Taxonomia e aspectos biogeográficos da flora planctônica de um sistema costeiro salobro - Lagoa Carapebus, município de Carapebus, RJ

A taxonomical and biogeographical survey of planktonic flora from Carapebus lagoon (22°50'S e 41º35'W), a brackish coastal system located in the northern Rio de Janeiro State belonging, in part, to Parque Nacional da Restinga de Jurubatiba werc presented. This is a shallow and oligohaline lagoon with dark and slightly alcaline waters. Taxonomical study was based on 145 samples collected by a plankton net and by passing a ílask along water subsurfce at fur stations in February, March, July and October 1996 (Period I), April, August and September 1997 (Period II), and at monthly intervals from May 2000 to April 2001 (Period III). Altogether 1 84 táxons were identified distributed into Chlorophyceae (23%), Cyanophyceae (18%), Euglenophyceae (17%), Bacillariophyceae (11%), Zygnematophyceae (8%), Coscinodicophyceae (5%), Xanthophyceae (4%), Cryptophyceae (4%), Dinophyceae (3%), Chrysophyceae (4%), Prasinophyceae (2%), Charophyceae (1%) e Ulvophyceae (1%). Nineteen species and four genera were new records fr Brazil. Forty-fve and 70 generic and infrageneric taxa were registered for the frst time fr Rio de Janeiro State and fr Brazilian brackish coastal lagoons, respectively. Seventeen taxa could not be identifed at specifc levei and probably almost them must be new to the Science. Concernig the salinity the populations from Carapebus lagoon werc, in general, represented by typical eurihaline limnobiont organisms (76%), fllowed by typical organisms fom brackish waters (10%) and eurihaline marine (3%). From a geographical point of view, of the total infrageneric taxa in Carapebus lagoon, 43% have a cosmopolitan distribution, 13% are widely distributed, 1 9% show scarce distribution and 4% have a temperate/arctic occurrence. Only 11% of the taxa present restricted distribution in tropics. Descriptions, illustrations, infrmations on geographical distribution by the world and in Brazil, and 1 2 indented keys fr the identifcation of all taxa presently registered were given. Taxonomical comments including phenotypic plasticity of the populations identifed as well as the similarity based on the floristic composition registered in quantitative analysis between Carapebus lagoon and three more brackish systems located in the southeastern and southern part of Brazil were discussed.CAPESFUJBForam estudadas a taxonomia e aspectos biogeográficos da flora planctônica da lagoa Carapebus (22º 50'S e 41 º 35'W), sistema costeiro salobro localizado no litoral norte do estado do Rio de Janeiro, em parte, inserido no Parque Nacional da Restinga de Jurubatiba. É um ambiente raso, oligohalino, de águas escuras levemente alcalinas. O estudo baseou-se em 1 45 amostras coletadas por passagem de rede de 25 µm de abertura de malha e · passagem de frasco na água de subsuperfície, em quatro estações, nos meses de fevereiro, março, julho e outubro de 1 996 (período I), abril, agosto e setembro de 1 997 (período II), e mensalmente de maio de 2000 a Bbril de 200 1 (período Ili). Um total de 1 84 táxons foi inventariado, distribuído nas classes Chlorophyceae (23 % ), Cyanophyceae (18%), Euglenophyceae (17%), Bacillariophyceae (11 %), Zygnematophyceae (8%), Coscinodiscophyceae (5%), Xanthophyceae (4%), Cryptophyceae (4%). Dinophyceae (3%), Chrysophyceae (3%), Prasinophyceae (2%), Charophyceae (1 %) e Ulvophyceae (1 %). Do total de táxons identificados, 19 espécies e quatro gêneros constituíram primeiras citações de ocorrência para o Brasil; 45 e 70 categorias genéricas e infragenéricas foram registradas pioneiramente para o estado do Rio de Janeiro e lagoas costeiras brasileiras, respectivamente. Dezessete táxons foram identificados apenas em nível genérico ou não tiveram suas identificações em nível específico confirmadas e, provavelmente, muitos destes táxons constituam novidades para a ciência, havendo, entretanto, necessidade de estudos mais acurados visando a real circunscrição destas populações. Em relação à salinidade, as populações da lagoa Carapebus estiveram representadas, em sua maioria, por indivíduos tipicamente limnobiontes eurihalinos (76%), seguidos por táxons típicos de águas salobras (10%) e marinhos eurihalinos (3%). Do ponto de vista biogeográfico, a flora esteve representada, principalmente, por táxons cosmopolitas (43%) ou ari:iplamente distribuídos (13%). Os demais estiveram representados por táxons de distribuição escassa (19%), temperado/ártico (4%) e tropicais (11 %). Para todos os táxons registrados foram fornecidas descrições, ilustrações, informações de distribuição geográfica no mundo e no Brasil além de 12 chaves endentadas para identificação dos gêneros e categorias infragenéricas. Foram apresentadas discussões sobre a plasticidade fenotípica observadas nas populações examinadas bem como a similaridade entre a lagoa Carapebus e três sistemas salobros brasileiros localizados nas regiões sudeste e sul, com base na composição florística registrada em análises quantitativas

