This work investigates, for the first time, the Pseudo-nitzschia (PN) dynamics in the western English Channel (L4) and the environmental factors impacting on domoic acid (DA) production in these waters. This is combined with laboratory studies examining key environmental factors and the multifactorial impact of multiple macronutrient and micronutrient availability on PN growth and DA production. An LC-MS method was established, optimised, and compared with ELISA for the accurate and reproducible extraction and determination of particulate and dissolved DA. The method was used to measure the seasonal variation in DA at L4 during 2009 and this was compared to PN seasonal abundance and diversity. Three groups a P. delicatissima-group, a P. seriata-group, and a P. pungens/multiseries-group were identified and were found to have different ecological distributions with the latter two groups significantly correlating with DA concentration. Macronutrients, in combination with other environmental factors, were found to influence PN populations at L4. Multifactorial laboratory culture experiments investigating the availability of nitrate, phosphate, and silicate, confirmed that the interrelatedness of all these nutrients significantly affected the growth, decline, and DA production of P. multiseries, and highlight the importance of both phosphate and silicate availability for DA production. When the impacts of both macronutrient (phosphate and silicate) and micronutrient (iron and copper) availability were investigated, limited growth and DA production was observed in P. multiseries cultures. Results revealed the complexity and interrelationship of factors affecting both PN growth and DA production. Furthermore, molecular methods were developed to elucidate the PN species present from 2009 Lugol’s-preserved L4 samples. DNA was successfully extracted and amplified from these samples which had been stored for up to 2 years. Initial sequence analysis identified the rbcL DNA marker as an informative site for future work with a number of L4 sequences closely relating to different Pseudo-nitzschia spp.

Domoic acid (DA) is a neurotoxin produced by the harmful algae Pseudo-nitzschia that has been directly linked to mass stranding events of the California Sea Lion (CSL). The purpose of this paper is to review the anthropogenic influence on the production of this neurotoxin and examine how human activities are impacting this marine mammal species. A comprehensive and interdisciplinary literature review was conducted to evaluate the future sustainability of the CSL population. It was found that while Pseudo-nitzschia bloom developments are vulnerable to anthropogenic influences, the incontestable existence of natural contributing factors adds a certain complexity to the determination of causalities and the development of solutions. Strong evidence exists to show that DA can cause major and irreversible neurological damage in CSLs. Rehabilitation of DA-impacted CSLs is a polarizing issue in the U.S. and presents interesting implications for sustainable development. While the CSL population is currently healthy and plenteous, the strong abundance of future uncertainties warrants concern. A balance must be found between the involving social, economic, and environmental factors to ensure a promising future for the CSL species.

The marine diatom genus Pseudo-nitzschia includes species that produce domoic acid, a neurotoxin responsible for illness and mortality in both humans and marine wildlife. Because of the expertise and time required for the microscopic discrimination of species, molecular methods that monitor environmental concentrations of Pseudo-nitzschia provide a rapid alternative for the early detection of blooms and prediction of toxin accumulation. We have developed a nucleic acid sequence-based amplification with internal control RNA (IC-NASBA) assay and a quantitative reverse transcription PCR (qRT-PCR) assay for the detection of the toxic species P. multiseries targeting the ribulose- 1,5-biphosphate carboxylase/oxygenase small subunit (rbcS) gene. Both methods use RNA amplification and fluorescence-based real-time detection. Due to a limited rbcS sequence database, primers were designed and used to sequence this gene from 14 strains of Pseudo-nitzschia (including four P. multiseries) and 19 other marine diatoms. The IC-NASBA and qRT-PCR assays had a limit of detection of one cultured cell of P. multiseries and were linear over four and five orders of magnitude, respectively (r2 ! 