Juvenile rainbow trout (Oncorhynchus mykiss) were fed either 5 or 20 μg 2,2′,4,4′,5,5′‐hexachlorobiphenyl (245‐HxCB)/g diet (wet wt.) for 4, 8, or 12 weeks. Hepatic xenobiotic‐metabolizing enzyme activities and dietary 245‐HxCB accumulation in liver, muscle, and remaining carcass were determined. Liver‐to‐body weight ratios were not altered by either of the two 245‐HxCB concentrations. Relative growth rate increased with time but was not altered by 245‐HxCB concentration. Bioaccumulation of 245‐HxCB was dose and time dependent in all tissues without reaching apparent steady state. Hepatic arylhydrocarbon hydroxylase (AHH) activities increased with 245‐HxCB dose and with time. Ethoxyresorufin‐O‐deethylase (EROD) activities also increased in fish fed 20 μg 245‐HxCB/g diet. No 245‐HxCB‐induced changes in uridine diphosphoglucuronosyl transferase (UDP‐GT) or NADPH‐cytochrome‐c reductase (NCCR) activities were determined. High‐resolution GC‐MS analysis of the 245‐HxCB standard revealed trace (0.4‐0.5%) contamination by two mono‐ortho pentachlorobiphenyls (PnCBs): 2,3,3′,4,4′‐PnCB and 2,3,4,4′,5‐PnCB. Total liver accumulation of these contaminants was inversely related with corresponding EROD and AHH activities and estimated to contribute minimally to their induction. Results from this study suggested that long‐term dietary 245‐HxCB exposures induced cytochrome P4501A activities in rainbow trout liver.

<p> Knowledge into uptake rate and interactions of the metals via the gastrointestinal tract of freshwater fish is vital, in order to provide tools to protect and to sustain aquatic biota. An in vitro stomach and gut sac technique was utilized to investigate uptake rates of essential metals (copper, zinc and nickel) and non-essential metals (cadmium, lead and nickel) at luminal concentrations of 50fJ.M via the gastrointestinal tract Metals had no effect on the fluid transport rates via the gastrointestinal tract except for copper at the stomach. The stomach emerged as small but important site for metal absorption and interaction. Essential metals were absorbed at approximately the same rate as nonessential metals via the gastrointestinal tract. Copper, zinc, nickel, silver, and lead showed statistical correlation between rate of absorption and mucus binding via gastrointestinal tract, an important first finding for the development of a Biotic Ligand Model (BLM) for the gastrointestinal tract of trout. </p> <p> There was an antagonistic effect of calcium on cadmium uptake at the stomach but not at the intestine. Zinc and calcium exhibited synergistic interaction at the stomach but no interaction at the intestine. These results showed the possibility of the transporters DMTl to mediate copper and cadmium uptake via the intestine; hZip 2 to mediate copper and zinc uptake at the stomach; and Mzip 4 or ZTLl to mediate zinc uptake via the gastrointestinal tract of trout. These results can be used to develop a BLM for the gastrointestinal tract of fish. </p> / Thesis / Master of Science (MSc)

<p> Juvenile rainbow trout (Oncorhynchus myldss) were chronically exposed (90 days) in synthetically softened water ([Ca2+]=50, [Na+]=100 J.tequiv·L-1), to sublethal low pH (5.2) and a simulated global warming scenario (+20C), added to the natural summer thermal cycle ofinshore Lake Ontario. Two studies were conducted over the periods June September 1993 and 1994 in order to examine the effects ofthe sublethal stressors under conditions ofunlimited food ration (satiation feeding twice daily= 10% dry body weight·day-1), and a limited food ration (4% dry body weight·day-1) respectively. The addition of 2°C and sulphuric acid was designed to result in four treatment conditions: i) Control conditions; ambient water temperature and pH; ii) ambient water temperature and pH 5.2; iii) simulated global warming at ambient pH; iv) a combination of simulated global warming and pH 5.2. Year to year variation in temperature provided the trout in the satiation-fed study with an ambient ~peraturerange of 13-24°C, while those in the limited ration study experienced a range of 16.5-21°C. Consequently, the trout in the treatments with an additional 2°C experienced temperatures close to the upper incipient lethal level, particularly the trout in the satiation feeding study. Apparent specific dynamic action raised routine metabolic rates in all treatments to -75% and 55% M02(max) in the satiation and limited ration studies respectively, the difference of 20% indicating the influence of an unlimited feeding regime on metabolism. Trout in the satiation feeding study increased in wet body mass by 30-50 g, while trout in the limited ration study increased by only 3-4 g. Whole body proximate composition of the trout fed to