Dissertations / Theses on the topic 'Algal feeding'

The effects of two applications of foliar sprays made from kelp (Macrocystis intearifolia Bory) on growth of beans (Phaseolus vulgaris L.) under three moisture regimes were investigated. Date of kelp harvest had little effect on plants grown in water excess or deficit conditions, although means for kelp collected in spring tended to be higher. On soils maintained near field capacity, spray made from kelp collected in July resulted in increases in some bean yield components beyond the effects of kelp collected in spring or fall. The effect of storage of liquefied kelp at room temperature was also investigated and found to be soil moisture dependent. Leaf and root weights of plants grown in field capacity and dry soil respectively were lower for plants treated with kelp aged for 118 days compared to plants treated with kelp stored for longer or shorter durations. In wet soil conditions, the effect of sprays on plant height was reduced by storage of the liquefied kelp. Kelp extracts were fractionated by solvent partition. The butanolic fraction was shown to increase significantly many yield variables under wet soil conditions. This fraction had cytokinin-like activity in two bioassay systems, and contained substances co-eluting with isopentenyl adenine and zeatin in column, thin layer, and gas-liquid chromatography systems. Non-significant increases for some plant yield components resulting from application of unfractionated kelp paralleled these increases. A kelp fraction with undefined constituents increased some yield variables of plants grown in field capacity soil, as did a fraction with auxin and gibberellin-like activities in bioassay. The presence of inhibitors in the kelp was indicated by significantly lower pod yields under dry soil conditions, and a reduction in cytokinin-like bioassay activity when increasing amounts of kelp were assayed. The possibility that phytohormone deficits resulting from root stress are ameliorated by some components of the kelp spray is discussed.
Land and Food Systems, Faculty of
Graduate

Consumers are concerned about antibiotic and ractopamine usage; therefore, alternatives need to be found. Objectives of this study were to investigate the effects of using seaweed as an alternative feed supplement and comparing performance, carcass, pork quality, and immune traits in pigs fed seaweed, control, and ractopamine diets. Pigs were allocated to one of three treatments (CON, SWE, RAC) at weaning (n = 40/treatment). Pigs were weighed every two weeks. Carcass characteristics, pork quality, and immune data were collected post-mortem. No differences were found between treatments for feed intake, growth, or feed efficiency. Pigs on RAC treatment had greater hot carcass weight and dressing percentage (P < 0.05). Chops from RAC pigs were lighter (P = 0.05), less red (P < 0.05), and tougher (P = 0.08). There were no differences between treatments for FABP2 gene expression, cell proliferation percentages, or crypt depths. Therefore, no negative effects of feeding seaweed to pigs were found in this study.

The biotechnology of production and utilisation of the cyanobacterium Spirulina has been well documented. Research has centred mainly on application in human and animal nutrition, and has been motivated by the high protein, vitamin, fatty acid and growth factor contents. The main obstacle in realising the full potential of this feed source has been the high production costs associated with its mass culture in defined media. The observation of blooms of Spirulina in tannery effluent evaporation ponds in Wellington, South Africa, prompted this investigation into the harvesting, and nutritional and toxicological evaluation of this potentially low-cost production system, with the ultimate aim of using the product in aquaculture rations. An investigation of the chemical gradient along the evaporation cascade showed a positive correlation between the prevailing chemical conditions and the dominant species populations. A standing crop of 9.5 tonnes/ha of Spirulina was found to be present in the latter alkaline ponds, characterised by relatively lower organic and sulphur contents. Initial harvesting of the biomass was achieved by the design, construction and implementation of a small-scale screen harvest, which yielded a 25 kg (dry weight) crop. A scale-up model was then designed, and implemented in a technical scale harvest, yielding a crop of 250 kg (dry weight). Both these harvests utilised the bloom of surface-autoflocculated biomass. Concentrated cell slurries were sun-dried on muslin beds, and milled to a coarse powder. An evaluation of the harvest revealed a chemical content similar to other published reports of defined media cultures, with the exception of the protein and amino acid contents. The observed lower levels of the latter two are almost certainly due to the sun-drying method employed, known to reduce the protein content due to thermal denaturation. Legislation demands the strict toxicological evaluation of new protein sources, and because of the effluent-nature of the growth medium of this source of Spirulina, its viability lies only in the application as an animal feed or supplement. A range of toxicological tests were chosen that were targeted to elucidate the possible toxicological constraints of this effluentgrown source of protein in animal nutrition. The nucleic acid and pesticide contents of the