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Trichodesmium

Trichodesmium is a genus of non-heterocystous, filamentous marine cyanobacteria renowned for their diazotrophic capabilities, forming visible colonies in oligotrophic tropical and subtropical oceans.^[1] These organisms, primarily represented by the species T. erythraeum, conduct both carbon fixation via photosynthesis and atmospheric nitrogen (N₂) fixation simultaneously during daylight hours, a unique adaptation that supports their role as keystone species in global biogeochemical cycles.^[2] Ecologically, Trichodesmium thrives in nutrient-poor waters where it contributes 30–50% of the new nitrogen entering marine ecosystems annually, fueling primary production and sustaining food webs in regions like the Atlantic and Pacific Oceans.^[2] Their colonies, often fusiform or spherical and composed of trichomes ranging from 3 to 150 cells, create microhabitats that harbor diverse microbial consortia, enhancing nutrient cycling through interactions such as iron acquisition from dust.^[1]^[3] This colonial lifestyle provides advantages like buoyancy regulation and protection from grazing, allowing blooms that can cover vast surface areas and appear as "sea sawdust."^[1]^[4] The nitrogenase enzyme in Trichodesmium operates under microaerobic conditions through spatial differentiation, where internal diazocytes perform nitrogen fixation while photosynthesis occurs throughout the trichome, enabling simultaneous processes during daylight, with end cells differing metabolically from internal cells.^[2] Recent studies highlight their resilience to iron limitation, a critical factor in open oceans, through mechanisms like enhanced siderophore production by associated bacteria.^[3] Historically observed by explorers like Charles Darwin, Trichodesmium blooms have influenced ocean color and naming conventions, such as the Red Sea's moniker from T. erythraeum.^[1] Overall, these cyanobacteria are pivotal for estimating global nitrogen budgets, with annual fixation rates approaching 60–80 Tg N.^[5]

Taxonomy and Diversity

Classification

Trichodesmium was first described in 1830 by Christian Gottfried Ehrenberg, who named the type species T. erythraeum based on observations of dense blooms discoloring waters in the Bay of Tor in the Red Sea. The genus name, derived from the Greek for "hair-like arrangement," reflected the filamentous nature of the organisms observed under early microscopes. Additional species, including T. thiebautii and T. hildebrandtii, were formally described by Maurice Gomont in 1892 within his monograph on the Oscillariaceae, establishing the genus as part of the blue-green algae (now recognized as cyanobacteria). Further species such as T. contortum, T. tenue, and T. radians were added by N. Wille in 1904, though subsequent taxonomic scrutiny has questioned the validity of some based on morphological overlap.^[6] Phylogenetically, Trichodesmium is positioned within the order Oscillatoriales of the class Cyanophyceae in the phylum Cyanobacteriota, a placement supported by 16S rRNA gene sequencing and multi-locus phylogenetic analyses that affiliate it with other non-heterocystous filamentous cyanobacteria. The genus is currently assigned to the family Microcoleaceae, though earlier classifications placed it in Oscillatoriaceae or Phormidiaceae, reflecting ongoing revisions in cyanobacterial taxonomy driven by molecular data. It forms a distinct clade sister to heterocystous cyanobacteria, with close relatives including the genus Katagnymene, highlighting its evolutionary position among marine diazotrophs.^[6]^[7] Key diagnostic characteristics for classifying Trichodesmium include its non-heterocystous filaments composed of aligned trichomes that aggregate into macroscopic colonies, gliding motility facilitated by type IV pili, and, in diazotrophic lineages, the ability to perform aerobic nitrogen fixation in daylight using specialized diazocytes rather than heterocysts. These traits distinguish it from other Oscillatoriales members, which typically lack such combined colonial formation and diazotrophy under oxic conditions. The absence of sheaths around trichomes and the presence of gas vacuoles for buoyancy further support its systematic placement.^[6] Recent taxonomic revisions, informed by post-2010 genomic and metagenomic studies, have confirmed the monophyly of the Trichodesmium clade while delineating internal structure into at least four subclades based on whole-genome comparisons and marker genes like hetR. For instance, analyses of cultured isolates and environmental samples have separated major groups corresponding to T. erythraeum (clade III) and T. thiebautii (clade I), with implications for niche partitioning and suggesting potential cryptic speciation. These findings, derived from high-throughput sequencing, have refined the genus boundaries and underscored its cohesive evolutionary history despite morphological conservatism.

