Karenia: The biology and ecology of a toxic genus

Brand, Larry E.; Campbell, Lisa; Bresnan, Eileen

doi:10.1016/j.hal.2011.10.020

Cited by 182 publications

(145 citation statements)

References 278 publications

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“…Our findings contrast with those of Errera and Campbell (22,23), who reported that "brevetoxin production increased in response to low salinity stress." Because of the substantial adverse effects of K. brevis and brevetoxins in the Gulf of Mexico and a desire to understand their regulation, Errera and Campbell's reported findings have garnered much attention from researchers (e.g., [25][26][27], as well as media outlets, but we found that their reported findings are not reproducible. Furthermore, their claims that they "close a critical gap in knowledge" are unsubstantiated.…”

Section: Discussionmentioning

confidence: 70%

Osmotic stress does not trigger brevetoxin production in the dinoflagellateKarenia brevis

Sunda

Burleson

Hardison

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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With the global proliferation of toxic harmful algal bloom species, there is a need to identify the environmental and biological factors that regulate toxin production. One such species, Karenia brevis, forms nearly annual blooms that threaten coastal regions throughout the Gulf of Mexico. This dinoflagellate produces brevetoxins, which are potent neurotoxins that cause neurotoxic shellfish poisoning and respiratory illness in humans, as well as massive fish kills. A recent publication reported that a rapid decrease in salinity increased cellular toxin quotas in K. brevis and hypothesized that brevetoxins serve a role in osmoregulation. This finding implied that salinity shifts could significantly alter the toxic effects of blooms. We repeated the original experiments separately in three different laboratories and found no evidence for increased brevetoxin production in response to low-salinity stress in any of the eight K. brevis strains we tested, including three used in the original study. Thus, we find no support for an osmoregulatory function of brevetoxins. The original publication also stated that there was no known cellular function for brevetoxins. However, there is increasing evidence that brevetoxins promote survival of the dinoflagellates by deterring grazing by zooplankton. Whether they have other as-yet-unidentified cellular functions is currently unknown. red tides | toxic blooms | HABs H armful algal blooms threaten human health and damage coastal ecosystems worldwide. In the Gulf of Mexico, the athecate dinoflagellate Karenia brevis causes nearly annual toxic blooms. The physiology, ecology, and adverse effects of K. brevis have been well studied since the species was described in the 1940s (1). Notably, K. brevis produces brevetoxins, a family of potent polyether neurotoxins that bind to voltage-activated sodium channels in cell membranes, preventing normal nerve and muscle activity (2, 3). A nontoxic polyether that inhibits brevetoxin function, brevenal, is also produced in small amounts by this species (4). In humans, brevetoxins cause neurotoxic shellfish poisoning, and brevetoxin-contaminated aerosols cause respiratory irritation and illness (2, 5). Blooms also cause massive fish kills (6), as well as bird and marine mammal mortalities (7,8). In 2005, a bloom of K. brevis lasted for more than a year and caused extensive mortalities at all trophic levels in lagoons, coastal ecosystems, and offshore reefs on the west Florida shelf (8, 9).Because of the extensive damage caused by K. brevis, there has been considerable interest in understanding the function and regulation of brevetoxins. Competition experiments reveal that K. brevis produces allelopathic compounds, which inhibit the growth of competing phytoplankton and thereby help enable this slowgrowing species to dominate; however, brevetoxins themselves do not appear to be responsible for this inhibition (10, 11). Recent studies support the hypothesis that brevetoxins serve as grazing deterrents, which promote population survival by decrea...

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Section: Discussionmentioning

confidence: 70%

Osmotic stress does not trigger brevetoxin production in the dinoflagellateKarenia brevis

Sunda

Burleson

Hardison

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…The frequency and cause of K. brevis blooms is important because this species produces a potent neurotoxin, brevetoxin. Brevetoxin has been associated with numerous negative water-quality impacts including marine mammal mortalities, extensive fish kills, human respiratory irritation, and illness in shellfish consumers (reviewed in Kirkpatrick et al 2004, Landsberg et al 2009, Fleming et al 2011, Brand et al 2012 as well as adverse socioeconomic problems. For example, economic losses associated with K. brevis blooms can reach $6.5 million per month to the tourism industry alone (2007 US dollars; Larkin & Adams 2007).…”

Section: Introductionmentioning

confidence: 99%

“…It is also common for Trichodesmium and Karenia brevis to co-occur, and correlations between Trichodesmium presence and K. brevis bloom events have been observed (Lenes et al 2001, Walsh & Steidinger 2001, Walsh et al 2006, Brand et al 2012 Bacterial populations within Karenia brevis blooms are also important to consider because bacteria serve as a nutrient source and sink, as well as potential predators and prey. In oligotrophic systems the balance between nutrient regenerators and competitors may be crucial to bloom initiation and proliferation (Bronk et al in press).…”

Section: Introductionmentioning

confidence: 99%

“…While we know that bacteria-algal interactions are common in aquatic systems, especially among harmful algal species, there is relatively little known about the role bacteria play in Karenia brevis growth (Kodama et al 2006, Jones et al 2010, Brand et al 2012. K. brevis has rarely, if ever, been successfully cultured axenically, suggesting that bacteria may be important for K. brevis growth.…”

Section: Introductionmentioning

confidence: 99%

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Trichodesmium-derived dissolved organic matter is a source of nitrogen capable of supporting the growth of toxic red tide Karenia brevis

Sipler¹,

Bronk²,

Seitzinger³

et al. 2013

Mar. Ecol. Prog. Ser.

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Dissolved organic nitrogen (DON) produced by the nitrogen-fixer Trichodesmium sp. has the potential to serve as a nitrogen source for the red tide dinoflagellate Karenia brevis. Dissolved organic matter (DOM) from laboratory cultures of Trichodesmium sp. was isolated, concentrated and then supplied as a nutrient source to K. brevis cells collected from the Gulf of Mexico. K. brevis abundance increased immediately after Trichodesmium sp. cellular exudate (TCE) addition, allowing the population to double within the first 24 h. There was rapid and complete utilization of the TCE DON as well as~89% of the TCE dissolved organic phosphorus (DOP). Additionally, terminal restriction fragment length polymorphism (TRFLP) was used to assess the bacterial community response to the addition of TCE . The number of bacterial operational taxonomic units (OTUs) initially increased after the TCE DOM addition, but decreased as K. brevis reached its maximum abundance. Electrospray ionization mass spectrometry (ESI-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to chemically characterize the DOM. Approximately 25% of compounds disappeared within the first 24 h, corresponding to the greatest increase in K. brevis abundance. Using FT-ICR MS, 391 DON and 219 DOP potentially bioavailable compounds were characterized. The bioavailable DON compounds were highly reduced and 44% had molar ratios indicative of lipid or protein-like compounds. The changes in DON concentration and compound composition show that Tricho desmium sp. provides a sufficient source of nitrogen to directly or indirectly support K. brevis blooms. KEY WORDS: Red tide · Trichodesmium · Karenia brevis · DON · FT-ICR MS · ESI-MSResale or republication not permitted without written consent of the publisher

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“…This globally distributed species, implicated in the formation of fish-killing blooms (22), is a particularly well-studied example (6,23,24) of dinoflagellates containing the light-harvesting carotenoid pigment fucoxanthin. The majority of photosynthetic dinoflagellates harbor red algal-derived chloroplasts, which contain the light-harvesting carotenoid pigment peridinin and have an unusual, highly reduced genome, which is fragmented into a number of small plasmid-like elements termed "minicircles" (4,11,(25)(26)(27).…”

mentioning

confidence: 99%

Functional remodeling of RNA processing in replacement chloroplasts by pathways retained from their predecessors

Dorrell

Howe

2012

Proc. Natl. Acad. Sci. U.S.A.

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Chloroplasts originate through the endosymbiotic integration of a host and a photosynthetic symbiont, with processes established within the host for the biogenesis and maintenance of the nascent chloroplast. It is thought that several photosynthetic eukaryotes have replaced their original chloroplasts with others derived from different source organisms in a process termed "serial endosymbiosis of chloroplasts." However, it is not known whether replacement chloroplasts are affected by the biogenesis and maintenance pathways established to support their predecessors. Here, we investigate whether pathways established during a previous chloroplast symbiosis function in the replacement chloroplasts of the dinoflagellate alga Karenia mikimotoi. We show that chloroplast transcripts in K. mikimotoi are subject to 3′ polyuridylylation and extensive sequence editing. We confirm that these processes do not occur in free-living relatives of the replacement chloroplast lineage, but are otherwise found only in the ancestral, red algalderived chloroplasts of dinoflagellates and their closest relatives. This indicates that these unusual RNA-processing pathways have been retained from the original symbiont lineage and made use of by the replacement chloroplast. Our results constitute an addition to current theories of chloroplast evolution in which chloroplast biogenesis may be radically remodeled by pathways remaining from previous symbioses.organelle | fucoxanthin | haptophyte | poly(U) | alveolate

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Karenia: The biology and ecology of a toxic genus

Cited by 182 publications

References 278 publications

Osmotic stress does not trigger brevetoxin production in the dinoflagellateKarenia brevis

Osmotic stress does not trigger brevetoxin production in the dinoflagellateKarenia brevis

Trichodesmium-derived dissolved organic matter is a source of nitrogen capable of supporting the growth of toxic red tide Karenia brevis

Functional remodeling of RNA processing in replacement chloroplasts by pathways retained from their predecessors

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