satiation changed over time with large increases in lipid content, small increases in protein content, and compensating decreases in water content in all treatments. No such changes occurred in the limited ration trout, although whole body lipid and carbohydrate were highly variable. In both studies, the addition of20C resulted in decreased growth, with an accompanying depression in appetite in the satiation fed trout, especially at peak temperatures. Surprisingly, trout exposed to low pH alone exhibited improved growth in both treatments. Energy budgets indicated that the addition of 2°C reduced gross energy intake and increased fecal (and Ulllidentified) energy losses resulting in lowered conversion efficiencies, while in limited ration trout, energy expenditure was slightly higher. Trout exposed to low pH exhibited higher gross energy intake and gain, and more efficient energy conversion under unlimited food conditions while trout with limited rations expended the least metabolic energy and exhibited lower nitrogen energy losses. The surprising lack of ionoregulatory disturbance in these pH 5.2 exposed trout in both studies suggests tbat the availability of NaCl in the diet was compensating for branchial ion losses, and perhaps driving appetite in the satiation fed trout Where ration was limited, reductions in activity level may have contributed to energy conservation and consequently improved growth. A 22Na+ flux experiment conducted at the end of the limited ration exposure, in which the fish were exposed to a challenge concentration of H+ (pH 4.2), provided evidence for improved recovery of ionoregulatory balance in trout which had been chronically exposed to low pH. Overall, the combination ofincreased global temperatures and sublethal low pH results in increased physiological costs for juvenile rainbow trout, most noticeably when summer temperatures peak. Ration level is of integral importance when considering the degree of impact of such environmental conditions. </p> / Thesis / Master of Science (MSc)

Largely through the use ofin vitro preparations there is now a generally accepted theory for ion transport for the seawater (SW) gill. However, to date there is no generally accepted freshwater (FW) model for the mechanisms of NaCl transport in the teleost gill. By using an Ussing chamber approach with the opercular epithelia of Fundulus heteroclitus and Oreochromis niloticus, and the urinary bladder of Oncorhynchus mykiss, all acclimated to FW, we hoped to establish one as a possible model for the study of FW ion regulation. FW Fundulus opercular epithelia displayed a serosal negative transepithelial potential (Vₜ) of-43.9 mV, transepithelial conductance (Gₜ) of 1.94 mS·cm⁻², and active transport of Cl⁻ from the mucosal FW against a strong electrochemical gradient. Na⁺ movement was dominated by passive diffusion. The opercular epithelia of Fundulus adapted to 10% SW exhibited properties similar to SW Fundulus by actively extruding Cl⁻ while Na⁺ moved passively into the mucosal 10% SW. With FW bathing the mucosal surface, FW Oreochromis opercular epithelia displayed a serosal positive Vₜ of +8.0 mV, Gₜ of 1.78 mS·cm⁻², and active reabsorption of Na⁺, Cl⁻ and Ca²⁺ against large electrical and/or chemical gradients. The FW Oreochromis opercular epithelia is the only FW in vitro preparation to date that exhibits active absorption (albeit at small absolute rates) of both Na⁺ and Cl⁻. FW 0. mykiss urinary bladders mounted in vitro under symmetrical saline conditions exhibited a transepithelial conductance (Gₜ) of-9.15 mS·cm⁻² and electroneutral active absorption of Na⁺ and Cl⁻ from the mucosal urine side. The transport of Na⁺ and Cl⁻ was a partially coupled process whereby removal of Na⁺ from the mucosal saline decreased Cl⁻ absorption by a 56% and removal of Cl⁻ inhibited Na⁺ absorption by 69%. However, active net absorption of both ions persisted when the counter-ion was replaced with a non-permeant ion. Under more realistic conditions with artificial urine bathing the mucosal surface, Vₜ increased to a serosal positive ~+7.6 mV and Gₜ decreased to ~1.47 mS·cm⁻² Unidirectional influx rates of both Na⁺ and Cl⁻ were much lower, but active absorption of both ions still occurred. Replacement of Na⁺ in the mucosal artificial urine caused no change in unidirectional influx of Cl⁻ and vice versa. The mucosal addition of DIDS, amiloride or bumetanide (10⁻⁴M) all had no affect on absorption rates of Na⁺ and/or Cl⁻, under either artificial urine or symmetrical saline conditions. When the mucosal surface was bathed in artificial urine, removal of mucosal Cl⁻· significantly reduced the maximum transport rate (Jₘₐₓ of Na⁺ (6.1 ~2.1 μmol·cm⁻²·h⁻¹) but had no effect on affinity for Na⁺ (Kₘ~27 mM). Similarly, removal of mucosal Na⁺ significantly reduced the Jₘₐₓ for Cl⁻ uptake (11.4 ~2.4 μmol·cm⁻²·h⁻¹) but had no effect on Cl⁻ Kₘ(~37 mM). The anterior portion of the urinary bladder transported Na⁺ and Cl⁻ at a faster rate than the posterior portion under symmetrical saline conditions, but there was no difference in measured Na⁺/K⁺ -ATPase activities between the two portions. In conclusion, opercular epithelia of Fundulus and Oreochromis demonstrated transport properties believed to be typical of FW teleosts; either preparation may eventually prove to be a good working model for studying FW transport mechanisms. The urinary bladder of Oncorhynchus mounted in vitro did not behave characteristically as the teleost gill is thought to function, but this model may be useful in characterizing various other mechanisms of ionic transport. / Thesis / Master of Science (MSc)

This thesis examined the function of the urinary bladder in vivo in the freshwater rainbow trout. In the first part of the study two new techniques were developed to examine the possible urine storage and ionoregulatory roles of the bladder in vivo. An indirect approach, using non-catheterized fish, involved "spot sampling" from the bladder to determine urine composition, and measurement of the appearance of ^3H polyethylene glycol-4000 (a glomerular filtration marker) in surrounding water to quantify urination events. The direct approach employed a new external catheterization technique to collect naturally discharged urine. Both methods demonstrated that resting trout urinate in intermittent bursts at 20-30 min intervals, and that natural urine flow rate (U.F.R.) is at least 20 % lower and urinary Na^+ and Cl^- excretion rates at least 40% lower than determined by the traditional internal bladder catheter technique. The urine is stored for approximately 25 min prior to discharge, and significant reabsorption of water and ions (Na^+, Cl^-, K^+, urea, and possibly other substances) occurs via the bladder epithelium during this period; a small residual volume is likely always maintained. The second part of the study employed the new external catheter and the traditional internal catheter to quantify the responses of the bladder, relative to those of the kidney, to two experimental disturbances. Chronic (32 h) infusion with 140 mM NaCl produced isosmotic volume loading without a change in plasma [Na^+], [Cl^-], or acid-base status. The kidney responded with a large increase in glomerular filtration rate (G.F.R.), a smaller increase in U.F.R., and increased reabsorption of water and ions. The bladder responded with a small increase in urination burst volume, a larger increase in burst frequency, and therefore a decreased urine storage time. Despite this increased throughput, Na^+ and Cl^- reabsorption rates across the bladder epithelium actually increased. Reabsorption of urea and K^+ remained constant, despite expected decreases due to decreased urine storage time. A similar infusion with 140 mM NaHCO_3 produced isosmotic volume loading together with metabolic alkalosis reflected m increased blood pH, increased plasma [HCO_3^-], decreased plasma [Cl^-], with no change in plasma [Na^+]. The response of the kidney was similar, though HCO_3^- filtration, reabsorption, and excretion rates all increased, while rates for Cl^- were proportionately lowered; renal Na^+ handling was unaffected. Bladder urination patterns and Na^+ reabsorption were also similar, but there was no evidence of bladder involvement in HCO_3^- secretion or reabsorption (ie. in acid-base regulation). It is concluded that previous studies using internal catheterization have greatly underestimated the ionoregulatory effectiveness of the entire renal system by negating bladder function. The external catheterization technique developed in this thesis provides researchers with a method to collect naturally vented urine, and thereby evaluate the role of the entire renal system, including the bladder, in response to experimental manipulations. / Thesis / Master of Science (MS)

