This study confirms the presence of Gambierdiscus sp., Ostreopsis sp. as well as other epiphytic benthic dinoflagellates associated with Ciguatera Fish Poisoning (CFP) in the Central Red Sea, highlighting the potential occurrence of CFP in this region. These species are reported for the first time in Saudi Arabian coastal waters. A total of 80 Turbinaria and Halimeda macroalgae samples were collected from coral reefs off the Saudi Arabian coast. Sample analyses indicated low average cell abundances (< 40 cells g-1 wet weight algae) of Gambierdiscus sp. and Ostreopsis sp. Subsequent statistical analyses indicated a significant difference in the cell abundances of both genera between sampling sites, between species and between inshore and offshore reefs. The presence of several potentially toxigenic dinoflagellate species in the Red Sea and the statistical differences in abundances between different sampling sites merits future study on possible impacts of these dinoflagellates on marine food webs and human health.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2015-05-22T12:36:13Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE versão biblioteca.pdf: 2567467 bytes, checksum: cbc9baab1ec205be3fca7faef6988926 (MD5) / Made available in DSpace on 2015-05-22T12:36:13Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE versão biblioteca.pdf: 2567467 bytes, checksum: cbc9baab1ec205be3fca7faef6988926 (MD5) Previous issue date: 2015-02-26 / CAPES / A praia de Porto de Galinhas, situada no litoral sul de Pernambuco, Brasil, cerca de 50 km de Recife, possui recifes de arenito do tipo franja e é alvo de intensa atividade turística. Com o intuito de avaliar a estrutura da comunidade fitoplanctônica e sua dinâmica associada com as variáveis ambientais no ecossistema recifal de Porto de Galinhas, amostras de água foram coletadas em quatro meses dos períodos chuvoso (maio, junho, julho e agosto de 2010) e de estiagem (outubro, novembro e dezembro de 2010 e janeiro de 2011), na superfície, em quatro pontos fixos, na preamar e baixa-mar, em marés de sizígia diurna. A pluviosidade seguiu a curva dos 15 anos anteriores, porém o mês de junho apresentou pluviosidade acima da média devido a um intenso Distúrbio Ondulatório de Leste (DOL). A transparência variou entre 0,63 e 6,5m, a temperatura variou entre 25 e 29ºC, a salinidade de 27 a 38, a taxa de saturação do oxigênio dissolvido de 87,80 a 135,28%, o nitrito foi <0.5μmol.L-1, o nitrato variou entre 0.1 e 5μmol.L-1, o N-amoniacal foi <0,97μmol.L-1, o fosfato foi <0.39μmol.L-1 e o silicato foi <39,2μmol.L-1; a clorofila a variou entre 0,42 e 5,66mg.m-3 e o índice trófico TRIX entre 0,98 e 3,46. A pluviosidade foi o principal fator condicionante nas variações ambientais. De acordo com a análise de componentes principais (ACP), a pluviosidade foi a forçante física mais importante para o sistema influenciando diretamente a clorofila a e nitrato e inversamente a transparência e salinidade. A estrutura da comunidade fitoplanctônica também oscilou em função da sazonalidade, além disso, apresentou maior densidade no período chuvoso. Foram identificados 192 táxons, pertencentes a 6 divisões, sendo Ochrophyta (64,6%) a mais representativa, seguida por Dynophyta (19,3%). Ostreopsis ovata, Trichodesmium eryhtraeum, Protoperidinium bispinum, Paralia sulcata, Thalassiosira leptopus e Fragilaria capucina foram as espécies mais representativas do ambiente. O. ovata se destacou por ser a única espécie muito frequente e dominante. O DOL contribuiu para a ocorrência de grande parte das espécies dulciaquícolas que ocorreram no local. O ambiente caracterizou-se como oligotrófico, tendendo a mesotrófico no período chuvoso. O elevado número de táxons, associado a uma alta equitabilidade foram indicativos de equilíbrio ambiental. A interferência continental pôde ser percebida através da variação dos parâmetros abióticos, assim como da variação na estrutura da comunidade fitoplanctônica. Apesar da área recifal sofrer forte pressão antrópica, esse impacto ainda não foi perceptível no ambiente pelágico.

