Rosa Isabel Figueroa

• PhD
• Scientific Researcher at Instituto Español de Oceanografia

Dinoflagellates in the family Symbiodiniaceae are obligate endosymbionts of diverse marine invertebrates, including corals, and impact the capacity of their hosts to respond to climate change-driven ocean warming. Understanding the conditions under which increased genetic variation in Symbiodiniaceae arises via sexual recombination can support effo...

The bloom-forming toxic dinoflagellate Alexandrium catenella was first detected in Southern Chile (39.5–55°S) 50 years ago and is responsible for most of the area’s cases of paralytic shellfish poisoning (PSP). Given the complex life history of A. catenella, which includes benthic sexual cysts, in this study we examined the potential link between l...

Harmful algal blooms (HABs) are recurrent in the NW Patagonia fjords system and their frequency has increased over the last few decades. Outbreaks of HAB species such as Alexandrium catenella, a causal agent of paralytic shellfish poisoning, and Protoceratium reticulatum, a yessotoxins producer, have raised considerable concern due to their adverse...

Harmful algal blooms (HABs) in southern Chile are a serious threat to public health, tourism, artisanal fisheries, and aquaculture in this region. Ichthyotoxic HAB species have recently become a major annual threat to the Chilean salmon farming industry, due to their severe economic impacts. In early austral autumn 2021, an intense bloom of the rap...

The changes in the cell physiology (growth rate, cell size, and cell DNA content), photosyn-thetic efficiency, toxicity, and sexuality under variable light and nutrient (phosphates) conditions were evaluated in cultures of the dinoflagellate Alexandrium minutum obtained from a red tide in the Ría de Vigo (NW Spain). The cells were grown at low (40...

Physiological responses and sexual compatibility within a massive toxic bloom of Alexandrium minutum is now available online. 50 days' free access (before April 08, 2025) --> https://authors.elsevier.com/a/1kdHE,asiDgly

Assessing the genomic diversity of a NW Spain bloom of Alexandrium minutum using satDNAs as chromosomal markers is now available online. 50 days' free access (before March 26, 2025) --> https://authors.elsevier.com/c/1kYnd5aloFnBDk

Harmful algal blooms (HABs) of toxin-producing microalgae are recurrent in Patagonian fjord systems. Like toxigenic HABs, high-biomass harmful algal blooms (HB-HABs) have important socio-economic repercussions, but most studies have focused on the former. Here we report the formation and development of an intense HB- HAB of Prorocentrum micans that...

Over the recent decades, an apparent worldwide rise in Harmful Algae Blooms (HABs) has been observed due to the growing exploitation of the coastal environment, the exponential growth of monitoring programs, and growing global maritime transport. HAB species like Alexandrium catenella—responsible for paralytic shellfish poisoning (PSP)—Protoceratiu...

The blooms of Alexandrium catenella, the main producer of paralytic shellfish toxins worldwide, have become the main threat to coastal activities in Southern Chile, such as artisanal fisheries, aquaculture and public health. Here, we explore retrospective data from an intense Paralytic Shellfish Poisoning outbreak in Southern Chile in Summer–Autumn...

The Galician Rías (NW Spain) support intensive aquaculture and fisheries due to the seasonal upwelling of subsurface cold and nutrient-rich water, which is responsible of a high primary productivity and periodical occurrence of algal blooms, including harmful species. The increasing occurrence of HABs, and the potential decreasing extension and int...

The frequency of harmful algal blooms (HABs) has increased over the last two decades, a phenomenon enhanced by global climate change. However, the effects of climate change will not be distributed equally, and Chile has emerged as one important, vulnerable area. The Chilean Patagonian region (41-56 • S) hosts two marine ecoregions that support robu...

Toxic and harmful algal blooms (HABs) are a global problem affecting human health, marine ecosystems, and coastal economies, the latter through their impact on aquaculture, fisheries, and tourism. As our knowledge and the techniques to study HABs advance, so do international monitoring efforts, which have led to a large increase in the total number...

Phytoplankton succession is related to hydroclimatic conditions. In this study we provide the rst description of a toxic phytoplankton succession in the Patagonian Fjord System. The shift was modulated by atmospheric- oceanographic forcing and consisted of the replacement of the marine dino agellate Dinophysis acuta in a highly strati ed water colu...