0.98). Neither of the assays detected closely related organisms outside the Pseudo-nitzschia genus, and the qRT-PCR assay was specific to P. multiseries. While cross-reactivity of primers with unknown species prevented reliable detection of P. multiseries in spiked environmental samples using IC-NASBA, the qRT-PCR assay had positive detection from 107 cells/L to 103 cells/L. Nearly a 1:1 relationship was observed between predicted and calculated cell concentrations using qRT-PCR. Based on a diel expression study, the rbcS transcript copy number per cell ranged from 2.16 x 104 to 5.35 x 104, with the highest expression during early to mid photoperiod. The rbcS qRT-PCR assay is useful for the detection and enumeration of low concentrations of P. multiseries in the environment.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 84-88). Description: x, 88 leaves : ill. ; 29 cm. / Along the Oregon coast blooms of Pseudo-nitzschia spp. have been an almost annual occurrence since monitoring began in the late 80's. This study looks at the distribution of Pseudo-nitzschia spp., in relation to meteorological and oceanographic conditions. A series of transects (1995-98) were done in Coos Bay and over the adjacent continental shelf under a variety of oceanographic conditions. An intense sampling program was undertaken in June 1998, with simultaneous nearshore and in bay (Coos Bay) sampling, including a nearshore grid, 24 hour anchor station in the bay, and an in bay incoming tide drift study. The results suggest that blooms develop nearshore after upwelling events. In conditions of relaxed upwelling highest cell concentrations were found immediately adjacent to the coast in surface and mid-depth waters. At stations in Coos Bay, Pseudonitzschia spp. concentrations increased with the incoming tide. Nearshore phytoplankton populations were transported into the bay, initially in the more saline bottom waters, but were rapidly mixed throughout the water column by the turbulent flow in the channels. On ebbing tides there was a reduced number of phytoplankton in the water column, possibly indicating consumption by in bay filter feeders or sinking and deposition on the bottom.

Diatomáceas são importantes constituintes do epifíton em ambientes costeiros. Estratégias de fixação conferem a estas algas vantagem adaptativa, no entanto, as mesmas estão sujeitas às variações ambientais, podendo responder com alterações da composição e estrutura da comunidade. Embora a relação entre epifíton e substrato seja pouco compreendida, a arquitetura do substrato parece influenciar na comunidade aderida. A composição, estrutura e variação sazonal de diatomáceas epifíticas foram avaliadas em ambientes de marismas no estuário da Lagoa dos Patos, sul do Brasil. Três sítios foram amostrados, Saco do Silveira, Ilha da Pólvora e São José do Norte, distantes 36, 18 e 9 km do oceano Atlântico, respectivamente. O epifíton aderido à Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. foi removido dos substratos com lâmina metálica, oxidado e montado em lâminas permanentes para a análise das diatomáceas. Ao total cento e vinte e sete táxons foram encontrados, destacaram-se pelo maior número de espécies os gêneros Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith. A sazonalidade, espacialidade, salinidade e tipo de substrato tiveram influência na composição e estrutura da comunidade. A maior distância da desembocadura do estuário proporcionou uma maior influência de águas continentais no sítio Saco do Silveira, resultando na formação de uma comunidade caracterizada pela presença de táxons dulciaquícolas. O período de inverno se caracterizou por maiores valores dos atributos da comunidade (riqueza, diversidade e equitabilidade). A maior complexidade da superfície de Scirpus maritimus proporcionou a formação de uma comunidade epifítica mais rica. A investigação taxonômica de Nitzschia e Tryblionella foi aprofundada, analisando-se também o microfitobentos da região. A espécie Nitzschia papillosa Bertolli et al. foi registrada pela primeira vez para a ciência, ocorrendo no epifíton e microfitobentos dos sítios Ilha da Pólvora e São José do Norte. A espécie possui formato linear-lanceolado, ápices cuneados e fíbulas irregularmente distribuídas como várias espécies do gênero, sua característica diagnóstica é a presença de excrecências de sílica arredondadas a quadradas situadas na costa transapical interna das valvas. O estudo do gênero Tryblionella revelou a presença de 11 espécies, duas foram registradas pela primeira vez para o Rio Grande do Sul e uma para o sul do Brasil. Além disso, duas espécies