Vera Veloso - Academia.edu (original) (raw)

Papers by Vera Veloso

Frontiers in Marine Science

The Atlantic Meridional Transect (AMT) program (www.amt-uk.org) provides the perfect opportunity ... more The Atlantic Meridional Transect (AMT) program (www.amt-uk.org) provides the perfect opportunity to observe the phytoplankton community size structure over a long latitudinal transect 50oN to 50oS, thereby covering the most important latitude-related basin-scale environmental gradients of the Atlantic Ocean. This work presents cell abundance data of phytoplankton taxa recently collected during cruises AMT28 and 29 (in 2018 and 2019, respectively) using flow cytometer and microscope observations, as well as the pigment composition of the community, to assess the abundance and spatial distribution of taxonomic groups across the Atlantic. The community size structure showed a clear consistency between cruises at large spatial scale, with a dominance of picoplanktonic Cyanobacteria in oceanic gyres, an increase in all groups in the equatorial upwelling region, and high biomass of microplankton size class at higher latitudes. Phytoplankton carbon biomass for oceanographic provinces, rang...

Scientific Reports

Estuaries are highly productive ecosystems, which are strongly affected by several anthropogenic ... more Estuaries are highly productive ecosystems, which are strongly affected by several anthropogenic pressures. Phytoplankton is a key element for assessing the ecological quality status in these transitional waters. Moreover, understanding physico-chemical and biological drivers is crucial to disentangle their effect on the structure of phytoplankton community. The present work aims to study the effect of the main physico-chemical drivers on the phytoplankton community structure and dynamics in a temperate well-mixed estuary (Sado Estuary). Four sampling stations were analyzed monthly in three regions of the estuary, from 2018 to 2019. Surface water samples were collected to analyze the phytoplankton community and several concomitant physico-chemical parameters. Temperature, turbidity, salinity, and nutrients availability were the drivers that best explained the spatio-temporal patterns observed in the phytoplankton community. The upper estuary was characterized by higher phytoplankton...

Frontiers in Marine Science

Changes in coccolithophore productivity in response to climate-driven ocean warming are likely to... more Changes in coccolithophore productivity in response to climate-driven ocean warming are likely to have cascading biogeochemical effects that feed back to the changing climate. This paper investigates the role (and interplay) of large-scale oceanographic and atmospheric processes across the North- and Equatorial Atlantic, including Saharan dust deposition, on the distribution of coccolithophore communities. The study is based on biological and hydrological data collected across the photic zone of the ocean, and aerosol data collected from the lower atmosphere, across 50°N–1°S during the Atlantic Meridional Transect in boreal Autumn of 2018 (AMT28), in synergy with Earth Observations. Results confirm existing understanding of the distribution of coccolithophore communities which are related to major meridional hydrological gradients across the North Atlantic. Dynamic, oxygenated and microphytoplankton-enriched waters at higher-latitudes were characterized by less diverse coccolithopho...

Frontiers in Marine Science, 2020

Early detection of dense harmful algal blooms (HABs) is possible using ocean colour remote sensin... more Early detection of dense harmful algal blooms (HABs) is possible using ocean colour remote sensing. Some algorithms require a training dataset, usually constructed from satellite images with a priori knowledge of the existence of the bloom. This approach can be limited if there is a lack of in situ observations, coincident with satellite images. A laboratory experiment collected biological and bio-optical data from a culture of Karenia mikimotoi, a harmful phytoplankton dinoflagellate. These data showed characteristic signals in chlorophyll-specific absorption and backscattering coefficients. The bio-optical data from the culture and a bio-optical model were used to construct a training dataset for an existing statistical classifier. MERIS imagery over the European continental shelf were processed with the classifier using different training datasets. The differences in positive rates of detection of K. mikimotoi between using an algorithm trained with purely manually selected areas...

