ABSTRACT Harmful algal blooms (HABs) can negatively affect coastal water quality, aquatic fauna, and human health from the consumption of toxin-contaminated seafood. Estuaries are especially prone to the incidence of these noxious events and sensitive to the associated damage. This study represents a comprehensive overview of previous investigations reporting the occurrence of harmful algae and/or phycotoxins in the Paranaguá Estuarine Complex (CEP), in Southern Brazil. Secondary data from 2002 to 2021 were combined with new results obtained from widely spaced sampling campaigns performed from 2018 to 2019 to assess the periods and estuarine sectors at greater risk for the incidence of HABs. In total, about 600 water/sediment samples containing harmful microalgae and 675 tissue samples of phycotoxin-contaminated fauna were analyzed. The most frequent and abundant species of potentially toxic microalgae were dinoflagellates belonging to the species complexes Dinophysis acuminata and Prorocentrum lima, producers of diarrhetic shellfish toxins (DSTs), and diatoms of the genus Pseudo-nitzschia, producers of amnesic shellfish toxins (ASTs). Okadaic acid, a DST, was by far the most common toxin in the fauna, reaching higher levels in primary consumers such as bivalve mollusks (mussels, oysters, and clams), zooplankton, and suspension-feeding crustaceans (ghost shrimps), and moderate to low levels in cephalopods, fishes, gastropods, echinoderms, sea turtles, seabirds, and cetaceans. Less rainy periods (winter-early spring) were associated with the highest incidence of DSTs and blooms of their producing algae P. lima and Dinophysis spp., mainly in the middle region of Paranaguá Bay and on the shallow continental platform adjacent to the estuarine mouth. However, certain HAB-forming species may be more successful in inner estuarine areas ( Prorocentrum cordatum) and during different periods, such as late summer—early fall ( Pseudo-nitzschia spp.). Continuous monitoring of harmful algae and toxins is therefore highly recommended to mitigate the effects of HABs in the entire estuary. (HABs quality toxincontaminated contaminated seafood damage andor or CEP, CEP , (CEP) Brazil 200 202 201 total 60 watersediment sediment 67 phycotoxincontaminated phycotoxin analyzed DSTs, (DSTs) Pseudonitzschia, Pseudonitzschia Pseudo nitzschia, nitzschia ASTs. ASTs . (ASTs) acid DST mussels, mussels (mussels oysters clams, clams clams) zooplankton suspensionfeeding suspension feeding ghost shrimps, shrimps shrimps) cephalopods fishes gastropods echinoderms turtles seabirds cetaceans winterearly winter early spring P spp spp. mouth However HABforming HAB forming cordatum summerearly summer spp.. spp.) estuary (CEP 20 6 (DSTs (ASTs 2

Abstract The Brazil-Malvinas Confluence (BMC) is a significant biological frontier where distinct currents meet, fostering optimal conditions for phytoplankton development. In this study we tested the hypothesis that eddys promote an increase in phytoplankton biomass at the Brazil-Malvinas Confluence (BMC), altering species diversity. Phytoplankton were collected with Niskin bottles and nutrient concentrations assessed at two depths (Surface and Deep Chlorophyll Maximum Layer – DCML) in areas outside and under the influence of Cold-Core (CCE) and Warm-Core (WCE) Eddies. Environmental variables were determined in situ using a CTD profiler. Four regions were separated based on environmental variables and phytoplankton species, namely, the Brazil Current (BC), Malvinas Current (MC), CCE, and WCE. Species diversity was higher in the eddies. The conditions of the WCE were different from those of the CCE, with low temperature and salinity and high cell density values in the latter. The phylum Bacillariophyta was predominant in terms of species richness in all regions and was responsible for the higher cell density in the MC, while dinoflagellates were dominant in the BC and eddies. Therefore, eddy activity alters the structure, diversity and biomass of the phytoplankton community in the BMC. BrazilMalvinas BMC (BMC meet development BMC, , Surface DCML ColdCore Cold Core CCE (CCE WarmCore Warm (WCE Eddies profiler namely BC, (BC) MC (MC) eddies latter Therefore structure (BC (MC