Abrupt changes in environmental conditions in estuaries and coastal waters have direct (physiological) and indirect (through changes in water column stability) effects on planktonic microalgae. Understanding and quantifying these effects is important to improve harmful algal bloom predictive models. Dinophysis spp. ( D. acuminata , D. acuta and D....

Harmful algal blooms, in particular recurrent blooms of the dinoflagellate Alexandrium catenella, associated with paralytic shellfish poisoning (PSP), frequently limit commercial shellfish harvests, resulting in serious socioeconomic consequences. Although the PSP-inducing species that threaten the most vulnerable commercial species of shellfish ar...

Harmful Algal Blooms (HAB) pose a severe socio-economic problem worldwide. The dinoflagellate species Alexandrium catenella produces potent neurotoxins called saxitoxins (STXs) and its blooms are associated with the human intoxication named Paralytic Shellfish Poisoning (PSP). Knowing where and how these blooms originate is crucial to predict bloom...

Alexandrium minutum blooms generally occur in semi-enclosed sites such as estuaries, harbours and lagoons, where enhanced stratification, restricted circulation and accumulation of resting cysts in the sediment set suitable habitat conditions for the proliferation of this paralytic shellfish poisoning toxigenic species. In the Galician Rías Baixas...

Dinoflagellates are a large group of protists whose exceptionally large genome is organized in permanently condensed nucleosome-less chromosomes. In this study, we examined the potential role of repetitive DNAs in both the structure of dinoflagellate chromosomes and the architecture of the dinoflagellate nucleus. Non-denaturing fluorescent in situ...

Fish-killing blooms of Heterosigma akashiwo and Pseudochattonella verruculosa have been devastating for the farmed salmon industry, but in Southern Chile the conditions that promote the growth and toxicity of these microalgae are poorly understood. This study examined the effects of different combinations of temperature (12, 15, 18 • C) and salinit...

The bloom-forming toxic dinoflagellate Alexandrium catenella was first detected in southern Chile (39.5–55° S) 50 years ago and is responsible for most of the area’s cases of paralytic shellfish poisoning (PSP). Given the complex life history of A. catenella, which includes benthic sexual cysts, in this study, we examined the potential link between...

Benthic dinoflagellates of the genus Gambierdiscus produce ciguatoxins, compounds that when metabolized in fish and consumed by humans cause ciguatera poisoning (CP). This syndrome, which is widespread in tropical and subtropical regions, has recently been reported also in subtropical-temperate latitudes such as the Canary Islands where CP events h...

Dinoflagellates are protists with exceptionally large genomes and chromosomes that lack nucleosomes. To date, information on their genome organization is scarce. Studies investigating the distribution of ribosomal RNA genes (rDNA) in plants and animals by fluorescence in situ hybridization (FISH) have provided important information to elucidate the...

In recent decades, the alteration of coastal food webs (via aquaculture, fishing, and leisure activities), nutrient loading, and an expansion of monitoring programs have prompted an apparent worldwide rise in Harmful Algae Blooms (HABs). Over this time, a parallel increase in HABs has also been observed in the Chilean southern austral region (Patag...

Dinoflagellates in the family Symbiodiniaceae are obligate endosymbionts of diverse marine invertebrates, including corals, and impact the capacity of their hosts to respond to climate change-driven ocean warming. Understanding the conditions under which increased genetic variation in Symbiodiniaceae arises via sexual recombination can support effo...

A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, an...

Chromosomal markers of the diversity and evolution of dinoflagellates are scarce because the genomes of these organisms are unique among eukaryotes in terms of their base composition and chromosomal structure. Similarly, a lack of appropriate tools has hindered studies of the chromosomal localization of 5S ribosomal DNA (rDNA) in the nucleosome-les...

A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, an...

Scrippsiella is a cosmopolitan dinoflagellate genus that is able to form Harmful Algal Blooms in coastal waters. The large physiological, morphological, and genetic variability that characterizes this genus suggest the existence of cryptic species. In this study, flow cytometric analyses were carried out to compare the cell cycle and life cycle of...

Dinoflagellates are a group of protists whose genome is unique among eukaryotes in terms of base composition, chromosomal structure and gene expression. Even after decades of research, the structure and behavior of their amazing chromosomes—which without nucleosomes exist in a liquid crystalline state—are still poorly understood. We used flow cytom...

