This study aims to document the dinoflagellate cyst biostratigraphy and paleoenvironmental record of the Maastrichtian Neylandville and Corsicana Formations and the lower part of the Danian Kincaid Formation from the Brazos River, Texas. Rock samples are exposed to standard palynological methods for biostratigraphic interpretations. The quantitative data collected from palynological samples are combined with δ13C and δ18O stable isotope geochemistry and TEX86 and BIT Index organic geochemistry data for paleoenvironmental interpretations. Biostratigraphically important species of dinoflagellates divide the section into three intervals. Interval 1 occurs within the Neylandville Formation, and the presence of Alterbidinium acutulum, Xenascus ceratioides and Isabelidinium cooksoniae indicate that this interval is not younger than early Maastrichtian. Interval 2 represents the Corsicana Formation. The presence of the late Maastrichtian species Disphaerogena carposphaeropsis, Palynodinium grallator and Deflandrea galeata at the base of the Corsicana Formation indicate that this interval is of late Maastrichtian age. Interval 3 occurs within the Kincaid Formation. The presence of Carpetalla cornuta and Damassadinium californicum at the base of the Kincaid Formation indicates that this interval is of Danian age. Previously published Gulf of Mexico palynology studies, as well as planktonic foraminifera and nannoplankton data confirm the age assignments of the studied interval. Dinoflagellate species assemblages increase in diversity upwards from Interval 1 to Interval 2, and then show a small decrease above the K-Pg boundary within Interval 3, indicating that the K-Pg event was not catastrophic for the dinoflagellates. The Cerodinium spp. and Spiniferites spp. complex comprise a large proportion of the species within the section. High abundance peaks of Glaphyrocysta spp., Cribroperidinium spp., and Yolkinigymnium lanceolatum occur within Interval 2. Two intervals in the section are dominated by peridinioid dinoflagellates, measured by the Peridinioid/Gonyaulacoid (P/G) ratio. The first one occurs within Interval 2 and contains peaks of the P/G ratio that correlate with increases in δ13C, suggestive of an increase in paleoproductivity. Two more peaks occur within Interval 3. Bottom water δ18O temperatures determined from benthic foraminifera and sea surface temperatures determined from TEX86 organic geochemistry show an overall cooling trend from Early Maastrichtian to the K-Pg boundary.

No description available.

University of Technology, Sydney. Faculty of Science. / Global climate change is leading to the rise of ocean temperatures and is triggering mass coral bleaching events on reefs around the world. This involves the expulsion of the symbiotic dinoflagellate algae, known as zooxanthellae, from the coral host. Coral bleaching is believed to occur as a result of damage to the photosynthetic apparatus of these symbionts, although the specific site of initial impact is yet to be conclusively resolved. This thesis examined a number of sites within the light reactions of photosynthesis and evaluated the efficiency of photoprotective heat dissipating pathways. Upon expulsion, the capacity for long-term survivorship of expelled zooxanthellae in the water column was also assessed. A reduction in photosystem II (PSII) photochemical efficiency during exposure to elevated temperature and high light (bleaching conditions) was found to be highly dependent upon the increase in abundance of QB non-reducing PSII centres (inactive PSII centres), indicating damage to the site of the secondary electron acceptor, QB, resulting in a limited capacity for its reduction. Therefore, this reduced the rate of the reoxidation of the primary electron acceptor, QA-. Fast induction curve (FIC) analysis of the rise from minimum fluorescence to maximum fluorescence revealed a lower amplitude in the J step along this curve, which was consistent with a reduction in the rate of QA reoxidation. This photoinhibition of PSII was found to occur once the effectiveness of excess energy dissipation through energy-dependent quenching and state-transition quenching was exceeded, suggesting that these mechanisms were incapable of preventing photodamage. Antenna size heterogeneity showed little change under bleaching conditions with a significant increase in PSIIbeta only apparent in one species of coral. The thermostability of the oxygen evolving complex (OEC) and thylakoid membrane were found to increase during exposure to bleaching conditions and exceeded bleaching thresholds of corals. This rapid rise in temperature-dependent thermostability also occurred over seasons, where variation in ocean temperatures was matched by gradual shifts in OEC and thylakoid membrane thermotolerance. Variation in thermostability between species was not found to be linked to zooxanthellae genotype, and instead was related to the bleaching susceptibility of the host. Despite this capacity for resilience to bleaching conditions, the PSII reaction centres did not exhibit such a mechanism for rapid acclimatisation. Corals can only be as tolerant to bleaching conditions as their most sensitive component allows. The formation of nonfunctional PSII centres is therefore suggested to be involved in the initial photochemical damage to zooxanthellae which leads to a bleaching response. Zooxanthellae were found to be expelled irrespective of OEC function and thylakoid membrane integrity, as these sites of the photosynthetic apparatus were still intact when cells were collected from the water column. Although zooxanthellae were photosynthetically competent and morphologically intact upon expulsion, their longevity in the water column was dependent on the time of expulsion following the onset of bleaching and the ambient water temperatures. The survivorship of these zooxanthellae was restricted to a maximum of 5 days in the water column which suggests that unless expelled zooxanthellae inhabit other environs of coral reefs which may be more favourable for survival, their capacity for persistence in the environment is extremely limited. Chlorophyll a fluorescence measurements are a common tool for investigating photosynthetic impacts to in hospite zooxanthellae of corals. Pathways causing dark-reduction of the plastoquinone pool are shown to be active in corals and affect measurements which require dark-adaptation. Pre-exposure to far-red light was found to be an effective procedure to oxidise the inter-system electron transport chain and ensure determination of the true maximum quantum yield of PSII and accurate FICs. It is concluded that the trigger for coral bleaching lies in the photosynthetic apparatus of zooxanthellae and evidence is presented in support of this impact site not being the OEC or thylakoid membrane.