novas para a ciência são propostas, Tryblionella Bertolli et Torgan, espécie semelhante a T. debilis Arnott ex O’Meara em microscopia óptica, mas que apresenta costelas transapicais assimétricas em microscopia eletrônica, e Bertolli et al., espécie que apresenta um padrão de ornamentação na face valvar semelhante à trama de uma renda. As espécies de Tryblionella e N. papillosa ocorreram concomitantemente no epifíton e no microfitobentos, evidenciando a interação entre as duas comunidades, promovida pela dinâmica do ambiente. / Diatoms are an important component of the epiphyton in coastal environments. The strategies of attachment provide adaptive advantages to these algae; however, they are susceptible to the environmental fluctuations, responding to them with changes in the community composition and structure. Although the relationship between epiphyton and substrate is poorly understood, the architecture of the substrate seems to influence the attached community. The composition, structure and seasonal variations of the epiphytic diatoms were evaluated in Patos Lagoon salt marshes. Three sampling sites were defined, Saco do Silveira, Ilha da Pólvora and São José do Norte, distant 36, 18 and 9 km from the Atlantic Ocean, respectively. The epiphyton attached to Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. was scraped with metal blade, oxidized and mounted on permanent slides for the analysis of the diatoms. A total of a hundred and twenty seven taxa were found. The genus Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith showed the highest number of species. The seasonality, spatiality, salinity and substrate influenced the composition and structures of the community. The higher distance of the estuary mouth provided a higher influence of continental waters in the site Saco do Silveira, resulting in a community characterized by freshwater taxa. The winter was characterized by higher values of the community attributes (richness, diversity and evenness). The more complex structure of S. maritimus surface provided the establishment of a richer community. The taxonomic investigation of Nitzschia and Tryblionella was more detailed, including the analysis of the microphytobenthos of the sites. The species Nitzschia papillosa Bertolli et al. was registered for the first time to science in Ilha da Pólvora and São José do Norte. The species has linear-lanceolate outline, cuneate apices and fibulae irregularly distributed, as many other species of the genus. Its main feature is the presence of rounded to squarer silica excrescences, situated on the transapical costae in the internal valve view. The study of the genus Tryblionella showed 11 species, two of them were registered for the first time in Rio Grande do Sul State and one in Southern Brazil. Besides that, two species new to science were proposed, Tryblionella Bertolli et Torgan, which is similar to T. debilis Arnott ex O’Meara in light microscopy, but present asymmetrical transapical ribs in scanning electron microscopy, and T. Bertolli et al. which presents an ornamentation pattern similar to a lace texture in the valve face. The species of Tryblionella and N. papillosa occurred concomitantly in the epiphyton and microphytobenthos, evidencing the interaction between both communities, promoted by the environment dynamics.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean.

Diatomáceas são importantes constituintes do epifíton em ambientes costeiros. Estratégias de fixação conferem a estas algas vantagem adaptativa, no entanto, as mesmas estão sujeitas às variações ambientais, podendo responder com alterações da composição e estrutura da comunidade. Embora a relação entre epifíton e substrato seja pouco compreendida, a arquitetura do substrato parece influenciar na comunidade aderida. A composição, estrutura e variação sazonal de diatomáceas epifíticas foram avaliadas em ambientes de marismas no estuário da Lagoa dos Patos, sul do Brasil. Três sítios foram amostrados, Saco do Silveira, Ilha da Pólvora e São José do Norte, distantes 36, 18 e 9 km do oceano Atlântico, respectivamente. O epifíton aderido à Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. foi removido dos substratos com lâmina metálica, oxidado e montado em lâminas permanentes para a análise das diatomáceas. Ao total cento e vinte e sete táxons foram encontrados, destacaram-se pelo maior número de espécies os gêneros Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith. A sazonalidade, espacialidade, salinidade e tipo de substrato tiveram influência na composição e estrutura