Marine phytoplankton produce extracellular metabolites which may be important in controlling the interactions among species or the competition for a limiting nutrient. While the absolute amount of these metabolites may be small compared to the primary organics released by the phytoplankton cell, the control of the production of these unique metabolites may be an important factor in the ecology of the producing species. These compounds have not been extensively studied due to the difficulty in isolating these minute quantities from seawater. In this thesis, two externally produced metabolites have been investigated. The concentration of 1 -(2,6,6-trimethyl-4-hydroxycyclohexenyl)- 1,3-butanedione, a nor-caroteniod commonly referred to as the β-diketone, was quantitatively determined during the exponential and senescent stages of growth of Prorocentrum mi n imum in P-, N-, and iron-deficient batch cultures. The β-diketone was released extracellularly in a single 'pulse' during the stationary stage of growth. Several factors such as temperature, irradiance, type of nutrient-deficiency (N, P, or Fe), and the ambient nitrate concentration were important in establishing the amount of the β-diketone produced. The environmental factors did not influence the temporal pattern of production, only the absolute amount of the β-diketone produced. The limits of the range of production of the β-diketone were narrower than the range of maximum growth for any environmental influence. The inhibition of growth and the heterotrophic uptake of glucose by marine bacteria, demonstrated the antibacterial properties of the β-diketone. The second extracellular organic examined was prorocentrin. Prorocentrin is the extracellular siderophore produced by Prorocentrum minimum, P. mariae-lebouriae, and P.gracile. Functionally similar compounds are produced by Thalassiosira pseudonana and Dunaliella tertiolecta. This study is first to characterize this type of high-affinity iron (111)-transport system in marine eukaryotic phytoplankton. The pattern of siderophore production by all species is the same, although the absolute amount of the material produced is species specific. There is no intracellular or extracellular siderophore production under iron-sufficient culture conditions. When iron was deficient there was a short period of rapid extracellular siderophore production during the stationary stage of growth. The intracellular prorocentrin concentration was very low which suggests that de novo synthesis of the prorocentrin occurs just prior to extracellular release. The persistence of the extracellular siderophore in the culture medium was brief. There was an increase in the in vivo fluorescence following the loss of the siderophore from the medium. The increase in in vivo fluorescence was not accompanied by an increase in cell concentration. An hypothesis concerning the mechanism of the iron-uptake system is proposed. Procedures for the isolation and characterization of prorocentrin are presented. Prorocentrin appears to be a tri-hydroxamate siderophore with a molecular weight between 560 and 590 daltons. The iron-prorocentrin complex is stable over a wide pH range. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Although the phytoplankton of the waters off the west coast of South Africa (the Benguela Current region) has been the subject of several detailed studies in the past, data on that of the S.W. Indian Ocean has been almost entirely restricted to incidental references in the reports of expeditions which have passed through the area. Consequently, little has been known of the species composition and distribution of the phytoplankton, and nothing of its seasonal fluctuations. This study was designed to provide a broad picture of the phytoplankton of the area, the primary objective being a critical determination of the species composition. The material was collected by the S.A.S. Natal on four seasonal cruises in the area as a contribution to the International Indian Ocean Expeditions. A net-sampling technique was used to provide the maximum amount of material for quantitative analysis. The phytoplankton was found to be extremely rich in variety, 402 taxa being identified from the 98 samples collected. Of these 233 were diatom taxa, 157 dinoflagellate taxa, and the remainder being composed of members of the Chrysophyeeae (coccolithophorids), Cyanophyceae and Xanthophyceae. These are listed in the systematic section together with original references and other references used by the author for their identification. The local and general distributions or the taxa are described and many of the taxa are illustrated by line drawings or microphotographs. 5 new species are described, as well as 1 new variety, and it was found necessary to provide new names for several species. Full systematic details are given for all new or rare taxa.