Abstract This review summarizes the state of knowledge on athecate dinoflagellates occurring within the South Atlantic Ocean and Atlantic sector of the Southern Ocean. We compiled data from 105 articles and selected 33 addressing any aspect of athecate dinoflagellate studies. Our aim is to discuss the patterns in athecate dinoflagellate distribution by building a thorough species list and an occurrence map based on species recorded in coastal and oceanic waters. We found 69 species totaling 141 occurrences in the entire South Atlantic Ocean basin. Contradicting global trends, most species distributed throughout this region are subtropical. We linked this trend to a higher local effort in dinoflagellate research instead of higher biodiversity, especially when compared to usual hotspots in biodiversity attributed to tropical oceans. The Subantarctic and Antarctic regions had a low number of occurrences, with 12 and 5, respectively. Except for the occurrence of Gyrodinium lachryma in the Antarctic Zone, all records are unique, poorly described and never recorded again for species such as Gymnodinium baccatum and Gymnodinium antarcticum. This demonstrates that the state of knowledge regarding athecate dinoflagellates in the South Atlantic and especially in the Antarctic region is still limited due to a lack of directed investigation. 10 3 studies waters 6 14 basin trends subtropical oceans 1 5 respectively Zone unique antarcticum investigation

Resumen La Reserva de la Biosfera Isla Guadalupe (RBIG) se localiza a 241 km de la costa occidental de México, siendo uno de los territorios insulares más distante del país. Por lo tanto, el estudio de su biodiversidad en el contexto biogeográfico resulta de gran interés. El objetivo del presente estudio fue presentar los primeros registros de dinoflagelados de la RBIG. Se enlistan e ilustran 34 especies y taxones infraespecíficos de dinoflagelados. Todas las especies ya han sido registradas para las aguas costeras mexicanas y dos de ellas, Dinophysis tripos y Phalacroma mitra, se han reportado en la literatura, como productoras de toxinas. Este estudio representa el primer aporte al conocimiento de los dinoflagelados de la RBIG.

Abstract The Guadalupe Island Biosphere Reserve (RBIG) is located 241 km from Mexico's western coast and is thus one of the most distant island territories in the country. Therefore, studying its biodiversity is of great interest in a biogeographic context. This study aimed to present the first records of dinoflagellates found in the RNIG. Thirty-four dinoflagellate species and infraspecific taxa were reported and illustrated. All species have been previously recorded in Mexican coastal waters, and two of them, Dinophysis tripos and Phalacroma mitra, have been reported in the literature as toxin producers. This study represents the first contribution to the knowledge of dinoflagellates in the RBIG.

Resumen Se registra por primera vez el género de dinoflagelado Metadinophysis (Dinophyceae: Dinophysales) en la bahía de Buenaventura y el Parque Nacional Natural Uramba- PNN Uramba en Bahía Málaga del Pacífico colombiano central, se analiza su densidad con los cambios de marea. Se registraron células con contorno subtriangular y reniforme en vista ventral, epiteca pequeña. Aleta sulcal izquierda con tres costillas y la derecha muy reducida o ausente, presentando tamaño promedio 43.1 μm de longitud total y 25.0 𝜇m de ancho total, la densidad del género se analizó bajo cuatro factores, la marea alta y la marea baja en la bahía de Buenaventura y en la bahía de Málaga. Se encontraron diferencias significativas entre la densidad en la marea alta y la marea baja para la bahía de Buenaventura, la diferencia entre la marea alta de la bahía de Málaga y la marea baja de la bahía de Buenaventura. Asimismo, se estableció que la distribución de la densidad no tiene ninguna estructura espacial en ninguno de los eventos mareales. Con el presente estudio se registra por primera vez el género de Metadinophysis en el pacífico colombiano, ampliando su distribución a nivel global.

Abstract The dinoflagellate genus Metadinophysis (Dinophyceae Dinophysales) is recorded for the first time in the Buenaventura Bay and Uramba National Natural Park-PNN Uramba in Málaga Bay in the central Colombian Pacific and its density is analyzed with tidal changes. Cells were recorded with subtriangular and reniform outline in ventral view and small epitheca. Left sulcal fin with three ribs and the right one very reduced or absent, presenting average size 43.1 μm total length and 25.0 μm total width, the density of the genus was analyzed under four factors, high tide and low tide in Buenaventura Bay and in Málaga Bay; significant differences were found between the density at high tide and low tide for Buenaventura Bay, the difference between high tide in Malaga Bay and low tide in Buenaventura Bay. Likewise, it was established that the density distribution has no spatial structure in any of the tidal events. With the present study, the genus Metadinophysis is recorded for the first time in the Colombian Pacific, extending its distribution globally.