da comunidade. A maior distância da desembocadura do estuário proporcionou uma maior influência de águas continentais no sítio Saco do Silveira, resultando na formação de uma comunidade caracterizada pela presença de táxons dulciaquícolas. O período de inverno se caracterizou por maiores valores dos atributos da comunidade (riqueza, diversidade e equitabilidade). A maior complexidade da superfície de Scirpus maritimus proporcionou a formação de uma comunidade epifítica mais rica. A investigação taxonômica de Nitzschia e Tryblionella foi aprofundada, analisando-se também o microfitobentos da região. A espécie Nitzschia papillosa Bertolli et al. foi registrada pela primeira vez para a ciência, ocorrendo no epifíton e microfitobentos dos sítios Ilha da Pólvora e São José do Norte. A espécie possui formato linear-lanceolado, ápices cuneados e fíbulas irregularmente distribuídas como várias espécies do gênero, sua característica diagnóstica é a presença de excrecências de sílica arredondadas a quadradas situadas na costa transapical interna das valvas. O estudo do gênero Tryblionella revelou a presença de 11 espécies, duas foram registradas pela primeira vez para o Rio Grande do Sul e uma para o sul do Brasil. Além disso, duas espécies novas para a ciência são propostas, Tryblionella Bertolli et Torgan, espécie semelhante a T. debilis Arnott ex O’Meara em microscopia óptica, mas que apresenta costelas transapicais assimétricas em microscopia eletrônica, e Bertolli et al., espécie que apresenta um padrão de ornamentação na face valvar semelhante à trama de uma renda. As espécies de Tryblionella e N. papillosa ocorreram concomitantemente no epifíton e no microfitobentos, evidenciando a interação entre as duas comunidades, promovida pela dinâmica do ambiente. / Diatoms are an important component of the epiphyton in coastal environments. The strategies of attachment provide adaptive advantages to these algae; however, they are susceptible to the environmental fluctuations, responding to them with changes in the community composition and structure. Although the relationship between epiphyton and substrate is poorly understood, the architecture of the substrate seems to influence the attached community. The composition, structure and seasonal variations of the epiphytic diatoms were evaluated in Patos Lagoon salt marshes. Three sampling sites were defined, Saco do Silveira, Ilha da Pólvora and São José do Norte, distant 36, 18 and 9 km from the Atlantic Ocean, respectively. The epiphyton attached to Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. was scraped with metal blade, oxidized and mounted on permanent slides for the analysis of the diatoms. A total of a hundred and twenty seven taxa were found. The genus Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith showed the highest number of species. The seasonality, spatiality, salinity and substrate influenced the composition and structures of the community. The higher distance of the estuary mouth provided a higher influence of continental waters in the site Saco do Silveira, resulting in a community characterized by freshwater taxa. The winter was characterized by higher values of the community attributes (richness, diversity and evenness). The more complex structure of S. maritimus surface provided the establishment of a richer community. The taxonomic investigation of Nitzschia and Tryblionella was more detailed, including the analysis of the microphytobenthos of the sites. The species Nitzschia papillosa Bertolli et al. was registered for the first time to science in Ilha da Pólvora and São José do Norte. The species has linear-lanceolate outline, cuneate apices and fibulae irregularly distributed, as many other species of the genus. Its main feature is the presence of rounded to squarer silica excrescences, situated on the transapical costae in the internal valve view. The study of the genus Tryblionella showed 11 species, two of them were registered for the first time in Rio Grande do Sul State and one in Southern Brazil. Besides that, two species new to science were proposed, Tryblionella Bertolli et Torgan, which is similar to T. debilis Arnott ex O’Meara in light microscopy, but present asymmetrical transapical ribs in scanning electron microscopy, and T. Bertolli et al. which presents an ornamentation pattern similar to a lace texture in the valve face. The species of Tryblionella and N. papillosa occurred concomitantly in the epiphyton and microphytobenthos, evidencing the interaction between both communities, promoted by the environment dynamics.