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以海洋浮游植物為載體生產高附加值代謝產物如多不飽和脂肪酸、類胡蘿蔔素和多糖受它們所生存的環境條件影響。本研究旨在從一些選定的海洋浮游植物中比較使用不利物理環境處理條件如紫外線和低溫為誘導因數的有效性。首先，以來自於五種不同門的海洋浮游植物如紫球藻、新月菱形藻、湛江等鞭金藻、亞心形扁藻和集胞藻為研究物件進行調查和比較各自細胞體內各種脂肪酸、色素、碳水化合物和胞外多糖以及總類菌胞素氨基酸的含量水準，以篩選這些代謝物含量豐富的物種來進行進一步的物理誘導研究。 同時，對這五種浮游植物的90%丙酮提取物的抗氧化活性進行了比較。最後，通過利用化學方法和透射電鏡技術以及蛋白質組學分析方法， 對紫外線光和低溫如何施加影響於浮游植物代謝物的回應機制進行了研究。 / 採用包括太陽紫外線光（紫外線A和紫外線B）和人工365納米紫外線A等紫外線輻射條件，本研究對於四種進一步優選的海洋浮游植物紫球藻、新月菱形藻、湛江等鞭金藻和亞心形扁藻的生長及其代謝物如多不飽和脂肪酸、類胡蘿蔔素、多糖和總類菌胞素氨基酸的合成影響進行了進一步的比較。 / 在有關太陽紫外線的研究中，作為對於強烈太陽紫外輻射的回應，在亞心形扁藻胞內的類胡蘿蔔素如岩藻黃素和新葉黃素可在早期培養階段顯著（< 0.05）積累。此外，長期暴露於太陽紫外線輻射條件能顯著增加（< 0.05）紫球藻胞內碳水化合物以及胞外多糖的合成與積累。然而，太陽紫外輻射對浮游植物脂肪酸的影響具有種屬特異性，已發現其雖能顯著（< 0.05）增加紫球藻以及亞心形扁藻胞內多不飽和脂肪酸的含量，然而卻抑制了新月菱形藻胞內多不飽和脂肪酸的合成。 / 在進行人工365納米紫外線A處理（進行為期3天的紫外線A脅迫及其後為期3天的無紫外線A輻射處理）的研究中，已發現紫外線A能促進兩種海洋浮游植物新月菱形藻和湛江等鞭金藻的生長、總體及個別多不飽和脂肪酸和類胡蘿蔔素以及總類菌胞素氨基酸的合成。紫外線A對浮游植物生長的影響也具有種屬特異性，在當前的研究中，與亞心形扁藻相比，365納米紫外線A更能顯著（< 0.05）抑制紫球藻的生長。但是，該波段紫外線A卻可提高紫球藻和扁藻這兩種浮游植物胞內多不飽和脂肪酸、總類胡蘿蔔素和總類菌胞素氨基酸的合成與生產及其扁藻的色素含量。 / 在低溫效應研究中，以低溫主要是極低溫度（0攝氏度）為誘導因數對進一步優選的紫球藻和亞心形扁藻（含豐富多不飽和脂肪酸和個別類胡蘿蔔素資源）的生長以及它們胞內代謝物如多不飽和脂肪酸和色素（主要為類胡蘿蔔素）的合成進行了比較研究。低溫特別是極低溫度對兩種浮游植物細胞膜的流動性的提高以及它們胞內總體及個別多不飽和脂肪酸和類胡蘿蔔素的積累具有正面作用。此外，我們提出了一些關於順勢結構不飽和脂肪酸和類胡蘿蔔素在細胞膜裏的可能的功能以及它們在調節和控制細胞膜中所扮演角色的假說，如不飽和脂肪酸的"升臂假說"和類胡蘿蔔素的"鉚釘加鎖和螺栓固定功能"假說。 / 此外，無細胞壁紫球藻和具細胞壁亞心形扁藻被進一步選擇用於透射電鏡觀察研究以比較它們的細胞在紫外線A和極低溫度處理前後超微結構的變化。結果顯示，通過部分影響一些細胞器的結構和尺寸而非影響正常生理功能，紫外線A對此兩種浮游植物的超微結構僅施加較少的損傷。另一方面，儘管極低溫度使這兩種浮游植物胞內大部分的細胞器收縮或變形從而導致它們的正常生理活動受到嚴重破壞，它們整體的細胞結構並未受到破壞。因此，此兩種處理方式下的透射電鏡照片顯示，這兩種浮游植物中各種代謝物的合成並未受到如此惡劣物理環境的影響。 / 利用一維凝膠蛋白質組學分析，我們鑒定了紫球藻和亞心形扁藻胞內的功能蛋白以及比較了它們在紫外線A和極低溫處理前後的表達差異。進一步的研究發現，這兩種浮游植物對於紫外線A的回應機制相當不同。紫外線A處理後，紫球藻胞內葡萄糖磷酸變位酶和磷酸甘露糖變位酶的表達提高可能有助於該浮游植物分泌多糖物質於胞外環境中以清除由紫外線A誘導產生的自由基，另外，紫球藻胞內的過氧化物酶體式抗壞血酸過氧化物酶被啟動來合成抗壞血酸鹽以應對胞內也由紫外線A誘導而產生的自由基。然而，亞心形扁藻細胞壁的存在可能導致其胞內無需一些抗氧化相關酶和一些和扁藻多不飽和脂肪酸以及類胡蘿蔔素合成有關的中間合成酶如葡萄糖磷酸變位酶和丙酮酸甲酸裂解酶的存在，這導致了一些高值代謝物如多不飽和脂肪酸和類胡蘿蔔素在扁藻中的合成受到了抑制。三磷酸腺苷合成酶在紫球藻胞內表達水準的提高可能目標在於合成大量三磷酸腺苷以修復由紫外線A導致而受到破壞的細胞器，然而，這些三磷酸腺苷合成酶在扁藻裏受到了抑制，顯示可能扁藻胞內的三磷酸腺苷合成酶可能對紫外線A敏感，也可能是紫外線A對扁藻胞內各種細胞器的損害要比對紫球藻小。紫球藻胞內的熱激蛋白可能有助於保持於紫外線A下的細胞活力，然而，扁藻胞內該蛋白在紫外線A下卻受到抑制，結果揭示可能熱激蛋白在扁藻胞內並不是主要的應激蛋白。借由通過上調核酮糖1，5二磷酸羧化酶/氧化酶的活性和同時下調一些光合作用反應中心的蛋白，紫外線A對紫球藻的光合作用產生影響，進而影響細胞生長。但是，在紫外線A下，上下調的蛋白在扁藻的光合作用中卻互換了角色。此外，紫球藻的光合作用因受核酮糖1，5-二磷酸羧化酶的上調以及光合系統反應蛋白的下調而受到影響，導致了對紫球藻生長的影響。然而，相反的結果發生在扁藻胞內。此外，3-磷酸甘油醛脫氫酶，葡萄糖載體蛋白以及磷酸丙糖異構酶活性的下調可能進一步影響到這兩種浮游植物的碳水化合物代謝和醣酵解功能。 / 在極低溫度下，依據酶動力學原理，此兩種浮游植物中各種蛋白的活性受到了抑制。在此0攝氏度下，紫球藻胞內與抗氧化相關的酶以及多糖合成酶的活性受到抑制從而對該浮游植物的代謝物合成系統產生影響。與此同時，一些與合成紫球藻代謝物相關的中間酶的合成活力也由此下降。14-3-3 蛋白，三磷酸鳥苷結合蛋白，Ras和Rab蛋白在紫球藻胞內的下調意味著其胞內的信號轉導系統效率下降。然而，與紫球藻比較，扁藻能保持一個更有效的信號轉導系統。此外，線粒體在極低溫度下的降解抑制了三磷酸腺苷在此兩種浮游植物中的合成。有趣地是，熱激蛋白在紫球藻胞內的表達水準保持穩定，這可能是由低溫應激產生的表達提高以及低溫抑制酶活力之間的一種平衡關係。但是，極低溫下扁藻胞內的熱激蛋白卻與在紫外線A脅迫條件下一樣，活性受到了抑制。同樣地，極低溫度也可能通過穩定核酮糖1，5二磷酸羧化酶/氧化酶的表達以及抑制一些光合作用反應中心蛋白的活性來部分影響紫球藻以及扁藻的光合作用系統。最後看來，磷酸葡糖異構酶和3-磷酸甘油醛脫氫酶在紫球藻胞內的活性降低以及扁藻胞內甘油醛-3-磷酸，磷酸甘油酸酯激酶，澱粉磷酸化酶，烯醇酶，葡萄糖載體蛋白和6-磷酸葡萄糖異構酶的表達下調可能導致了對這兩種浮游植物碳水化合物運輸和代謝能力產生抑制作用。 / 所有上述結果促進了我們對不利物理條件如紫外輻射和低溫如何能被利用于以海洋浮游植物為生物反應器來提高高附加值代謝物產量的理解並揭示了它們潛在的生物技術應用前景。 / The production of valuable metabolites such as polyunsaturated fatty acids (PUFAs), carotenoids and polysaccharides by marine phytoplanktons is affected by environmental conditions in which they are living. This study aimed at comparing the effectiveness of using adverse physical treatment conditions including ultraviolet radiation and low temperature as the induction factors for enhancing the production of these useful metabolites from some selected marine phytoplanktons. Various levels of metabolite profiles including fatty acids, pigments, carbohydrates and exopolysaccharides as well as total mycosporine-like amino acids (MAAs) based on five marine phytoplanktons from different phyla including Porphyridium cruentum, Nitzschia closterium, Isochrysis zhangjiangensis, Platymonas subcordiformis and Synechocystis pevalekii were firstly compared to screen the metabolite-rich species for further physical induction study. The antioxidant activities of 90% acetone extracts in these five phytoplanktons were also compared. The underlying mechanisms by which ultraviolet light and low temperature exert their effects on the phytoplankton metabolites were investigated by using chemical methods and TEM techniques as well as proteomic analysis. / The effects of ultraviolet radiation (UVR) including solar UV light [band A (UVA) and band B (UVB)] and artificial 365-nm UVA light on the growth and production of metabolites such as PUFAs, carotenoids, polysaccharides and MAAs of P. cruentum, N. closterium, I. zhangjiangensis and P. subcordiformis were compared. / In the study of solar UVR, carotenoids such as fucoxanthin and neoxanthin in P. subcordiformis could be significantly (p<0.05) accumulated inside this species at the early cultivation stage as a response to intensive solar UVR. Furthermore, longer exposure to solar UVR could significantly increase (p<0.05) the synthesis and accumulation of intracellular carbohydrates and extracellular polysaccharides in P. cruentum. The effects of solar UVR on phytoplankton fatty acids were species-specific, with significant increase (p<0.05) in PUFA contents being found in P. cruentum and P. subcordiformis whereas pronounced decrease in PUFAs being found in N. closterium compared with the control. / In the study of artificial 365-nm UVA treatment (3-day UVA-stress and 3-day UVA-recovery treatment), UVA was found to promote the growth, total and individual PUFAs and carotenoids as well as total MAAs of N. closterium and I. zhangjiangensis. The effects of UVA-stress on the growth of phytoplanktons were also species-specific. UVA radiation of 365-nm inhibited the growth of P. cruentum more than that of P. subcordiformis in the present study. However, this 365-nm artificial UVA radiation also enhancedthe synthesis and production of PUFAs, total carotenoids and MAAs in both phytoplanktons, as well as pigments in P. subcordiformis. / The effects of low temperature including extremely low temperature (0°C) on the growth of phytoplanktons and production of their metabolites