title: Development of a quantitative PCR method to explore the historical occurrence of a nuisance microalga under expansion.
abstract: A number of marine and freshwater harmful algal bloom (HAB) species have colonized new areas and expanded their habitat range in recent years. Nevertheless it is notoriously difficult to establish when colonization first occurred, what the dispersal routes are, and to separate recent invasion from increases in existent but small populations. The freshwater raphidophyte Gonyostomum semen is a nuisance species that has expanded its habitat range and increased in abundance in northern Europe during the past decades. To evaluate to what extent sediments can be used for determining historic occurrence of G. semen, a quantitative real-time PCR method for detecting cysts of this algae was developed. This paper presents a qPCR protocol with a set of primers that are specific to Gonyostomum and with PCR conditions optimized for sediment samples from humic lakes, which are the common habitat of G. semen. With this sensitive method as few as 1.6 cysts per PCR reaction could be reliably quantified, corresponding to 320 cysts per g wet weight sediment. Cysts were present in sediments with ages ranging from years to decades and their persistence allows detection of historic populations up to at least 50 years old. With this qPCR assay it will be possible to trace the presence of G. semen in environments prior to the onset of algae-specific monitoring programs as well as for quantification in water column samples.
authors.affiliation: Department of Biology, Aquatic Ecology, Lund University, Sweden; Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Sweden.
authors.forename: Karin S L
authors.initials: KS
authors.lastname: Johansson
authors.affiliation: Department of Biology, Aquatic Ecology, Lund University, Sweden.
authors.forename: Katharina
authors.initials: K
authors.lastname: Lührig
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, Sweden.
authors.forename: Jonatan
authors.initials: J
authors.lastname: Klaminder
authors.affiliation: Department of Biology, Aquatic Ecology, Lund University, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Rengefors
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D005060:Europe; D005618:Fresh Water; D057097:Harmful Algal Bloom; D060888:Real-Time Polymerase Chain Reaction; D058009:Stramenopiles / Q000235:genetics* / Q000502:physiology
keywords: Benthic cysts; Colonization; Gonyostomum semen; Invasion; Raphidophyceae; qPCR