Examination of the Seasonal Dynamics of the Toxic Dinoflagellate Alexandrium catenella at Redondo Beach, California, by Quantitative PCR

Abstract

The presence of neurotoxic species within the genus Alexandrium along the U.S. coastline has raised concern of potential poisoning through the consumption of contaminated seafood. Paralytic shellfish toxins (PSTs) detected in shellfish provide evidence that these harmful events have increased in frequency and severity along the California coast during the past 25 years, but the timing and location of these occurrences have been highly variable. We conducted a 4-year survey in King Harbor, CA, to investigate the seasonal dynamics of Alexandrium catenella and the presence of a particulate saxitoxin (STX), the parent compound of the PSTs. A quantitative PCR (qPCR) assay was developed for quantifying A. catenella in environmental microbial assemblages. This approach allowed for the detection of abundances as low as 12 cells liter ؊1 , 2 orders of magnitude below threshold abundances that can impact food webs. A. catenella was found repeatedly during the study, particularly in spring, when cells were detected in 38% of the samples (27 to 5,680 cells liter ؊1 ). This peak in cell abundances was observed in 2006 and corresponded to a particulate STX concentration of 12 ng liter ؊1 , whereas the maximum STX concentration of 26 ng liter ؊1 occurred in April 2008. Total cell abundances and toxin levels varied strongly throughout each year, but A. catenella was less abundant during summer, fall, and winter, when only 2 to 11% of the samples yielded positive qPCR results. The qPCR method developed here provides a useful tool for investigating the ecology of A. catenella at subbloom and bloom abundances.

Short‐term displacement of Planktothrix rubescens (cyanobacteria) in a pre‐alpine lake observed using an autonomous sampling platform

“…For each depth, two 400 mL volumes were filtered through glass fiber filter membranes. The filters were processed as crude lysates, as in Garneau et al (2011), and filtered through a 0.22 mm, low-binding cellulose acetate syringe-tip filters to efficiently remove cellular debris and filter remnants. The P. rubescens filaments were quantified following the qPCR TaqMan assay on the 16S ribosomal deoxyribonucleic acid (rDNA) gene developed by Ostermaier and Kurmayer (2009).…”

Molecular discrimination of toxic and non-toxicAlexandriumspecies (Dinophyta) in natural phytoplankton assemblages from the Scottish coast of the North Sea

“…Garneau et al (2011) reported a rather weak correlation (r s ¼ 0.54, P < 0.0001) in a study on PSPtoxigenic A. catenella (Group I) from California, based upon a similar number of samples (n ¼ 91). In Garneau et al's study, the highest peak in cell numbers did not match the highest amount of measured PSP toxin in the samples and sometimes the Alexandrium cells detected and the toxin concentration did not match at all.…”

“…There has been extensive application of various qPCR methods to determine changes in phytoplankton communities (Handy et al, 2006(Handy et al, , 2008 and they have also been used successfully for the detection of harmful microalgae (e.g. Galluzzi et al, 2004;Dyhrman et al, 2006;Touzet et al, 2009;Garneau et al, 2011), including cysts of Alexandrium spp. (Kamikawa et al, 2005(Kamikawa et al, , 2007, in laboratory cultures and field samples.…”

“…Dyhrman et al (2006) designed a genus-specific forward primer for Alexandrium and employed an oligonucleotide (NA1, Anderson et al, 1999) specific for the A. tamarense Group I as a reverse primer in a SYBR Green qPCR assay. Touzet et al (2009) designed a qPCR assay based on a hybridization probe specific for A. minutum (Global clade), whereas Garneau et al (2011) developed a qPCR assay with a molecular beacon to specifically detect A. catenella Group I. Very recently, Murray et al (2011) developed a SYBR green qPCR assay to detect and quantify a gene (sxtA) purportedly involved in the synthesis of saxitoxin, one of the key PSP toxins.…”

Approaches for the detection of harmful algal blooms using oligonucleotide interactions

“…The expanse of this real-time PCR research has been significant, with a number of methods being reported for dinoflagellates, diatoms and members of Raphidophyceae, Haptophyceae, Pelagophyceae and Cyanophyceae [61]. Applications directed at the detection of Alexandrium species such as A. catenella [62][63][64][65][66], A. minutum [26,67], A. fundyense [68,69], A. taylori [64] and A. tamarense [62,63,70] have been thoroughly reported. Similarly, real-time PCR methods were developed for the dinoflagellate species Dinophysis acuta and D. acuminata [71].…”