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Toxins Jun 2024Despite the fact that the first red tide reported on the coasts of the Iberian Peninsula was due to , knowledge about their frequency and, particularly, about the...
Despite the fact that the first red tide reported on the coasts of the Iberian Peninsula was due to , knowledge about their frequency and, particularly, about the environmental conditions contributing to bloom initiation is still scarce. For this reason, bloom episodes were observed and studied in three Galician rias during the summer season based on the 1993-2008 record database period; additionally, samples were collected in summer 2008. Proliferations of occurred in the rias of Ares and Barqueiro in June and August, respectively, while in the Ria of Coruña, they persisted from the end of June to early September. Red tides developed when the surface temperature reached 17 °C, with "seasonal thermal window" conditions, and when salinities were ≥30, i.e., an "optimal salinity window"; when these parameters were lower than these thresholds, cyst germination decreased. A cyst transport mechanism from sediments to the surface must also exist; this mechanism was found to be natural (tidal currents) in the ria of Barqueiro or anthropogenic (dredging) in the rias of Ares and Coruña. Surface temperatures during summer were usually favorable for cyst germination (85 to 100%) during the 1993-2008 period; however, water temperatures below 10 m depth only rarely reached the 17 °C threshold (2 to 18%). During this 16-year period, dredging activities could explain 71% (Coruña) and 44% (Ares) of the recorded bloom events. When a bloom episode developed in early summer, favorable conditions did not lead to a new red tide, probably due to the lag period required by cysts for germination. Moreover, blooms did not develop when high densities of diatoms (>1,000,000 cells·L) remained in the water column as a result of summer upwelling pulses occurring in specific years. The temperature-sediment disturbance pattern found in this study provides a useful tool for the prevention of eventual risks resulting from red tides of this dinoflagellate.
Topics: Dinoflagellida; Spain; Harmful Algal Bloom; Temperature; Seasons; Environmental Monitoring; Seawater; Geologic Sediments; Salinity
PubMed: 38922174
DOI: 10.3390/toxins16060280 -
Marine Drugs Jun 2024Ichthyotoxic red tide is a problem that the world is facing and needs to solve. The use of antialgal compounds from marine macroalgae to suppress ichthyotoxic red tide...
Ichthyotoxic red tide is a problem that the world is facing and needs to solve. The use of antialgal compounds from marine macroalgae to suppress ichthyotoxic red tide is considered a promising biological control method. Antialgal substances were screened and isolated from , , , , , , and sp. to obtain new materials for the development of algaecides against ichthyotoxic red tide microalgae using bioactivity-guided isolation methods. The fractions of seven macroalgae exhibited selective inhibitory activities against and , of which the ethyl acetate fractions had the strongest and broadest antialgal activities for the two tested red tide microalgae. Their inhibitory effects on . and . were even stronger than that of potassium dichromate, such as ethyl acetate fractions of . , . , and sp. Thin-layer chromatography and ultraviolet spectroscopy were further carried out to screen the ethyl acetate fraction of sp. Finally, a new glycolipid derivative, 2--eicosanoyl-3--(6-amino-6-deoxy)--D-glucopyranosyl-glycerol, was isolated and identified from sp., and it was isolated for the first time from marine macroalgae. The significant antialgal effects of 2--eicosanoyl-3--(6-amino-6-deoxy)--D-glucopyranosyl-glycerol on . and . were determined.
Topics: Seaweed; Glycolipids; Harmful Algal Bloom; Microalgae; Dinoflagellida
PubMed: 38921590
DOI: 10.3390/md22060279 -
Marine Drugs May 2024Microalgae are currently considered an attractive source of highly valuable metabolites potentially exploitable as anticancer agents, nutraceuticals and cosmeceuticals...
Microalgae are currently considered an attractive source of highly valuable metabolites potentially exploitable as anticancer agents, nutraceuticals and cosmeceuticals and for bioenergy purposes. Their ease of culturing and their high growth rates further promote their use as raw material for the production of specialty products. In the present paper, we focused our attention on specific glycerol-based lipid compounds, monoacylglycerols (MAGs), which displayed in our previous studies a selective cytotoxic activity against the haematological U-937 and the colon HCT-116 cancer cell lines. Here, we performed a quali/quantitative analysis of MAGs and total fatty acids (FAs) along with a profiling of the main lipid classes in a panel of 12 microalgal species, including diatoms and dinoflagellates. Our results highlight an inter- and intraspecific variability of MAG profile in the selected strains. Among them, (strain FE7) has emerged as the most promising source for possible biotechnological production of MAGs.