ABSTRACT This study analyzes the spatial and temporal variability of phytoplankton biomass and taxonomic composition in the surface waters of Todos Santos Bay, a semi-enclosed bay within the upwelling zone of the Baja California peninsula (México). Two methodological approaches (microscopy and chemotaxonomy [CHEMTAX]) were used to describe the variability of some genera and species (observed under the microscope) and the importance of those groups that cannot be observed microscopically. Phytoplankton biomarker pigments were measured with high-resolution liquid chromatography and used as input to run the CHEMTAX software to determine the contribution of the main phytoplankton groups to chlorophyll-a (Chl-a). The microscopic analyses showed that diatoms and dinoflagellates comprised 65 and 33% of the total cells, respectively. Dinoflagellates were most abundant in the inner bay and during cold months; the most frequent and abundant genera were Tripos, Protoperidinium, and Prorocentrum. Among diatoms, the most frequent genera were Cylindrotheca, Guinardia, Navicula, Pseudo-nitzschia, and Chaetoceros. CHEMTAX indicated that, together with diatoms, the flagellates prymnesiophytes and chlorophytes contributed a median of 80% to Chl-a, with chlorophytes as the most important group (29.9%). The high contribution of these flagellates suggests that they are represented by small-sized cells not visible by the light microscopy used. However, CHEMTAX largely underestimated the contribution of dinoflagellates (due to the presence of many mixotrophic species). Hence, our results emphasize the importance of using both techniques for a more detailed evaluation of the taxonomic composition of phytoplankton in this and other coastal regions.

Abstract Despite its small area, Araçá Bay (AB) holds cultural, historical, and economic value and displays great benthic biodiversity. Thus, it is crucial to monitor its environmental health, including knowing the main groups of phytoplankton and their temporal variability. The shallow waters of Araçá Bay are continuously modified by the complex hydrography of the adjacent São Sebastião channel (SSC), challenging standard experimental designs for phytoplankton collection. Here we report changes in phytoplankton composition at intervals of five to six weeks from September 2013 to August 2014 in both Araçá Bay and SSC. Samples were collected twice daily for three consecutive days to increase taxonomic resolution. Our goal was to provide an inventory of species occurrences to aid future public policies and environmental management of the area. Analyses revealed high species richness and 166 different phytoplankton taxa. Diatoms and dinoflagellates were always numerically dominant, but taxa occurrence changed markedly. Diatoms of the genera Pseudo-nitzschia were abundant during spring and summer concurrently to signatures of South Atlantic Central Water in the SSC, while Thalassiosira occurred when waters displayed relatively lower salinity. The inventory demonstrated several potentially harmful species of microalgae and cyanobacteria, strongly suggesting investments in monitoring programs in this area that currently experience an increase in population. AB (AB cultural historical biodiversity Thus health variability SSC , (SSC) collection 201 resolution 16 dominant markedly Pseudonitzschia Pseudo nitzschia salinity cyanobacteria population (SSC 20 1 2

Resumo Apesar de sua pequena área, a baía do Araçá (AB) possui grande valor cultural, histórico e econômico, e biodiversidade bentônica. Assim, é fundamental monitorar sua saúde ambiental, que inclui conhecer os principais grupos de fitoplâncton e sua variabilidade temporal. As águas rasas da baía do Araçá são continuamente modificadas pela hidrografia complexa do canal de São Sebastião (SSC), desafiando desenhos experimentais convencionais para coleta de fitoplâncton. Aqui relatamos mudanças sazonais na composição do fitoplâncton, em intervalos de 4 a 6 semanas, de setembro de 2013 a agosto de 2014 na baía do Araçá e no SSC, sendo coletadas duas vezes ao dia por três dias consecutivos em cada campanha de amostragem para aumentar a resolução taxonômica. Nosso objetivo foi fornecer um inventário de ocorrência de espécies para auxiliar futuras políticas públicas e gestão ambiental na área. As análises revelaram alta riqueza de espécies e 166 táxons fitoplanctônicos diferentes. Diatomáceas e dinoflagelados foram numericamente dominantes, mas a ocorrência de táxons mudou acentuadamente entre observações. As diatomáceas do gênero Pseudo-nitzschia foram abundantes durante a primavera e o verão concomitantemente às assinaturas da Água Central do Atlântico Sul no CSS, enquanto Thalassiosira ocorreu durante períodos de salinidade relativamente mais baixa. O inventário demonstrou várias espécies potencialmente nocivas de microalgas e cianobactérias, sugerindo fortemente investimentos para programas de monitoramento nesta área que vem registrando aumento populacional contínuo. AB (AB cultural econômico bentônica Assim temporal SSC , (SSC) semanas 201 taxonômica 16 diferentes dominantes observações Pseudonitzschia Pseudo nitzschia CSS baixa cianobactérias contínuo (SSC 20 1 2