Three hundred rainbow trout from each of two strains (Wytheville and the Soap Lake) were exposed in equal numbers to three non-overlapping wavebands of light (red, green, blue). One hundred fish from each strain were used as a control. These fish were exposed to unfiltered light of intensity equal to that of the three spectral treatments (21.4 lux). All fish were exposed to continuous light of the assigned experimental spectra for 53 days. Fish were fed trout chow twice daily at a rate previously found to maximize growth and efficiency. This feeding rate was determined by consulting hatchery records and the feeding charts developed by Haskell (1959). Mean length and mean weight of test animals may be affected by the rearing of individuals under specific wavebands of light (α = .001). Fish grown under blue or green light had the greatest mean length and fish grown under control or green light had the greatest mean weight while those reared under red light had the lowest mean length and mean weight. Although differences in coefficient of condition, yield, ferd conversion ratio, and survival were not Significant between light treatments (α = 0.05) in my study, significant differences may possibly be found in studies with a larger sample size. Although high variability and small sample size limit interpretation, this study suggests that certain light treatments used in conjunction with certain strains of fish could improve hatchery production. / Master of Science

Strains evaluated were Ennis (EN, domestic), Fish Lake (FL, wild), Mcconaughy (MC, wild), FGL Standard Winter (SW, domestic), and Sand Creek (SC, semiwild). In 1981, four Virginia put-and-take streams were stocked with 150 and 50 of each strain in March and May, respectively. Creel and electrofishing surveys were conducted to determine harvest, movement and survival after fishing. A reference (unfished) stream was also selected and stocked with 50 of each strain, and electrofishing surveys were conducted to determine survival, growth and movement. SW and EN strains were caught by anglers primarily during opening weekend (April 4-5, 1981), while the FL and SC strains were caught throughout the creel survey period. The MC strain was consistently lowest for total estimated harvest, while the SC and SW strains were equally high in total estimated harvest. Significant differences occurred in the proportional relationships of strain harvests among streams. May harvest results generally corroborated April results, except that significant differences among streams were not found. Greater survival for strains with low harvests during April was not evident in fished streams. Natural mortality rates in the reference stream did not differ significantly among strains between May 20 and October 22, 1981. Change in average length of the strains over four months in Spring Branch ranged from -4.3 mm for EN to +18.9 mm for SW. Percentage of stocked biomass of the SW strain remaining after five months (20.8%) in the reference stream was more than twice that remaining for the EN (9.6%) and SC (9.4%) strains. No significant differences in downstream movement, and no significant upstream movements, were observed for strains in the fished and reference streams. / Master of Science

Thesis (MPhil)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: trout was conducted at the Jonkershoek trout research station of the Division of Aquaculture, University of Stellenbosch. Treatments consisted of ten experimental diets containing increasing levels of Spirulina (0%, 0.05%, 0.1%, 0.15%, 0.3%, 0.6%, 1.25%, 2.5%, 5% and 10%). The data was analyzed through means of a one-way ANOVA and Tukey’s pair wise comparison test for significant differences between treatments for the various parameters of flesh pigmentation and growth. The results indicates that the inclusion of Spirulina in the diets of rainbow trout will cause a undesirable yellowing of fillets, particularly at levels of inclusion at 5 percent and above, which may limit its use in diets for rainbow trout. There was an inconsistent increase in b* (yellowblue) and Chroma values with increasing levels of Spirulina inclusion, which may indicate the deposition of carotenoids (yellow-orange colour range) instead of the desired deposition of xanthophylls (pink-red colour range) in the flesh of the rainbow trout. This increase in b* (yellow-blue) values was significantly higher (P<0.05) at inclusion levels above 5 percent. Spirulina had no significant effect on weight gain of rainbow trout at any level of inclusion. No significant differences (P>0.05) were observed in any of the other production performance parameters (growth rate, feed intake, feed conversion ratio, viscerosomatic index, hepatosomatic index, and liver lipid content) that were evaluated. Low mortality rates were observed with no significant differences between treatments. A trend of decreased feed intake with increased levels of Spirulina inclusion became significant at the 2.5 percent level of inclusion, caused by deterioration in the palatability of the feed. A significantly higher dress-out percentage was observed at levels of Spirulina inclusion above 5 percent. A trend of decreased liver lipid content with increased Spirulina inclusion was observed, though not significant at any level of Spirulina inclusion. This observation justifies further investigation because of its potential to improved