includingPUFAs and pigments (carotenoids in particular) were compared in P. cruentum and P. subcordiformis due to their rich PUFA and individual carotenoid levels. The positive influence of low temperature, especially extremely low temperature (0°C) was shown on the increase in membrane fluidities of P. cruentum and P. subcordiformis as well as on enhancing the synthesis of total and individual PUFAs as well as individual carotenoids in their cells. In addition, some new insight into the possiblefunctions and the roles of cis-structure UFAs and carotenoids playing on adjusting and administering phytoplankton cellular membrane were also proposed by means of "arm-raising" hypothesis and "rivet-locking and screw-bolt fastening carotenoids" hypothesis, respectively. / P. cruentum (cell-wall-free) and P. subcordiformis (with cell wall) were further used for TEM observation study by comparing the variations of their ultrastructures after treated by UVAR and extremely-low-temperature as compared to the control. It was demonstrated that UVAR exerted less damage on the ultrastructures of these two phytoplanktons by partially affecting only the structures and sizes of some organelles rather than their normal physiological functions. On the other hand, although extremely-low-temperature shrunk or deformed most of the organelles in these two phytoplanktons severely affecting their normal physiological activities, their cellular structure seemed not to be destroyed. Therefore, the TEM images under both treatments indicated that the syntheses of metabolites in these two phytoplanktons were not affected by such harsh environments. / By use of one-dimensional gels in proteomic analysis, some functional proteins that were differentially expressed before and after UVAR-stress and extremely-low-temperature-stress in P. cruentum and P. subcordiformis were compared. The responsive mechanisms of these two phytoplanktons to UVAR-stress were rather different. After artificial UVAR-stress, the up-regulation of phosphoglucomutase and phosphomannomutase in P. cruentum might help to secrete exopolysaccharides into the extracellular circumstance to scavenging free radicals induced by UVAR.Peroxisome type ascorbate peroxidase inside the P. cruentum cell was activated to synthesize potent ascorbate to deal with intracellular free radicals also induced by UVAR. The existence of P. subcordiformis cell wall did not requireantioxidant-related enzymes and some intermediate enzymes such as phosphoglucomutase and pyruvate-formate lyase. This resulted in the down-regulation of the synthesis of valuable metabolites such as PUFAs and carotenoids in P. subcordiformis, The up-regulation of ATP synthases in P. cruentum might aim to synthesize large amounts of ATP to repair the organelles damaged by UVAR whereas those of ATPases in P. subcordiformis were down-regulated, indicating that ATPases in P. subcordiformis might be sensitive to UVAR and the damage of UVAR on various organelles of P. subcordiformis was less than those of P. cruentum. The enhanced expression of heat shock proteins in P. cruentum might help to maintain cellular viability under UVAR-stress whereas those in P. subcordiformis were suppressed, revealing that heat shock proteins in P. subcordiformis might not act as the important stress proteins. In addition, the photosynthesis in P. cruentum was affected by an up-regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase whereas there was a down-regulation of photosystem reaction proteins, leading to the influence on cellular growth in P. cruentum. However, an opposite result was observed at P. subcordiformis. The down-regulation of glyceraldehyde-3-phosphate dehydrogenase, glucose transporter and triosephosphate isomerase might affect carbohydrate catabolism and glycolysis in these two phytoplanktons. / Under extremely-low-temperature-stress, the activities of various proteins in these two phytoplanktons were suppressed due to the principle of enzyme kinetics. At 0°C, the activities of antioxidant-related enzymes and polysaccharide synthases were down-regulated and the synthetic system of P. cruentum may be partially affected. Simultaneously, the synthetic capabilities of some intermediate enzymes on the synthesis of metabolites in P. subcordiformis were also significantly down-regulated. The down-regulation of 14-3-3 proteins, GTP-binding, Ras and Rab proteins in P. cruentum indicated an ineffective system of signal transduction whereas P. subcordiformis had a moreeffective signal transduction ability than P. cruentum. In addition, the degradation of mitochondria resulted in the suppression of ATP synthesis in both phytoplanktons. Interestingly, the levels of heat shock 70 proteins in P. cruentum were kept stable, which might be the balance between stress enhancement and enzyme activity inhibited by low temperature. However, heat shock 70 proteins in P. subcordiformis were significantly inhibited as those in the same species under UVAR-stress. Also, extremely-low-temperature might partially influence the photosynthetic system of P. cruentum and P. subcordiformis by stabilizing ribulose-1,5-bisphosphate carboxylase and inhibiting the activities of some photosystem reaction center proteins at the same time. Finally, the down-regulation of phosphoglucose isomerase and glyceraldehyde-3-phosphate dehydrogenase in P. cruentum as well as glyceraldehyde-3-phosphate, phosphoglycerate kinase, glycogen/starch/alpha-glucan phosphorylases, enolase, glucose transporter and glucose-6-phosphate isomerase in P. subcordiformis might lead to the inhibition on the capabilities of carbohydrate transport and catabolism in these two phytoplanktons. / All these results advance our understanding on how adverse physical conditions such as UVR and low temperature can be used to increase the production of valuable metabolites by using marine phytoplanktons as the bioreactor and indicate their potential biotechnological applications. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Huang, Junhui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 445-522). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Thesis Committee --- p.ii / Acknowledgements --- p.iii / Content Page --- p.iv / Content --- p.v / List of Tables --- p.xviii / List of Figures --- p.xxiii / Abbreviations --- p.xxix / 摘要 --- p.xl / Abstract --- p.xlv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- A brief introduction of marine phytoplankton --- p.1 / Chapter 1.2 --- Microalgal metabolites --- p.6 / Chapter 1.2.1 --- Polyunsaturated fatty acids (PUFAs) --- p.7 / Chapter 1.2.1.1 --- The important polyunsaturated fatty acids and their functions on human body and diseases --- p.7 / Chapter 1.2.1.1.1 --- cis-9,12-Linoleic acid (C₁₈[subscript:]₂, n-6, LA) --- p.7 / Chapter 1.2.1.1.2 --- cis-9,12,15-Linolenic acid (C₁₈[subscript:]₃, n-3, ALA) or α-Linolenic acid (cis-9,12,15-Octadecatrienoic acid) --- p.10 / Chapter 1.2.1.1.3 --- cis-6,9,12-Linolenic acid (C₁₈[subscript:]₃, n-6, GLA) or γ-Linolenic acid (cis-6,9, 12-Octadecatrienoic acid) --- p.11 / Chapter 1.2.1.1.4 --- Arachidonic acid (C₂₀[subscript:]₄, n-6, ARA) or cis-5,8,11,14-eicosatetraenoic acid --- p.13 / Chapter 1.2.1.1.5 --- Eicosapentaenoic acid (C₂₀[subscript:]₅, n-3, EPA) or cis-5,8,11,14,17- eicosapentaenoic acid (Timnodonic acid) --- p.15 / Chapter 1.2.1.1.6 --- Docosapentaenoic acid (C₂₂[subscript:]₅, n-3, DPA) or cis-7,10,13,16,19- docosapentaenoic acid (Timnodonic acid) --- p.19 / Chapter 1.2.1.1.7 --- Docosahexaenoic acid (C₂₂[subscript:]₆, n-3, DHA) or cis-4,7,10,13,16,19- docosahexaenoic acid (Cervonic acid) --- p.21 / Chapter 1.2.1.2 --- The physiological function of fatty acids in phytoplankton cells --- p.27 / Chapter 1.2.1.3 --- The synthetic pathways of unsaturated fatty acids in phytoplankton cells --- p.27 / Chapter 1.2.1.4 --- Important phytoplankton fatty acid synthases --- p.35 / Chapter 1.2.1.4.1 --- Important phytoplankton fatty acid elongases --- p.35 / Chapter 1.2.1.4.2 --- The important phytoplankton fatty acid desaturases --- p.37 / Chapter 1.2.2 --- Carotenoids (CRTs) --- p.44 / Chapter 1.2.2.1 --- The important carotenoids and their functions on human body and diseases --- p.47 / Chapter 1.2.2.1.1 --- Zeaxanthin --- p.49 / Chapter 1.2.2.1.2 --- Lutein --- p.50 / Chapter 1.2.2.1.3 --- Astaxanthin --- p.52 / Chapter 1.2.2.1.4 --- α-carotene --- p.53 / Chapter 1.2.2.1.5 --- β-carotene --- p.53 / Chapter 1.2.2.1.6 --- Lycopene --- p.55 / Chapter 1.2.2.1.7 --- Violaxanthin --- p.56 / Chapter 1.2.2.1.8 --- Canthaxanthin --- p.56 / Chapter 1.2.2.1.9 --- Fucoxanthin --- p.57 / Chapter 1.2.2.2 --- The physiological functions of carotenoids in phytoplankton cells --- p.58 / Chapter 1.2.2.3 --- The biosynthetic pathways of carotenoids in phytoplankton cells --- p.59 / Chapter 1.2.2.4 --- The important phytoplankton carotenoids synthases --- p.63 / Chapter 1.2.3 --- Polysaccharides (PS) --- p.68 / Chapter 1.2.3.1 --- The important phytoplankton monosaccharides --- p.70 / Chapter 1.2.3.1.1 --- Fucose --- p.70 / Chapter 1.2.3.1.2 --- α-L-Rhamnose --- p.70 / Chapter 1.2.3.1.3 --- D(-)Ribose --- p.71 / Chapter 1.2.3.1.4 --- L(+)Arabinose --- p.71 / Chapter 1.2.3.1.5 --- D(+)Xylose --- p.71 / Chapter 1.2.3.1.6 --- D(+)Mannose --- p.72 / Chapter 1.2.3.1.7 --- D(+)Galactose --- p.72 / Chapter 1.2.3.1.8 --- D(+)-Glucosamine --- p.72 / Chapter 1.2.3.1.9 --- D(+)-Galactosamine --- p.73 / Chapter 1.2.3.2 --- The important physiological functions and characteristics of polysaccharides in phytoplanktons --- p.73 / Chapter 1.2.3.2.1 --- Porphyridium sp. polysaccharides (Rhodophyta) (PorPS) --- p.73 / Chapter 1.2.3.2.2 --- Spirulina sp. polysaccharides (Cyanophyta) (SpiPS) --- p.74 / Chapter 1.2.3.2.3 --- Aphanothece halophytica exopolysaccharides (Cyanophyta) (AhEPS) --- p.74 / Chapter 1.2.3.2.4 --- Trichodesmium thiebautii exopolysaccharides (Cyanophyta) (TtEPS) --- p.74 / Chapter 1.2.3.2.5 --- Microcystic aeruginosa acidic polysaccharides (Cyanophyta) (MaAPS) --- p.74 / Chapter 1.2.3.2.6 --- Cyanospira capsulate exopolysaccharides (Cyanophyta) (CcEPS) --- p.74 / Chapter 1.2.3.2.7 --- Platymonas subcordiformis (Will) Hazen polysaccharides (Chlorophyta) (PsPS) --- p.74 / Chapter 1.2.3.2.8 --- Botryococcus braunii Kützing exopolysaccharides (Chlorophyta) (BbEPS) --- p.75 / Chapter 1.2.3.2.9 --- Dwraliella salina exopolysaccharides (Chlorophyta) (DsEPS) --- p.75 / Chapter 1.2.3.2.10 --- Chlorella sp. exopolysaccharides (Chlorophyta) (ChlEPS) --- p.75 / Chapter 1.2.3.2.11 --- Crypthecodinium cohnii polysaccharides (Pyrrophyta) (CcPS) --- p.75 / Chapter 1.2.3.2.12 --- Isochrysis galbana exopolysaccharides (Chrysophyta) (IgEPS) --- p.75 / Chapter 1.2.3.2.13 --- Nitzschia closterium exopolysaccharides (Bacillariophyta) (NcEPS) --- p.75 / Chapter 1.2.3.3 --- The various applications of phytoplankton polysaccharides