Topics: Microalgae; Humans; Monoglycerides; Fatty Acids; Diatoms; Antineoplastic Agents; Cell Line, Tumor; Aquatic Organisms; Dinoflagellida; HCT116 Cells
PubMed: 38921569
DOI: 10.3390/md22060258 -
PeerJ 2024Bioluminescence is light chemically produced by an organism. It is widespread across all major marine phyla and has evolved multiple times, resulting in a high diversity...
Bioluminescence is light chemically produced by an organism. It is widespread across all major marine phyla and has evolved multiple times, resulting in a high diversity of spectral properties and first flash kinetic parameters (FFKP). The bioluminescence of a system is often a good proxy for planktonic biomass. The species-specific parameters of bioluminescent displays can be measured to identify species and describe planktonic biodiversity. Most bioluminescent organisms will flash when mechanically stimulated , when subjected to supra-threshold levels of shear stress. Here we compare first flash kinetic parameters such as flash duration, peak intensity, rise time, decay time, first-flash mechanically stimulated light and e-folding time obtained with the commercially available Underwater Bioluminescence Assessment Tool (UBAT). We provide descriptions of the first flash kinetic parameters of several species of dinoflagellates , , , , and two zooplankton (the ctenophore and the larvacean ). FFKPs are then compared and discussed using non-parametric analyses of variance (ANOVAs), hierarchical clustering and a linear discriminant analysis to assess the ability to use bioluminescence signatures for identification. Once the first flash kinetic parameters of a bioluminescent species have been described, it is possible to detect its presence using emissions collected by bathyphotometers. Assessing abundance and diversity of bioluminescent species may therefore be possible.
Topics: Zooplankton; Animals; Dinoflagellida; Biodiversity; Luminescent Measurements; Species Specificity
PubMed: 38881863
DOI: 10.7717/peerj.17516 -
The Science of the Total Environment Sep 2024Global warming has been shown to harmfully affect symbiosis between Symbiodiniaceae and other marine invertebrates. When symbiotic dinoflagellates (the genus Breviolum)...
Global warming has been shown to harmfully affect symbiosis between Symbiodiniaceae and other marine invertebrates. When symbiotic dinoflagellates (the genus Breviolum) were in vitro exposed to acute heat stress of +7 °C for a period of 5 days, the results revealed the negative impact on all physiological and other cellular parameters measured. Elevated temperatures resulted in a severe reduction in algal density of up to 9.5-fold, as well as pigment concentrations, indicating the status of the physiological stress and early signs of photo-bleaching. Reactive oxygen species (ROS) were increased in all heated dinoflagellate cells, while the antioxidant-reduced glutathione levels initially dropped on day one but increased under prolonged temperature stress. The cell viability parameters were reduced by 97 % over the heating period, with an increased proportion of apoptotic and necrotic cells. Autofluorescence (AF) for Cy5-PE 660-20 was reduced from 1.7-fold at day 1 to up to 50-fold drop at the end of heating time, indicating that the AF changes were highly sensitive to heat stress and that it could be an extremely sensitive tool for assessing the functionality of algal photosynthetic machinery. The addition of the drug 5-AZA-2'-deoxycytidine (5-AZA), which inhibits DNA methylation processes, was assessed in parallel and contributed to some alterations in algal cellular stress response. The presence of drug 5-AZA combined with the temperature stress had an additional impact on Symbiodiniaceae density and cell complexity, including the AF levels. These variations in cellular stress response under heat stress and compromised DNA methylation conditions may indicate the importance of this epigenetic mechanism for symbiotic dinoflagellate thermal tolerance adaptability over a longer period, which needs further exploration. Consequently, the increased ROS levels and changes in AF signals reported during ongoing heat stress in dinoflagellate cells could be used as early stress biomarkers in these microalgae and potentially other photosynthetic species.
Topics: Dinoflagellida; Oxidative Stress; Heat-Shock Response; Symbiosis; Reactive Oxygen Species; Hot Temperature
PubMed: 38866148
DOI: 10.1016/j.scitotenv.2024.173916 -
Scientific Reports Jun 2024The diversity of marine cyanobacteria has been extensively studied due to their vital roles in ocean primary production. However, little is understood about the...