The Genus Alexandrium (Dinophyceae, Dinophyta) in Brazilian Coastal Waters

A review of the dinoflagellate genus Alexandrium occurring in Brazilian coastal waters is presented based on both published information and new data. Seven Alexandrium species have been recorded from Brazil so far: Alexandrium catenella, Alexandrium fraterculus, Alexandrium gaardnerae, Alexandrium kutnerae, Alexandrium tamiyavanichi, Alexandrium tamutum, and Alexandrium sp. While A. gaardnerae and A. kutnerae were identified based only on morphological characteristics, phylogenetic analysis (ITS and LSU rDNA) were performed for the remaining species based on cultures and/or field populations. Monoclonal cultures of the analyzed species were isolated from field samples obtained from Bahia (A. tamiyavanichi, two strains), Rio de Janeiro (A. tamutum, three strains; Alexandrium sp., two strains), Santa Catarina (A. fraterculus, one strain), and Rio Grande do Sul (Alexandrium tamarense, three strains). This is the first record of A. tamutum for the South Atlantic. In addition, molecular data for Brazilian strains of A. fraterculus are presented for the first time, as well as sequences from the ITS region for A. catenella (previously reported as A. tamarense) from Brazilian coastal waters. The morphological characters of the three species corresponded to those typically recorded in the literature and their identification was confirmed by molecular analysis. Based on the LSU rDNA and ITS regions, the three strains of A. catenella showed a high degree of similarity with strains from Southern Chile and North America. The implications and limitations of these findings for the monitoring protocols within the global and regional context are discussed

An evaluation of the genus Amphidinium (Dinophyceae) combining evidence from morphology, phylogenetics, and toxin production, with the introduction of six novel species

The genus Amphidinium is an important group of athecated dinoflagellates because of its high abundance in marine habitats, its member’s ability to live in a variety of environmental conditions and ability to produce toxins. Furthermore, the genus is of particular interest in the biotechnology field for its potential in the pharmaceutical arena. Taxonomically the there is a history of complication and confusion over the proper identities and placements of Amphidinium species due to high genetic variability coupled with high morphological conservation. Thirteen years has passed since the most recent review of the group, and while many issues were resolved, some remain. The present study used microscopy, phylogenetics of the 28S region of rDNA, secondary structure of the ITS2 region of rDNA, compensatory base change data, and cytotoxicity data from Amphidinium strains collected world-wide to elucidate remaining confusion. This holistic approach using multiple lines of evidence resulted in a more comprehensive understanding of the morphological, ecological, and genetic characteristics that are attributed to organisms belonging to Amphidinium, including six novel species: A. fijiensis, A. magnum, A. paucianulatum, A. pseudomassartii, A. theodori, and A. tomasii

Salinity-Growth Response and Ichthyotoxic Potency of the Chilean Pseudochattonella verruculosa

Despite salmon farmers suffering the worst damage from a harmful algal bloom in Chile’s history (US$800M) due to a massive outbreak of the dictyochophyte Pseudochattonella verruculosa in 2016 (∼7000–20,000 cells ml−1), the effect of environmental drivers and the potency of lytic toxins produced by the local clones of this species remain still largely unexplored. Based on the drastic oceanographic anomalies observed in the Chilean fjords during the 2016-El Niño “Godzilla” event, the role of salinity (15 to 35 psu) on Pseudochattonella cell growth and cytotoxicity was studied by culturing, scanning electron microscopy (SEM) and using a rainbow trout cell line RTgill-W1 assay to define: (1) vegetative growth rates, (2) cell taxonomy, (3) ichthyotoxicity of monoclonal cultures at 25 and 35 psu in salinity, (4) differences in toxicity of lysed cells and supernatant at different cell concentrations (from 10 to 100,000 cells ml−1), and (5) temporal stability of lytic compounds. This study formally confirms the presence of P. verruculosa in Chilean waters using the large subunit (LSU) of the nuclear ribosomal RNA gene. The Chilean P. verruculosa ARC498 strain showed maximum cell densities at 30 psu (max. 84,333 ± 4,833 cells ml−1) and maximum growth rates (μmax) at 20 psu (1.44 cells d−1). Cultures at 15 psu showed suppressed maximum cell density (max. 269 ± 71 cell ml−1) but high μmax were recorded at the beginning of the exponential growth (1.31 cells d−1). No significant differences were observed between lysed cells and supernatant treatments in the two salinity levels, suggesting that the most lytic portion is released into the cell-free media instead of remaining cell bound. Cytotoxicity was correlated to cell abundance, reducing gill cell viability down to 80 and 65% compared to controls at 10,000 and 100,000 cells ml−1, respectively. Unexpectedly, lytic compounds from P. verruculosa ARC498 at 35 psu showed to be less toxic than cultures at 25, where a noticeable presence of peripheral mucocysts were observed by SEM. Lytic compounds from in vitro experiments are weakly toxic even at high cell concentrations, highly unstable and rapidly degraded in the light after 5 days of storage at 15°C. Our results point to the important effect of salinity on growth and ichthyotoxic potency of Pseudochattonella species and highlight the need for a deeper insight into the role of mucocysts in fish gill damage, which would provide a greater understanding as to the harmful modes of action of this species

