title: Role of resting cysts in Chilean Alexandrium catenella dinoflagellate blooms revisited.
abstract: The detection of sparse Alexandrium catenella-resting cysts in sediments of southern Chilean fjords has cast doubts on their importance in the recurrence of massive toxic dinoflagellate blooms in the region. The role of resting cysts and the existence of different regional Chilean populations was studied by culturing and genetic approaches to define: (1) cyst production; (2) dormancy period; (3) excystment success; (4) offspring viability and (5) strain mating compatibility. This study newly revealed a short cyst dormancy (minimum 69 days), the role of key abiotic factors (in decreasing order salinity, irradiance, temperature and nutrients) controlling cyst germination (max. 60%) and germling growth rates (up to 0.36-0.52div.day-1). Amplified fragment length polymorphism (AFLP) characterization showed significant differences in genetic distances (GD) among A. catenella populations that were primarily determined by the geographical origin of isolates and most likely driven by oceanographic dispersal barriers. A complex heterothallic mating system pointed to variable reproductive compatibility (RCs) among Chilean strains that was high among northern (Los Lagos/North Aysén) and southern populations (Magallanes), but limited among the genetically differentiated central (South Aysén) populations. Field cyst surveys after a massive 2009 bloom event revealed the existence of exceptional high cyst densities in particular areas of the fjords (max. 14.627cystscm-3), which contrast with low cyst concentrations (<221.3cystscm-3) detected by previous oceanographic campaigns. In conclusion, the present study suggests that A. catenella resting cysts play a more important role in the success of this species in Chilean fjords than previously thought. Results from in vitro experiments suggest that pelagic-benthic processes can maintain year-round low vegetative cell concentrations in the water column, but also can explain the detection of high cysts aggregations after the 2009-bloom event. Regional drivers that lead to massive outbreaks, however, are still unknown but potential scenarios are discussed.
authors.affiliation: Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia. Electronic address: jorge.mardones@utas.edu.au.
authors.forename: Jorge I
authors.initials: JI
authors.lastname: Mardones
authors.affiliation: Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Bolch
authors.affiliation: Instituto de Fomento Pesquero, IFOP, Balmaceda 252, Puerto Montt 5480000, Chile.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Guzmán
authors.affiliation: Centro i-mar, Universidad de los Lagos, Casilla 557, Puerto Montt, Chile; Facultad de Ciencias del Mar, Departamento de Biología Marina, Programa de Doctorado en Biología y Ecología Aplicada, Universidad Católica del Norte, Chile.
authors.forename: Javier
authors.initials: J
authors.lastname: Paredes
authors.affiliation: Centro i-mar, Universidad de los Lagos, Casilla 557, Puerto Montt, Chile.
authors.forename: Daniel
authors.initials: D
authors.lastname: Varela
authors.affiliation: Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia.
authors.forename: Gustaaf M
authors.initials: GM
authors.lastname: Hallegraeff
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D002677:Chile; D004141:Dinoflagellida / Q000166:cytology / Q000502:physiology*; D063366:Estuaries; D005068:Eutrophication / Q000502:physiology*
keywords: AFLPs; Alexandrium catenella; Chilean cysts field data; Excystment; Mandatory dormancy; Mating compatibility/encystment