harvested biomass were within the prescribed safety ranges. Atomic absorption showed minimal accumulation of minerals and heavy metals from the effluent. A bioassay with the brine shrimp Anemia salina showed that the biomass contained no toxicologically active water-soluble components. A short term feeding trial with new-born chicks showed that supplementation with Spirulina had no effect on the growth rates and feed conversion ratios of the different feeding groups. Pathological analyses showed that the liver was the only target organ to elicit a change in response to supplementation of the diets with Spirulina. A general decrease in liver weight was noted, with Cu, Ca, Fe and Zn being significantly accumulated. A histopathological examination however, showed no cellular and functional aberration from the control animals. The toxicological analyses gave the preliminary safe go-ahead for the evaluation of effluent-grown Spirulina in aquaculture nutrition. The South African abalone Haliotis midae, and the rainbow trout Oncorhynchus mykiss were chosen as representative species of edible cultured organisms. The technology for the culture of the perlemoen abalone is being established in South Africa, with the main area of research being the development of an artificial diet for high density culture. A 40 day growth trial demonstrated that lower concentrations of Spirulina supplemented to an agar-based fishmeal diet resulted in growth rates and feed conversion ratios similar to the control fishmeal and purified-casein diets, and thus has application potential in the nutrition of this high-cost marine delicacy. The aquaculture technology of freshwater rainbow trout is already well established. An eight week feeding trial with various concentrations of Spirulina showed that this effluent-grown protein source can partially replace fishmeal in semi-purified diets. Fish fed Spirulina did not exhibit decisive manifestations of toxicity, as determined in a histopathological study. In addition, Spirulina supplementation resulted in enhanced colouration of the skin and flesh, which may have implications in the aesthetic marketing of this sought-after table fish. The primary aim of this preliminary investigation thus concerned the determination of the biotechnological potential of this effluent-source of Spirulina. A technology transfer from the economically unfeasible defined-media culture was implemented. This project is ultimately aimed as a contribution towards the treatment of tannery wastewater, by the removal of contaminants from the effluent in the form of organic biomass.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009.
An 84-day study was conducted to find a suitable diet and feeding level for the culture of South African abalone (Haliotis midae) in Namibia. Two experimental diets, namely, a seaweed diet (SWD) Laminaria pallida (macrophytic algae) and a formulated diet (FD) (macro-algae), for use in abalone (Haliotis midae) feed development, were evaluated. The animals used in this study were juveniles (24.33 ± 3.14 mm shell length; 2.72 ± 0.83 g live weight, mean ± SE) and sub-adults (58.07 ± 10.33 mm shell length and 41.96 ± 20.61 g live weight, mean ± SE). The nutrient profile of the SWD and FD displayed no differences in the protein and carbohydrate levels. Crude protein levels ranged from 4.91 to 17.68% (dry matter (DM) basis). The lipid levels in the FD (0.25%) were almost 0.56% lower than that in the SWD (0.76%). The feed conversion ratio (FCR) and protein efficiency ratio (PER) for the sub-adult abalone ranged from 2.80 to 10.90 and 0.10 to 0.40, respectively. The juvenile abalone fed on the FD yielded significantly lower (P < 0.05) FCRs (0.8) and higher PERs (1.20) than their counterparts fed on the SWD. A similar trend was observed for the sub-adult abalone although the differences were not significant (P > 0.05). The relative growth rate (RGR) of juvenile fed on the FD was 25% lower compared to those fed on the SWD, while that of the sub-adult abalone fed on the FD was 29% lower compared to the abalone fed on the SWD. From the daily growth rate (DGR) in terms of daily body weight (DGRBW) calculated after the 84-day period, repeated-measures ANOVA (RANOVA) indicated no interaction between time period and diet. Although slightly lower, the DGRBW for the juvenile abalone fed on the SWD diet (0.033 g/day) did not differ significantly from the DGRBW of abalone fed on the FD (0.079 g/day). In contrast, sub-adult abalone fed on the SWD exhibited significantly higher DGRBW compared to those fed on the FD. Although the abalone fed on the FD was slightly higher in nutritional content, there was no significantly difference (P > 0.05) in the nutritional profile of the abalone soft body tissue fed on either the SWD or FD. There was no significant (P > 0.05) difference in preference when comparing the aroma of the abalone meat samples fed on either the SWD or FD. However, there was a significant difference (P < 0.05) in the consumers’ preference in terms of flavour for the abalone sample fed on the FD. The trained taste panel results indicated that there was no difference in the aroma and flavour of the abalone fed on the different diets (P > 0.05). This study showed that cultured juvenile H. midae, readily accepted a FD, producing high consumption and survival rates. The FD still warrants further refinement and testing for it to become a more effective mariculture feed with commercial potential.