Abstract We evaluated the seasonal phosphorus (P) status of the plankton community in the Ombla Estuary (OE) by using its specific alkaline phosphatase activity (sAPA). Microphytoplankton (MICRO) indicated a substantially higher P deficiency than nanophytoplankton (NANO) and picoplankton (PICO). We found that the prolonged increase in the temperature of the surface estuarine water supported a notable growth of the dinoflagellate Prorocentrum spp. in late spring-early summer (June). In the summer (August), we found the maximum microphytoplankton sAPA (MICRO sAPA) (307.8 nmol μg C-1 h-1) in the surface water, in which (84%) dinoflagellates predominated within MICRO with the maximum alkaline phosphatase activity (APA) in all size fractions, including free enzymes. Persistently low discharge of Ombla during summer-early autumn caused a transition from phosphorus- to potentially nitrogen-limited MICRO in the surface water in early autumn (October). Nutrient stress disappeared in winter, in which a significant amount of dissolved orthosilicate, dissolved inorganic nitrogen (DIN), and soluble reactive phosphorus (SRP) enriched the estuary via maximal river discharge and inflow of nutrient-rich coastal waters. MICRO (coccolithophorids and diatoms) had very low APA (surface water) and quantitatively undetectable APA (bottom water) in the nutrient-rich water column in January. This study shows a more significant impact of nutrient concentrations on MICRO than other size classes of the plankton community. Because of the similarity in seasonal hydrological features, we assume that the general pattern of switching from P- to N-limitation of phytoplankton growth also occurs in other highly stratified estuaries along the coastal karst of the eastern Adriatic Sea during the lowest river discharges and groundwater activities in summer-early autumn before the rainy season. This study indicates that a common highly stratified estuary on the eastern Adriatic coast can serve as a natural laboratory to explore connections between nutrient limitations and phytoplankton successions. (P OE (OE sAPA. . (sAPA) NANO (NANO PICO. PICO (PICO) spp springearly spring June. June (June) August, August , (August) 307.8 3078 307 8 (307. C1 C 1 C- h1 h h-1 84% 84 (84% (APA fractions enzymes summerearly nitrogenlimited limited October. October (October) winter orthosilicate DIN, DIN (DIN) SRP (SRP nutrientrich rich waters coccolithophorids diatoms bottom January features Nlimitation N limitation season successions (sAPA (PICO (June (August 307. 30 (307 h- (84 (October (DIN 3 (30 (8 (3 (

Abstract: Background and Aims: The order Gymnodiniales is composed of 11 families, 63 genera and 641 taxonomically valid species. These dinoflagellates are characterized by having a very fragile cell wall. In addition, some species can produce phycotoxins and form dense blooms. In the case of the Mexican Pacific coast, studies focused on knowing the diversity of this group are still limited, despite the economic, social, and ecological importance of these microorganisms. Therefore, the objective of this study was to make a floristic list from a bibliographical review, integrating only the records supported by micrographs, to know the diversity of athecate dinoflagellates of the order Gymnodiniales present in the Mexican Pacific Ocean, with emphasis on those that form harmful algal blooms. Methods: The search for information was carried out in publications (articles and book chapters), from the first record (1943) to the present (November 2022). Each record was confirmed only by the existence of optical and scanning electron micrographs. Key results: The Mexican Pacific is made up of 11 coastal states, where the presence of 10 families, 31 genera and 103 species (which represents 16% of the total number of species recorded worldwide) is currently reported for the order Gymnodiniales. Of the 11 families that make up this order, the Gymnodiniaceae family grouped 29% of the total number of species recorded for the Mexican Pacific, where the genera Gymnodinium and Gyrodinium presented the largest number of species. Conclusions: The evidence presented in this study showed that there is a low diversity for this order in the Mexican Pacific, so it is necessary to implement a greater sampling effort, in addition to venturing into different molecular tools that allow obtaining a better approximation of the diversity in the Mexican coasts.

