Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries.

Ocean warming (OW) and acidification (OA) are expected to interactively impact key phytoplankton groups such as diatoms, but the underlying mechanisms, particularly under long-term acclimation, remain poorly understood. In this study, we investigated the responses of the toxic diatom Pseudo-nitzschia multiseries to combined changes in temperature (20 °C and 30 °C) and CO concentration (pCO 400 μatm and 1000 μatm) using a multi-omics approach over an acclimation period of at least 251 generations. Physiological data suggest that elevated temperature, either alone or in combination with CO, reduced the net photosynthesis and nitrate uptake rate, thus inhibiting P.

Molecular mechanism of a coastal cyanobacterium sp. PCC 7002 adapting to changing phosphate concentrations.

Unlabelled: Phosphorus concentration on the surface of seawater varies greatly with different environments, especially in coastal. The molecular mechanism by which cyanobacteria adapt to fluctuating phosphorus bioavailability is still unclear. In this study, transcriptomes and gene knockouts were used to investigate the adaptive molecular mechanism of a model coastal cyanobacterium sp.

Marine heatwaves alter competition between the cultured macroalga Gracilariopsis lemaneiformis and the harmful bloom alga Skeletonema costatum.

Seaweed cultivation can inhibit the occurrence of red tides. However, how seaweed aquaculture interactions with harmful algal blooms will be affected by the increasing occurrence and intensity of marine heatwaves (MHWs) is unknown. In this study, we run both monoculture and coculture systems to investigate the effects of a simulated heatwave on the competition of the economically important macroalga Gracilariopsis lemaneiformis against the harmful bloom diatom Skeletonema costatum.

Simulated upwelling and marine heatwave events promote similar growth rates but differential domoic acid toxicity in Pseudo-nitzschia australis.

Along the west coast of the United States, highly toxic Pseudo-nitzschia blooms have been associated with two contrasting regional phenomena: seasonal upwelling and marine heatwaves. While upwelling delivers cool water rich in pCO and an abundance of macronutrients to the upper water column, marine heatwaves instead lead to warmer surface waters, low pCO, and reduced nutrient availability. Understanding Pseudo-nitzschia dynamics under these two conditions is important for bloom forecasting and coastal management, yet the mechanisms driving toxic bloom formation during contrasting upwelling vs.

Importance of mobile genetic element immunity in numerically abundant Trichodesmium clades.

The colony-forming cyanobacteria Trichodesmium spp. are considered one of the most important nitrogen-fixing genera in the warm, low nutrient ocean. Despite this central biogeochemical role, many questions about their evolution, physiology, and trophic interactions remain unanswered.

Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification.

Ocean warming (OW) and acidification (OA) are recognized as two major climatic conditions influencing phytoplankton growth and nutritional or toxin content. However, there is limited knowledge on the responses of harmful algal bloom species that produce toxins. Here, the study provides quantitative and mechanistic understanding of the acclimation and adaptation responses of the domoic acid (DA) producing diatom Pseudo-nitzschia multiseries to rising temperature and pCO using both a one-year in situ bulk culture experiment, and an 800-day laboratory acclimation experiment.

Molecular mechanisms underlying iron and phosphorus co-limitation responses in the nitrogen-fixing cyanobacterium Crocosphaera.

In the nitrogen-limited subtropical gyres, diazotrophic cyanobacteria, including Crocosphaera, provide an essential ecosystem service by converting dinitrogen (N) gas into ammonia to support primary production in these oligotrophic regimes. Natural gradients of phosphorus (P) and iron (Fe) availability in the low-latitude oceans constrain the biogeography and activity of diazotrophs with important implications for marine biogeochemical cycling. Much remains unknown regarding Crocosphaera's physiological and molecular responses to multiple nutrient limitations.

Temperature variability interacts with mean temperature to influence the predictability of microbial phenotypes.

Despite their relatively high thermal optima (T ), tropical taxa may be particularly vulnerable to a rising baseline and increased temperature variation because they live in relatively stable temperatures closer to their T . We examined how microbial eukaryotes with differing thermal histories responded to temperature fluctuations of different amplitudes (0 control, ±2, ±4°C) around mean temperatures below or above their T . Cosmopolitan dinoflagellates were selected based on their distinct thermal traits and included two species of the same genus (tropical and temperate Coolia spp.

Two co-dominant nitrogen-fixing cyanobacteria demonstrate distinct acclimation and adaptation responses to cope with ocean warming.

The globally dominant N -fixing cyanobacteria Trichodesmium and Crocosphaera provide vital nitrogen supplies to subtropical and tropical oceans, but little is known about how they will be affected by long-term ocean warming. We tested their thermal responses using experimental evolution methods during 2 years of selection at optimal (28°C), supra-optimal (32°C) and suboptimal (22°C) temperatures. After several hundred generations under thermal selection, changes in growth parameters, as well as N and C fixation rates, suggested that Trichodesmium did not adapt to the three selection temperature regimes during the 2-year evolution experiment, but could instead rapidly and reversibly acclimate to temperature shifts from 20°C to 34°C.

Why Environmental Biomarkers Work: Transcriptome-Proteome Correlations and Modeling of Multistressor Experiments in the Marine Bacterium .

Ocean microbial communities are important contributors to the global biogeochemical reactions that sustain life on Earth. The factors controlling these communities are being increasingly explored using metatranscriptomic and metaproteomic environmental biomarkers. Using published proteomes and transcriptomes from the abundant colony-forming cyanobacterium (strain IMS101) grown under varying Fe and/or P limitation in low and high CO, we observed robust correlations of stress-induced proteins and RNAs (i.

Acclimation and adaptation to elevated pCO increase arsenic resilience in marine diatoms.

Arsenic pollution is a widespread threat to marine life, but the ongoing rise pCO levels is predicted to decrease bio-toxicity of arsenic. However, the effects of arsenic toxicity on marine primary producers under elevated pCO are not well characterized. Here, we studied the effects of arsenic toxicity in three globally distributed diatom species (Phaeodactylum tricornutum, Thalassiosira pseudonana, and Chaetoceros mulleri) after short-term acclimation (ST, 30 days), medium-term exposure (MT, 750 days), and long-term (LT, 1460 days) selection under ambient (400 µatm) and elevated (1000 and 2000 µatm) pCO.

Long-Term m5C Methylome Dynamics Parallel Phenotypic Adaptation in the Cyanobacterium Trichodesmium.

A major challenge in modern biology is understanding how the effects of short-term biological responses influence long-term evolutionary adaptation, defined as a genetically determined increase in fitness to novel environments. This is particularly important in globally important microbes experiencing rapid global change, due to their influence on food webs, biogeochemical cycles, and climate. Epigenetic modifications like methylation have been demonstrated to influence short-term plastic responses, which ultimately impact long-term adaptive responses to environmental change.

Distinct Responses of the Nitrogen-Fixing Marine Cyanobacterium to a Thermally Variable Environment as a Function of Phosphorus Availability.

Surface temperature in the ocean is projected to be elevated and more variable in the future, which will interact with other environmental changes like reduced nutrient supplies. To explore these multiple stressor relationships, we tested the influence of thermal variation on the key marine diazotrophic cyanobacterium GBRTRLI101 as a function of the limiting nutrient phosphorus (P). Two constant temperature treatments represented current winter (22°C) and summer (30°C) mean values.

Functional Genomics and Phylogenetic Evidence Suggest Genus-Wide Cobalamin Production by the Globally Distributed Marine Nitrogen Fixer .

Only select prokaryotes can biosynthesize vitamin B (i.e., cobalamins), but these organic co-enzymes are required by all microbial life and can be vanishingly scarce across extensive ocean biomes.

Nitrogen Fixation by Trichodesmium and unicellular diazotrophs in the northern South China Sea and the Kuroshio in summer.

Distribution of diazotrophs and their nitrogen fixation activity were investigated in the northern South China Sea (nSCS) and the Kuroshio from July 16th to September 1st, 2009. N fixation activities in whole seawater and <10 μm fraction at the surface were measured by acetylene reduction assay. Higher activities were observed at the East China Sea (ECS) Kuroshio and the nSCS shelf.

Nutrient-Colimited Trichodesmium as a Nitrogen Source or Sink in a Future Ocean.

Nitrogen-fixing (N) cyanobacteria provide bioavailable nitrogen to vast ocean regions but are in turn limited by iron (Fe) and/or phosphorus (P), which may force them to employ alternative nitrogen acquisition strategies. The adaptive responses of nitrogen fixers to global-change drivers under nutrient-limited conditions could profoundly alter the current ocean nitrogen and carbon cycles. Here, we show that the globally important N fixer fundamentally shifts nitrogen metabolism toward organic-nitrogen scavenging following long-term high-CO adaptation under iron and/or phosphorus (co)limitation.