Thesis (Ph.D.) - James Cook University, 2004. / "Met een samenvatting in het Nederlands" -- T.p. "Ter verkrijging van der graad van doctor aan de Universiteit Utrecht, op gezang van de Rector Magnificus, Prof. Dr. W. H. Gispen, ingevolge het besluit van het College voor Promoties in het openbaar te verdedigen op donderdag 30 septembber 2004 des morgens om 10:30 uur" -- T.p. Typescript (photocopy) Bibliography: leaves 175-181.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 69-79.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 103-116). Also available in electronic version.

Dinoflagellates are a diverse group of flagellated eukaryotes, the majority of which are marine plankton, and are one of the most important groups of primary producers in the world’s oceans. The dinoflagellate fossil record is based on their zygotic resting cysts; this record indicates that the Bajocian of the Mid Jurassic (~170–168 Ma) represents a critical interval in dinoflagellate evolutionary history, marked by a rapid increase in the diversity of cysts from the family Gonyaulacaceae. From the Bajocian onwards, the Gonyaulacaceae have remained one of the most diverse and abundant groups of dinoflagellate cysts in the fossil record. Even so, Bajocian dinoflagellate cysts themselves have received relatively little study, leaving the patterns of this radiation unresolved. In this thesis, I examine the Bajocian diversification of gonyaulacacean dinoflagellate cysts in northwest Europe via quantitative palynological analysis, and relate this into a broader stratigraphic and palaeoenvironmental context. The dinoflagellate cyst record of the three key study areas demonstrates an increase in gonyaulacacean dinoflagellate cyst diversity through the Bajocian, irrespective of differing palaeoenvironmental settings. However, palynological and sedimentological data record systematic changes in lithostratigraphic composition and/or depositional environment which reflect changes in sea level. The integration of these data with biostratigraphic records indicates that the pattern of the radiation in Europe was strongly influenced by sea level, with the increase in gonyaulacacean diversity mirroring a major second-order transgression. On a finer scale, the main pulses of first appearances correlate with third-order transgressive episodes. A rise in sea level, coupled with changes in the tectonic configuration of ocean gateways, appears to have controlled the pattern of diversification in Europe. These palaeoceanographic changes may have enhanced water-mass transfer between Europe, the northwest Tethys Ocean, and the Hispanic Corridor, which promoted the floral interchange of dinoflagellates. Comparison to global data demonstrates that gonyaulacacean dinoflagellate cysts increased in diversity on a global scale through the Mid Jurassic. Whilst sea level rise and associated large-scale palaeoenvironmental shifts appear to have controlled the pattern of dinoflagellate cyst appearances in several regions (e.g. eastern Canada, Israel), there is no direct correlation between dinoflagellate cyst diversity and sea level rise on a global scale. Within dinoflagellate cyst assemblages from Europe, the spatial and temporal distribution of key taxa can be related to differing palaeoenvironmental settings of the basins studied; but certain patterns may reflect wider palaeoenvironmental drivers. Carbon isotope records generated for this thesis, and their correlation to other European sections, demonstrate that the Early Bajocian in Europe was marked by a positive shift in δ13C. Previous work has linked this carbon cycle perturbation to a phase of enhanced continental weathering and associated run-off. In several European basins, the Early Bajocian was marked by an acme of the genus Dissiliodinium; this genus may have bloomed in response to elevated nutrient levels. Intriguingly, a similar pattern is seen within dinoflagellate cyst assemblages from Australia, indicating this interval of palaeoenvironmental change may have had a global extent.

No description available.

Small non-coding RNAs such as microRNAs (miRNAs), small interfering RNAs (siRNAs) and Piwi-interacting RNAs (piRNAs) play a big role in regulating gene expression in cells. In my work, I focus primarily on miRNAs, which represses the expression of the mRNA targets post-transcriptionally. For Drosophila melanogaster, I predicted the tissue-specific expression of several miRNAs based on the expression levels of the predicted mRNA targets in those tissues. The computational predictions are then followed up by quantitative PCR validation of miRNA expression levels in dissected fly tissues. For Stylophora pistillata (a species of coral found in the Red Sea) and Symbiodinium sp. (a photosynthetic, symbiotic algae present in the coral cell), my collaborators and I strived to study the genome, transcriptome and proteome of both organisms. At present, there is another coral genome available — from Acropora digitifera — but the large evolutionary distance between both corals (about 240 million years apart) warrants in-depth study of our coral of interest. On the other hand, our Symbiodinium genome will be the first of its kind for any dinoflagellate. My role in the project was to investigate the small RNAome of both organisms via small RNAseq. As the presence of a thick cell wall in Symbiodinium sp. poses a unique challenge to RNA extraction, and compounded by the dearth of literature regarding RNA extraction from the dinoflagellate, we optimised a procedure that consistently produced high quality RNA for downstream sequencing. From our draft proteome, I showed that the RNA interference (RNAi) machinery is very likely to be present in both organisms. Based on our short RNAseq data, I predicted miRNAs in both organisms. Two of the predicted miRNAs in S. pistillata have been identified in other organisms, while all of the predicted miRNAs in Symbiodinium sp. were novel.

Harmful algae studies, in particular toxic dinoflagellates, and their response to global warming in the Red Sea are still limited. This study was aimed to be the first to characterize the identity, thermal responses and toxin production of four Prorocentrum strains isolated from the Central Red Sea, Saudi Arabia. Morphological and molecular phylogenetic analysis identified the strains as P. elegans, P. rhathymum and P. emarginatum. However, the identity of strain P. sp.6 is currently unresolved, albeit sharing close affinity with P. leve. Growth experiments showed that all species could grow at 24-32°C, but only P. sp.6 survived the 34°C treatment. The optimum temperatures (Topt) estimated from the Gaussian model corresponded to 27.17, 29.33, 26.87, and 27.64°C for P. sp.6, P. elegans, P. rhathymum and P. emarginatum, respectively. However, some discrepancy with the Topt derived from the growth performance were observed for P. elegans and P. emarginatum, as thermal responses differed from the typical Gaussian fit. The Prorocentrum species examined showed a sharp decrease after the optimum temperature resulting in very high activation energies for the fall slope, especially for P. elegans and P. emarginatum. The minimum critical temperature limit for growth was not detected within the range of temperatures examined. Subsequently, high performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis revealed all species as non okadaic acid (OA, common toxin of the Prorocentrum genus) producers at any temperature treatment. However, other forms of toxin (i.e. fast acting toxins) not examined here could be produced. Therefore, further investigations are required. The results of this study provided significant contribution to our knowledge regarding the presence, thermal response and toxin production of four Prorocentrum species from the Central Red Sea, Saudi Arabia.