Species

The genus Trichodesmium includes four to five valid species based on morphological and molecular criteria, with Trichodesmium erythraeum serving as the type species and being the most widespread in tropical and subtropical oceans.^[8] T. thiebautii is characterized by larger filaments and is commonly observed in open ocean blooms, while T. hildebrandtii is rarer and predominantly reported from Atlantic waters; T. tenue represents a thinner filamentous variant.^[9]^[10] Distinctions among species rely on filament width, such as 5-10 μm for T. erythraeum, cell morphology (cylindrical in T. erythraeum versus more barrel-shaped in T. thiebautii), and genetic differences including variants in the nifH gene used for nitrogen fixation.^[11]^[12] These traits help differentiate T. thiebautii (filaments up to 12 μm wide) from narrower forms like T. tenue.^[13]^[14] Historical nomenclature includes resolved synonyms, such as Oscillatoria thiebautii now accepted as T. thiebautii, with current taxonomic status verified in databases like AlgaeBase and CyanoDB.^[15]^[13]^[16] Metagenomic analyses from Pacific Ocean blooms in the 2020s reveal evidence for 2-3 undescribed or cryptic lineages within the genus, including nondiazotrophic species that are abundant and widespread in open oceans, expanding recognized diversity beyond traditional morphological species.^[17]

Morphology and Cell Structure

Individual Cells

Trichodesmium cells are cylindrical in shape and form unbranched filamentous trichomes, with individual cells typically 2–10 μm long and 5–8 μm wide.^[18] These dimensions contribute to their relatively large volume compared to many other unicellular marine cyanobacteria, such as Prochlorococcus.^[19] Cell division occurs via binary fission, allowing trichomes to elongate as new cells are added at the ends.^[20] Key organelles in Trichodesmium cells include thylakoids, which are arranged in parallel, peripheral arrays to support oxygenic photosynthesis.^[21] Carboxysomes, polyhedral microcompartments containing the enzyme RuBisCO, facilitate efficient carbon fixation by concentrating CO₂ near the photosynthetic apparatus.^[21] Gas vacuoles, composed of stacked cylindrical structures, occupy a significant portion of the cell volume (up to 60–70%) and enable buoyancy regulation by adjusting cell density in response to light and pressure. The cell wall of Trichodesmium follows the Gram-negative bacterial architecture, featuring a thin peptidoglycan layer in the periplasm between inner and outer membranes, overlaid by an external mucilaginous slime sheath that aids in colony formation. Type IV pili are present on the cell surface, facilitating gliding motility and cell-cell interactions within filaments. Intracellular inclusions include polyphosphate granules, which serve as phosphorus storage under nutrient-limited conditions, and cyanophycin granules, which act as a nitrogen reserve polymer that accumulates and degrades in a diel cycle.^[22]

Colony Formation

Trichodesmium forms multicellular colonies through the aggregation of trichomes, which are linear chains of cells, resulting in distinct morphologies that enhance ecological fitness in oligotrophic marine environments. The primary colony types include spherical puffs, typically ranging from 0.2 to 1 mm in diameter with a radial arrangement of trichomes; flat, elongated rafts composed of loosely packed, twisted filaments; and spindle-shaped tufts featuring tightly bundled, fusiform structures. These morphologies arise from the coordinated alignment and intertwining of trichomes, allowing colonies to optimize interactions with light, nutrients, and particles in the water column.^[23]^[24]^[25] Colony formation begins with cell division occurring in multiple planes within trichomes, promoting the transition from solitary filaments to three-dimensional aggregates. This process is facilitated by trichome motility, where cells exhibit reversible gliding movements that enable attachment and bundling. Extracellular polymeric substances (EPS), primarily polysaccharides and proteins secreted under nutrient-limited conditions, play a crucial role in maintaining cohesion by forming a matrix that binds trichomes together and reduces diffusive losses of metabolites. In laboratory cultures, aggregation is triggered rapidly—within 10 to 48 hours under iron limitation or 5 to 7 days under phosphorus limitation—highlighting the mechanistic link between environmental cues and structural development.^[23]^[26]^[27] Mature colonies can reach sizes up to 1 cm, typically containing hundreds of trichomes with each trichome comprising tens to hundreds of cells, yielding a total of thousands of cells per aggregate. Buoyancy regulation is achieved through gas vacuoles, cylindrical proteinaceous structures present in all cells of the colony, which collectively adjust turgor pressure to enable synchronized vertical migration toward optimal light and nutrient layers. Developmental progression from single trichomes to mature colonies is modulated by light availability, with aggregates forming preferentially during illuminated periods under a diurnal cycle, and nutrient cues such as iron or phosphorus scarcity driving the initial motility and assembly phases.^[23]^[28]^[26]

Physiology

Metabolism

Trichodesmium conducts oxygenic photosynthesis through both photosystem I and photosystem II, generating ATP and NADPH essential for driving the Calvin-Benson cycle and carbon assimilation.^[29] This process occurs simultaneously with other metabolic activities during daylight hours, distinguishing it from many diazotrophs that separate these functions temporally or spatially.^[29] To enhance the efficiency of carbon fixation despite low ambient CO₂ levels in marine environments, Trichodesmium employs a CO₂-concentrating mechanism that relies on carboxysomes. These microcompartments encapsulate RuBisCO and carbonic anhydrase, converting actively transported bicarbonate (HCO₃⁻) into CO₂ to minimize photorespiration and mimic aspects of a C4-like pathway.^[30] Bicarbonate uptake is primarily facilitated by the high-affinity BicA transporter, allowing sustained photosynthesis under varying inorganic carbon availability.^[30] Carbon fixation rates in Trichodesmium typically range up to 10–20 pg C cell⁻¹ day⁻¹ under optimal irradiance, with diurnal patterns exhibiting peak photosynthetic activity midday when light intensity supports maximal electron transport.^[31] These rates reflect an adaptive response to fluctuating light, where morning accumulation of fixed carbon fuels later metabolic demands.^[32] Nutrient acquisition in Trichodesmium involves specialized ABC transporters for key elements; phosphate is taken up via the Pst system under low-phosphorus conditions, while iron—critical for photosynthetic electron transport and other enzymes—is acquired through the FutABC transporter for ferric iron forms.^[33] Iron requirements are particularly high due to its role in multiple metabolic pathways, including those supporting oxygenic photosynthesis.^[34] For energy management, Trichodesmium accumulates glycogen as a primary storage polysaccharide during daylight photosynthesis, which is mobilized at night to sustain basal metabolism.^[35] Respiratory rates remain low overall, particularly during the day, to reduce intracellular oxygen levels and avoid interference with oxygen-sensitive processes.^[32] This integrated metabolic strategy provides the energetic foundation necessary to support nitrogen fixation.^[29]

Nitrogen Fixation

Trichodesmium is renowned for its non-heterocystous diazotrophy, a unique strategy that allows aerobic nitrogen fixation in the oxygen-rich surface ocean without the specialized heterocyst cells found in many other diazotrophic cyanobacteria. Within its colonial filaments, nitrogen fixation is spatially segregated: it occurs exclusively in differentiated diazocytes, which constitute approximately 2–30 cells per trichome (about 15% of the total), while adjacent vegetative cells conduct oxygenic photosynthesis. This compartmentalization minimizes oxygen exposure to the nitrogenase enzyme during daylight hours, enabling Trichodesmium to fix nitrogen concurrently with carbon assimilation in sunlit waters.^[19] The core of this process is the nitrogenase enzyme complex, encoded by the nifHDK operon, which reduces atmospheric dinitrogen (N₂) to ammonia (NH₃). In Trichodesmium, nifHDK transcription follows a diurnal pattern, with peak expression and enzyme synthesis occurring midday, and activity peaking during daylight hours around midday, protected by mechanisms that lower intracellular oxygen levels. Regulation is mediated by the global nitrogen transcription factor NtcA, which responds to nitrogen starvation by activating nif genes and other assimilation pathways, and the nif-specific activator NifA, which fine-tunes expression in diazocytes. The fixed ammonia is rapidly assimilated via the glutamine synthetase–glutamate synthase (GS-GOGAT) pathway, with elevated GS activity in diazocytes preventing feedback inhibition.^[19]^[36] The nitrogenase reaction is highly energy demanding, as depicted by the equation:

\ce{N2 + 8 H+ + 8 e- + 16 ATP -> 2 NH3 + H2 + 16 ADP + 16 P_i}

This stoichiometry highlights the enzyme's inefficiency, producing one molecule of hydrogen (H₂) as a byproduct and consuming 16 ATP per N₂ reduced, underscoring the metabolic cost that links nitrogen fixation to broader autotrophy.^[37] To safeguard the oxygen-labile nitrogenase, Trichodesmium employs protective mechanisms such as intensified respiratory oxygen consumption, which can utilize up to 80% of daily fixed carbon to scavenge O₂ and maintain microaerobic conditions within filaments. Extracellular polymeric substances (EPS) form diffusive barriers around colonies and diazocytes, further restricting O₂ ingress, while the Mehler reaction in vegetative cells diverts photosynthetic electrons to reduce O₂ to water. Iron plays a critical role, as nitrogenase contains multiple Fe atoms; co-limitation by iron enhances activity by optimizing enzyme assembly under nutrient-scarce conditions prevalent in oligotrophic waters.^[27]^[19] Field measurements indicate nitrogen fixation rates of 0.5–60 nmol N L⁻¹ day⁻¹ in regions with Trichodesmium blooms, with depth-integrated contributions supporting up to 50% of new production in oligotrophic gyres, where Trichodesmium dominates diazotrophy.^[38]^[39]

Ecology and Distribution

Habitats

Trichodesmium thrives in warm, oligotrophic surface waters of tropical and subtropical oceans, where temperatures typically range from 20 to 30°C.^[40] These conditions support its growth and nitrogen fixation, as cooler temperatures below 20°C limit its activity and distribution.^[40] Optimal salinity levels fall between 30 and 37 parts per thousand (ppt), with maximal growth observed in this range and significant declines at higher salinities, such as an 83% reduction at 43 ppt.^[41] The organism prefers nutrient-poor environments characterized by low dissolved inorganic nitrogen and an imbalanced nitrogen-to-phosphorus ratio, which favors its role as a diazotroph in phosphorus-limited settings.^[40] Light intensities exceeding 200 μmol photons m⁻² s⁻¹ are essential, with growth and nitrogen fixation saturating around 180 μmol photons m⁻² s⁻¹ and remaining stable up to higher levels under light-dark cycles.^[42] Within these waters, Trichodesmium occupies microhabitats in the euphotic zone, generally from 0 to 50 m depth, where light penetration is sufficient for photosynthesis.^[40] Highest densities often occur between 10 and 50 m, particularly in the upper mixed layer during periods of low wind stress.^[40] The cyanobacterium maintains buoyancy through gas vesicles, allowing vertical positioning at density gradients to optimize light exposure while avoiding excessive surface irradiance.^[40] This regulation enables it to exploit clear, stratified waters with deep light penetration, up to 50–70 m compensation depths in oligotrophic conditions.^[40] Trichodesmium exhibits tolerances to abiotic factors typical of its marine habitat, including pH levels from 7.8 to 8.35, though lower pH reduces nitrogen fixation efficiency by up to 50% due to impaired iron uptake.^[43] It shows sensitivity to ultraviolet (UV) radiation, which inhibits photosynthesis and nitrogen fixation, but mitigates this through accumulation of mycosporine-like amino acids (MAAs) that absorb UV wavelengths, particularly in high-light-acclimated cells.^[44] The area of suitable thermal niches for Trichodesmium has expanded by 32% from the Last Glacial Maximum to the present day.^[45]

Global Distribution

Trichodesmium is predominantly found in tropical and subtropical regions of the world's oceans, spanning the Atlantic, Pacific, and Indian Oceans, where it thrives in warm, stratified waters of oligotrophic gyres. Hotspots include the Sargasso Sea in the North Atlantic gyre, the South Pacific Subtropical Gyre, and areas like the Mozambique Channel in the Indian Ocean, where it can constitute up to 30-40% of the bacterioplankton in larger size fractions.^[46] These distributions are shaped by preferences for low-nutrient, high-light environments, as detailed in habitat studies.^[47] Seasonally, Trichodesmium populations in the Northern Hemisphere peak during summer months, coinciding with maximum sea surface temperatures and stratification, while vertical distributions often concentrate at the subsurface chlorophyll maximum, such as depths of 30-100 meters in stations like ALOHA in the North Pacific.^[46] In the Southern Hemisphere, patterns shift with austral summer peaks in regions like the South Atlantic.^[48] It is notably rare in polar waters and coastal upwelling zones, where cooler temperatures and nutrient-rich conditions limit its occurrence.^[49] Monitoring of Trichodesmium relies on satellite remote sensing, such as MODIS imagery for detecting pigments like phycourobilin, which enables mapping of surface accumulations across large scales, and in situ sampling techniques that reveal baseline abundances of 10⁴ to 10⁶ cells L⁻¹ in oligotrophic waters.^[50] These methods, including metagenomic nifH gene analysis from datasets like Tara Oceans, have confirmed its global yet patchy presence, with densities typically ranging from 1 to 40 filaments L⁻¹ in non-bloom conditions.^[46]^[51] Recent trends show increased frequency and altered timing of Trichodesmium occurrences in warming regions, with projections indicating a 173% expansion in areas optimal for growth (considering SST, irradiance, and iron) by 2100 under climate change scenarios, and observed unusual winter blooms in the southeastern Arabian Sea linked to 1°C above-climatology warming in the 2020s. As of 2023, winter blooms have been documented in the Andaman Sea, indicating ongoing shifts due to warming.^[52]^[53]^[54] Overall, the ocean area within its thermal niche has expanded by 32% since the Last Glacial Maximum, reflecting sensitivity to global temperature rises.^[52]

Ecological Role and Impacts

Blooms

Trichodesmium blooms are large-scale aggregations of colonies that form visible surface slicks in oligotrophic tropical and subtropical oceans, often triggered by nutrient pulses such as iron from atmospheric dust deposition and periods of calm winds that reduce mixing and allow buoyancy-driven accumulation at the surface.^[55]^[40] These conditions enable growth rates up to 0.5 day⁻¹ under optimal temperatures of 24–30°C and sufficient iron availability (0.2–1.2 nM dissolved Fe), which alleviates limitations on nitrogen fixation and cell division.^[56]^[55] These blooms typically span areas of 10–1000 km² and persist for weeks, with examples including a 1000 km² event in the North Pacific gyre lasting several weeks in 1989.^[57]^[58] Biomass concentrations can reach up to 100 mg C m⁻³ in the upper water column, contributing significantly to local primary production during these episodic events.^[51]^[40] Blooms arise through two primary mechanisms: seed-bank initiation from overwintering cells that accumulate in subsurface layers and rise during favorable conditions, or de novo formation from dispersed trichomes that aggregate under low turbulence.^[40]^[59] Diurnal vertical migrations of 10–100 m, facilitated by gas vacuoles for daytime ascent to access light and carbohydrate ballast for nighttime descent to acquire nutrients, further enhance bloom dynamics by optimizing resource acquisition.^[60]^[40] Remote sensing via satellites such as SeaWiFS (1997–2010), MODIS (ongoing since 2002), and VIIRS (ongoing since 2011) has detected these blooms through enhanced water-leaving radiance and reflectance at 443 nm, attributed to light scattering by dense colony structures, enabling mapping of their spatial extent and frequency in regions such as the South Atlantic Bight as of 2025.^[61]^[62] Historical analyses from this period reveal recurrent bloom patterns tied to seasonal dust inputs and wind regimes, with recent satellite data (e.g., 2023) confirming ongoing blooms around Australia.^[61]^[63]

Nutrient Cycling

Trichodesmium plays a pivotal role in the marine nitrogen cycle by contributing 25-50% of the nitrogen input to oligotrophic ocean regions through dinitrogen (N₂) fixation, with global estimates ranging from 60 to 80 Tg N yr⁻¹.^[64]^[65] This fixed nitrogen supports primary production in nutrient-poor waters and is partially exported to deeper layers via sinking aggregates and colonies, facilitating nutrient transfer from surface to subsurface ecosystems. Recent studies (as of 2025) indicate that Trichodesmium aggregates can sink at velocities up to 400 m d⁻¹, enhancing remineralization and carbon/nitrogen export efficiency in a warming ocean.^[66]^[67]^[68] In the carbon cycle, Trichodesmium contributes approximately 0.6–1% of global oceanic primary production through its photosynthetic activity, particularly during blooms that enhance CO₂ drawdown in tropical and subtropical surface waters (estimates as of 2020). This process sequesters atmospheric CO₂ into organic matter, with a portion exported vertically alongside fixed nitrogen, influencing long-term carbon storage in the ocean.^[52] Trichodesmium also contributes to phosphorus cycling by producing alkaline phosphatase enzymes under phosphorus limitation, enabling the hydrolysis and recycling of dissolved organic phosphorus into bioavailable forms for itself and surrounding microbial communities.^[26]^[69] Additionally, iron serves as a critical mediator in its nitrogen fixation, as the nitrogenase enzyme requires iron-rich cofactors, with iron availability often limiting fixation rates in iron-depleted open ocean waters.^[70] Modeling efforts estimate Trichodesmium's nitrogen fixation rates as a function of light intensity and iron concentration multiplied by biomass, such as \text{N-fix rate} = f(\text{[light](/page/Light)}, \text{Fe}) \times \text{[biomass](/page/Biomass)}, where f incorporates physiological dependencies.^[71] These models highlight uncertainties in vertical export, with 20-50% of fixed nitrogen potentially lost to the deep ocean through sinking, affecting net nutrient availability in surface layers. Climate projections suggest expanded Trichodesmium distributions and increased fixation potential by 2100 due to warming and stratification, amplifying these cycling impacts.^[72]^[71]^[73]

Interactions with Other Organisms

Trichodesmium forms various symbiotic associations with other marine organisms, particularly through its colonial structure that supports microbial consortia on colony surfaces. These epibionts include diverse heterotrophic bacteria that engage in mutualistic interactions, such as aiding in iron acquisition from atmospheric dust deposition, which benefits Trichodesmium's nitrogen fixation under nutrient-limited conditions.^[3] Metagenomic analyses of Trichodesmium colonies reveal a rich microbiome dominated by Proteobacteria and Bacteroidetes, with functional genes for nutrient cycling that enhance the holobiont's resilience in oligotrophic waters. Recent observations (as of 2024) document recurrent associations with amoebae (e.g., Trichosphaerium), which may influence colony dynamics and microbial food webs.^[74]^[75] Grazing pressure on Trichodesmium is generally low due to the production of toxins, including the neurotoxin β-N-methylamino-L-alanine (BMAA), which deters many zooplankton species such as the copepod Acartia tonsa.^[76] Intact Trichodesmium cells are ingested but often cause reduced feeding and increased mortality in generalist grazers when toxins are released upon cell lysis.^[77] However, selective grazing occurs by specialized organisms like appendicularians (e.g., Oikopleura spp.), which use mucous filters to capture Trichodesmium filaments without significant toxicity effects, incorporating them into the food web.^[78] Trichodesmium engages in competitive interactions with other diazotrophs, such as Crocosphaera watsonii, primarily for limiting resources like light and iron in the euphotic zone.^[79] Under iron deficiency, Crocosphaera exhibits enhanced growth and nitrogen fixation compared to Trichodesmium, potentially shifting community dominance in low-iron regions.^[79] Additionally, Trichodesmium exerts allelopathic effects through extracellular polymeric substances (EPS), which inhibit the growth of co-occurring phytoplankton by disrupting cell membranes and reducing photosynthetic efficiency.^[80] Recent metagenomic studies have uncovered evidence of phage infections as key regulators of Trichodesmium populations, with viral communities associated with colonies including cyanophage sequences that target nitrogenase genes.^[81] These phages, often integrated into the Trichodesmium virome, can lyse cells during blooms, releasing nutrients and controlling bloom termination, with estimates of 10⁴ to 10⁵ virus-like particles per colony contributing to population dynamics.^[82] CRISPR-Cas systems in certain Trichodesmium clades provide immunity against these phages, influencing clade abundance in natural assemblages.^[83]

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Aug 5, 2025 · ... The ecological niche preferred by Trichodesmium is characterized by high light intensities that reach about 2000 µmol photons m -2 s -1 of ...
[43]
Ocean acidification slows nitrogen fixation and growth in the ... - PNAS
To compensate in part for the impaired N2 fixation, Trichodesmium synthesizes more nitrogenase at low than at high pH, with an increase by a factor of 1.7 at ...
[44]
Effects of ultraviolet radiation on photosynthetic performance and N ...
... UV-absorbing compounds, most likely mycosporine-like amino acids (MAAs). After acclimation under natural sunlight, the specific growth rate was lower (by up ...
[45]
(PDF) Projected expansion of Trichodesmium's geographical ...
May 24, 2025 · We also found that the area of the ocean where sea surface temperatures (SST) are within Trichodesmium's thermal niche increased by 32% from ...Missing: 2020s | Show results with:2020s
[46]
Global distribution patterns of marine nitrogen-fixers by imaging and ...
Jul 6, 2021 · Single-cell free-living NCDs are by far the most abundant diazotrophs in the surface ocean, however, Trichodesmium dominates in terms of ...
[47]
Large-scale latitudinal distribution of Trichodesmium spp. in the ...
Filament size was quite variable during our study. The average number of cells per filament was 70. Figure 3a shows the concentrations of colonies found ...Missing: width | Show results with:width
[48]
Spatial and temporal distribution of Trichodesmium blooms in the ...
Dec 15, 2006 · As expected, Trichodesmium blooms are rare, occurring <5–10% of the time over most of the tropical and subtropical oceans for the time period ...
[49]
Defining the Realized Niche of the Two Major Clades of ... - Frontiers
Jun 29, 2022 · The Trichodesmium genus is composed of six different species, grouped into two major clades (Hynes et al., 2011; Rouco et al., 2014).
[50]
Three decades of ocean-color remote-sensing Trichodesmium spp ...
Using these advanced spectral algorithms, ocean-color remote-sensing products are now applied to a number of extended purposes including: water quality ...
[51]
[PDF] Biomass and primary productivity of the cyanobacterium ...
Atlantic were predominantly composed of Trichodesmium thiebautii. Individual cells of T. thiebautii were relatively large, typically about 10 μm in dia. (range ...
[52]
Environmental Change Journal | Wiley Online Library
Sep 1, 2020 · Projected expansion of Trichodesmium's geographical distribution and increase in growth potential in response to climate change · 5 CONCLUSION.
[53]
(PDF) Is rising Trichodesmium blooms an indication of the warming ...
Nov 23, 2021 · Thus, the increasing sea surface temperature might be the triggering factor for the advancement of the onset of Trichodesmium bloom along SEAS ...Missing: 2020s | Show results with:2020s
[54]
[PDF] Emerging patterns of marine nitrogen fixation
Marine nitrogen fixation is a process where N2 gas is reduced to ammonia, providing new nitrogen for carbon export. It is carried out by diazotrophs, and is ...Missing: diazocytes | Show results with:diazocytes
[55]
Rapid mode switching facilitates the growth of Trichodesmium - NIH
May 3, 2024 · Results show that a rapid switch between photosynthetic and non-photosynthetic states increases Trichodesmium growth rates by improving metabolic efficiencies.
[56]
[PDF] Trichodesmium blooms and new nitrogen in the north Pacific gyre
Photographic documentation of the Trichodesmium bloom showing the massive surface water accumulations of colonies: [A] shipboard view of the bloom from the SSP ...<|separator|>
[57]
https://ftp.soest.hawaii.edu/dkarl/misc/dave/Reprints/1992Trichodesmium-Blooms-219-237.pdf
[58]
[PDF] Contributions in Marine Science - University of Texas at Austin
was initiated de novo and is not the result of trans port and seeding from the eastern bay bloom. This southern bay bloom also was accompanied by a large ...
[59]
[PDF] Thin Phytoplankton Layers: Characteristics, Mechanisms, and ...
1998), and there is evidence that colonies of the nonmotile cyanobacterium Trichodesmium perform vertical migrations to great depths (potentially >100 m) on a ...
[60]
[PDF] Detecting Trichodesmium blooms in SeaWiFS imagery - USC Dornsife
... reflectance and the spectral shape of remote sensing reflectance at 443, 490 and 555 nm. Analysis suggests that the spatial structure of. Trichodesmium ...
[61]
Detecting Trichodesmium blooms in SeaWiFS imagery - ADS
This study demonstrates the potential of mapping Trichodesmium from space using spectral observations, even in waters as optically complex as the South Atlantic ...
[62]
Epibionts dominate metabolic functional potential of Trichodesmium ...
May 23, 2017 · In the oligotrophic oceans where Trichodesmium occurs, there is intense competition for resources such as phosphorus and iron, which can ...
[63]
A Synthesis of Viral Contribution to Marine Nitrogen Cycling - PMC
Apr 25, 2022 · The amount of nitrogen fixed by Trichodesmium per year was estimated to be about 60–80 Tg N year−1 globally (Capone et al., 1997; Mahaffey et ...
[64]
Do Trichodesmium spp. populations in the North Atlantic export most ...
Jan 22, 2014 · A key change in the model structure is a direct pathway for vertical export of Trichodesmium spp., which allows the solution to reach the ...
[65]
Sinking Trichodesmium fixes nitrogen in the dark ocean - PMC - NIH
Jul 14, 2022 · We conclude that sinking Trichodesmium provides ammonium, dissolved organic matter and biomass to mesopelagic prokaryotes.Missing: paper | Show results with:paper
[66]
Possible transport pathway of diazotrophic Trichodesmium ... - Nature
Feb 5, 2024 · Diazotrophic cyanobacteria such as Trichodesmium play a crucial role in the nitrogen budget of the oceans due to their capability to bind ...Introduction · Results · Discussion
[67]
Phosphorus Release and Regeneration Following Laboratory Lysis ...
Apr 8, 2021 · One strategy is the production of alkaline phosphatase (APase), which allows hydrolysis of larger dissolved organic phosphorus (DOP) compounds ...
[68]
Distinct Responses of the Nitrogen-Fixing Marine Cyanobacterium ...
Jun 11, 2019 · ... Trichodesmium blooms have been observed (Bell et al., 1999). The ... weeks, until they achieved consistent P-limited growth rates. Cool ...
[69]
[PDF] Modeling the distribution of Trichodesmium and nitrogen fixation in ...
Jun 4, 2004 · In section 3.1 we compare the model-estimated mixed layer depth variability to seasonal climatological fields, and we describe how this ...
[70]
[PDF] Do Trichodesmium spp. populations in the North Atlantic export most ...
Abstract A new observational synthesis of diazotrophic biomass and nitrogen fixation provides the opportunity for systematic quantitative evaluation of ...
[71]
Nitrogen fixation and transfer in open ocean diatom–cyanobacterial ...
Mar 31, 2011 · We estimated that Richelia fix 81–744% more N than needed for their own growth and up to 97.3% of the fixed N is transferred to the diatom ...
[72]
Microbiome of Trichodesmium Colonies from the North Pacific ...
Filamentous diazotrophic Cyanobacteria of the genus Trichodesmium, often found in colonial form, provide an important source of new nitrogen to tropical and ...Missing: cryptic | Show results with:cryptic
[73]
Diverse taxa of cyanobacteria produce β-N-methylamino-l-alanine, a ...
Previous analysis of marine blooms of Trichodesmium thiebautii and Trichodesmium erythraeum have revealed high neurotoxicity to mice, but the low molecular ...Missing: zooplankton | Show results with:zooplankton
[74]
Toxic effect of the bloom-forming Trichodesmium sp. (Cyanophyta ...
Aug 5, 2025 · Healthy intact cells of Trichodesmium sp. were not toxic to A. tonsa and were ingested by A. tonsa when no other foods were available. However, ...
[75]
Trichodesmium spp. - Inter-Research Science Publisher
Field measurements were normalized per colony and culture measurements were normalized per unit. N. An average colony was estimated to be 0.1 to 0.2 pg. N ...
[76]
Iron deficiency increases growth and nitrogen-fixation rates ... - Nature
Jun 27, 2014 · We examined the consequences of Fe and P co-deficiency for the growth and N2-fixation rates of Crocosphaera watsonii and Trichodesmium ...
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[PDF] Screening on the toxicity and toxin content of Trichodesmium ...
May 30, 2009 · Trichodesmium spp. is related mainly to allelopathic functions, which may be very important since these organisms live in environments with ...Missing: allelopathy | Show results with:allelopathy
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Characterization of Trichodesmium-associated viral communities in ...
Three viral metagenomes were constructed from experimentally lysed Trichodesmium collected from two locations in the eastern Gulf of Mexico.Nucleic Acid Amplification... · Viral Metagenome... · Results And Discussion
[79]
Microbial community gene expression within colonies of the ... - Nature
Jul 2, 2009 · The phage and viral sequences recovered may have originated in either Trichodesmium or the associated organisms. The large number of cyanophage ...Rna In Vitro Amplification · Double-Stranded Cdna... · Unannotated Sequence ReadsMissing: infections | Show results with:infections
[80]
Importance of mobile genetic element immunity in numerically ...
Feb 23, 2023 · The colony-forming cyanobacteria Trichodesmium spp. are considered one of the most important nitrogen-fixing genera in the warm, ...