Resumen: Antecedentes y Objetivos: El orden Gymnodiniales está compuesto por 11 familias, 63 géneros y 641 especies taxonómicamente válidas. Estos dinoflagelados se caracterizan por presentar una pared celular muy frágil. Además, algunas especies pueden llegar a producir potentes toxinas e incluso tienen la capacidad para formar grandes florecimientos. Los estudios enfocados en conocer la diversidad de este grupo, en el caso de las costas del Pacífico Mexicano, siguen siendo limitados, a pesar de la importancia económica, social y ecológica de estos microorganismos. Por lo tanto, el objetivo de este estudio fue realizar un listado florístico a partir de una revisión bibliográfica, que integre únicamente a los registros respaldados por micrografías, para conocer la diversidad de dinoflagelados atecados del orden Gymnodiniales presentes en el Pacífico Mexicano, con énfasis en aquellos formadores de florecimientos algales nocivos. Métodos: La búsqueda de información se realizó en publicaciones (artículos y capítulos de libros), desde el primer registro (1943) hasta la actualidad (noviembre 2022). Cada registro fue confirmado únicamente mediante la existencia de micrografías ópticas y de electrónicas de barrido. Resultados clave: El Pacífico Mexicano está conformado por 11 estados costeros, donde actualmente se tiene reportada la presencia de 10 familias, 31 géneros y 103 especies (16% del total de las registradas a nivel mundial) para el orden Gymnodiniales. De las 11 familias que conforman a este orden, la familia Gymnodiniaceae agrupó 29% del total de especies registradas para el Pacífico Mexicano, donde los géneros Gymnodinium y Gyrodinium presentaron el mayor número de especies. Conclusiones: La evidencia presentada en este estudio demostró que existe una baja diversidad para este orden en el Pacífico Mexicano, por lo que es necesario implementar un mayor esfuerzo de muestreo, además de incursionar en diferentes herramientas moleculares que permitan obtener una mejor aproximación a la diversidad alfa en las costas mexicanas.

Resumo O presente estudo relata variações sazonais e espaciais na diversidade, na distribuição e na abundância de dinoflegelados e indica a presença de espécies de HAB nas águas do Paquistão. Um total de 179 táxons, registrados nesse estudo de águas offshore e próximas à costa, pertence a 41 gêneros em 26 famílias e 10 ordens. A alta contagem de espécies (149 espécies) foi registrada na estação offshore da Ilha de Manora (MI-1) e 105 spp., 109 spp. e 115 spp. foram encontrados na estação offshore da vila de Mubarak (MV-1), Manora perto da estação costeira (MI- 2) e estação próxima à costa da Vila de Mubarak (MV-2), respectivamente. Tripos furca foi a espécie dominante e de ocorrência frequente (> 1 x103 a > 25 x103 células L-1 da costa e > 1x 105 células Ll de estações próximas à costa), além de Alexandrium catenella menos abundante, Alexandrium sp., Alexandrium minutum e Prorocentrum micans (> 103 a 25x 103 células/L). Outras 44 espécies ocorreram em números relativamente baixos (< 103 células L-1). Setenta espécies foram encontradas durante o período de estudo em todas as quatro estações. Foi registrado um alto número de espécies em três gêneros (Tripos (38), Protoperidinium (34) e Prorocentrum (20). Potencialmente tóxicos (16 gêneros e 43 espécies) e HAB relacionados (19 gêneros e 30 espécies), táxons de dinoflagelados também foram registrados. A contribuição percentual de dinoflagelados na população fitoplanctônica total geralmente permaneceu abaixo de 20%, exceto em alguns casos. As estações da Ilha de Manora tinham índice de Shannon comparativamente mais alto e equitabilidade e índice de dominância ligeiramente mais baixos. O gráfico de PCA mostrou forte correlação positiva entre concentração de clorofila-a e oxigênio dissolvido, número total de fitoplânctons e dinoflagelados.

