did not find that any polychaete species was restricted to mangroves only as they all were also found in the habitat adjacent mangrove forest. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2003.

Concentrations of heavy metals (Cu, Cd, Cr, Zn, Mn, Fe and Pb) in the water columns, aquatic plants and sediments of fourteen lakes of varied levels of pollution were measured. Correlation analysis was carried out between heavy metal concentrations in aquatic plants and heavy metal concentrations in water and sediment. The aquatic plants which accumulated heavy metals in their tissues in proportion to that in water and sediments were identified. The aquatic plants studied were: 8/yxa auberti Rich, Cabomba caroliniana Gray, Ceratophyllum demersum L, Ceratopteris thalictroides (L.) Bron, Chara globularis, Eichhornia crassipes Solmn, Hydrilla verticillata Royle, Ipomoea aquatica Forsk, Limnophila aromatica (Lam.) Merr., Ludwigia adscendens (L) Hara, Nelumbo nucifera Gaertn, Nymphaea stallata Linn, Nymphoides indica (L.) Kuntze, Typha angustata Bony & Chaub and Utricularia aurea Lour. Metal uptake by aquatic plants varied between different species and within the same species depending on lake water contamination levels. The level of metal uptake to a great extent was a function of the environment water metal concentration. Results showed that Utricularia accumulated Mn, Zn, Cr, Cd and Pb in direct proportion to the overlying waters (r2 = 0.69, 0.63, 0.69, 0.65 and 0.39 respectively). Hydrilla accumulated Cu, Mn, Zn, Fe, Cr, Cd and Pb in direct proportion to the overlying waters (r2 = 0.65, 0.66, 0.44, 0.72, 0.38, 0.63, and 0.73 respectively). Blyxa leaves accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the overlying waters (r2 = 0.74, 0.74, 0.72, 0.60 and 0.82 respectively). Echhornia leaf accumulated only Cr in direct proportion to the overlying waters r2 = 0.81. Nymphaea leaf and Chara did not accumulate any metal in direct proportion to the overlying waters. Roots of Blyxa auberti, Ceratopteris thalictroides, and Eichhornia crassipes contained higher concentrations of heavy metals than their leaves. Roots of Blyxa accumulated Cr, Cd and Pb in direct proportion to the overlying waters (r2 = 0.91, 0.65 and 0.69 respectively). Echhornia root accumulated Cd in direct proportion to the overlying waters with r2 = 0.90. Nymphaea stem showed no significant correlations between the metal concentrations in the waters and in the plant. Utricularia accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the metals in the underlying sediment extracted by cold hydrochloric acid (r2 = 0.84, 0.51, 0.47, 0.68 and 0.80 respectively). Hydrilla accumulated Cu, Zn, Cr, Cd and Pb in direct proportion to the underlying sediment (r2 = 0.34, 0.37, 0.91, 0.49 and 0.96 respectively). Blyxa accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the underlying sediments (r2 = 0.99, 0.61, 0.82, 0.75 and 0.64 respectively) . Echhornia leaf showed significant correlation between the Cu (r2 = 0.83) and Cr (i2 = 0.88) concentration in underlying sediment and the plant. Nymphaea leaf showed a significant correlation between the Zn (r2 = 0.83) concentration in the plant and the underlying sediments. Roots of Blyxa showed significant correlation between concentrations of Cu, Cr and Pb in sediment extracted by hydrochloric acid and plant (r2 = 0.9, 0.7 and 0.9 respectively). Roots of Echhornia had no significant correlation with the sediment metal concentrations (hydrochloric acid extractable). Two techniques (cold hydrochloric acid extractable and nitric acid extractable) to extract metals from sediment were compared. Based on correlations of metal concentrations in plant tissue and metal extracted from the sediment, it was concluded that the cold hydrochloric acid extractable metal technique is more suitable for determining bioavailable sediment metal concentration in environmental studies. Laboratory studies investigations on the bioaccumulation of Zn and Cu in Hydrilla confirmed that Hydrilla is a good bioindicator of Cu as it accumulated 20360 ug/g dry weight of Cu in 72 hours. Hydrilla showed higher bioaccumulation factor with low concentration of Cu in the solution, in the laboratory studies. Hydrilla was determined to be the best indicator species as it reflected the heavy metal concentration in the environment which was supported by the laboratory studies.