Journal of the Science of Food and Agriculture, 1996

ABSTRACT Dry biomass obtained from stressed cells of Chlorella vulgaris (rich in carotenoid pigme... more ABSTRACT Dry biomass obtained from stressed cells of Chlorella vulgaris (rich in carotenoid pigments) was used as such in animal feed, instead of the commercial synthetic pigment. The in vivo effect of microalgal biomass as substitute pigment was ascertained with Hisex brown hens kept laying during 37 days under conventional conditions, and strongly suggested that yolk pigmentation was comparable to that obtained using commercial pigments, when comparable weight of colourant was formulated into the feed.

Bioresource Technology, 1991

7he results of a three month investigation on the outdoor mass culture of Phaeodactylum tricornut... more 7he results of a three month investigation on the outdoor mass culture of Phaeodactylum tricornutum Bohlin are reported. Experiments" carried out from January to March 1989 gave an average output rate of 4"O g m-2 day-I in ash-free dry weight (AFD W) basis for semicontinuous mode (days 0-74) and 2"0 gm-: day-1 for batch mode (days 74-84). Eicosapentaenoic acid (20.'5 ~o3 EPA) was the predominant fatty acid synthesized by this diatom during semicontinuous growth constituting 3"9% of AFD W, yielding 0.15 g m : day-i. 7he content of EPA was decreased to 0"7% of AFD W during batch mode, 16:0 and 16:1 becoming the main fatty acids. The relationship between optical density and output productivity rate was studied. In the range studied, the lower the concentration the higher the productivity and the lower the lipid production rate. Several flocculant systems were tried and calcium hydroxide, Ca(OH):, was found to be best at concentrations from 30 to 100 mg litre-~, in an apparently random way. The addition of chitosan did not improve the efficiency of flocculation.

Frontiers in Marine Science

Phytoplankton biomass, through its proxy, Chlorophyll a, has been assessed at synoptic temporal a... more Phytoplankton biomass, through its proxy, Chlorophyll a, has been assessed at synoptic temporal and spatial scales with satellite remote sensing (RS) for over two decades. Also, RS algorithms to monitor relative size classes abundance are widely used; however, differentiating functional types from RS, as well as the assessment of phytoplankton structure, in terms of carbon remains a challenge. Hence, the main motivation of this work it to discuss the links between size classes and phytoplankton groups, in order to foster the capability of assessing phytoplankton community structure and phytoplankton size fractionated carbon budgets. To accomplish our goal, we used data (on nutrients, photosynthetic pigments concentration and cell numbers per taxa) collected in surface samples along a transect on the Atlantic Ocean, during the 25th Atlantic Meridional Transect cruise (AMT25) between 50° N and 50° S, from nutrient-rich high latitudes to the oligotrophic gyres. We compared phytoplankto...

Bioresource Technology, 1996

The onset of carotenogenesis in Chlorella vulgaris and the change in nature and concentration of ... more The onset of carotenogenesis in Chlorella vulgaris and the change in nature and concentration of pigments with time was studied. The succession of pigments observed was interpreted in terms of relative efficiencies of carotenoid interconversion pathways, and this might be used to monitor the progress of the carotenogenic process. This work is relevant to the use of dry Chlorella biomass, as a naturally encapsulated form of a natural colouring ingredient, in animal feed. Copyright

Bioresource Technology, Jan 31, 1996

The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically ... more The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically valuable w3 polyunsaturated fatty acid eicosapentaenoic acid (EPA). The results of indoor continuous growth of Phaeodactylum tricornutum Bohlin are reported. The relationships between dilution rate (D), nitrate concentration and chemical composition were studied. Higher biomass and lipid productivities were obtained at low D values. EPA was found to be an intermediate metabolite and the best productivity (6 mg 1-r day-r) was achieved for D values ranging from 0.32 to 0.50 day-'. Under optimum conditions, 84 and 1170, respectively, of total recovered EPA were present in monogalactosyldia~lglycerol (MGDG) and in triacylglycerol (TG) moieties, respectively. Recorded EPAI! and EPA/20,4 03 ratios for all tested dilution rates were among the highest values ever reported, showing EPA purification to be easier to perform from this starting material than from many others commonly in use.

Bioresource Technol, 1996

The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically ... more The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically valuable w3 polyunsaturated fatty acid eicosapentaenoic acid (EPA). The results of indoor continuous growth of Phaeodactylum tricornutum Bohlin are reported. The relationships between dilution rate (D), nitrate concentration and chemical composition were studied. Higher biomass and lipid productivities were obtained at low D values. EPA was found to be an intermediate metabolite and the best productivity (6 mg 1-r day-r) was achieved for D values ranging from 0.32 to 0.50 day-'. Under optimum conditions, 84 and 1170, respectively, of total recovered EPA were present in monogalactosyldia~lglycerol (MGDG) and in triacylglycerol (TG) moieties, respectively. Recorded EPAI! and EPA/20,4 03 ratios for all tested dilution rates were among the highest values ever reported, showing EPA purification to be easier to perform from this starting material than from many others commonly in use.

Estuarine, Coastal and Shelf Science, 2015

ABSTRACT Trends in abundance, temporal occurrence and spatial distribution of marine and brackish... more ABSTRACT Trends in abundance, temporal occurrence and spatial distribution of marine and brackish non-indigenous species (NIS) are part of the indicators to assess the compliance of Good Environmental Status in the European Marine Strategy Framework Directive (EU-MSFD). European-wide regional and national databases for NIS will be useful for the implementation of the EU-MSFD but there are still spatial gaps for some regions and taxonomic groups. In 2009, Portugal was among the countries with the lowest reported numbers of NIS in Europe and a national online database on NIS was not available. This study provides an updated list of NIS registered in Portuguese coastal and estuarine waters, including mainland Portugal and the Azores and Madeira archipelagos. A list of 133 NIS was cataloged, most of which recorded in the last three decades, showing that this area of the North Atlantic is no less prone to introductions than neighboring areas. Most NIS reported in the current inventory are native in the Indo-Pacific region. Fouling and ballast water are the most likely introduction vectors of NIS in the studied area but shipping routes connecting to the NIS native regions are rare, indicating that most species are secondary introductions. The high number of NIS in the Azores and Madeira islands indicates that this ecosystem type seems to be more susceptible to invasions but these preliminary results might be biased by a higher number of studies and knowledge on the NIS occurrence on the islands.

ABSTRACT Specimens belonging to the mixotrophic genus Fragilidium were isolated from coastal wate... more ABSTRACT Specimens belonging to the mixotrophic genus Fragilidium were isolated from coastal waters of west Iberia (NE Atlantic). Based on plate morphology and LSU rDNA sequences two species were identified: F. subglobosum and F . cf. duplocampanaeforme . The life-cycle is similar in both species. The asexual cycle is characterized by an alternation between a thecate motile stage and a reproductively active coccoid stage. The sexual cycle is characterized by heterogamous anisogamy and includes a sexual benthic hypnozygote. The first apical plate in vegetative cells does not touch the apical pore plate while in gametes it does, confirming in Fragilidium the homology of what is frequently referred as the first pre-cingular with the first apical plate in Gonyaulacales. Both species were observed to prey on Ceratium horridum . Molecular phylogenetic analyses with strains isolated from other geographical areas and Fragilidium gene sequences available in GenBank identified three different clades. One clade comprising F. subglobosum from the type locality and strains from Iberian waters; a second clade comprising the morphological species F. cf. duplocampanaeforme from Iberia and other strains from NE Atlantic, SE Atlantic and S Pacific and a third clade with an unassigned species from the SE Atlantic.

Biotechnology Techniques, 1997

The photo- and chemo-taxisms of Dunaliella salina were used to induce a cell concentration in a l... more The photo- and chemo-taxisms of Dunaliella salina were used to induce a cell concentration in a layer of fresh water pumped to the top of a saline culture through a circular diffuser. When two consecutive operations were imposed to a 2.2 m 2 raceway type algae pond, 90% of the biomass (at 0.7 dry cells/l) was recovered in 16% of

Microscopy and Microanalysis, 2013

The coccolithophores are a marine phytoplankton group that can play an important role in selectiv... more The coccolithophores are a marine phytoplankton group that can play an important role in selective uptake of Cadmium (Cd) in neritic environments. Under project Cd-ToxCoN (PTDC/MAR/102800/2008) studies were conducted to investigate the in vitro reaction of Emiliania huxleyi to Cd exposure, namely changes in the crystal lattice of (cocco)liths, the calcite elements of the exoskeleton (coccosphere).Uni-algal cultures of E. huxleyi were obtained by multiple cell isolation from the same water sample collected from Portuguese offshore waters, during opportunity cruises (Portuguese Marine Navy). Several morphotypes of E. huxleyi are currently recognized. The identification of the morphotype of E. huxleyi from Portuguese coastal waters was done by morphological analysis of the exoskeleton using scanning electron microcopy (JEOL JSM-5200LV and FEG-SEM JEOL 7001F) and by DNA sequencing of tufA gene following.Experiments were conducted in batch cultures grown in enriched sea-water medium (K/1...

Microscopy and Microanalysis, 2009

Several species of the chain-forming marine diatom genus Pseudo-nitzschia produce domoic acid (DA... more Several species of the chain-forming marine diatom genus Pseudo-nitzschia produce domoic acid (DA), a neuroexcitant amino acid, responsible for a human amnesic syndrome after consumption of toxified shellfish (ASP). Since 1995, the Portuguese monitoring program has regularly detected the presence of DA in shellfish. So far only P. australis has been implicated, and references therein. Identification of the causative species of Pseudo-nitzchia in natural samples is hampered by difficulties in identification at the light microscope level. Recent studies have shown that ultrastructural details of the wall, observed by transmission electron microscopy, allow the identification of species in good agreement with the phylogenetic and biological species concept.

Frontiers in Marine Science

The Atlantic Meridional Transect (AMT) program (www.amt-uk.org) provides the perfect opportunity ... more The Atlantic Meridional Transect (AMT) program (www.amt-uk.org) provides the perfect opportunity to observe the phytoplankton community size structure over a long latitudinal transect 50oN to 50oS, thereby covering the most important latitude-related basin-scale environmental gradients of the Atlantic Ocean. This work presents cell abundance data of phytoplankton taxa recently collected during cruises AMT28 and 29 (in 2018 and 2019, respectively) using flow cytometer and microscope observations, as well as the pigment composition of the community, to assess the abundance and spatial distribution of taxonomic groups across the Atlantic. The community size structure showed a clear consistency between cruises at large spatial scale, with a dominance of picoplanktonic Cyanobacteria in oceanic gyres, an increase in all groups in the equatorial upwelling region, and high biomass of microplankton size class at higher latitudes. Phytoplankton carbon biomass for oceanographic provinces, rang...

Scientific Reports

Estuaries are highly productive ecosystems, which are strongly affected by several anthropogenic ... more Estuaries are highly productive ecosystems, which are strongly affected by several anthropogenic pressures. Phytoplankton is a key element for assessing the ecological quality status in these transitional waters. Moreover, understanding physico-chemical and biological drivers is crucial to disentangle their effect on the structure of phytoplankton community. The present work aims to study the effect of the main physico-chemical drivers on the phytoplankton community structure and dynamics in a temperate well-mixed estuary (Sado Estuary). Four sampling stations were analyzed monthly in three regions of the estuary, from 2018 to 2019. Surface water samples were collected to analyze the phytoplankton community and several concomitant physico-chemical parameters. Temperature, turbidity, salinity, and nutrients availability were the drivers that best explained the spatio-temporal patterns observed in the phytoplankton community. The upper estuary was characterized by higher phytoplankton...

Frontiers in Marine Science

Changes in coccolithophore productivity in response to climate-driven ocean warming are likely to... more Changes in coccolithophore productivity in response to climate-driven ocean warming are likely to have cascading biogeochemical effects that feed back to the changing climate. This paper investigates the role (and interplay) of large-scale oceanographic and atmospheric processes across the North- and Equatorial Atlantic, including Saharan dust deposition, on the distribution of coccolithophore communities. The study is based on biological and hydrological data collected across the photic zone of the ocean, and aerosol data collected from the lower atmosphere, across 50°N–1°S during the Atlantic Meridional Transect in boreal Autumn of 2018 (AMT28), in synergy with Earth Observations. Results confirm existing understanding of the distribution of coccolithophore communities which are related to major meridional hydrological gradients across the North Atlantic. Dynamic, oxygenated and microphytoplankton-enriched waters at higher-latitudes were characterized by less diverse coccolithopho...

Frontiers in Marine Science, 2020

Early detection of dense harmful algal blooms (HABs) is possible using ocean colour remote sensin... more Early detection of dense harmful algal blooms (HABs) is possible using ocean colour remote sensing. Some algorithms require a training dataset, usually constructed from satellite images with a priori knowledge of the existence of the bloom. This approach can be limited if there is a lack of in situ observations, coincident with satellite images. A laboratory experiment collected biological and bio-optical data from a culture of Karenia mikimotoi, a harmful phytoplankton dinoflagellate. These data showed characteristic signals in chlorophyll-specific absorption and backscattering coefficients. The bio-optical data from the culture and a bio-optical model were used to construct a training dataset for an existing statistical classifier. MERIS imagery over the European continental shelf were processed with the classifier using different training datasets. The differences in positive rates of detection of K. mikimotoi between using an algorithm trained with purely manually selected areas...

Journal of the Science of Food and Agriculture, 1996

ABSTRACT Dry biomass obtained from stressed cells of Chlorella vulgaris (rich in carotenoid pigme... more ABSTRACT Dry biomass obtained from stressed cells of Chlorella vulgaris (rich in carotenoid pigments) was used as such in animal feed, instead of the commercial synthetic pigment. The in vivo effect of microalgal biomass as substitute pigment was ascertained with Hisex brown hens kept laying during 37 days under conventional conditions, and strongly suggested that yolk pigmentation was comparable to that obtained using commercial pigments, when comparable weight of colourant was formulated into the feed.

Bioresource Technology, 1991

7he results of a three month investigation on the outdoor mass culture of Phaeodactylum tricornut... more 7he results of a three month investigation on the outdoor mass culture of Phaeodactylum tricornutum Bohlin are reported. Experiments" carried out from January to March 1989 gave an average output rate of 4"O g m-2 day-I in ash-free dry weight (AFD W) basis for semicontinuous mode (days 0-74) and 2"0 gm-: day-1 for batch mode (days 74-84). Eicosapentaenoic acid (20.'5 ~o3 EPA) was the predominant fatty acid synthesized by this diatom during semicontinuous growth constituting 3"9% of AFD W, yielding 0.15 g m : day-i. 7he content of EPA was decreased to 0"7% of AFD W during batch mode, 16:0 and 16:1 becoming the main fatty acids. The relationship between optical density and output productivity rate was studied. In the range studied, the lower the concentration the higher the productivity and the lower the lipid production rate. Several flocculant systems were tried and calcium hydroxide, Ca(OH):, was found to be best at concentrations from 30 to 100 mg litre-~, in an apparently random way. The addition of chitosan did not improve the efficiency of flocculation.

Frontiers in Marine Science

Phytoplankton biomass, through its proxy, Chlorophyll a, has been assessed at synoptic temporal a... more Phytoplankton biomass, through its proxy, Chlorophyll a, has been assessed at synoptic temporal and spatial scales with satellite remote sensing (RS) for over two decades. Also, RS algorithms to monitor relative size classes abundance are widely used; however, differentiating functional types from RS, as well as the assessment of phytoplankton structure, in terms of carbon remains a challenge. Hence, the main motivation of this work it to discuss the links between size classes and phytoplankton groups, in order to foster the capability of assessing phytoplankton community structure and phytoplankton size fractionated carbon budgets. To accomplish our goal, we used data (on nutrients, photosynthetic pigments concentration and cell numbers per taxa) collected in surface samples along a transect on the Atlantic Ocean, during the 25th Atlantic Meridional Transect cruise (AMT25) between 50° N and 50° S, from nutrient-rich high latitudes to the oligotrophic gyres. We compared phytoplankto...

Bioresource Technology, 1996

The onset of carotenogenesis in Chlorella vulgaris and the change in nature and concentration of ... more The onset of carotenogenesis in Chlorella vulgaris and the change in nature and concentration of pigments with time was studied. The succession of pigments observed was interpreted in terms of relative efficiencies of carotenoid interconversion pathways, and this might be used to monitor the progress of the carotenogenic process. This work is relevant to the use of dry Chlorella biomass, as a naturally encapsulated form of a natural colouring ingredient, in animal feed. Copyright

Bioresource Technology, Jan 31, 1996

The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically ... more The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically valuable w3 polyunsaturated fatty acid eicosapentaenoic acid (EPA). The results of indoor continuous growth of Phaeodactylum tricornutum Bohlin are reported. The relationships between dilution rate (D), nitrate concentration and chemical composition were studied. Higher biomass and lipid productivities were obtained at low D values. EPA was found to be an intermediate metabolite and the best productivity (6 mg 1-r day-r) was achieved for D values ranging from 0.32 to 0.50 day-'. Under optimum conditions, 84 and 1170, respectively, of total recovered EPA were present in monogalactosyldia~lglycerol (MGDG) and in triacylglycerol (TG) moieties, respectively. Recorded EPAI! and EPA/20,4 03 ratios for all tested dilution rates were among the highest values ever reported, showing EPA purification to be easier to perform from this starting material than from many others commonly in use.

Bioresource Technol, 1996

The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically ... more The marine diatom Phaeodactylum tricornutum Bohlin is a potential source of the pharmaceutically valuable w3 polyunsaturated fatty acid eicosapentaenoic acid (EPA). The results of indoor continuous growth of Phaeodactylum tricornutum Bohlin are reported. The relationships between dilution rate (D), nitrate concentration and chemical composition were studied. Higher biomass and lipid productivities were obtained at low D values. EPA was found to be an intermediate metabolite and the best productivity (6 mg 1-r day-r) was achieved for D values ranging from 0.32 to 0.50 day-'. Under optimum conditions, 84 and 1170, respectively, of total recovered EPA were present in monogalactosyldia~lglycerol (MGDG) and in triacylglycerol (TG) moieties, respectively. Recorded EPAI! and EPA/20,4 03 ratios for all tested dilution rates were among the highest values ever reported, showing EPA purification to be easier to perform from this starting material than from many others commonly in use.

Estuarine, Coastal and Shelf Science, 2015

ABSTRACT Trends in abundance, temporal occurrence and spatial distribution of marine and brackish... more ABSTRACT Trends in abundance, temporal occurrence and spatial distribution of marine and brackish non-indigenous species (NIS) are part of the indicators to assess the compliance of Good Environmental Status in the European Marine Strategy Framework Directive (EU-MSFD). European-wide regional and national databases for NIS will be useful for the implementation of the EU-MSFD but there are still spatial gaps for some regions and taxonomic groups. In 2009, Portugal was among the countries with the lowest reported numbers of NIS in Europe and a national online database on NIS was not available. This study provides an updated list of NIS registered in Portuguese coastal and estuarine waters, including mainland Portugal and the Azores and Madeira archipelagos. A list of 133 NIS was cataloged, most of which recorded in the last three decades, showing that this area of the North Atlantic is no less prone to introductions than neighboring areas. Most NIS reported in the current inventory are native in the Indo-Pacific region. Fouling and ballast water are the most likely introduction vectors of NIS in the studied area but shipping routes connecting to the NIS native regions are rare, indicating that most species are secondary introductions. The high number of NIS in the Azores and Madeira islands indicates that this ecosystem type seems to be more susceptible to invasions but these preliminary results might be biased by a higher number of studies and knowledge on the NIS occurrence on the islands.