The aim of this study was to evaluate the nutritional value of algae and zooplankton grown in an algal integrated ponding system for poeciliids. The available information on the nutritional requirements of poeciliids was compared with a proximate analysis of the algae and zooplankton. The effluent grown algae and zooplankton had a crude protein value of 41.47 ± 0.2% and 36.84 ± 0.3%, a lipid content of 4.8 ±. 0.4% and 11.1 ± 0.8% and a carbohydrate content of 35.13 ± 0.8% and 31.06 ± 0.6% respectively. These values compared favourably with those of the known nutritional requirements of poeciliids. To test if the nutritional value of the algae and zooplankton in the AlPS was constant, the species composition of the algae and the crude protein content of the algae and zooplankton in the high rate oxidation ponds were measured monthly and bi-weekly for a year respectively. The species composition remained fairly stable for the duration of the experiment and the average protein composition of the algae and zooplankton was 43.4 ± 4.4% and 38.6 ±2.8% respectively. This indicated that the algae and zooplankton in the AlPS provided high protein biomass through the year. The quality of the effluent grown algal and zooplankton biomass was evaluated by analysing their amino acid composition and comparing it with the amino acid composition of the body tissue of X. helleri. With respect to the amino acid composition of the body tissue of X. helleri, the amino acid profile of the algae had a 69% and the zooplankton a 63% similarity. The quality of the pure algal and zooplankton protein was also tested biologically, by feeding them directly to poeciliids during a ten week growth trial. The algae and zooplankton diets did not result in adequate growth compared to poeciliids which were fed a formulated control diet. The initial growth trial also evaluated the effect of processing on the chemical composition of the algae and its biological effect on fish fed with it. There were no significant differences in the chemical composition of fresh and sun dried algae and this was reflected in the growth rates of the fish which did not differ significantly. Freeze dried algae had a lower crude protein content than fresh and sun dried algae and a poorer amino acid composition. Fish fed freeze dried algae exhibited poorer growth and survival in comparison to the other treatments. The gut transit times of X. helleri and the gastric evacuation times of poeciliids were determined using colour dyes incorporated in the diet and by sacrificing fish at predetermined intervals after feeding respectively. The gut transit time of X. helleri fed a sun dried algal diet and a formulated diet was 225 ± 8.55 minutes and 261.93 ± 10.86 minutes respectively. The gastric evacuation times of X. helleri, P. reticu/ata and P. velifera were 7, 9 and 8 hours respectively. Since the maximum amount of food in the hindgut after feeding was detemined to be 3, 5 and 3 hours in X. helleri, P. reticulata and P. velifera respectively, fish were sacrificed at these times in the digestibility study. The digestibility of sun dried algae was determined using 1 % chromic oxide as an internal marker in the algae. The apparent crude protein digestibility of sun dried effluent grown algae ranged from 65%-75% in the three poeciliid species. Based on the results of the chemical and biological analysis of the algae and zooplankton, conventional diets incorporating algae at 5% and 20% protein inclusion levels were formulated. These diets and a treatment in which zooplankton, reared in the AlPS were fed as a dietary supplement to a formulated diet were fed to poeciliids for twelve weeks. No significant differences in the growth of poeciliids fed any of the test diets were observed. It was concluded that the algae could be incorporated into poeciliid formulated diets up to level of 20% protein inclusion without any negative effect on the growth of the fish. The chemical and biological evaluation of the algae suggested that it had a similar nutritional quality to soyabean meal. Poeciliid growth was not enhanced with a zooplankton supplement, however a possible low feeding rate by poeciliids on the zooplankton as a result of their small size may have affected the result. The colour enhancement potential of effluent grown algae and zooplankton was evaluated biologically in ten and twelve week growth trials using visual observation (31 people) and by using a chromameter. While pure, sun dried algae significantly enhanced the colour of P. reticulata, no significant differences in the colour of poeciliids were observed or recorded when fish were fed diets incorporating sun dried algae up to levels of 20% protein inclusion. The effect of effluent grown algae and zooplankton on poeciliid health was also tested biologically in the ten and twelve week growth trials. The high mortalities (75%-84%) recorded for X. hel/eri when fed the pure algal and zooplankton diets were considered to be as a result of the nutritional inadequacy of the diets since there were significantly less mortalities in fish fed the formulated control diet and 63% of the fish that died during the course of the trial were emaciated. In addition, fewer mortalities (10%-40%) were recorded in X. hel/eri fed the nutritionally adequate formulated diets in the twelve week growth trial. No symptoms of disease were recorded in the twelve week growth trial and the algae was considered to have no toxicological or pathological effects on poeciliids. Centrifugation, sand filtration, sedimentation, microstraining and biological harvest were evaluated as methods of small scale algal harvest from the high rate oxidation ponds. Algae could be harvested most efficiently with little associated labour by sedimentation (without flocculating agents) and by microstraining with 60IJm mesh. Effluent grown algae can replace conventional feed ingredients up to a level of 20% protein inclusion without negatively effecting the growth, colour, health or survival of poeciliids.

