Harmful Algal Blooms (HAB) in a changing world : the case of S and W Iberian Bays

This thesis aimed to investigate, in two wide-open sheltered bays (Lisbon and Lagos) influenced by upwelling, how the meteorological and oceanographic (MetOc) setting may affect phytoplankton communities. Results of a 9-year time series data showed a high interannual variability of phytoplankton biomass, estimated as chlorophyll a (Chl-a). Nevertheless, the Chl-a sinusoidal model showed different temporal variability patterns in each bay: a uni-modal pattern with a short peak and low Chl-a concentrations in Lagos, and a weak bi-modal pattern with a long period of high Chl-a concentrations in Lisbon. Cross-correlation analyses performed for Chl-a and different MetOc variables indicated that PAR contributed most to Chl-a in winter/early-spring, while upwelling and SST were the main drivers in late-spring/summer. Analysis performed during 1-year showed significant spatial differences in phytoplankton assemblages between the bays. On a temporal scale, significant differences were observed on phytoplankton communities in both bays in the 4-meteorological seasons. However, results from a nearshore station studied in Lagos only indicated the occurrence of 3-biological seasons, with no significant differences between summer and autumn communities. This study suggests that Lagos region has a higher probability for the occurrence of HABs (in higher cell concentrations and persistence). The ecology of the benthic genus Ostreopsis was studied based on 7-years of water samples. Two species were identified reaching maximum cell densities in late-summer/early-autumn: Ostreopsis cf. ovata restricted to the south coast and Ostreopsis cf. siamensis present in both Portuguese coasts. Ostreopsis was much more abundant in Lagos (nearshore) and maxima concentrations were related to positive SST anomalies. High densities in the plankton were often recorded after a period of more than 2-weeks of low sea state, followed by short-time events of onshore wind and moderate waves. In Lisbon, O. cf. siamensis was seldom recorded in the plankton and no clear relationship could be established with the studied MetOc drivers. The recent records of Ostreopsis in this bay are interpreted as an early colonization stage of an invasion process. The present work highlights the relevance of the peculiarities of regional setting in determining phytoplankton dynamics in wide-open coastal bays influenced by upwelling, even at short latitudinal distance.Instituto Português do Mar e da Atmosfera (MAR2020-P02M01-1490P)Centro de Ciências do Mar e do Ambiente da Faculdade de Ciências da Universidade de Lisboa (UIDB/04292/2020)Centro de Ciências do Mar da Universidade do Algarve (UID/Multi/04326/2020

Caracterização de comunidades planctónicas no Banco Submarino Condor (sudoeste da ilha do Faial, Açores) : associação dos principais padrões de distribuição com factores ambientais subjacentes

Dissertação de Mestrado em Estudos Integrados dos Oceanos.Os ecossistemas de bancos submarinos são considerados de elevada importância uma vez que contém elevada biodiversidade marinha, tendo assim um elevado interesse económico. Este trabalho teve como local de estudo o banco submarino Condor, que se localiza sensivelmente a 10 milhas náuticas a Sudoeste da ilha do Faial. Foram objectivos principais deste estudo caracterizar qualitativamente e quantitativamente as comunidades planctónicas e determinar as suas variações no tempo e no espaço, bem como associar os respectivos padrões de distribuição aos factores físicos e ambientais envolventes. Para esse efeito foram realizados no âmbito do projecto CONDOR (PT0040 co-financiado pelo programa EEA Grants Financial Mechanism - Iceland, Liechtenstein and Norway) sete cruzeiros oceanográficos a bordo do N/I “Arquipélago” entre Março de 2009 e Março de 2010. Recolheram-se um total de 103 amostras de água para análise fitoplanctónica e 110 amostras para determinar a concentração de clorofila a. Obtiveram-se simultaneamente dados de CTD e foi recolhido um total de 59 amostras de zooplâncton. Com o processamento de algumas das respectivas amostras em laboratório, identificaram-se em termos taxonómicos, o fitoplâncton e zooplâncton, bem como, foram estimadas as abundâncias e as biomassas de zooplâncton. O presente trabalho concerne apenas a 7 estações de amostragem biológica/caracterização físico/química da água (versus um total de cerca de 20 estações de amostragem realizados em cada um dos cruzeiros). Os resultados obtidos pelos perfis de CTD revelaram uma coluna de água estratificada no Verão e bastante misturada no Inverno/Primavera, bem como um máximo de oxigénio também em Julho e não em Março como seria de esperar. Os resultados também mostram forte variação sazonal das comunidades em estudo, com maiores abundâncias planctónicas a ocorrer nos meses de Março (Inverno/Primavera) e menores em Novembro (Outono). Igualmente, constataram-se diferenças significativas ao nível da diversidade e abundância de plâncton dentro e entre as estações do ano estudadas. Verificou-se uma relação directa entre a profundidade da DCM e a profundidade onde se registou maior diversidade e abundância fitoplanctónica, ocorrendo esta sensivelmente aos 75 m no Verão e aos 25 m no Inverno/Primavera. A biomassa máxima de zooplâncton foi registada em Março durante a noite (57,47 mg.m-3) e a mínima em Junho durante a noite (2,98 mg.m-3). Foi igualmente em Março, o mês com maiores valores de abundância e onde se registou a menor diversidade taxonómica de zooplâncton, com um total de 95% de copépodes. Este estudo forneceu pela primeira vez informação acerca das comunidades planctónicas no banco submarino Condor, assim como demonstrou que a realização de estudos multidisciplinares e contínuos são de elevada importância para se poder realizar uma boa avaliação/interpretação da relação entre os processos biológicos e oceanográficos.ABSTRACT: The seamount ecosystems are considered highly important due to an increased marine biodiversity, and thus, high economical interest. The study site of this work was the Condor seamount, located about 10 nautical miles southwest of the island of Faial. The main objectives of this study were to characterize the planktonic communities qualitatively and quantitatively and determine their variation in time and space, as well as associate their respective distribution patterns to physical and environmental factors. For this purpose under the framework of CONDOR project (PT0040 co-financed by the EEA Grants Financial Mechanism - Iceland, Liechtenstein and Norway) seven oceanographic cruises were carried aboard R/V "Archipelago" between March 2009 and March 2010. A total of 103 water samples for phytoplankton analysis and 110 samples to determine chlorophyll a concentration were collected. CTD casts and a total of 59 samples of zooplankton were also obtained. In laboratory samples were processed, phyto and zooplankton were taxonomically identified, as well as their abundance and zooplankton biomass. The present work concerns only seven stations of biological sampling and physical/chemistry characterization of water (versus a total of about 20 sampling stations achieved in each of the cruises). The results obtained by CTD profiles revealed a stratified water column in summer and very mixed water in the Winter/Spring, as well as an oxygen maximum in July and not in March as expected. The results obtained in this work show strong seasonal variation of the communities in study, and the highest planktonic abundance occurred in March (Winter/Spring) and the lowest in November (autumn). The existence of significant differences of its diversity and abundance within and between the stations of the year studied were also indicated. A direct relationship between the depth of DCM and the depth where there was greater phytoplanktonic diversity and abundance was found occurring at 75 m in the summer and 25 m in Winter/Spring. The maximum zooplankton biomass was registered in March during the night (57,47 mg.m-3), while the minimum was in June during the day (2,98 mg.m-3). The lowest zooplankton taxonomical diversity was also registered in March, the month with highest values of abundance, with a total of 95% Copepoda. This study provided for the first time information about planktonic communities in Condor seamount and, in addition, has shown that multidisciplinary and continuous studies are of high importance to a good evaluation/interpretation of the relationship between the biological and oceanographical processes