ABSTRACT Specimens belonging to the mixotrophic genus Fragilidium were isolated from coastal wate... more ABSTRACT Specimens belonging to the mixotrophic genus Fragilidium were isolated from coastal waters of west Iberia (NE Atlantic). Based on plate morphology and LSU rDNA sequences two species were identified: F. subglobosum and F . cf. duplocampanaeforme . The life-cycle is similar in both species. The asexual cycle is characterized by an alternation between a thecate motile stage and a reproductively active coccoid stage. The sexual cycle is characterized by heterogamous anisogamy and includes a sexual benthic hypnozygote. The first apical plate in vegetative cells does not touch the apical pore plate while in gametes it does, confirming in Fragilidium the homology of what is frequently referred as the first pre-cingular with the first apical plate in Gonyaulacales. Both species were observed to prey on Ceratium horridum . Molecular phylogenetic analyses with strains isolated from other geographical areas and Fragilidium gene sequences available in GenBank identified three different clades. One clade comprising F. subglobosum from the type locality and strains from Iberian waters; a second clade comprising the morphological species F. cf. duplocampanaeforme from Iberia and other strains from NE Atlantic, SE Atlantic and S Pacific and a third clade with an unassigned species from the SE Atlantic.

Biotechnology Techniques, 1997

The photo- and chemo-taxisms of Dunaliella salina were used to induce a cell concentration in a l... more The photo- and chemo-taxisms of Dunaliella salina were used to induce a cell concentration in a layer of fresh water pumped to the top of a saline culture through a circular diffuser. When two consecutive operations were imposed to a 2.2 m 2 raceway type algae pond, 90% of the biomass (at 0.7 dry cells/l) was recovered in 16% of

Microscopy and Microanalysis, 2013

The coccolithophores are a marine phytoplankton group that can play an important role in selectiv... more The coccolithophores are a marine phytoplankton group that can play an important role in selective uptake of Cadmium (Cd) in neritic environments. Under project Cd-ToxCoN (PTDC/MAR/102800/2008) studies were conducted to investigate the in vitro reaction of Emiliania huxleyi to Cd exposure, namely changes in the crystal lattice of (cocco)liths, the calcite elements of the exoskeleton (coccosphere).Uni-algal cultures of E. huxleyi were obtained by multiple cell isolation from the same water sample collected from Portuguese offshore waters, during opportunity cruises (Portuguese Marine Navy). Several morphotypes of E. huxleyi are currently recognized. The identification of the morphotype of E. huxleyi from Portuguese coastal waters was done by morphological analysis of the exoskeleton using scanning electron microcopy (JEOL JSM-5200LV and FEG-SEM JEOL 7001F) and by DNA sequencing of tufA gene following.Experiments were conducted in batch cultures grown in enriched sea-water medium (K/1...

Microscopy and Microanalysis, 2009

Several species of the chain-forming marine diatom genus Pseudo-nitzschia produce domoic acid (DA... more Several species of the chain-forming marine diatom genus Pseudo-nitzschia produce domoic acid (DA), a neuroexcitant amino acid, responsible for a human amnesic syndrome after consumption of toxified shellfish (ASP). Since 1995, the Portuguese monitoring program has regularly detected the presence of DA in shellfish. So far only P. australis has been implicated, and references therein. Identification of the causative species of Pseudo-nitzchia in natural samples is hampered by difficulties in identification at the light microscope level. Recent studies have shown that ultrastructural details of the wall, observed by transmission electron microscopy, allow the identification of species in good agreement with the phylogenetic and biological species concept.