title: Climate variability and Dinophysis acuta blooms in an upwelling system.
abstract: Dinophysis acuta is a frequent seasonal lipophilic toxin producer in European Atlantic coastal waters associated with thermal stratification. In the Galician Rías, populations of D. acuta with their epicentre located off Aveiro (northern Portugal), typically co-occur with and follow those of Dinophysis acuminata during the upwelling transition (early autumn) as a result of longshore transport. During hotter than average summers, D. acuta blooms also occur in August in the Rías, when they replace D. acuminata. Here we examined a 30-year (1985-2014) time series of D. acuta from samples collected by the same method in the Galician Rías. Our main objective was to identify patterns of distribution and their relation with climate variability, and to explain the exceptional summer blooms of D. acuta in 1989-1990. A dome-shaped relationship was found between summer upwelling intensity and D. acuta blooms; cell maxima were associated with conditions where the balance between upwelling intensity and heating, leading to deepened thermoclines, combined with tidal phase (3 days after neap tides) created windows of opportunity for this species. The application of a generalized additive model based on biological (D. acuta inoculum) and environmental predictors (Cumulative June-August upwelling CUIJJA, average June-August SSTJJAand tidal range) explained more than 70% of the deviance for the exceptional summer blooms of D. acuta, through a combination of moderate (35,000-50,000m3s-1km-1) summer upwelling (CUIJJA), thermal stratification (SSTJJA>17°C) and moderate tidal range (∼2.5m), provided D. acuta cells (inoculum) were present in July. There was no evidence of increasing trends in D. acuta bloom frequency/intensity nor a clear relationship with NAO or other long-term climatic cycles. Instead, the exceptional summer blooms of 1989-1990 appeared linked to extreme hydroclimatic anomalies (high positive anomalies in SST and NAO index), which affected most of the European Atlantic coast.
authors.affiliation: Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Vigo, Subida a Radio Faro 50, 36390 Vigo, Spain; Programa de Investigación Pesquera & Instituto de Acuicultura, Universidad Austral de Chile, PO Box 1327, Los Pinos s/n, Balneario Pelluco, Puerto Montt, Chile. Electronic address: patriciodiaz@uach.cl.
authors.forename: Patricio A
authors.initials: PA
authors.lastname: Díaz
authors.affiliation: Instituto Español de Oceanografía (IEO), Centro Oceanográfico de A Coruña, Muelle das Ánimas s/n, 15001 A Coruña, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Ruiz-Villarreal
authors.affiliation: Instituto Tecnolóxico para o Control do Medio Mariño de Galicia (INTECMAR), Peirao de Vilaxoán s/n, 36611 Vilagarcía de Arousa, Pontevedra, Spain.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Pazos
authors.affiliation: Instituto Português do Mar e da Atmosfera (IPMA), Av. Brasília, 1449-006 Lisboa, Portugal.
authors.forename: Teresa
authors.initials: T
authors.lastname: Moita
authors.affiliation: Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Vigo, Subida a Radio Faro 50, 36390 Vigo, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Reguera
mesh_terms: D001267:Atlantic Ocean; D002980:Climate; D004141:Dinoflagellida / Q000502:physiology*; D004784:Environmental Monitoring; D008954:Models, Biological; D011174:Portugal; D012623:Seawater; D014872:Water Movements
keywords: Climate anomalies; Dinophysis acuta; Exceptional summer blooms; Galician Rías; Thermal stratification; Upwelling intensity