Chlorophyll-a (chl-a) concentration is an indicator of the trophic status and is extensively used as a measurement of the algal biomass which affects the level of eutrophication in aquatic systems. High concentration of chl-a may indicate high biomass of phytoplankton which can decrease the quality of water or eliminate important functional groups in the ecosystem. Predicting chl-a concentrations is desirable to understand how great impact chl-a may have in aquatic systems for different scenarios during long-time periods and seasonal variation. Several models of predicting annual or summer chl-a concentration have been designed using total phosphorus, total nitrogen or both in combination as in-parameters. These models have high predictive power but are not constructed for evaluating the long-term change or predicting the seasonal variation in a system since the input parameters often are annual values or values from other specific periods. The models are in other words limited to the range where they were constructed. The aim with this thesis was to complement these models with other methods and models which gives a more appropriate image of how the chl-a concentration in an aquatic system acts, both in a short as well as a long-time perspective. The results showed that with a new method called Statistically meaningful trend the Baltic Proper have not had any change in chl-a concentrations for the period 1975 to 2007 which contradicts the old result observing the p-value from the trend line of the raw data. It is possible to predict seasonal variation of median chl-a concentration in lakes from a wide geographically range using summer total phosphorus and latitude as an in-parameter. It is also possible to predict the probability of reaching different monthly median chl-a concentrations using Markov chains or a direct relationship between two months. These results give a proper image of how the chl-a concentration in aquatic systems vary and can be used to validate how different actions may or may not reduce the problem of potentially harmful algal blooms. / Koncentrationen av klorofyll-a (chl-a) är en indikator på vilken trofinivå ett akvatiskt system har och används som ett mått på algbiomassa som påverkar övergödningen i akvatiska system. Höga koncentrationer av chl-a i sjöar kan indikera hög biomassa av fytoplankton och försämra kvalitén i vattnet eller eliminera viktiga funktionella grupper i ett ekosystem. Det är önskvärt att kunna prediktera chl-a koncentrationer för att förstå hur stor påverkan chl-a kan ha för olika scenarier i akvatiska system under längre perioder samt under säsongsvariationer. Flera modeller har tagits fram som predikterar årsvärden eller sommarvärden av chl-a koncentrationer och i dessa ingår totalfosfor, totalkväve eller en kombination av båda som inparametrar. Dessa modeller har hög prediktiv kraft men är inte utvecklade för att kunna utvärdera förändringar över längre perioder eller prediktera säsongsvariationer i ett system eftersom inparametrarna ofta är årsmedelvärden eller värden från andra specifika perioder. Modellerna är med andra ord begränsade till den domän som de togs fram för. Målet med denna avhandling var att komplettera dessa modeller med andra metoder och modeller vilket ger en bättre förståelse för hur chl-a koncentrationer i akvatiska system varierar, både i ett kortsiktigt och ett längre perspektiv. Resultaten visade att med en ny metod som kallas för Statistiskt meningsfull trend så har egentliga Östersjön inte haft någon förändring av chl-a koncentrationer under perioden 1975 till 2007 vilket motsäger tidigare resultat då p-värdet tas fram från en trendlinje av rådata. Det är möjligt att prediktera säsongsvariationer av median chl-a koncentrationer i sjöar från en bred geografisk domän med totalfosfor från sommar och latitud som inparametrar. Det är även möjligt att beräkna sannolikhetenav ett predikterat värde för olika månadsmedianer av chl-a koncentrationer med Markovkedjor eller ett direkt samband mellan två månader. Dessa resultat ger en reell förståelse för hur chl-a koncentrationer i akvatiska system varierar och kan användas till att validera hur olika åtgärder kan eller inte kan reducera problemet av de potentiellt skadliga algblomningarna.