Traditionally, differential-equation models for population dynamics have considered organisms as "fixed" entities in terms of their behaviour and characteristics. However, there have been many observations of adaptivity in organisms, both at the level of behaviour and as an evolutionary change of traits, in response to the environmental conditions. Taking such adaptiveness into account alters the qualitative dynamics of traditional models and is an important factor to be included, for example, when developing reliable model predictions under changing environmental conditions. In this thesis, we consider piecewise-smooth and smooth dynamical systems to represent adaptive change in a 1 predator-2 prey system. First, we derive a novel piecewise-smooth dynamical system for a predator switching between its preferred and alternative prey type in response to prey abundance. We consider a linear ecological trade-off and discover a novel bifurcation as we change the slope of the trade-off. Second, we reformulate the piecewise-smooth system as two novel 1 predator-2 prey smooth dynamical systems. As opposed to the piecewise-smooth system that includes a discontinuity in the vector fields and assumes that a predator switches its feeding strategy instantaneously, we relax this assumption in these systems and consider continuous change in a predator trait. We use plankton as our reference organism because they serve as an important model system. We compare the model simulations with data from Lake Constance on the German-Swiss-Austrian border and suggest possible mechanistic explanations for cycles in plankton concentrations in spring.

The aim of the present study was to determine the potential impact of intertidal grazers on the distribution of macro algae on the south coast of South Africa. Particular attention was paid to the large patellid limpet, Patella oculus, which is found thoughout the intertidal zone. Studies of gut contents revealed that Patella oculus was capable of ingesting not only the thallus of foliose (eg. Ulva spp.) and encrusting coralline macroalgae, but also spores and diatoms. The inclusion of these relatively small particles in the diet was surprising, as electron micrographs of the radula of P.oculus revealed that it is typically docoglossan in structure. Such radulae are thought to be poorly suited for collecting small food particles. Sand made up a significantly higher proportion of the gut contents than other particles at all shore heights, which suggests that P.oculus might be capable of excavating the rocky substratum, or of sweeping up sand, while searching for food. Analysis of the gut contents of other local herbivorous molluscs, was also carried out. These species included the winkles, Oxystele variegata and O.sinensis, and the small pulmonate limpets, Siphonaria concinna, S.capensis, and S.serrata. The guts of all species contained mainly spores and diatoms, although small fragments of Ulva sp. were found. The population structure of Patella oculus was investigated at two sites, Cannon Rocks and Old Woman's River. At Cannon Rocks, mean shell length of low-shore animals was significantly lower than that of both mid- and high-shore animals, while at Old Woman's River, no significant difference was found among shore heights. A regression equation for In (shell length) vs In (dry weight) was calculated, and based on length data, the biomass density (g dry mass.m⁻²) of P.oculus at Old Woman's River was estimated. Values ranged from 2.8 on the low- and midshore to 0.37 on the high-shore. A manipulative field experiment was used to determine the impact of mesograzers and macrograzers (such as Patella oculus) on the distribution of intertidal macro algae on the mid- and low-shore at Old Woman's River. Grazers were excluded using mesh cages (mesh size = 3mm), in two separate experiments, one in winter and the other in spring. Percentage cover of macroalgal species and sessile invertebrates was estimated at approximately 6 week intervals for up to 3 months. MANOV A showed that treatments did not significantly affect cover of macroalgae or barnacles during winter. However, towards the end of the spring experiment (midshore only) cover of barnacles and green foliose turfs did increase in those plots from which mesograzers and/or macro grazers were excluded. The failure of the statistical tests to detect significant differences at some time intervals may have been caused by high levels of variation among replicates. This suggests that factors other than grazing are of overriding importance in determining the distribution of local macroalgae. The existence of a possible symbiotic relationship between Patella oculus and the red foliose alga, Gelidium pristoides, was investigated. The availability of various substratum types, including rock, limpet shells, barnacles etc., and the proportion of the total cover of G.pristoides on each, was calculated. It was shown that a significantly higher proportion of the alga grew on limpet shells, although the availability of this substratum type was low. It is thought that the aggressive behaviour of P.oculus prevents all but juvenile Patella longicosta from grazing on its shell, thus providing a refuge from grazing for G.pristoides.