Diatomáceas são importantes constituintes do epifíton em ambientes costeiros. Estratégias de fixação conferem a estas algas vantagem adaptativa, no entanto, as mesmas estão sujeitas às variações ambientais, podendo responder com alterações da composição e estrutura da comunidade. Embora a relação entre epifíton e substrato seja pouco compreendida, a arquitetura do substrato parece influenciar na comunidade aderida. A composição, estrutura e variação sazonal de diatomáceas epifíticas foram avaliadas em ambientes de marismas no estuário da Lagoa dos Patos, sul do Brasil. Três sítios foram amostrados, Saco do Silveira, Ilha da Pólvora e São José do Norte, distantes 36, 18 e 9 km do oceano Atlântico, respectivamente. O epifíton aderido à Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. foi removido dos substratos com lâmina metálica, oxidado e montado em lâminas permanentes para a análise das diatomáceas. Ao total cento e vinte e sete táxons foram encontrados, destacaram-se pelo maior número de espécies os gêneros Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith. A sazonalidade, espacialidade, salinidade e tipo de substrato tiveram influência na composição e estrutura da comunidade. A maior distância da desembocadura do estuário proporcionou uma maior influência de águas continentais no sítio Saco do Silveira, resultando na formação de uma comunidade caracterizada pela presença de táxons dulciaquícolas. O período de inverno se caracterizou por maiores valores dos atributos da comunidade (riqueza, diversidade e equitabilidade). A maior complexidade da superfície de Scirpus maritimus proporcionou a formação de uma comunidade epifítica mais rica. A investigação taxonômica de Nitzschia e Tryblionella foi aprofundada, analisando-se também o microfitobentos da região. A espécie Nitzschia papillosa Bertolli et al. foi registrada pela primeira vez para a ciência, ocorrendo no epifíton e microfitobentos dos sítios Ilha da Pólvora e São José do Norte. A espécie possui formato linear-lanceolado, ápices cuneados e fíbulas irregularmente distribuídas como várias espécies do gênero, sua característica diagnóstica é a presença de excrecências de sílica arredondadas a quadradas situadas na costa transapical interna das valvas. O estudo do gênero Tryblionella revelou a presença de 11 espécies, duas foram registradas pela primeira vez para o Rio Grande do Sul e uma para o sul do Brasil. Além disso, duas espécies novas para a ciência são propostas, Tryblionella Bertolli et Torgan, espécie semelhante a T. debilis Arnott ex O’Meara em microscopia óptica, mas que apresenta costelas transapicais assimétricas em microscopia eletrônica, e Bertolli et al., espécie que apresenta um padrão de ornamentação na face valvar semelhante à trama de uma renda. As espécies de Tryblionella e N. papillosa ocorreram concomitantemente no epifíton e no microfitobentos, evidenciando a interação entre as duas comunidades, promovida pela dinâmica do ambiente. / Diatoms are an important component of the epiphyton in coastal environments. The strategies of attachment provide adaptive advantages to these algae; however, they are susceptible to the environmental fluctuations, responding to them with changes in the community composition and structure. Although the relationship between epiphyton and substrate is poorly understood, the architecture of the substrate seems to influence the attached community. The composition, structure and seasonal variations of the epiphytic diatoms were evaluated in Patos Lagoon salt marshes. Three sampling sites were defined, Saco do Silveira, Ilha da Pólvora and São José do Norte, distant 36, 18 and 9 km from the Atlantic Ocean, respectively. The epiphyton attached to Spartina alterniflora Loisel., Spartina densiflora densiflora Brogn., Scirpus maritimus L. e Juncus kraussii Hochst. was scraped with metal blade, oxidized and mounted on permanent slides for the analysis of the diatoms. A total of a hundred and twenty seven taxa were found. The genus Navicula Bory, Nitzschia Hassall e Tryblionella W. Smith showed the highest number of species. The seasonality, spatiality, salinity and substrate influenced the composition and structures of the community. The higher distance of the estuary mouth provided a higher influence of continental waters in the site Saco do Silveira, resulting in a community characterized by freshwater taxa. The winter was characterized by higher values of the community attributes (richness, diversity and evenness). The more complex structure of S. maritimus surface provided the establishment of a richer community. The taxonomic investigation of Nitzschia and Tryblionella was more detailed, including the analysis of the microphytobenthos of the sites. The species Nitzschia papillosa Bertolli et al. was registered for the first time to science in Ilha da Pólvora and São José do Norte. The species has linear-lanceolate outline, cuneate apices and fibulae irregularly distributed, as many other species of the genus. Its main feature is the presence of rounded to squarer silica excrescences, situated on the transapical costae in the internal valve view. The study of the genus Tryblionella showed 11 species, two of them were registered for the first time in Rio Grande do Sul State and one in Southern Brazil. Besides that, two species new to science were proposed, Tryblionella Bertolli et Torgan, which is similar to T. debilis Arnott ex O’Meara in light microscopy, but present asymmetrical transapical ribs in scanning electron microscopy, and T. Bertolli et al. which presents an ornamentation pattern similar to a lace texture in the valve face. The species of Tryblionella and N. papillosa occurred concomitantly in the epiphyton and microphytobenthos, evidencing the interaction between both communities, promoted by the environment dynamics.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate