Transition from a mixotrophic/heterotrophic protist community during the dark winter to a photoautotrophic spring community in surface waters of Disko Bay, Greenland.

Unicellular eukaryotic plankton communities (protists) are the major basis of the marine food web. The spring bloom is especially important, because of its high biomass. However, it is poorly described how the protist community composition in Arctic surface waters develops from winter to spring.

Cytotoxicity of Prymnesium parvum extracts and prymnesin analogs on epithelial fish gill cells RTgill-W1 and the human colon cell line HCEC-1CT.

Harmful algal blooms kill fish populations worldwide, as exemplified by the haptophyte microalga Prymnesium parvum. The suspected causative agents are prymnesins, categorized as A-, B-, and C-types based on backbone carbon atoms. Impacts of P.

The combined effect of pH and dissolved inorganic carbon concentrations on the physiology of plastidic ciliate Mesodinium rubrum and its cryptophyte prey.

Ocean acidification is caused by rising atmospheric partial pressure of CO (pCO) and involves a lowering of pH combined with increased concentrations of CO and dissolved in organic carbon in ocean waters. Many studies investigated the consequences of these combined changes on marine phytoplankton, yet only few attempted to separate the effects of decreased pH and increased pCO. Moreover, studies typically target photoautotrophic phytoplankton, while little is known of plastidic protists that depend on the ingestion of plastids from their prey.

Long-read genome sequencing provides novel insights into the harmful algal bloom species Prymnesium parvum.

Prymnesium parvum is a toxin-producing haptophyte that causes harmful algal blooms worldwide, which are often associated with massive fish-kills and subsequent economic losses. In here, we present nuclear and plastid genome assemblies using PacBio HiFi long reads and DNBseq short reads for the two P. parvum strains UTEX 2797 and CCMP 3037, representing producers of type A prymnesins.

Local adaptation through countergradient selection in northern populations of .

Marine microorganisms have the potential to disperse widely with few obvious barriers to gene flow. However, among microalgae, several studies have demonstrated that species can be highly genetically structured with limited gene flow among populations, despite hydrographic connectivity. Ecological differentiation and local adaptation have been suggested as drivers of such population structure.

Effects of Glacial Flour on Marine Micro-plankton: Evidences from Natural Communities of Greenlandic Fjords and Experimental Studies.

Meltwater runoff from glaciers carries particles, so-called glacial flour that may affect planktonic organisms and the functioning of marine ecosystems. Protist microplankton is at the base of marine food webs and thus plays an important role in sustaining important ecosystem services. To assess the effect of glacial flour on photoautotrophic, heterotrophic and mixotrophic microplankton, the spatial distribution of these trophic groups was studied in four Greenlandic fjords during summer.

The coupling between irradiance, growth, photosynthesis and prymnesin cell quota and production in two strains of the bloom-forming haptophyte, Prymnesium parvum.

Prymnesium parvum causes harmful algal blooms worldwide that are often associated with massive fish-kills and subsequent economic losses. Most of our knowledge of the toxicity of P. parvum derives from bioassays since methods for the identification and quantification of their toxins have been lacking.

Gill Transcriptomic Responses to Toxin-producing Alga in Rainbow Trout.

The gill of teleost fish is a multifunctional organ involved in many physiological processes, including protection of the mucosal gill surface against pathogens and other environmental antigens by the gill-associated lymphoid tissue (GIALT). Climate change associated phenomena, such as increasing frequency and magnitude of harmful algal blooms (HABs) put extra strain on gill function, contributing to enhanced fish mortality and fish kills. However, the molecular basis of the HAB-induced gill injury remains largely unknown due to the lack of high-throughput transcriptomic studies performed on teleost fish in laboratory conditions.

Retention of Prey Genetic Material by the Kleptoplastidic Ciliate cf. .

Many marine ciliate species retain functional chloroplasts from their photosynthetic prey. In some species, the functionality of the acquired plastids is connected to the simultaneous retention of prey nuclei. To date, this has never been documented in plastidic species.

Metabolic Reliance on Photosynthesis Depends on Both Irradiance and Prey Availability in the Mixotrophic Ciliate, cf. .

Many species of the ciliate genus can acquire functional chloroplasts from a wide range of algal prey and are thus classified as generalist non-constitutive mixotrophs. Little, however, is known about the influence of irradiance and prey availability on their ability to exploit the photosynthetic potential of the chloroplasts, and how this may explain their spatial and temporal distribution in nature. In this study, inorganic carbon uptake, growth, and ingestion rates were measured for cf.

Physiological Responses of Mesodinium major to Irradiance, Prey Concentration and Prey Starvation.

Ciliates within the Mesodinium rubrum/Mesodinium major species complex harbor chloroplasts and other cell organelles from specific cryptophyte species. Mesodinium major was recently described, and new studies indicate that blooms of M. major are just as common as blooms of M.

An under-ice bloom of mixotrophic haptophytes in low nutrient and freshwater-influenced Arctic waters.

The pelagic spring bloom is essential for Arctic marine food webs, and a crucial driver of carbon transport to the ocean depths. A critical challenge is understanding its timing and magnitude, to predict its changes in coming decades. Spring bloom onset is typically light-limited, beginning when irradiance increases or during ice breakup.

Limits to the cellular control of sequestered cryptophyte prey in the marine ciliate Mesodinium rubrum.

The marine ciliate Mesodinium rubrum is famous for its ability to acquire and exploit chloroplasts and other cell organelles from some cryptophyte algal species. We sequenced genomes and transcriptomes of free-swimming Teleaulax amphioxeia, as well as well-fed and starved M. rubrum in order to understand cellular processes upon sequestration under different prey and light conditions.

Effects of the DSP-toxic dinoflagellate Dinophysis acuta on clearance and respiration rate of the blue mussel, Mytilus edulis.

Diarrheic Shellfish Poisoning toxins (DST) are a severe health risk to shellfish consumers and can be a major problem for the shellfish industry. Bivalve molluscs can accumulate DST via ingestion of toxic dinoflagellates like Dinophysis spp., which are the most prominent producers of DST.

Dynamic CO and pH levels in coastal, estuarine, and inland waters: Theoretical and observed effects on harmful algal blooms.

Rising concentrations of atmospheric CO results in higher equilibrium concentrations of dissolved CO in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and CO concentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.

Distributions of three Alexandrium species and their toxins across a salinity gradient suggest an increasing impact of GDA producing A. pseudogonyaulax in shallow brackish waters of Northern Europe.

Blooms of Alexandrium spp. are a well-known phenomenon in Northern European waters. While A.

The Cost of Toxicity in Microalgae: Direct Evidence From the Dinoflagellate .

Empirical evidence of the cost of producing toxic compounds in harmful microalgae is completely lacking. Yet costs are often assumed to be high, implying substantial ecological benefits with adaptive significance exist. To study potential fitness costs of toxin production, 16 strains including three species of the former species complex were grown under both carbon limitation and unlimited conditions.