Abstract The present study reports on seasonal and spatial variations in diversity, distribution and abundance of dinoflegellates and indicates the presence of HAB species in Pakistan waters. A total of 179 taxa, recorded in this study from offshore and near-shore waters, belong to 41 genera in 26 families and 10 orders. The high species count (149 species) was recorded from Manora Island offshore station (MI-1) and 105 spp, 109 spp and 115 spp were encountered from the Mubarak village offshore station (MV-1), Manora near shore station (MI-2) and Mubarak Village near-shore station (MV-2) respectively. Tripos furca was the dominant and frequently occurring species (> 1 x103 to > 25 x103 cells L-1 from coastal and >1x 105 cells L-l from near-shore stations) in addition to less abundant Alexandrium catenella, Alexandrium sp., Alexandrium minutum, and Prorocentrum micans (>103 to 25x 103cells/L). Another 44 species occurred in relatively low numbers (<103 cell L-l). Seventy species were found throughout the study period at all four stations. High number of species in three genera (Tripos (38), Protoperidinium (34) and Prorocentrum (20) was recorded. Potently toxic (16 genera 43 species) and HAB related (19 genera and 30 species) dinoflagellate taxa were also recorded. The percent contribution of dinoflagellates in total phytoplankton population generally remained below 20% except for a few instances. Manora Island stations had comparatively higher Shannon index and equitability and slightly lower dominance index. The PCA plot showed strong positive correlation among chlorophyll-a concentration, dissolved oxygen, total number of phytoplankton and dinoflagellates.

Resumo Objetivo Objetivamos caracterizar a estrutura da comunidade fitoplanctônica e identificar os principais fatores ambientais que impulsionam a comunidade em cinco reservatórios construídos na região do alto rio Paraná. Métodos O fitoplâncton e as variáveis ambientais foram coletados na região lacustre do reservatório, entre novembro de 2013 e novembro de 2014, com intervalo entre as coletas de 3 a 6 meses. A riqueza e a biomassa da comunidade fitoplanctônica foram utilizadas como resposta à variabilidade ambiental espacial e temporal dos reservatórios. Os dados das variáveis ambientais foram analisados por meio de uma Análise de Componentes Principais (PCA). Foram realizadas Análises de Escalonamento Multidimensional Não-Métrico (NMDS) aos dados de riqueza e biomassa da comunidade fitoplanctônica. Resultados Identificamos 80 táxons distribuídos em 11 classes, dos quais Cyanobacteria e Chlorophyceae foram os mais representados. Não observamos variação temporal significativa para variáveis ambientais ou atributos da comunidade fitoplanctônica, o que pode estar relacionado à prolongada estiagem neste período no sudeste brasileiro. Os maiores valores de riqueza e biomassa fitoplanctônica foram encontradas em Três Irmãos (Rio Tietê), reservatório localizado na bacia mais antropizada do país. Cianobactérias e dinoflagelados dominaram a biomassa em todos os reservatórios durante o período estudado. Os reservatórios de Ilha Solteira, Jupiá e Porto Primavera apresentaram tendência de diminuição nos valores de riqueza e biomassa fitoplanctônica, sendo que os reservatórios construídos em série no rio Paraná provavelmente possuem forte interdependência, de acordo com o conceito do CRCC. Conclusões A variação espacial dos atributos fitoplanctônicos foi influenciada principalmente pela posição ocupada pelo reservatório na bacia hidrográfica, tempo de retenção de água (TR) e concentrações de nutrientes em cada reservatório.

Abstract Aim We aimed to characterize the structure of the phytoplankton community and identify the main environmental factors driving the community in five reservoirs constructed in the region of the high Paraná River. Methods The phytoplankton and environmental variables were collected at the lacustrine region of the reservoir, between November 2013 and November 2014, with interval between collections ranged from 3 to 6 months. The richness and biomass of the phytoplankton community were measured as a response to the spatial and temporal environmental variability. Data from environmental variables was analyzed by Principal Component Analysis (PCA). Non-Metric Multidimensional Scaling Analyzes (NMDS) were performed on the richness and biomass data of the phytoplankton community. Results We identified 80 taxa distributed in 11 taxonomic classes, from which Cyanobacteria and Chlorophyceae were best represented. We did not observe significant temporal variation for either environmental variables or attributes of the phytoplankton community, which may be related to the prolonged drought in this period in the Brazilian Southwest. Higher phytoplankton richness and biomass were found in the Três Irmãos (Tiete River), reservoir located in the most anthropized basin in the country. Cyanobacteria and dinoflagellates dominated the biomass in all reservoirs during the studied period. The Ilha Solteira, Jupiá and Porto Primavera reservoirs showed a tendency to decrease in the values of phytoplankton richness and biomass, and the reservoirs built in series in the Paraná River probably have strong interdependence, according to the CRCC concept. Conclusions Spatial variation in phytoplankton attributes was influenced mainly by the position occupied by the reservoir in the hydrographic basin, water retention time (RT) and nutrient concentrations in each reservoir.