carbohydrate metabolism in carnivorous fish Results confirm that up to 10% Spirulina can effectively replaced soybean meal in the control diets for rainbow trout while simultaneously improving carcass dress-out at high inclusion levels. / AFRIKAANSE OPSOMMING: rantsoen van reënboog forel te evalueer. Die eksperiment is opgestel by die Akwakultuur Divisie, van die Universiteit van Stellenbosch, se navorsingstelsel in Jonkershoek, buite Stellenbosch. Reënboog forel (Oncorhynchus mykiss) vingerlinge van gemiddeld 20 gram is gebruik en ingedeel in 20 ronde tenks volgens kommersieële digthede (250 per tenk). Die rantsoene is gemeng met verskeie vlakke van Spirulina insluiting (0%, 0.05%, 0.1%, 0.15%, 0.3%, 0.6%, 1.25%, 2.5%, 5% en 10%). Twee herhalings van elke rantsoen is gevolg vir ‘n periode van 3 maande. Die vis is ad lib (volgens behoefte) gevoer, drie maal per dag. Daar was ‘n neiging tot ‘n verhoging in b* (geel-blou) en Chroma waardes met verhoogde insluitingsvlakke van Spirulina. Hierdie is wel ‘n aanduiding van die deponeering van karoteen, maar val in die geel-oranje kleur reeks en is nie die verlangde pienk-rooi (xantofil) kleur in die spier weefsel van die vis nie. Die verhoging in b* (geel-blou) waardes was statisties betekenisvol (P<0.05) bo die 5% insluitings vlak. In vergelyking met die kontrole (0%) rantsoen, was daar geen betekenisvolle massa toename na afloop van die proef tussen die verskeie behandelings nie. Behalwe vir ‘n verskil in voer inname, was daar geen statisties betekenisvolle verskil (P>0.05) waarneembaar tussen die verskillende behandelings ten opsigte van die verskeie produksie prestasie parameters nie. Daar was wel ‘n afnemende neiging in voer inname met verhoogde vlakke van Spirulina wat betekenisvol geraak het bo 2.5% insluitingsvlak. Smaaklikheid kan die moontlike rede hiervoor wees. Baie lae mortaliteite is ervaar by al die insluitings vlakke. Daar was ook ‘n neiging in hoër uitslag persentasie by verhoogde insluitingsvlakke van Spirulina wat betekenisvol geraak het bo 5 % insluiting. ‘n Afnemende vlak van lewer lipied inhoud is waargeneem maar was nie betekenisvol by enige van die insluitingsvlakke nie. Resultate van die proef dui daarop dat 10% Spirulina insluiting effektief kan dien as ‘n gedeeltelike plaasvervanger vir soyaboon meel in forel rantsoene. Die hoër uitslag persentasies hou belofte in. Die onverlangde vergeeling van die filette mag die gebruik van Spirulina beperk by reënboog forel rantsoene veral bo 5 % insluitings vlakke. Die verlaging in lewer lipied vlakke by ‘n verhoging van Spirulina insluiting regverdig vêrdere navorsing oor die potensiaal van Spirulina om die metabolisme van koolhidrate te verbeter by karnivoor visspesies.

Indole-3-carbinol (I3C) inhibits chemically induced tumor formation in rodents and rainbow trout. This study examines the effect of I3C and its analog, indole-3-acetonitrile (I3N) on xenobiotic-metabolizing enzyme systems. The modulation of these enzyme systems have been shown to have significant effects on the interaction of chemical carcinogens and cellular constituents. Rainbow trout were fed 500, 1000 and 2000 ppm dietary levels of I3C and 50, 500 and 1000 ppm dietary levels of I3N for 8 days. β-napthoflavone (BNF), which is also an effective anticarcinogen in the trout, was fed at a 500 ppm dietary level and was used as a positive LM4b (a cytochrome P-450 isozyme) inducing control. Enzyme activities assayed were: ethoxyresorufin-O-deethylase (EROD), ethoxycoumarin-O-deethylase (ECOD), glutathione S-transferase (GST), and uridine diphosphoglucuronosyl transferase (UDPGT). Total cytochrome P-450 content was determined spectrophotometrically by the CO reduced method. The specific P-450 isozymes, LM2 and LM4b, were detected quantitatively using the western blot method. The BNF diet induced EROD and ECOD activities by an average of 17 fold and 5.5 fold, respectively. Total P-450 content was increased 2-fold; the P-450 isozyme LM4b was induced more than 5-fold, but LM2 content remained unchanged. This diet increased UDPGT activity 1.5-2-fold, but GST activity was not induced by dietary BNF. Neither I3C nor I3N induced the activity levels of the enzymes assayed at any administered dietary levels, which have previously shown to inhibit tumor formation and reduce formation of carcinogen-DNA adducts. Thus, the anticarcinogenic mechanism of I3C may proceed in trout by mechanisms other than enzyme induction. Further experiments on the effect of I3C and I3C acid condensation products (RXN) on in vitro AFB1-DNA binding resulted in a 40% and 48% inhibition of AFB1-DNA binding by I3C and RXN, respectively. Additions of RXN at levels much lower than those estimated to exist in vivo in hepatic tissue resulted in a significant reduction in AFB1-DNA formation suggesting that even small levels of RXN offers protection against the genotoxic effect of AFB1. However, in vitro additions of neither I3C nor RXN had an effect on DNA binding using AFBI-CI₂, an aflatoxin analog that does not require enzymatic activation. These results suggest that the primary mechanism for I3C inhibition of AFB1 induced carcinogenesis may proceed by inhibiton of formation of the ultimate electrophile, i.e. by reversible inhibition of cytochrome P-450. / Graduation date: 1989