Cryptic species in the parasitic Amoebophrya species complex revealed by a polyphasic approach

As critical primary producers and recyclers of organic matter, the diversity of marine protists has been extensively explored by high-throughput barcode sequencing. However, classification of short metabarcoding sequences into traditional taxonomic units is not trivial, especially for lineages mainly known by their genetic fingerprints. This is the case for the widespread Amoebophrya ceratii species complex, parasites of their dinoflagellate congeners. We used genetic and phenotypic characters, applied to 119 Amoebophrya individuals sampled from the same geographic area, to construct practical guidelines for species delineation that could be applied in DNA/RNA based diversity analyses. Based on the internal transcribed spacer (ITS) regions, ITS2 compensatory base changes (CBC) and genome k-mer comparisons, we unambiguously defined eight cryptic species among closely related ribotypes that differed by less than 97% sequence identity in their SSU rDNA. We then followed the genetic signatures of these parasitic species during a three-year survey of Alexandrium minutum blooms. We showed that these cryptic Amoebophrya species co-occurred and shared the same ecological niche. We also observed a maximal ecological fitness for parasites having narrow tointermediate host ranges, reflecting a high cost for infecting a broader host range. This study suggests that a complete taxonomic revision of these parasitic dinoflagellates is long overdue to understand their diversity and ecological role in the marine plankton

Importance of nanophytoplankton biomass during summer 2019 in a retreating marine-terminating glacier-fjord system, Marian Cove, West Antarctica (62°S)

The biogeochemical dynamics of fjords around Antarctica are strongly influenced by cryospheric, climatic, and oceanographic processes that occur on a seasonal scale. Furthermore, as global climate change continues, there is a growing awareness of the impact of ocean warming on glacier melting, which is expected to affect the composition of phytoplankton community structure in West Antarctica’s nearshore marine areas. In this study, we describe the role of hydrographic forcing on the short-term summer variability of the phytoplankton community in Marian Cove, an Antarctic glacial fjord (62°S). Phytoplankton and hydrographic variables were measured at five stations along the Marian Cove during summer 2019 (January–February). The highest concentrations of microphytoplankton biomass were found in the outer area of the fjord, whereas nanophytoplankton biomass displayed continued dominance during most of the summer period in Marian Cove. Hydrographic assessment showed that freshwater inputs from the glacier influenced the surface layer of the fjord, modulating phytoplankton biomass, which was dominated by nanodiatoms (Minidiscus sp., Thalassiosira spp.) and nanophytoflagellates (Cryptomonas spp., Phaeocystis sp.). Concurrent measurement of phytoplankton biomass and environmental conditions during December 2018–January 2019 indicated that a period of weak southeastern winds generated vertical stability, which led to the development of a major peak of microphytoplankton biomass in the outer cove, driven by warm, allochthonous, oceanic, nutrient-rich waters. High carbon biomass dominated by nanodiatoms and nanophytoflagellates was observed in cold, fresh, and low-light subsurface waters of the cove. Our results highlight the effects of a warming ocean, which may favor the summer resurgence of nanodiatom and nanophytoflagellate communities in Antarctic fjords due to increased glacial meltwater inputs

Harmful Algal Blooms: A Prolific Issue in Urban Stormwater Ponds

Nutrient-driven cyanobacteria blooms are an increasingly common issue in freshwater environments, particularly in anthropogenically altered landscapes. As stormwater runoff is one of the largest sources of nutrients for freshwater bodies, stormwater retention ponds in urban and suburban areas are likely environments for harmful cyanobacteria blooms and were thus targeted for an in-depth investigation assessing taxonomic composition, bloom morphological composition, toxicity, and impact of nutrients and other environmental drivers. Eighty-seven algal blooms were sampled from 2019 to 2022 in the greater Wilmington, North Carolina, area. Physicochemical parameters were recorded, and blooms were classified by type (defined as surface mat, surface scum, water column distribution, or benthic mat) and dominant taxa. Blooms of potentially toxic cyanobacteria genera in the water column of stormwater retention ponds were most prevalent. Dissolved inorganic phosphorus was significantly related to chlorophyll-a, Microcystis bloom formation, and the production of microcystin. Seventeen potentially toxic cyanobacteria genera were identified in retention ponds, some of whose blooms demonstrated detectable microcystin. Monoclonal cultures isolated from some blooms were found to produce anabaenopeptin and saxitoxin. The results demonstrate a higher incidence of potentially toxic cyanobacteria over other bloom-forming taxa (chlorophytes, euglenoids, chrysophytes, dinoflagellates, and diatoms) in the 39 water bodies sampled. The frequency of blooms occurring in stormwater ponds and the diversity of potentially toxic cyanobacteria identified suggest such harmful blooms are likely widespread in similar freshwater environments across multiple urbanizing areas. The blooms sampled in this study were all within residential, commercial, or recreational areas easily accessible to people, presenting serious hazards to both environmental and public health