The diversity of marine cyanobacteria has been extensively studied due to their vital roles in ocean primary production. However, little is understood about the diversity of cyanobacterial species involved in symbiotic relationships. In this study, we successfully sequenced the complete genome of a cyanobacterium in symbiosis with Citharistes regius, a dinoflagellate species thriving in the open ocean. A phylogenomic analysis revealed that the cyanobacterium (CregCyn) belongs to the marine picocyanobacterial lineage, akin to another cyanobacterial symbiont (OmCyn) of a different dinoflagellate closely related to Citharistes. Nevertheless, these two symbionts are representing distinct lineages, suggesting independent origins of their symbiotic lifestyles. Despite the distinct origins, the genome analyses of CregCyn revealed shared characteristics with OmCyn, including an obligate symbiotic relationship with the host dinoflagellates and a degree of genome reduction. In contrast, a detailed analysis of genome subregions unveiled that the CregCyn genome carries genomic islands that are not found in the OmCyn genome. The presence of the genomic islands implies that exogenous genes have been integrated into the CregCyn genome at some point in its evolution. This study contributes to our understanding of the complex history of the symbiosis between dinoflagellates and cyanobacteria, as well as the genomic diversity of marine picocyanobacteria.
Topics: Dinoflagellida; Symbiosis; Cyanobacteria; Phylogeny; Genome, Bacterial; Evolution, Molecular
PubMed: 38834652
DOI: 10.1038/s41598-024-63502-0 -
PloS One 2024The dinoflagellate Alexandrium catenella is a well-known paralytic shellfish toxin producer that forms harmful algal blooms, repeatedly causing damage to Chilean coastal...
The dinoflagellate Alexandrium catenella is a well-known paralytic shellfish toxin producer that forms harmful algal blooms, repeatedly causing damage to Chilean coastal waters. The causes and behavior of algal blooms are complex and vary across different regions. As bacterial interactions with algal species are increasingly recognized as a key factor driving algal blooms, the present study identifies several bacterial candidates potentially associated with Chilean Alexandrium catenella. This research narrowed down the selection of bacteria from the Chilean A. catenella culture using antibiotic treatment and 16S rRNA metabarcoding analysis. Subsequently, seawater from two Chilean coastal stations, Isla Julia and Isla San Pedro, was monitored for two years to detect Alexandrium species and the selected bacteria, utilizing 16S and 18S rRNA gene metabarcoding analyses. The results suggested a potential association between Alexandrium species and Spongiibacteraceae at both stations. The proposed candidate bacteria within the Spongiibacteraceae family, potentially engaging in mutualistic relationships with Alexandrium species, included the genus of BD1-7 clade, Spongiibbacter, and Zhongshania.
Topics: Dinoflagellida; Chile; RNA, Ribosomal, 16S; Symbiosis; Bacteria; Harmful Algal Bloom; Seawater; Phylogeny; RNA, Ribosomal, 18S
PubMed: 38833478
DOI: 10.1371/journal.pone.0301343 -
Harmful Algae May 2024Previous research on phytoplankton blooms has often focused on the initiation of blooms, while studies on the mechanisms underlying bloom decline and termination have...
Previous research on phytoplankton blooms has often focused on the initiation of blooms, while studies on the mechanisms underlying bloom decline and termination have been more limited. This study aimed to explore the extent of which Acartia tonsa (copepod) grazing does or does not contribute to Margalefidinium polykrikoides (dinoflagellate) bloom decline. M. polykrikoides is a prominent harmful algal bloom (HAB) species that forms dense blooms in coastal and estuarine systems around the world with known ichthyotoxic effects. Sampling occurred in the lower York River Estuary, Virginia, USA in 2021 and 2022 during two M. polykrikoides blooms. Prey removal experiments were conducted using organisms collected from the field to estimate A. tonsa ingestion rates on M. polykrikoides. While A. tonsa was capable of ingesting M. polykrikoides at low abundance, when M. polykrikoides abundance exceeded 2000 cells mL, A. tonsa experienced nearly 100% mortality in the 24-hour prey removal experiments. This suggests that A. tonsa likely cannot exert any top-down control on M. polykrikoides blooms, rather, at high concentrations, M. polykrikoides may act as its own grazing deterrent. Extensive M. polykrikoides blooms could therefore continue to persist due to a reduction in grazing pressure, rather than an increase. This would suggest that the decline of M. polykrikoides blooms is likely caused by another factor. As the frequency, duration, and magnitude of HABs are expected to increase in the future, these findings provide key insights to the trophic interactions that may be influencing the duration of M. polykrikoides blooms.