Les proliférations de microalgues peuvent être nocives. L'augmentation récente de la fréquence et de l’étendue géographique des efflorescences de dinoflagellés benthiques toxiques comme Ostreopsis cf. ovata peut poser de réels problèmes de santé publique. La côte méditerranéenne Nord-Occidentale (lieu de cette étude) est l'une des nombreuses régions méditerranéennes où les proliférations d'algues nuisibles représentent une menace pour l’économie touristique. Dans les années à venir, une attention particulière devra être portée à la gestion et la prévision des proliférations de ces microalgues nuisibles benthiques et c'est dans ce contexte que cette étude a été menée. Une étude bibliographique portant sur les proliférations d’Ostreopsis spp. indique un manque important de données en relation avec l'écologie d’O. cf. ovata, en particulier concernant les substrats biotiques, ainsi que les communautés les habitats benthiques et, par conséquent, les rôles éventuels que ceux-ci peuvent jouer en tant que stimulateurs majeurs des efflorescences d’Ostreopsis spp. Durant les étés 2015 et 2016, des expériences in situ de courte durée ont été menées sur les récifs côtiers et ont été complétées par des expériences en laboratoire. Les résultats obtenus ont permis d’établir que quatre communautés distinctes de macroalgues abritent des abondances différentes d’O. cf. ovata. En particulier, les abondances les plus élevées ont été enregistrées dans des sites dominés par des structures communautaires peu complexes ; Turf et Dictyotales, alors que les sites dominés par des communautés complexes de Cystoseira n’ont montré aucune prolifération significative de microalgues. Ces résultats impliquent que les régions côtières dominées par les communautés composées de Cystoseira spp. pourraient potentiellement réduire les proliférations de Ostreopsis spp. En outre, d’autres facteurs abiotiques, tels que les concentrations en nutriments et métaux traces, ne contribuent pas (ou peu) à expliquer la dynamique des populations de O. cf. ovata. Les multiples facteurs de stress d’origine anthropique continueront à influencer le fonctionnement de l’écosystème marin. La compréhension de ces impacts et la façon dont ils influencent la dynamique des dinoflagellés benthiques toxiques est impérative pour prévoir, gérer et éventuellement réduire ces proliférations, à l’échelle de l’océan mondial. / Algal blooms can be harmful. The global management and forecasting of benthic harmful algal blooms (BHABs) will be of increasing importance in the years ahead and that is what this study sets out to address. The increase over recent decades, in both frequency and geographical range, of the potentially harmful benthic dinoflagellate Ostreopsis cf. ovata can pose real problems for human health. The French Côte d’Azur, the location for this study, is just one of many Mediterranean areas where harmful algal blooms pose a potential economic threat to a tourist-based economy. A review of the existing literature on Ostreopsis spp. blooms shows a severe lack of information about the ecology of O. cf. ovata in relation to biotic substrates, communities and habitats and thus any possible roles these may play in fostering major Ostreopsis spp. blooms. Through a series of in situ experiments on temperate reefs on the Côte d’Azur over the summers of 2015 and 2016 with follow-up experiments in the laboratory, this study establishes that four distinct macroalgal communities harbour different O. cf. ovata abundances. The results indicated that higher abundances were recorded in sites which were dominated by less complex community structures; Turf and Dicyotales, while sites with Cystoseira spp. communities present did not harbour significant microalgal blooms. These results imply that coastal regions with a dominance of Cystoseira-composed-communities could potentially be less prone to blooms or even inhibit Ostreopsis spp. proliferation. Although, no clear relationship was found between inorganic nutrient concentrations and O. cf. ovata abundances, it was observed that in the bloom onset period, nitrogen compounds were higher than in the rest of the study period (both in 2015 and 2016). Multiple human stressors will continue to impact marine vegetation, understanding these impacts and how they then influence bloom dynamics is imperative for the global management and mitigation of BHABs.

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.