Zooplankton community structure was studied monthly in Myponga and South Para Reservoirs in South Australia from January 2008 to June 2009. Myponga Reservoir is a highly managed reservoir with prolong artificial mixing while South Para Reservoir is non-managed and has less human perturbation. The total number of taxa in Myponga and South Para Reservoirs were 16 and 20 respectively. Cladocera was the dominant taxonomic group in relation to the total number of taxa but in terms of total density, Copepoda were the numerically dominant group in both reservoirs. The most frequently occurring Cladocera were Ceriodaphnia cf. quadrangula, Ceriodaphnia cornuta and Bosmina meridionalis while Asplanchna priodonta was the predominant Rotifera throughout the study. Copepoda were dominated by Calamoecia ampulla and Microcyclops sp., making up the largest portion of total zooplankton density. Differences with regard to species richness were due to the sole occurrence of Polyarthra dolichoptera, Keratella slacki, Anuraeopsis fissa and Pompholyx complanata in South Para Reservoir. Observations showed relatively consistent species diversity and density throughout the study in Myponga Reservoir except for low densities during summer for Cladocera and Copepoda groups while seasonal variations in zooplankton composition and abundance are features of South Para Reservoir. Shallow locations have greater zooplankton densities compared to deep locations in both reservoirs. Nevertheless, vertical migration in shallow locations was inexplicit as compared to deep locations in Myponga Reservoir. Physico-chemical factors particularly water temperature and biological factors including the occurrence of green algae and cyanobacteria may influence zooplankton abundance and the dynamics of the community. Thermal stratification and circulation resulted in brief population dispersion and consequently had a fluctuation of seasonal distribution pattern of zooplankton. Both horizontal gradients and stratification are strong factors enhancing zooplankton richness at South Para Reservoir. The functional responses of Daphnia carinata, D. lumholtzi and Ceriodaphnia cf. quadrangula to six algal species at three concentrations are described. The ingestion and filtration rates were measured by Low Revolutions per Minute Tumbler (LRPMT) for 2 hours at 20oC. Ingestion and filtration rates varied with algal species and concentrations. Daphnia carinata removed algal cells at a higher rate than other two species when feeding on uni- and multi-algal species suspensions. Quantitative differences in the rate of food intake were found in suspensions of Ankistrodesmus falcatus, Scenedesmus obliquus, Chlorella vulgaris, Chlamydomonas reinhardtii, Anabaena circinalis and Microcystis flos-aquae. Small cells of green algae were more readily ingested by grazers. Ingestion rate increased linearly with cell concentration up to a maximal rate. Comparison of the ingestion rate on a green and blue-green algal mixture demonstrated the importance of edible algae in zooplankton selective feeding. Filamentous Anabaena circinalis and colonial Microcystis flos-aquae were less favourable as food particularly in a multi-algal suspension. In contrast, both these blue-green algal species can also be utilized by the grazers when presented as a unialgal suspension although these species were previously reported to have lethal toxic effects on cladocerans. Therefore, a management strategy using cladocerans for controlling undesirable cyanobacteria is contemplated to be necessary in the future. As the grazing rates would be correlated with zooplankton taxonomy composition, monitoring data is important in order to know the dominant zooplankton taxa in the reservoirs.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2012

碩士
國立中山大學
海洋資源學系研究所
92
The environment of bivalve Sanguinolaria rostrata growth and reproduction is affected by temperature, salinity and algal concentration.The growth and fattening of the bivalves is closely associated with filter-feeding. Hence, the present work was to investigate the effect of temperature, salinity and algal concentration on the filter-feeding of the bivalves. The salinity ranging from 5 to 30 at the interval of 5 psu, four temperatures at 20°, 25°, 27° and 30℃, and three algal concentrations of each Isochrysis galbana and each Chaetoceros gracilis, 104 , 105 and 106 cells/ml, were used. Algal concentration was measured each hour and each test run last for 6 hours. A peak appeared at the salinity of 20 psu in each clearance rate vs salinity curve and clearance rate decreased with increasing algal concentration; a peak also appeared at the salinity of either 15∼20 psu in the ingestion rate vs salinity curve; and ingestion rate and the amount of pseudofaeces increased with increasing algal concentration. Under the conditions of algal concentration 104 cells/ml and temperature range 20°~30℃, a peak appeared at 25℃ in each clearance rate and each ingestion rate vs temperature curves, and the greatest peak of clearance rate was 1.13 l/h; and the amount of pseudofaeces was the greatest at 25℃ and 20 psu. The bivalves fed with Isochrysis galbana have greater clearance and ingestion rates but less amount of pseudofaeces, compared to those fed with Chaetoceros gracilis.

Nutrition is considered to have an important influence upon the life history of the green sea turtle including regulation of its growth rate, age at sexual maturity, egg production and remigration intervals amongst other influences. It would therefore be expected that the green turtle would select dietary items that would maximise its nutrient intake and balance its energy budget as predicted by optimal,foraging models. Although the feeding ecology of green turtles in seagrass communities has received attention, no study to date has investigated the feeding ecology of green turtles in an algal community. This was the first study to describe the diet and feeding ecology of green turtles foraging in an algal-based community (Heron Reef, Queensland) where seagrasses were absent. Algae account for the greatest areal cover of benthic biota on Heron Reef with over four times the areal cover of living corals. Heron Reef supports over 115 species of algae although only seven of these ever exceed more than 2% of the total algal cover. The main component of the algal assemblage is the algal turf which accounts for 56% of the total areal cover of algae. The algal community on Heron Reef is composed of species that are dynamic in distribution and diverse in chemistry. Although no trends or patterns could be detected, there is a significant spatial and temporal variation in the areal cover of algae both within and between reef habitats. The lipid, carbohydrate, ash and energy content of macroalgae species on Heron Reef varied significantly from each other but did not change significantly over time. In contrast, the change in levels of nitrogen was significant over time. Green sea turtles on Heron Reef include both resident and migrant turtles. The resident green turtles include animals from all age classes z35 cm in curved carapace length with immature animals accounting for 74% of the resident population. The sex ratio of the resident turtles is not significantly different than 1:1. Algae are the most important and almost the exclusive diet item of green turtles of all age classes and both sexes on Heron Island during all seasons. Green turtles on Heron Reef demonstrate diet preference and avoidance of undesirable species. The diet varies significantly both temporally and between age classes although there is no continuity or discernible pattern to these changes. The differences observed between the age classes may disappear when desirable dietary species become available. There are no discernible differences in diet between sexes. The diet of individual turtles captured on repeat occasions varied over time although there is no apparent pattern or continuity to this change. Some individuals exhibited considerable shifts in diet while others remained rather constant in their dietary choices. Green turtles of all age classes appear to have a base diet of algal turf but they will opportunistically exploit desirable monogeneric stands of algae when they become available. Optimal foraging models that predict diet based upon a single variable do not serve as useful predictors of diet in green turtles feeding in complex algal communities. Although diet selection does occur, green turtles on Heron Reef do not select dietary items as an exclusive function of their availability, nutrient, ash, energy or secondary compound profiles. The green turtle appears to select dietary items in response to a complex interdependent matrix of variables that influences the nutritive and energy potential of their diet while reducing the effects of algal secondary compounds. Diet selection is most likely a combination of positive and negative (avoidance) diet selection decisions. When confronted with constantly changing algal chemistry and availability, the green turtle's optimal strategy may be to forage within the heterogenous algal turf. Such a strategy would ensure that at least some superior species were included in the diet while at the same time possibly mitigating the influences of secondary compounds while optimising the benefits of diet mixing. As the composition of the algal turf is dynamic, this strategy would also ensure the inclusion of newly available species in the diet.

Continuous culture fermentation (CCF) was used to test the hypotheses that: marine microalgae (MA) and macroalgae (seaweeds) alter rumen microbial metabolism; MA types differ in abilities to provide rumen escape n-3 polyunsaturated fatty acids (PUFA); and algae have the potential to reduce enteric methane emission. The CCF system of Teather and Sauer (1988) was modified to reduce clogging, refrigerate effluent, and allow for determination of gas production. The CCF systems were inoculated with pooled rumen fluid from 4 cows. Total mixed ration was fed at the rate of 30 g DM d-1. Temperature was maintained at 39 oC, and buffered with artificial saliva to maintain pH 6.2. Response variables were measured from effluent digesta (fatty acids, NH4+-N, digestibility), fermentor contents (CCF density, volatile fatty acids), and the gas phase (CO2, CH4). The experimental design for MA testing was a 3**3 factorial. Treatments consisted of heterotrophic and photoautotrophic MA as well as a 1:1 blend with protection levels of zero, 33 and 50 % of encapsulation (w/w), and fluid turnover rates of 5, 7.5, and 10 % h-1. The seaweed treatments consisted of a PEI shoreweed mix containing Laminaria longicruris and Fucus vesiculosus tested as a component of the mix, and Chondrus crispus and Furcellaria fastigiata tested individually. The design for seaweed testing was an unbalanced 5*5 Latin square. The heterotrophic MA destabilized the digesta mat while the autotroph improved stability. Biohydrogenation was extensive for C18 FA in the basal ration (> 90 %) and less for C22:6n3 (75 %) from the heterotroph and C20:5n3 (60 %) from the photoautotroph. The recovery of PUFA was improved by encapsulation, however PUFA in the MA were not greatly affected and digestibility was improved by turnover rate. Seaweeds had no effect on CCF stability, however they reduced CH4 production without reduction in OM digestibility. The heterotroph reduced overall fermentation resulting in diminished density and volatile fatty acids and NH4+-N concentrations. Seaweed supplementation decreased NH4+-N, CO2 and CH4 production, and increased density.

Ma Wing-chi, Joyce.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references (leaves 131-148).
Abstracts in English and Chinese.
Abstract (in English) --- p.i
Abstract (in Chinese) --- p.iv
Acknowledgement --- p.vi
Contents --- p.viii
Abbreviation --- p.xii
List of Tables --- p.xiii
List of Figures --- p.xv
Chapter 1. --- Introduction --- p.1
Chapter 2. --- Literature review --- p.5
Chapter 2.1 --- Fisheries in Hong Kong --- p.5
Chapter 2.2 --- Flavor of seafood --- p.6
Chapter 2.2.1 --- Lipid-derived volatile aroma compounds --- p.7
Chapter 2.2.2 --- "Alcohols, aldehydes and ketones" --- p.8
Chapter 2.2.3 --- Enzymatic conversion of sulfur- and nitrogen-containing precursors --- p.9
Chapter 2.2.4 --- Thermally generated compounds --- p.9
Chapter 2.2.5 --- Bromophenols --- p.10
Chapter 2.2.5.1 --- General properties of bromophenols --- p.11
Chapter 2.2.5.2 --- Threshold of bromophenols --- p.14
Chapter 2.2.5.3 --- Toxicity of bromophenols --- p.17
Chapter 2.2.5.4 --- Previous studies about bromophenols --- p.19
Chapter 2.2.5.5 --- Bromophenols in aquacultured seafood --- p.20
Chapter 2.2.5.6 --- Possible dietary sources of bromophenols --- p.20
Chapter 2.2.5.7 --- Possibility of increasing bromophenol content in aquacultured fish --- p.23
Chapter 2.3 --- Criteria for selecting experimental fish model --- p.24
Chapter 3. --- Distribution of Bromophenols in selected Hong Kong seafoods --- p.27
Chapter 3.1 --- Introduction --- p.27
Chapter 3.2 --- Materials and methods --- p.28
Chapter 3.2.1 --- Sample collection and preparation --- p.28
Chapter 3.2.2 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.30
Chapter 3.2.3 --- Gas chromatography / mass spectrometry (GC/MS) --- p.30
Chapter 3.2.4 --- Compound identification and quantification --- p.31
Chapter 3.2.5 --- Recoveries --- p.33
Chapter 3.2.6 --- Moisture determination --- p.34
Chapter 3.2.7 --- Statistical analysis --- p.34
Chapter 3.3 --- Results and discussion --- p.34
Chapter 3.3.1 --- Distribution of bromophenols in seafoods --- p.34
Chapter 3.3.1.1 --- Bromophenols in marine fishes --- p.49
Chapter 3.3.1.2 --- Bromophenols in mollusks --- p.49
Chapter 3.3.1.3 --- Bromophenols in crustaceans --- p.50
Chapter 3.3.2 --- Seasonal variations of TBCs --- p.51
Chapter 3.3.3 --- Bromophenols in diet contents --- p.52
Chapter 3.3.4 --- Bromophenol contents of freshwater fish --- p.53
Chapter 3.3.5 --- Relationship between the living habitats and bromophenol contents --- p.56
Chapter 3.3.6 --- Bromophenols as flavor compounds in seafoods --- p.58
Chapter 3.4 --- Conclusion --- p.59
Chapter 4. --- Distribution of Bromophenols in selected Hong Kong seaweeds --- p.61
Chapter 4.1 --- Introduction --- p.61
Chapter 4.2 --- Materials and methods --- p.62
Chapter 4.2.1 --- Sample collection and preparation --- p.62
Chapter 4.2.2 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.63
Chapter 4.2.3 --- Gas chromatography / mass spectrometry (GC/MS) --- p.64
Chapter 4.2.4 --- Compound identification and quantification --- p.65
Chapter 4.2.5 --- Recoveries --- p.66
Chapter 4.2.6 --- Moisture determination --- p.67
Chapter 4.3 --- Results and discussion --- p.67
Chapter 4.3.1 --- Distribution of bromophenols in marine algae --- p.67
Chapter 4.3.2 --- Seasonal variations --- p.76
Chapter 4.3.3 --- Functions of bromophenols in marine algae --- p.79
Chapter 4.3.4 --- Marine algae as sources of bromophenols in marine environment --- p.80
Chapter 4.4 --- Conclusion --- p.81
Chapter 5. --- Enhancement of bromophenol contents in aquacultured fish by the development of bromophenol-rich fish feeds --- p.83
Chapter 5.1 --- Introduction --- p.83
Chapter 5.2 --- Materials and methods --- p.85
Chapter 5.2.1 --- Preparation of fish feeds --- p.85
Chapter 5.2.2 --- Storage conditions of fish feeds --- p.88
Chapter 5.2.3 --- Experimental animals --- p.88
Chapter 5.2.4 --- Solvent and chemicals --- p.90
Chapter 5.2.5 --- Extraction and quantification of bromophenols --- p.90
Chapter 5.2.5.1 --- Simultaneous steam distillation-solvent extraction (SDE) --- p.90
Chapter 5.2.5.2 --- Gas chromatography / mass spectrometry (GC/MS) --- p.91
Chapter 5.2.5.3 --- Compound identification and quantification --- p.92
Chapter 5.2.5.4 --- Recoveries --- p.93
Chapter 5.2.6 --- Moisture determination --- p.94
Chapter 5.2.7 --- Statistical analysis --- p.94
Chapter 5.2.8 --- Sensory test --- p.95
Chapter 5.3 --- Results and discussion --- p.96
Chapter 5.3.1 --- Bromophenol contents in wild-harvested and aquacultured fish --- p.96
Chapter 5.3.2 --- Development of bromophenol-rich fish feed --- p.99
Chapter 5.3.3 --- Effect of feeding the fish with the fish feed developed --- p.105
Chapter 5.3.4 --- Sensory evaluation on the flesh of the fish fed with different fish feeds --- p.121
Chapter 5.3.5 --- Growth of the fish fed with different fish feeds --- p.124
Chapter 5.4 --- Conclusion --- p.126
Chapter 6. --- General conclusion and significance of the study --- p.128
References --- p.131