Harmful algal blooms (HABs) of toxin-producing microalgae, mainly Alexandrium catenella, Dinophysis spp., and Pseudo-nitzschia australis, cause the severe illnesses referred to as paralytic, diarrheic, and amnesic shellfish poisoning. They therefore threaten the sustainable exploitation of bivalves, including in northern and southern Chile, sites o...

Dinoflagellates possess some of the largest known genomes. However, the study of their chromosomes is complicated by their similar size and their inability to be distinguished by traditional banding techniques. Dinoflagellate chromosomes lack nucleosomes and are present in a liquid crystalline state. In addition, approaches such as fluorescent in s...

In Chile, 90% of the fish farms and major natural shellfish beds are located in the region surrounding the Inland Sea, where over the last few decades harmful phytoplankton blooms have often been observed. The onset and recurrence of bloom events are often related to the resuspension and germination of resting cysts that have accumulated in the sed...

In Chile, 90% of the fish farms and major natural shellfish beds are located in the region surrounding the Inland Sea, where over the last few decades harmful phytoplankton blooms have often been observed. The onset and recurrence of bloom events are often related to the resuspension and germination of resting cysts that have accumulated in the sed...

Asexual and sexual life cycle events were studied in cultures of the toxic marine dinoflagellate Protoceratium reticulatum. Asexual division by desmoschisis was characterized morphologically and changes in DNA content were analyzed by flow cytometry. The results indicated that haploid cells with a C DNA content occurred only during the light period...

In the present study the geographical distribution, abundance and composition of Gambierdiscus was described over a 600km longitudinal scale in the Canary Islands. Samples for cell counts, isolation and identification of Gambierdiscus were obtained from five islands (El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote). Average densities...

Recent studies of marine protists have revealed parasites to be key components of marine communities. Here we describe a new species of the parasitoid genus Parvilucifera that was observed infecting the dinoflagellate Durinskia baltica in salt marshes of the Catalan coast (NW Mediterranean). In parallel, the same species was detected after the incu...

Alexandrium ostenfeldii is present in a wide variety of environments in coastal areas worldwide and is the only dinoflagellate known species that produces paralytic shellfish poisoning (PSP) toxins and two types of cyclic imines, spirolides (SPXs) and gymnodimines (GYMs). The increasing frequency of A. ostenfeldii blooms in the Baltic Sea has been...

Dinoflagellates are haploid eukaryotic microalgae in which rapid proliferation causes dense blooms, with harmful health and economic effects to humans. The proliferation mode is mainly asexual, as the sexual cycle is believed to be rare and restricted to stressful environmental conditions. However, sexuality is key to explaining the recurrence of m...

DNA content groups in the cross culture during 3rd to 5th Light:Dark periods. The control sample (in orange at the bottom of the graphs) lacked the S phase [34] and was used to determine the position of the C and 2C peaks. The DNA content of the population during the light period manifested as a single, wide peak identified as S phase (C→2C). Durin...

DNA content groups in the cross culture during the 8th Light:Dark period. The control sample (in orange at the bottom of the graphs) lacked the S phase [34] and was used to determine the position of the C and 2C peaks. The eighth L:D period (S2 Fig) was chosen due to the detection at day PS9 of the first resting cysts in the culture and it was char...

Parasites exert important top-down control of their host populations. The host-parasite system formed by Alexandrium minutum (Dinophyceae) and Parvilucifera sinerae (Perkinsozoa) offers an opportunity to advance our knowledge of parasitism in planktonic communities. In this study, DNA extracted from 73 clonal strains of P. sinerae, from 10 differen...

Workshop on Plankton resting stages: ecological, evolutionary and geological perspectives. Tvärminne Zoological Station, Finland. 5-8 October 2015. Planktonic microalgae inhabit freshwater, brackish water and seawater environments and play a key role as phototrophs in the aquatic systems. The life cycles of most microalgal species are complex, wit...

Planktonic microalgae inhabit freshwater, brackish water and seawater environments and play a key role as phototrophs in the aquatic systems. The life cycles of most microalgal species are complex, with stages characterized by radically different morphologies and highly diverse environmental interactions. The two most common life stages are plankto...