Abstract Iron is a limiting nutrient for Symbiodiniaceae (colloquially known as zooxanthellae), with low solubility in seawater. The use of stable, soluble, and chemically defined iron complexes is proposed as a strategy to control the supply of this metal to target organisms. In this work, we investigated the effect of iron(II) and derivatives of iron(III) (desferrioxamine, deferiprone, deferasirox, and HBED) over the growth and metal loading of five Symbiodiniaceae species. Iron supplementation did not affect growth or metal load in species with high iron stocks. In contrast, for species with low iron stocks, hydrophobic Fe(DFX)2 was very efficient in inducing growth and iron loading. Also, the desferrioxamine derivative of iron Fe(DFO) appeared as an interesting, ecologically friendly source of the nutrient. The effect of iron supplementation on the growth of Breviolum minutum submitted to heat shock was also studied. Iron supplementation prior to the heat shock episode increased the heat tolerance of B. minutum. Such findings provide new insights for the strategy of iron supplementation to improve the fitness of Symbiodiniaceae, both in vitro and in the environment.

Summary Background and aims : Planktonic dinoflagellates have a great ecological significance in marine environments. While some dinoflagellate species commonly reach bloom concentrations and are thus conspicuous components of marine phytoplankton, others occur in very low abundances which make them difficult to detect in field studies. Here we analyzed dinoflagellate composition and abundance in five oceanographic expeditions carried out in continental shelf and slope waters of the Argentine Sea. M&M : Plankton abundance was estimated by the Utermohl method, using inverted microscopy, whereas further optical and scanning electron microscopy was applied for the identification of dinoflagellate species. Results : We focused on the occurrence of seven dinoflagellates that have been previously poorly documented or overlooked in marine environments worldwide: Dinophysis microstrigiliformis; Gyrodinium sp.; Karlodinium elegans; Oxytoxum laticeps; Peridiniella danica; Peridiniella globosa and Prorocentrum nux. The latest and K. elegans are observed for the first time in field conditions after their original descriptions based on cell cultures. While most species were detected in low or moderate abundances, P. nux, which is the smallest Prorocentrum species, reached 82,000 cells L-1 in slope waters. Very small Gyrodinium cells (11.5 |jm long; 8.7 |jm wide) with a distribution restricted to slope waters during spring, were not possible to be accurately assigned to a species. Conclusions : This study contributes to the understanding of dinoflagellate diversity in the Argentine Sea and the worldwide distribution of little known species.

Resumen Introducción y objetivos : Los dinoflagelados planctónicos son de gran relevancia en los ecosistemas marinos. Mientras que algunas especies suelen forman floraciones y ser componentes conspicuos del fitoplancton, otras se encuentran en abundancias muy bajas, lo cual hace difícil su detección. Aquí analizamos la composición y abundancia de dinoflagelados en cinco expediciones oceanográficas realizadas en aguas de la plataforma continental y del talud del Mar Argentino. M&M : La abundancia se estimó con microscopio invertido (método Utermohl) y se utilizó microscopía óptica y electrónica de barrido para la identificación específica. Resultados : Nos enfocamos en la ocurrencia de siete dinoflagelados que previamente han sido poco documentados en ambientes marinos de todo el mundo: Dinophysis microstrigiliformis; Gyrodinium sp.; Karlodinium elegans; Oxytoxum laticeps; Peridiniella danica; Peridiniella globosa y Prorocentrum nux. Esta última especie y K. elegans se observan por primera vez en el campo desde su descripción basada en cultivos celulares. Si bien la mayoría de las especies se detectaron en abundancias bajas o moderadas, P. nux, el Prorocentrum más pequeño, alcanzó 82.000 células L-1 en aguas del talud. Células pequeñas de Gyrodinium sp. (11,5 jm de largo y 8,7 jm de ancho), con un una distribución restringida a las aguas del talud durante la primavera, no pudieron ser asignadas con precisión a nivel específico. Conclusiones : Este estudio contribuye al conocimiento de la diversidad de dinoflagelados en el Mar Argentino y la distribución mundial de especies poco conocidas.