Transcriptional Activities of the Microbial Consortium Living with the Marine Nitrogen-Fixing Cyanobacterium Trichodesmium Reveal Potential Roles in Community-Level Nitrogen Cycling.

is a globally distributed cyanobacterium whose nitrogen-fixing capability fuels primary production in warm oligotrophic oceans. Like many photoautotrophs, serves as a host to various other microorganisms, yet little is known about how this associated community modulates fluxes of environmentally relevant chemical species into and out of the supraorganismal structure. Here, we utilized metatranscriptomics to examine gene expression activities of microbial communities associated with (strain IMS101) using laboratory-maintained enrichment cultures that have previously been shown to harbor microbial communities similar to those of natural populations.

The Trichodesmium consortium: conserved heterotrophic co-occurrence and genomic signatures of potential interactions.

The nitrogen (N)-fixing cyanobacterium Trichodesmium is globally distributed in warm, oligotrophic oceans, where it contributes a substantial proportion of new N and fuels primary production. These photoautotrophs form macroscopic colonies that serve as relatively nutrient-rich substrates that are colonized by many other organisms. The nature of these associations may modulate ocean N and carbon (C) cycling, and can offer insights into marine co-evolutionary mechanisms.

Molecular and physiological evidence of genetic assimilation to high CO2 in the marine nitrogen fixer Trichodesmium.

Most investigations of biogeochemically important microbes have focused on plastic (short-term) phenotypic responses in the absence of genetic change, whereas few have investigated adaptive (long-term) responses. However, no studies to date have investigated the molecular progression underlying the transition from plasticity to adaptation under elevated CO for a marine nitrogen-fixer. To address this gap, we cultured the globally important cyanobacterium Trichodesmium at both low and high CO for 4.

Mechanisms of increased Trichodesmium fitness under iron and phosphorus co-limitation in the present and future ocean.

Nitrogen fixation by cyanobacteria supplies critical bioavailable nitrogen to marine ecosystems worldwide; however, field and lab data have demonstrated it to be limited by iron, phosphorus and/or CO2. To address unknown future interactions among these factors, we grew the nitrogen-fixing cyanobacterium Trichodesmium for 1 year under Fe/P co-limitation following 7 years of both low and high CO2 selection. Fe/P co-limited cell lines demonstrated a complex cellular response including increased growth rates, broad proteome restructuring and cell size reductions relative to steady-state growth limited by either Fe or P alone.

Irreversibly increased nitrogen fixation in Trichodesmium experimentally adapted to elevated carbon dioxide.

Nitrogen fixation rates of the globally distributed, biogeochemically important marine cyanobacterium Trichodesmium increase under high carbon dioxide (CO2) levels in short-term studies due to physiological plasticity. However, its long-term adaptive responses to ongoing anthropogenic CO2 increases are unknown. Here we show that experimental evolution under extended selection at projected future elevated CO2 levels results in irreversible, large increases in nitrogen fixation and growth rates, even after being moved back to lower present day CO2 levels for hundreds of generations.

High CO2 and silicate limitation synergistically increase the toxicity of Pseudo-nitzschia fraudulenta.

Anthropogenic CO(2) is progressively acidifying the ocean, but the responses of harmful algal bloom species that produce toxins that can bioaccumulate remain virtually unknown. The neurotoxin domoic acid is produced by the globally-distributed diatom genus Pseudo-nitzschia. This toxin is responsible for amnesic shellfish poisoning, which can result in illness or death in humans and regularly causes mass mortalities of marine mammals and birds.

INTERACTIVE EFFECTS OF IRRADIANCE AND CO2 ON CO2 FIXATION AND N2 FIXATION IN THE DIAZOTROPH TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA)(1).

The diazotrophic cyanobacteria Trichodesmium spp. contribute approximately half of the known marine dinitrogen (N2 ) fixation. Rapidly changing environmental factors such as the rising atmospheric partial pressure of carbon dioxide (pCO2 ) and shallower mixed layers (higher light intensities) are likely to affect N2 -fixation rates in the future ocean.