Background Marine microbial protists, in particular, dinoflagellates, produce polyketide toxins with ecosystem-wide and human health impacts. Species of Gambierdiscus produce the polyether ladder compounds ciguatoxins and maitotoxins, which can lead to ciguatera fish poisoning, a serious human illness associated with reef fish consumption. Genes as...

Dinoflagellates are microscopic aquatic eukaryotes with huge genomes and an unusual cell regulation. For example, most genes are present in numerous copies and all copies seem to be obligatorily transcribed. The consequence of the gene copy number (CPN) for final protein synthesis is, however, not clear. One such gene is sxtA, the starting gene of...

Elucidation of the cell cycle of dinoflagellates is essential to understand the processes leading to their massive proliferations, known as harmful algal blooms. In this study, we used imaging flow cytometry (IFC) to monitor the changes in DNA content and nuclear and cell morphology that occur during clonal growth of the toxic species Alexandrium m...

Abstract Cell abundances and distributions of Alexandrium catenella resting cysts in recent sediments were studied along time at two locations in the Chilean Inland Sea exposed to different oceanographic conditions: Low Bay, which is much more open to the ocean than the more interior and protected Ovalada Island. The bloom began in interior areas b...

Intra-specific variability in size of the studied strain was greater than that reported in the Gambierdiscus literature.•Smallest cells displayed interesting morphological differences from the other cells, especially their globular shape rather than the lenticular shape typical of discoid Gambierdiscus.•The nuclear morphology of karyokinesis, and c...

The dynamics and consequences of host–parasite coevolution depend on the nature of host genotype-by-parasite genotype interactions (G × G) for host and parasite fitness. G × G with crossing reaction norms can yield cyclic dynamics of allele frequencies (“Red Queen” dynamics) while G × G where the variance among host genotypes differs between parasi...

ICHA

Dinoflagellates are a group of protists whose genome differs from that of other eukaryotes in terms of size (contains up to 250 pg per haploid cell), base composition, chromosomal organization, and gene expression. But rDNA gene mapping of the active nucleolus in this unusual eukaryotic genome has not been carried out thus far. Here we used FISH in...

The life cycle of many dinoflagellates includes at least one nonflagellated benthic stage (cyst). In the literature, the different types of dinoflagellate cysts are mainly defined based on morphological (number and type of layers in the cell wall) and functional (long-or short-term endurance) differences. These characteristics were initially though...

Within dinoflagellate research the fields of geology and biology come together in studies of the resting stage, the cyst. Studies of this stage and life-cycle transitions can tie together the geological fossil record of dinoflagellates and the ecology of living dinoflagellates. This review focuses on possible new research areas within ploidy shifts...

This study investigates the genetic structure of an eukaryotic microorganism, the toxic dinoflagellate Alexandrium ostenfeldii, from the Baltic Sea, a geologically young and ecologically marginal brackish water estuary which is predicted to support evolution of distinct, genetically impoverished lineages of marine macroorganisms. Analyses of the in...

Description of AFLP primer characteristics. (DOCX)

Genetic difference and distance between populations based on ITS regions (572 bp). (DOCX)

AFLP reaction protocol. (DOCX)

Most probable number of genetic populations as determined from STRUCTURE (2.3.3.) analysis 84 individual A. ostenfeldii AFLP-genotypes. (TIF)

Sampling area and rate of culture survival. (DOCX)

Information on strains and species used for ITS phylogenetic analysis. (DOCX)

The field of genetic diversity in protists, particularly phytoplankton, is under expansion. However, little is known regarding variation in genetic diversity within populations over time. The aim of our study was to investigate intrapopulation genetic diversity and genetic differentiation in the freshwater bloom-forming microalga Gonyostomum semen...

We isolated eleven strains of the harmful algal bloom (HAB)-forming dinoflagellate Karlodinium veneficum during a bloom event in the NW Mediterranean coastal waters and we studied the inter-strain variability in several of their physiological and biochemical traits. These included autotrophic growth parameters, feeding capabilities (mixotrophy), li...

The factors regulating dinoflagellate life‐cycle transitions are poorly understood. However, their identification is essential to unravel the causes promoting the outbreaks of harmful algal blooms (HABs) because these blooms are often associated with the formation and germination of sexual cysts. Nevertheless, there is a lack of knowledge on the fa...