The novel application of combination, or two stage, photochemical and microbial degradation systems for removal of resin acids from natural river water and single stage photolysis for degradation of naphthenic acids in natural river water was investigated. The organic compounds included in this project comprise naphthenic acid model compounds and mixtures as well as four resin acids. Naphthenic acids are crude oil-derived and accumulate to significant concentrations (>100 mg/L) in tailings pond water at oil sands extraction facilities. Resin acids are pulp and paper mill-derived compounds that tend to persist at low levels in receiving waters. For each compound group, analytical methods utilizing liquid chromatography negative ion electrospray ionization mass spectrometry (LC/ESI/MS) were developed. The main hurdle to developing analytical methods for the naphthenic acids and resin acids are related to their polarity, complexity, and lack of available standards for the various individual components. As well, co-extractives, such as humic and fulvic acids, tend to interfere with the detection of naphthenic acids in aquatic samples (Headley et al., 2002a). Resin acid mixtures are not as complex as the naphthenic acids, although each group of hydrocarbon acids may include several isomeric compounds. The application of photochemical degradation prior to biodegradation was proven to be effective here for rapid degradation of the resin acids. In general, the resin acid precursors were more susceptible to the photolysis than were the naphthenic acids. Through thermal maturation and increased complexity, the naphthenic acids seemingly become more resistant to degradation, as evidenced by their commercial use as anti-microbial agents and the observed resistance to photolysis noted in this research. The results of this research may be significant for the design of staged treatment for reduced microbial shock loading and increased bioavailability (defined here as the ability of microbial organisms to degrade the target contaminants) in both bioremediation systems and receiving waters. Specifically, four selected pulp and paper mill-associated resin acids were exposed to several ultraviolet/visible (UV/vis) spectrum radiation sources in water collected from the River Saale in Germany. Background resin acid concentrations were observed in water collected in 2001 and 2002 from various locations along the well-forested River Saale and a manuscript detailing these results published. Analyses of water samples collected in the pulp and paper milling region of the river (in the state of Thuringia) indicated that resin acids persist through biodegradation treatment systems and for several hundred kilometres downstream. All four resin acids were degraded by facile photochemical and microbial degradation with pseudo-first-order kinetics. Half-life values were in the ranges of 18 to 200 minutes for photolysis applications, 8 to 40 hours for biodegradation applications and 3 to 25 hours for two-stage photochemical-microbial degradation processes, in which photolysis was limited to three hours. From these results, it was shown conclusively that photolysis pre-treatment is a viable and efficient method for reducing both resin acid concentrations and the associated acute toxicity. The naphthenic acids investigated in this study were not effectively degraded via UV/vis radiation, including UV-A/UV-B radiation between 300-400 nm, near-monochromatic UV254-radiation, full spectrum artificial solar radiation and natural sunlight. The photochemical degradation potential of three model naphthenic acid compounds and three naphthenic acid mixtures (one extract from the Athabasca Oil Sands and two commercial mixtures) were examined in Athabasca River water. Photolysis at UV254 was the most successful degradation source in all instances, although most naphthenic acids were not significantly degraded by any of the radiation sources. Therefore, it was determined that photolysis is not likely to contribute significantly to environmental degradation and attenuation in the aquatic ecosystem. The results observed from the various naphthenic acids photodegradation processes, coupled with their low affinity for adsorption to soils, reveal that naphthenic acids are likely to persist in the water column. However, UV/vis radiation is capable of significantly changing the composition of mixtures in the aquatic ecosystem, but not reducing overall naphthenic acid concentrations. This may not be a beneficial as there is the potential for increased toxicity toward the lower molecular weight naphthenic acids.