ABSTRACT The phytoplankton community’s temporal variability associated with environmental factors and harmful algal blooms in Acapulco Bay was analyzed. Phytoplankton samples were taken monthly at three sites (MSL: Morro de San Lorenzo, CDO: Casa Díaz Ordaz, and PP: Playa Palmitas) over 11 months in 2018. The physical and chemical variables of surface water were measured in situ, and the composition and community structure of phytoplankton were analyzed. The physical and chemical characteristics studied varied significantly. The highest temperatures were obtained in September and October (September: 29.6 ± 3.58°C, October: 34.61 ± 1.83°C), whereas the highest salinities and chlorophyll-α concentrations occurred from February to May (salinity: 34.06 ± 0.38, chlorophyll-α: 2.73 ± 0.15 μg L-1). The highest oxygen concentrations were recorded during the rainy season (June 91.8% and December 100%). A total of 201 phytoplankton species were identified: 94 diatoms, 101 dinoflagellates, 4 cyanobacteria, and 2 silicoflagellates. Diatoms dominated during the rainy season, whereas dinoflagellates dominated during the dry season (June to December). A total of 17 harmful species were identified; four toxin-producing species included a diatom genus (Pseudonitszchia sp.) and three dinoflagellate species (Gymnodinium catenatum, Dinophysis caudata, and Phalacroma rotundata). One species that produces oxygen reactive species and hemolysis (Margalefidinium polykrikoides) caused a harmful algal bloom at the CDO and PP stations. The temperature is one of the most critical factors for its bloom in October.

Abstract The genus Blepharocysta Ehrenberg currently comprises 5 species of truly marine planktonic thecate dinoflagellates, which are solitary, globose, subspherical and heterotrophic cells, lack typical depressed cingulum and sulcus, and are mainly distributed in tropical areas. The morphology of 2 species, Blepharocysta splendor-maris and B. paulsenii, found in net samples from the tropical Mexican Pacific, was studied by LM and SEM, especially plate arrangement and theca ornamentation. Blepharocysta splendor-maris showed more ovoid cells, developed sulcal lists, and theca with shallow poroids having a relative low density, whereas B. paulsenii had more spherical cells, shorter epitheca, reduced and slightly ornamented sulcal lists, and theca with deep poroids having a relatively higher density. The thecal tabulation in both species agrees with conventional tabulation, including the anterior intercalary plate in B. paulsenii. A comparison of both morphological and ecological characteristics among all species of the genus is done, outstanding shape of cells, relative size, development of sulcal lists, and especially the theca ornamentation as important morphological characters to distinguish species. Blepharocysta splendor-maris is the only species distributed from tropical to Antarctic waters, whereas the others are limited to tropical and subtropical waters.

Resumen El género Blepharocysta Ehrenberg comprende 5 especies de dinoflagelados tecados, planctónicos marinos. Incluye células solitarias, globulares, subesféricas y heterótrofas, que carecen de cingulum y sulcus típicos, de distribución principal en áreas tropicales. Se estudió la morfología de las especies Blepharocysta splendor-maris y B. paulsenii, encontradas en muestras de red del Pacífico mexicano tropical, usando ML y MEB, particularmente el arreglo de placas y ornamentación de la teca. Blepharocysta splendor-maris mostró una forma ovoide, aletas sulcales desarrolladas, teca con poroides poco profundos y mediana densidad, mientras que B. paulsenii tuvo forma más esférica, epiteca más corta, aletas sulcales reducidas, ligeramente ornamentadas y teca con poroides profundos, de mayor densidad. La tabulación de placas en ambas especies concuerda con la tabulación convencional, incluida la placa intercalar anterior en B. paulsenii. Se comparan las características morfológicas y ecológicas de las especies del género, destacando forma de células, tamaño relativo, desarrollo de las aletas sulcales y especialmente la ornamentación de la teca como caracteres morfológicos para distinguir especies. Blepharocysta splendor-maris es la única especie distribuida desde aguas tropicales a antárticas, mientras que las otras están limitadas a aguas tropicales y subtropicales.