A parasite threat stimulates adaptive shifts in the life-history strategy (sexual recombination rate) of the toxic bloom-forming dinoflagellate Alexandrium minutum Halim. This microalgae divides asexually when clonal but can also form mobile zygotes (planozygotes) when compatible clones are crossed. Planozygotes usually form resistant dormant stage...

Small-scale turbulence and parasite infection are 2 important factors that govern the dynamics and fate of phytoplankton populations. We experimentally investigated the influence of turbulent mixing on the infectivity of the parasite Parvilucifera sinerae to dinoflagellates. Natural phytoplankton communities were collected during 3 stages of a bloo...

A study of Gymnodinium catenatum and Alexandrium minutum blooms on the Galician coast was conducted from 2005 to 2007 in order to increase knowledge of the mechanisms governing recurrent blooms of these species. Considerable differences in their bloom dynamics were observed. G. catenatum blooms occurred in autumn and winter, following the pattern p...

The chain-forming dinoflagellate Gymnodinium catenatum Graham is responsible for outbreaks of paralytic shellfish poisoning (PSP), a human health threat in coastal waters. Sexuality in this species is of great importance in its bloom dynamics, and has been shown to be very complex but lacks an explanation. For this reason, we tested if unreported h...

The terms “temporary”, “pellicle”, and “ecdysal” cyst have been employed arbitrarily in the literature of the dinoflagellate life cycle to describe a non-motile and single-layered-wall stage with no mandatory dormancy period, of asexual or sexual origin. These three terms have been used more or less synonymously, but more specific definitions, taki...

The difficulties encountered in attempts to differentiate between dinoflagellate species of the genera Alexandrium and Karlodinium using morphological characteristics are well-known. For this reason, species of these genera were analyzed by flow cytometry to determine whether haploid DNA content served as a valid criterion for species identificatio...

Decreased net population growth rates and cellular abundances have been observed in dinoflagellate species exposed to small-scale turbulence. Here, we investigated whether these effects were caused by alterations in the cell cycle and/or by cell mortality and, in turn, whether these two mechanisms depended on the duration of exposure to turbulence....

Biosurfactants have been suggested as a method to control harmful algal blooms (HABs), but warrant further and more in-depth investigation. Here we have investigated the algicidal effect of a biosurfactant produced by the bacterium Pseudomonas aeruginosa on five diverse marine and freshwater HAB species that have not been tested previously. These i...

Kryptoperidinium foliaceum is a binucleate dinoflagellate that contains an endosymbiont nucleus of diatom origin. However, it is unknown whether the binucleate condition is permanent or not and how the diatom nucleus behaves during the life history processes. In this sense, it is also unknown if there is a sexual cycle or a resting stage during the...

A new species of parasite, Parvilucifera sinerae sp. nov., isolated from a bloom of the toxic dinoflagellate Alexandrium minutum in the harbor of Arenys de Mar (Mediterranean Sea, Spain), is described. This species is morphologically, behaviourally, and genetically (18S rDNA sequence) different from Parvilucifera infectans, until now the only speci...

Alexandrium peruvianum (Balech et Mendiola) is a noxious phototrophic marine dinoflagellate. During the life cycle of this species, two kinds of cysts are produced: resting cysts, which are long-lasting and double-walled, and temporary cysts, which are short-lasting and thin-walled. In addition, short-lasting, but resting-like cysts can also be for...

The chain-forming dinoflagellate Gymnodinium catenatum is responsible for outbreaks of paralytic shellfish poisoning (PSP); however, the relative importance of benthic-planktonic life-cycle transitions in the appearance of blooms of this species needs to be clarified. By coupling field and laboratory experiments, the present study is the first to a...

Annual recurrent blooms of the toxic dinoflagellates Alexandrium catenella and Alexandrium minutum were detected from 2000 to 2003 along the Catalan coast associated with harbours. The interrelation study between the occurrence of the blooms and specific external conditions in the different waters demonstrated that different factors are required fo...

The microalgal genus Alexandrium includes species known to produce paralytic shellfish poisoning (PSP). Due to the importance of discriminating between HAB-forming species, we compared the undescribed life-cycle pattern of Alexandrium tamutum Montresor, Beran et U. John and of its toxic relative Alexandrium minutum Halim. Sexual stages, asexual and...