and their important physiological functions in human body --- p.76 / Chapter 1.2.3.3.1 --- Improved preparation of agricultural soil --- p.76 / Chapter 1.2.3.3.2 --- Coagulant characteristics on environment --- p.77 / Chapter 1.2.3.3.3 --- Anti-coagulant characteristics on human body --- p.77 / Chapter 1.2.3.3.4 --- Anti-viral characteristics --- p.77 / Chapter 1.2.3.3.5 --- Anti-bacterial characteristics --- p.79 / Chapter 1.2.3.3.6 --- Cytotoxicity characteristics --- p.79 / Chapter 1.2.3.3.7 --- Anti-hyperlipidemic activity --- p.79 / Chapter 1.2.3.3.8 --- Immunostimulatory effects --- p.80 / Chapter 1.2.3.3.9 --- Hematopoiesis --- p.80 / Chapter 1.2.3.3.10 --- Anti-cancer characteristics --- p.80 / Chapter 1.2.3.4 --- The biosynthetic pathways of polysaccharides in phytoplankton cells --- p.81 / Chapter 1.2.3.5 --- The important polysaccharide synthases --- p.85 / Chapter 1.2.4 --- Microalgal UV-absorbing mycosporine-like amino acids (MAAs) --- p.88 / Chapter 1.2.4.1 --- The biosynthetic pathway of UV-absorbing mycosporine-like amino acids (MAAs) --- p.90 / Chapter 1.2.4.2 --- The important UV-absorbing mycosporine-like amino acids synthases --- p.93 / Chapter 1.2.5 --- Currently commercial applications of PUFAs, carotenoids and polysaccharides --- p.95 / Chapter 1.3 --- Environmental factors and phytoplankton metabolites --- p.97 / Chapter 1.3.1 --- Relations between chemical environments and phytoplankton PUFAs as well as carotenoids production --- p.97 / Chapter 1.3.1.1 --- CO₂ concentration --- p.98 / Chapter 1.3.1.2 --- O₂ concentration --- p.98 / Chapter 1.3.1.3 --- Nitrogen starvation --- p.99 / Chapter 1.3.1.4 --- Phosphorus starvation --- p.100 / Chapter 1.3.2 --- Adverse physical environments on phytoplanktons and their metabolites --- p.100 / Chapter 1.3.2.1 --- Ultraviolet radiation on phytoplanktons --- p.100 / Chapter 1.3.2.1.1 --- Ultraviolet radiation on phytoplankton growths --- p.102 / Chapter 1.3.2.1.2 --- Negative effects of UVR on unsaturated fatty acids of phytoplanktons --- p.103 / Chapter 1.3.2.1.3 --- Positive effects of UVR on unsaturated fatty acids of phytoplanktons --- p.106 / Chapter 1.3.2.1.4 --- Ultraviolet radiation and PUFA synthases --- p.110 / Chapter 1.3.2.1.5 --- The positive effect of UVA on carotenoid production in phytoplanktons --- p.111 / Chapter 1.3.2.1.6 --- The negative effect of UVB on phytoplankton carotenoids production --- p.112 / Chapter 1.3.2.1.7 --- Ultraviolet radiation and phytoplankton carotenoids synthases --- p.114 / Chapter 1.3.2.1.8 --- Ultraviolet radiation on polysaccharides synthesis of phytoplankton and algae --- p.114 / Chapter 1.3.2.1.9 --- Ultraviolet radiation on algal MAAs synthesis --- p.115 / Chapter 1.3.2.1.10 --- Changes of phytoplankton cell organelles under ultraviolet radiation observed by Transmission Electron Microscopy (TEM) --- p.116 / Chapter 1.3.2.1.11 --- Effect of ultraviolet radiation on the expression of phytoplankton proteins --- p.119 / Chapter 1.3.2.2 --- Low temperature on phytoplanktons and higher plants --- p.121 / Chapter 1.3.2.2.1 --- Low temperature on unsaturated fatty acids of phytoplanktons --- p.122 / Chapter 1.3.2.2.2 --- Effect of low temperature on PUFAs of higher plants --- p.126 / Chapter 1.3.2.2.3 --- The association of low temperature and fatty acids composition with photoinhibition --- p.126 / Chapter 1.3.2.2.4 --- Low temperature and phytoplankton PUFA synthases --- p.127 / Chapter 1.3.2.2.5 --- Low temperature on phytoplankton carotenoids --- p.128 / Chapter 1.3.2.2.6 --- Changes of phytoplankton and algal cell organelles under low temperature observed by Transmission Electron Microscopy (TEM) --- p.129 / Chapter 1.3.2.2.7 --- Effect of low temperature on the expression of phytoplankton proteins --- p.130 / Chapter 1.4 --- Research proposal --- p.131 / Chapter 1.4.1 --- Key issues and problems --- p.134 / Chapter 1.4.2 --- Objectives --- p.135 / Chapter 1.4.3 --- Experimental design --- p.135 / Chapter 1.4.4 --- Possible outcomes --- p.135 / Chapter Chapter 2 --- Materials and Methods --- p.138 / Chapter 2.1 --- Materials --- p.138 / Chapter 2.1.1 --- Marine phytoplanktons --- p.138 / Chapter 2.1.1.1 --- Porphyridium cruentum CTCCCAS 8001 (Rhodophyta) --- p.138 / Chapter 2.1.1.2 --- Nitzschia closterium CTCCCAS 2045 (Bacillariophyta) --- p.140 / Chapter 2.1.1.3 --- Isochrysis zhangjiangensis MBCCC chy-3 (Chrysophyta) --- p.141 / Chapter 2.1.1.4 --- Platymonas subcordiformis CTCCCAS 1030 (Chlorophyta) --- p.142 / Chapter 2.1.1.5 --- Synechocystis pevalekii CTCCCAS 898 (Cyanophyta) --- p.143 / Chapter 2.1.2 --- Culture medium --- p.145 / Chapter 2.1.3 --- Marine phytoplankton metabolites standards --- p.145 / Chapter 2.2 --- Methods --- p.147 / Chapter 2.2.1 --- Culture conditions under adverse physical environments --- p.147 / Chapter 2.2.1.1 --- Solar ultraviolet radiation treatment --- p.147 / Chapter 2.2.1.2 --- Artificial ultraviolet band A (UVA) treatment condition --- p.152 / Chapter 2.2.1.3 --- Low temperature treatment condition --- p.154 / Chapter 2.2.2 --- Harvest of phytoplanktons --- p.156 / Chapter 2.2.3 --- Determination of phytoplankton biomass --- p.156 / Chapter 2.2.4 --- Determination of fatty acid profile --- p.156 / Chapter 2.2.4.1 --- Sample preparation for gas chromatography (GC) --- p.156 / Chapter 2.2.4.2 --- Gas chromatography (GC) --- p.157 / Chapter 2.2.4.2.1 --- GC analysis --- p.157 / Chapter 2.2.4.2.2 --- Fatty acids quantification --- p.158 / Chapter 2.2.4.3 --- Designed parameters for evaluating the fluidity of phytoplankton cellular membrane --- p.158 / Chapter 2.2.4.3.1 --- cis-unsaturated fatty acid double bond index (cis-UFADBI) --- p.158 / Chapter 2.2.4.3.2 --- cis-double bond unsaturated degree (cis-DBUD) --- p.159 / Chapter 2.2.5 --- Determination of phytoplankton pigment profile --- p.159 / Chapter 2.2.5.1 --- Sample preparation for High performance liquid chromatography (HPLC) --- p.160 / Chapter 2.2.5.2 --- High performance liquid chromatography (HPLC) --- p.161 / Chapter 2.2.5.2.1 --- Gradient reversed-phase HPLC analysis (Agilent 1100 Series) --- p.161 / Chapter 2.2.5.2.2 --- Gradient reversed-phase HPLC analysis (Waters 600E Series) --- p.161 / Chapter 2.2.5.2.3 --- Pigment identification, calibration and quantification --- p.162 / Chapter 2.2.5.3 --- Determination of Chlorophyll a in phytoplankton acetone extract --- p.163 / Chapter 2.2.5.4 --- Determination of total carotenoids in phytoplankton --- p.163 / Chapter 2.2.6 --- Determination of antioxidant activities in phytoplankton acetone extracts --- p.164 / Chapter 2.2.6.1 --- DPPH radical scavenging activity assay --- p.164 / Chapter 2.2.6.2 --- Ferric reducing antioxidant power (FRAP) assay --- p.165 / Chapter 2.2.6.3 --- Trolox equivalent antioxidant capacity (TEAC) assay --- p.166 / Chapter 2.2.6.4 --- Determination of total phenolic content --- p.167 / Chapter 2.2.6.5 --- Calculated parameters for evaluating the antioxidant capacities of phytoplankton acetone extract --- p.167 / Chapter 2.2.6.5.1 --- Total conjugated double bond system mole index (TCDBSMI) [or total conjugated double bond system number index (TCDBSNI)] --- p.167 / Chapter 2.2.6.5.2 --- Total antioxidant capacity index (TAOCI) --- p.168 / Chapter 2.2.7 --- Determination of monosaccharide profile, total sugars and total acidic sugars --- p.169 / Chapter 2.2.7.1 --- Determination of monosaccharide profile by Gas Chromatography-Mass Spectrometry (GC-MS) --- p.169 / Chapter 2.2.7.1.1 --- Monosaccharide standard preparation --- p.169 / Chapter 2.2.7.1.2 --- Sample preparation --- p.169 / Chapter 2.2.7.1.3 --- GC-MS --- p.170 / Chapter 2.2.7.2 --- Determination of total sugar by phenol-sulfuric acid method --- p.172 / Chapter 2.2.7.3 --- Determination of acidic sugars by measurement of uronic acid content --- p.172 / Chapter 2.2.8 --- Determination of total protein content by Lowry-Folin method --- p.173 / Chapter 2.2.9 --- Determination on total UV-absorbing mycosporine-like amino acids (MAAs) --- p.174 / Chapter 2.2.10 --- Transmission Electron Microscopy (TEM) --- p.175 / Chapter 2.2.10.1 --- Preparation of Phosphate Buffer Solution (PBS) --- p.176 / Chapter 2.2.10.2 --- Preparation of spur --- p.176 / Chapter 2.2.10.3 --- Harvest of phytoplanktons for TEM observation --- p.176 / Chapter 2.2.10.4 --- Routine preparation procedure for TEM observation --- p.177 / Chapter 2.2.10.5 --- TEM observation --- p.178 / Chapter 2.2.11 --- One-dimensional gel electrophoresis (1-D GE) --- p.179 / Chapter 2.2.11.1 --- Preparation of solution and buffer --- p.179 / Chapter 2.2.11.2 --- Harvest of phytoplanktons cells for 1-D GE --- p.179 / Chapter 2.2.11.3 --- Phytoplankton protein extractions --- p.180 / Chapter 2.2.11.4 --- Quantitative determination on extracted proteins of phytoplanktons for 1-D GE --- p.181 / Chapter 2.2.11.5 --- 1-D GE protocol --- p.182 / Chapter 2.2.11.6 --- In-gel tryptic digestion --- p.182 / Chapter 2.2.11.7 --- nESI-LC-MS/MS analysis --- p.183 / Chapter 2.3 --- Statistical Analysis --- p.185 / Chapter Chapter 3 --- Results and Discussion --- p.186 / Chapter 3.1 --- Chemical analysis of marine phytoplankton metabolites --- p.186 / Chapter 3.1.1 --- Fatty acid profiles of marine phytoplanktons --- p.186 / Chapter 3.1.2 --- Pigment profiles of marine phytoplanktons and the antioxidant activities of their acetone extracts --- p.193 / Chapter 3.1.2.1 --- The pigment profiles of marine phytoplanktons from different phyla --- p.193 / Chapter 3.1.2.2 --- Antioxidant activities of 90% acetone extracts from marine phytoplanktons --- p.201 / Chapter 3.1.2.3 --- Correlation between antioxidant activities and pigment profile of phytoplanktons --- p.203 / Chapter 3.1.3 --- Carbohydrate content and composition of phytoplanktons and their exopolysaccharides --- p.206 / Chapter 3.1.3.1 --- Total carbohydrates, total acidic sugars as well as the sugar content and composition of intracellular carbohydrates of marine phytoplanktons --- p.206 / Chapter 3.1.3.2 --- The sugar content and composition of exopolysaccharides (EPS) of marine phytoplanktons --- p.213 / Chapter 3.1.4 --- The total UV-absorbing mycosporine-like amino acids (MAAs) of marine phytoplanktons --- p.219 / Chapter 3.1.5 --- The total protein contents of five selected marine phytoplanktons --- p.219 / Chapter 3.1.6 --- The distributions of all the metabolites investigated in five marine phytoplanktons from different phyla --- p.220 / Chapter 3.2 --- Effects of ultraviolet radiation on phytoplankton growth and their metabolites --- p.227 / Chapter 3.2.1 --- Effects of solar full-band ultraviolet radiation (PAB) on phytoplankton growth and their metabolites --- p.228 / Chapter 3.2.1.1 --- Effects of PAB radiations on phytoplankton growth --- p.228 / Chapter 3.2.1.2 --- Effects of PAB radiations on the phytoplankton carotenoids production and pigment profile of Platymonas subcordiformis --- p.231 / Chapter 3.2.1.3 --- Effects of PAB on total conjugated double bond system number index (TCDBSNI) in Platymonas subcordiformis --- p.235 / Chapter 3.2.1.4 --- Effects of PAB on fatty acid composition of phytplankton lipids --- p.235 / Chapter 3.2.1.5 --- Effects of PAB on cis-unsaturated fatty acid double bond index (cis-UFADBI) in phytoplanktons --- p.241 / Chapter 3.2.1.6 --- Effects of PAB on Porphyridium cruentum total intracellular carbohydrates and extracellular polysaccharides synthesis --- p.241 / Chapter 3.2.1.7 --- Discussion --- p.243 / Chapter 3.2.2 --- Effects of UVA radiation on fatty acids, carotenoids and UV-absorbing pigments in Nitzschia closterium and Isochrysis zhangjiangensis --- p.250 / Chapter 3.2.2.1 --- Effects of UVA-stress on the growth of N. closterium and I. zhangjiangensis --- p.251 / Chapter 3.2.2.2 --- Effects of UVA-stress on fatty acid composition in N. closterium and I. zhangjiangensis --- p.251 / Chapter 3.2.2.3 --- Effects of UVA-stress on cis-unsaturated fatty acid double bond index (cis-UFADBI) in N. closterium and I. zhangjiangensis --- p.256 / Chapter 3.2.2.4 --- Effects of UVA-stress on total carotenoid contents and pigment profiles in N. closterium and I. zhangjiangensis --- p.256 / Chapter 3.2.2.5 --- Effects of UVA-stress on total conjugated double bond system number index (TCDBSNI) in N. closterium and I. zhangjiangensis --- p.266 / Chapter 3.2.2.6 --- Effects of UVA-stress on the total UV-absorbing mycosporine-like amino acids (MAAs) of N. closterium and I. zhangjiangensis --- p.267 / Chapter 3.2.2.7 --- Discussion --- p.269 / Chapter 3.2.3 --- Effects of UVA radiation on polyunsaturated fatty acids, carotenoids and UV-absorbing pigments in Porphyridium cruentum and Platymonas subcordiformis --- p.280 / Chapter 3.2.3.1 --- Effects of UVA-stress on growth of P. cruentum and P. subcordiformis --- p.280 / Chapter 3.2.3.2 --- Effects of UVA-stress on fatty acids in P. cruentum and P. subcordiformis --- p.281 / Chapter 3.2.3.3 --- Effects of UVA-stress on cis-double bond unsaturated degree (cis-DBUD) in P. cruentum and P. subcordiformis --- p.285 / Chapter 3.2.3.4 --- Effects of UVA-stress on pigments in P. cruentum and P. subcordiformis --- p.286 / Chapter 3.2.3.5 --- Effects of UVA-stress on the total UV-absorbing mycosporine-like amino acids (MAAs) in P. subcordiformis --- p.291 / Chapter 3.2.3.6 --- Discussion --- p.292 / Chapter 3.3 --- Effects of low temperature on the growth of phytoplanktons and their metabolites --- p.296 / Chapter 3.3.1 --- Effects of low temperature treatment on the growth of Porphyridium cruentum and Platymonas subcordiformis --- p.297 / Chapter 3.3.2 --- Effects of low temperature treatment on fatty acid composition of phytoplanktons --- p.299 / Chapter 3.3.2.1 --- Effects of low temperature treatment on fatty acid composition of Porphyridium cruentum --- p.300 / Chapter 3.3.2.2 --- Effects of low temperature treatment on fatty acid composition of Platymonas subcordiformis --- p.306 / Chapter 3.3.3 --- cis-unsaturated fatty acid double bond index (cis-UFADBI) of Porphyridium cruentum and Platymonas subcordiformis under low temperature treatments --- p.311 / Chapter 3.3.4 --- Effects of low temperature treatment on pigment profile of phytoplanktons --- p.312 / Chapter 3.3.4.1 --- Effects of low temperature treatment on pigment profile of Porphyridium cruentum --- p.313 / Chapter 3.3.4.2 --- Effects of low temperature treatment on pigment profile of Platymonas subcordiformis --- p.318 / Chapter 3.3.5 --- Discussion --- p.324 / Chapter 3.4 --- Effects of artificial UVA (365-nm) radiation and extreme low temperature (0°C) on cellular ultrastructures of Porphyridium cruentum and Platymonas subcordiformis using Transmission Electron Microscopy (TEM) --- p.336 / Chapter 3.4.1 --- The ultrastructures of Porphyridium cruentum and Platymonas subcordiformis --- p.337 / Chapter 3.4.1.1 --- The ultrastructures of Porphyridium cruentum --- p.337 / Chapter 3.4.1.2 --- The ultrastructures of Platymonas subcordiformis --- p.340 / Chapter 3.4.2 --- Effects of artificial UVA (365-nm) lamp on the ultrastructures of Porphyridium cruentum and Platymonas subcordiformis --- p.343 / Chapter 3.4.2.1 --- Artificial UVAR-stress effect on the ultrastructures of Porphyridium cruentum --- p.343 / Chapter 3.4.2.2 --- Artificial UVAR-stress effect on the ultrastructures of Platymonas subcordiformis --- p.346 / Chapter 3.4.3 --- Effects of extremely low temperature (0°C) on the ultrastructures of Porphyridium cruentum and Platymonas subcordiformis --- p.349 / Chapter 3.4.3.1 --- Extremely low temperature effect on the ultrastructure of Porphyridium cruentum --- p.349 / Chapter 3.4.3.2 --- Extremely low temperature effect on the ultrastructure of Platymonas subcordiformis --- p.353 / Chapter 3.4.4 --- Discussion --- p.359 / Chapter 3.5 --- Proteomics analyses of P. cruentum and P. subcordiformis under UVA-stress and extremely-low-temperature-stress by one- dimensional gel electrophoresis --- p.366 / Chapter 3.5.1 --- The protein profiles of Porphyridium cruentum and Platymonas subcordiformis --- p.366 / Chapter 3.5.1.1 --- The protein profile of Porphyridium cruentum --- p.374 / Chapter 3.5.1.2 --- The protein profile of Platymonas subcordiformis --- p.380 / Chapter 3.5.2 --- Effects of artificial UVA (365-nm) lamp on the expression variations of proteins in Porphyridium cruentum and Platymonas subcordiformis --- p.384 / Chapter 3.5.2.1 --- Artificial UVAR-stress effect on the protein profile of Porphyridium cruentum --- p.385 / Chapter 3.5.2.2 --- Artificial UVAR-stress effect on the protein profile of Platymonas subcordiformis --- p.388 / Chapter 3.5.3 --- Effects of extremely low temperature (0°C) on the expression variations of proteins in Porphyridium cruentum and Platymonas subcordiformis --- p.391 / Chapter 3.5.3.1 --- Extremely low temperature effect on the protein profile of Porphyridium cruentum --- p.392 / Chapter 3.5.3.2 --- Extremely low temperature effect on the protein profile of Platymonas subcordiformis --- p.395 / Chapter 3.6 --- Design of bioreactor for large scale production of phytoplankton metabolites under ultraviolet-stress and low-temperature-stress --- p.424 / Chapter 3.6.1 --- The main characteristics of the bioreactor --- p.424 / Chapter 3.6.2 --- Innovative design of the bioreactor --- p.426 / Chapter 3.6.2.1 --- The characteristic of “low carbon (energy and room saved) --- p.430 / Chapter 3.6.2.2 --- Recycled light using the reflecting-film-wrapped wall of bioreactor --- p.430 / Chapter 3.6.2.3 --- Stirring function and natural backflow system by the air distribution pipes --- p.431 / Chapter 3.6.2.4 --- Special function of 200-litre air-lift and reflected light (low carbon) bioreactor --- p.432 / Chapter 3.6.2.5 --- Perspex with higher transmissivity than common glass --- p.432 / Chapter Chapter 4 --- Conclusion and prospect --- p.433 / Chapter 4.1 --- Conclusion --- p.433 / Chapter 4.2 --- Future prospect --- p.443 / References --- p.445 / Related publications --- p.523

Phytoplankton succession and abundance in estuaries is known to be influenced by the relative strengths of various seasonally changing physical and chemical factors. Previous studies of Swan River Estuary phytoplankton biomass and composition have identified salinity, temperature, rainfall and nutrients as the most important controlling factors. These conclusions are generally based on analysis of data from river length transects and depth integrated day-time sampling. They describe influences ,affecting whole system phytoplankton abundance and succession. Many of the typical seasonal bloom that develop are ephemeral and only extend over relatively small areas. The focus of this study is a single site, Ron Courtney Island, considered typical of the upper estuary region. This region of the estuary was chosen as representative of the section of river most influenced by allochthonous nutrient input. It has been the region of most frequent and intense algal blooms over the past decade. The factors, physical, biological or physiological, that have the greatest influence on controlling phytoplankton biomass under various ambient conditions for this system are determined. While previous studies have recognised the importance of nitrogen to phytoplankton growth in the Swan River Estuary, they have focused on NO;, with only anecdotal reference to the importance of the alternative nitrogen source, NH4+. This is the first study to explore the influence of different nitrogen source fluxes on phytoplankton biomass in the upper Swan River Estuary. The roles of physiological adaptation to, and preferences for, 'new' (NO,), recycled (NH4+) and organic (urea) nitrogen sources in relation to ambient nutrient levels are explored. / Specific uptake rates (v), normalised to chlorophyll a, for NO;, NH4+ and urea were 0.2 ± 0.04 - 1831.1 ± 779.19, 0.5 ± 0.26 - 1731.6 ± 346.67 and 3.0 ± 0.60 - 2241.2 ± 252.56 ng N μg Chla-1 respectively. Urea concentration (14.8 - 117.7 μg urea-N 1-1) remained relatively constant over the 12 month study period. Measured ambient specific uptake rates for urea represent between 27.5% and 40.4% of total N uptake over the annual period February 1998 -January 1999. Seasonal nitrate uptake over the same period constituted only 11.3% (±10.77%, n=12) to 24.4% (± 13.02%, n=12) with the highest percentage during winter, when nitrate levels are elevated. It is suggested that urea provides a nutrient intermediary over the spring - summer period during transition from autotrophic to heterotrophic dominated communities. Grazing ,and nitrogen recycling are intricately connected by simultaneously providing top-down biomass control and bottom-up nutrient supply. Zooplankton (> 44 μm) grazing has been shown to reduce up to 40% of phytoplankton standing stock at times. Microheterotrophs (<300 pm) can reduce phytoplankton biomass production by up to 100% (potential production grazed, 11.1% day' - 99.6 % day-1) over an annual cycle. This correlated to mean seasonal day-time grazing loss of 80.47 ± 3.5 ngN μg Chla-1 in surface waters and 20.17 ± 9.7 ngN μg Chla-1 at depth (4.5m). Night time grazing for surface and bottom depths resulted in similar nitrogen loss rates (13.03 ± 4.84 ngN μg Chla-1). / Uptake rates for nitrate (r2 0.501) and urea (r2 0.512), doing with temperature (r2 0.605) were shown to have the greatest influence on phytoplankton distribution over depth and time. This research emphasises the need for more detailed investigations into the physiology of nutrient uptake and the effects of nutrient fluxes on phytoplankton biomass and distribution. Further research into the roles of organic nitrogen and pico and nanoplankton in this system is recommended.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 199-222).