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.

Toxins produced by harmful algal blooms (HABs) are known to pose contamination risks to seafood products (e.g. fish and shellfish) consumed by human. In order to control contamination risks, monitoring regimes have to be performed rigorously. The effort to monitor the amount of toxins in consumable products has to rely on continuous supply to analytical standards. The current work presents the strategy in optimising the production of major diarrhetic shellfish poisoning (DSP) toxins, OA and DTX1, from Prorocentrum lima. The organism is also known to produce peridinin, a carotenoid pigment that has been found to have pharmaceutical potential. Results from this study showed that cultivation of P. lima CCAP 1136/11 was still, although not completely, reliant on supply of natural seawater. Characterisation of compounds produced by P. lima CCAP 1136/11 in batch culture identified three major bioactive compounds (OA, DTX1 and peridinin) and two minor OA-related compounds. Recovery of these major compounds was further optimised with two-stage extraction procedure. Several important considerations for the cultivation process include standardisation of inoculum age and initial cell density. These and several other growth parameters such as temperature, light and CO2 supplementation have been shown to affect the growth and production of DSP toxins and peridinin in the culture. One of the main highlights in this study revealed that providing culture with light and dark cycle at frequency of 0.5 hour benefit in the enhancement of OA, DTX1 and peridinin yield from P. lima CCAP 1136/11. As the last part of this study, a simple and scalable design of reactor has been proposed. Contrary to common observations for dinoflagellate culture, P. lima CCAP 1136/11 was found to be able to withstand increased sparging within the culture system, resulting in concomitant increased of growth and production of OA, DTX1 and peridinin. Future works have been suggested to focus on: (1) exploitation of different cultivation system, such as continuous or semicontinuous systems, and (2) exploration on genetic modification to enable commercial scale production of DSP toxins and peridinin.

Publicación a texto completo no autorizada por el autor / El documento digital no refiere asesor / Describe las Floraciones Algales Nocivas (FAN) o Mareas Rojas, que son decoloraciones del agua visible a simple vista debido a la proliferación de uno o más microorganismos planctónicos como las microalgas, estas pueden alcanzar niveles altos y producir efectos adversos a la salud humana, como también, causar daños a otros organismos marinos cercanos a la costa. Por tal motivo, existió el interés de aislar, identificar y hacer un estudio filogenético de la especie Prorocentrum minimum encontrada en la Bahía del Callao- Perú. Se realizaron varias tomas de muestras de agua de mar para su posterior identificación morfológica, se les efectuó la técnica de purificación de la microalga, y a su vez, se adquirió un estándar de Prorocentrum minimum del Instituto Provasoli- Guillard National Center for Culture of Marine Phytoplankton (CCMP), USA. Se realizó la curva de crecimiento para la concentración de la densidad microalgal, posteriormente se efectuó la extracción de ADN y la filogenia molecular a partir de las secuencias de las subunidades del ribosoma LSU rRNA de la especie Prorocentrum minimum. Se identificó P. minimum y P gracile, que fueron especies epibentónicos cercanas por ser más recientes evolutivamente. Para la confirmación de la presencia ausencia de alguna biotoxina marina en el cultivo de Prorocentrun minimum, se estableció un análisis cuantitativo de la dosis respuesta del animal en el bioensayo en ratón. Se logró obtener la purificación de cultivo de Prorocentrum minimum y estandarizar el protocolo de trabajo, se confirmó la filogenia de la especie de microalgas. No se logró obtener la toxina DSP del cultivo de la microalga. / Tesis

De la profondeursur 2 sites en Guadeloupe pendant la saison sèche et la saison humide (Chapitre 3). A u cours de cette étude,les genres Ostreopsis et Prorocentrum étaient les plus abondants. Aucune influence de la profondeur n'a é;étrouvée sur l'abondance totale des dinoflagellés benthiques ; cependant les genres Ostreopsis et GambiericLscusétaient principalement abondants en surface, alors que le genre Coolia était présent plus en profondeur.L'approche d'écologie trophique concernait le lien trophique entre dinoflagellés benthiques toxiqueset méiofaune (Chapitre 1). Les transferts au sein des réseaux trophiques de phycotoxines synthétisées par lesdinoflagellés benthiques toxiques sont généralement étudiés chez les organismes de grande taille, délaissantles organismes de μeLile Laille qui sulll pourtant en contact direct avec les microalgues. Au cours de cetteétude, une attention particulière a été portée aux copépodes harpacticoïdes qui composent ia méiofaune.Cette étude expérimentale, par marquage des microalgues aux isotopes stables, s'est focalisée sur lescopépodes harpacticoïdes et a permis de mesurer le taux d'ingestion d'Amphidinium sp. et d'Ostreopsis sp ..Cette étude démontre que les organismes de la méiofaune peuvent constituer une voie d'entrée des toxinessynthétisées par les dinoflagellés benthiques dans les réseaux trophiques. / The distribution of benthic toxiï rlinofüeefü1tes is 1111known in (Juadeloupe and Martinique even if at theCaribbean basin spatial scale, those microalgae are responsible for serious poisoning such as ciguatera.During this thesis, the ecology of benthic toxic dinoflagellates μreseul was sLudieJ using: spatio-temporalstudies (Chapters 1, 2, 3) and a trophic ecology approach (Chapter 4).First, 27 sites were explored to describe the spatial distribution of benthic dinoflagellatf's prPsf'nt inGuadeloupe and Martinique (Chapter 1). Only the most abundant macrophytes (biological substrates ofbenthic dinoflagellates) at the different sites were considered. ln this study, 161 samples were analyzed and 7times more taxie benthic dinoflagellates were found in Guadeloupe than in Martinique. The genus Ostreopsisdominated the benthic dinoflagellate community in both islands, although this trend has only rarely beenfound in the Caribbean basin.Then, 3 sites per department were chosen in order to set up a monthly monitoring of benthicdinoflagellates abundances duringl8 months (Chapter 2). The sites selected i) had a high abundance ofbenthic toxic dinoflagellates and ii) were identified as potentially dangerous by the Agence Régionale de laSanté. During this study, 927 samples of macrophytes were analyzed and 5 times more benthic toxicdinoflagellates were found in Guadeloupe than in Martinique. Ostreopsis and Prorocentrum genera dominatedrespectively in Guadeloupe and in Martinique. Two times more Gambierdiscus were found in Martinique thanin Guadeloupe even if Guadeloupe is located in the high prevalence area and this genus being responsible forciguatera. This result suggested that species with different toxicities structured the benthic toxicdinoflagellates community in this area. The abundances of benthic dinoflagellates were little influenced byabiotic parameters (temperature and salinity) but structured by biotic parameters (host macrophytes).Halophila stipulacea an invasive angiosperm in the Lesser Antilles has been identified as promoting thedevelopment of the genus Gambierdiscus.. The distribution of benthic toxic dinoflagellates was also studied according to the depth at 2 sites inGuadeloupe during the dry and the wet seasons (Chapter 3). ln order to avoid bias due to the presence ofdifferent macrophytes, this experiment was conducted only on H. stipulacea constituting mono-specificmeadows along a strong depth gradient. ln this study, the Ostreopsis and Prorocentrum genera were the mostabundant. No influence of the depth was found on total abundance of benthic dinoflagellates; however,Ostreopsis and Gambierdiscus genera were mainly abundant near the surface while the genus Coolia was presentdeeper.The trophic ecology approach focused on the trophic link between taxie benthic dinoflagellates andmeiofauna (Chapter 4). Transfers within the food webs of phycotoxins synthesized by benthic dinoflagellatesare mainly studied in large organisms neglecting smaller ones in direct contact with microalgae. Thisexperimental study, by labeling the microalgae with stable isotopes, focused on harpacticoides copepod andmeasured for the first time their ingestion rates of Amphidinium sp. and Ostreopsis sp.. This studydemonstrated that meiofauna organisms can constitute an input channel of phycotoxins from benthicdinoflagellates in food webs.