Topics: Dinoflagellida; Animals; Harmful Algal Bloom; Copepoda; Virginia; Food Chain; Estuaries
PubMed: 38830711
DOI: 10.1016/j.hal.2024.102634 -
Harmful Algae May 2024This article presents the first results on shellfish toxicity in the Slovenian sea (Gulf of Trieste, Adriatic Sea) since the analytical methods for the detection of...
Okadaic acid as a major problem for the seafood safety (Mytilus galloprovincialis) and the dynamics of toxic phytoplankton in the Slovenian coastal sea (Gulf of Trieste, Adriatic Sea).
This article presents the first results on shellfish toxicity in the Slovenian sea (Gulf of Trieste, Adriatic Sea) since the analytical methods for the detection of biotoxins (PSP, ASP, DSP and other lipophilic toxins) in bivalve molluscs were included in the national monitoring program in 2013. In addition to toxins, the composition and abundance of toxic phytoplankton and general environmental characteristics of the seawater (surface temperature and salinity) were also monitored. During the 2014-2019 study period, only lipophilic toxins were detected (78 positive tests out of 446 runs), of which okadaic acid (OA) predominated in 97 % of cases, while dinophysistoxin-2 and yessotoxins only gave a positive result in one sampling event each. The number of samples that did not comply with the EC Regulation for the OA group was 17 or 3.8 % of all tests performed, all of which took place from September to November, while a few positive OA tests were also recorded in December, April, and May. This toxicity pattern was consistent with the occurrence pattern of the five most common DSP-producing dinoflagellates, which was supported by the development of warm and thermohaline stratified waters: Dinophysis caudata, D. fortii, D. sacculus, D. tripos and Phalacroma rotundatum. The strong correlation (r = 0.611, p < 0.001) between D. fortii, reaching abundances of up to 950 cells L, and OA suggests that D. fortii is the main cause of OA production in Slovenian waters. Strong interannual variations in OA and phytoplankton dynamics, exacerbated by the effects of anthropogenic impacts in this coastal ecosystem, reduce the predictability of toxicity events and require continuous and efficient monitoring. Our results also show that the introduction of the LC-MS/MS method for lipophilic toxins has improved the management of aquaculture activities, which was not as accurate based on mouse bioassays.
Topics: Okadaic Acid; Animals; Phytoplankton; Marine Toxins; Slovenia; Mytilus; Seafood; Seawater; Dinoflagellida
PubMed: 38830710
DOI: 10.1016/j.hal.2024.102632 -
PeerJ 2024Monitoring coral cover can describe the ecology of reef degradation, but rarely can it reveal the proximal mechanisms of change, or achieve its full potential in...
Monitoring coral cover can describe the ecology of reef degradation, but rarely can it reveal the proximal mechanisms of change, or achieve its full potential in informing conservation actions. Describing temporal variation in Symbiodiniaceae within corals can help address these limitations, but this is rarely a research priority. Here, we augmented an ecological time series of the coral reefs of St. John, US Virgin Islands, by describing the genetic complement of symbiotic algae in common corals. Seventy-five corals from nine species were marked and sampled in 2017. Of these colonies, 41% were sampled in 2018, and 72% in 2019; 28% could not be found and were assumed to have died. Symbiodiniaceae ITS2 sequencing identified 525 distinct sequences (comprising 42 ITS2 type profiles), and symbiont diversity differed among host species and individuals, but was in most cases preserved within hosts over 3 yrs that were marked by physical disturbances from major hurricanes (2017) and the regional onset of stony coral tissue loss disease (2019). While changes in symbiont communities were slight and stochastic over time within colonies, variation in the dominant symbionts among colonies was observed for all host species. Together, these results indicate that declining host abundances could lead to the loss of rare algal lineages that are found in a low proportion of few coral colonies left on many reefs, especially if coral declines are symbiont-specific. These findings highlight the importance of identifying Symbiodiniaceae as part of a time series of coral communities to support holistic conservation planning. Repeated sampling of tagged corals is unlikely to be viable for this purpose, because many Caribbean corals are dying before they can be sampled multiple times. Instead, random sampling of large numbers of corals may be more effective in capturing the diversity and temporal dynamics of Symbiodiniaceae metacommunities in reef corals.
Topics: Animals; Coral Reefs; Anthozoa; Symbiosis; Caribbean Region; United States Virgin Islands; Dinoflagellida
PubMed: 38827291
DOI: 10.7717/peerj.17358