Nanotechnology is a rapidly growing industry of global economic importance, with new technologies exploiting the novel characteristics of materials manufactured at the nanoscale being developed for use within the biomedical, electronic, energy production and environmental sectors. The unusual properties of engineered nanomaterials (ENMs) that make them useful in such applications have led to concerns regarding their potential impact on the environment. The aquatic environment is particularly at risk of exposure to ENPs, yet, there is currently little known about their behaviour in aquatic systems, their capacity to be taken up by aquatic organisms or their potential toxic effects. The studies that were conducted during this work sought to investigate the ecotoxicology of a range of metal and metal oxide nanoparticles using fish as a vertebrate model. In order to gain a better understanding of the uptake and effects of ENMs in fish, rainbow trout (Oncorhynchus mykiss) were exposed to nanoparticulate (34 nm) and bulk (>100 nm) titanium dioxide particles via the water column (500 and 5000 µg L-1), and to titanium dioxide nanoparticles via the diet (0.1 and 1 mg g-1 food) and via intravenous injection (1.3 mg kg-1 body weight). Uptake of titanium dioxide into the tissues of trout after waterborne and dietary exposure was found to be very low, suggesting limited bioavailability of the nanoparticles to the fish, although small amounts of uptake of titanium dioxide across the gill epithelial membrane were observed using coherent anti-stokes Raman scattering. Intravenously injected titanium dioxide accumulated and was retained in the kidneys for up to 21 days, but no adverse effect on kidney function was detected. Silver nanoparticles are already in widespread use in a variety of consumer products such as wound dressings, food containers, sock fabrics and paints, principally for their antimicrobial activity. Despite its growing commercialisation, there is little known about the environmental effects of the use of nanoparticulate silver in these products. In order to investigate these potential effects, rainbow trout were also exposed to 10 nm, 35 nm and bulk (0.6-1.6 µm) silver particles via the water column at concentration of 10 and 100 µg L-1. Uptake of silver in the gills and liver of trout occurred, with smaller nanoparticles showing a greater propensity for association with gill tissue, but with no significant differences in uptake between particles of different sizes in the liver. No increases in lipid peroxidation were detected in gills, liver or blood plasma of trout, however, expression of cyp1a2 was significantly up-regulated in exposures to 10 nm silver particles in the gill, suggesting an increase in oxidative metabolism. In an attempt to develop an effective high through-put in vitro screening assay for ENMs, the suitability of isolated rainbow trout primary hepatocytes was examined as a potential model for in vitro screening of a range of toxicological endpoints in response to nanoparticles and for studying uptake of nanoparticles into cells. The hepatocytes retained a good level of functionality after culturing as evidenced by vitellogenin production in response to the synthetic oestrogen, 17β-oestradiol. The cultured hepatocytes, however, showed limited responses on exposure to titanium dioxide, zinc oxide, cerium oxide and silver nanoparticles for lipid peroxidation and glutathione-s-transferase activity assays. Furthermore, the hepatocytes were unresponsive to the induction of these biological responses in the positive controls, suggesting they are not a good model for investigating the potential toxic effects of ENMs in terms of these endpoints. Uptake of the nanoparticles into the cells, however, was demonstrated by coherent anti-stokes Raman spectroscopy, indicating that this in vitro assay may provide a useful model for studying uptake of ENPs into cells. The studies conducted in this thesis contribute the science base regarding the bioavailability of ENPs in aquatic media as well as highlighting the importance of characterisation of ENPs in understanding their behaviour, uptake and effects in aquatic systems and in fish.