Applied simulations and Integrated modeling for the understanding of toxic and harmful algal blooms

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Mesoscale dynamics and niche segregation of two Dinophysis species in Galician-Portuguese coastal waters

Publication . Díaz, Patricio; Reguera, Beatriz; Calixto De Jesus Moita Garnel, Maria Teresa; Bravo, Isabel; Ruiz-Villarreal, Manuel; Fraga, Santiago

Blooms of Dinophysis acuminata occur every year in Galicia (northwest Spain), between spring and autumn. These blooms contaminate shellfish with lipophilic toxins and cause lengthy harvesting bans. They are often followed by short-lived blooms of Dinophysis acuta, associated with northward longshore transport, at the end of the upwelling season. During the summers of 1989 and 1990, dense blooms of D. acuta developed in situ, initially co-occurring with D.acuminata and later with the paralytic shellfish toxin-producer Gymnodiniumcatenatum. Unexplored data from three cruises carried out before, during, and following autumn blooms (13⁻14, 27⁻28 September and 11⁻12 October) in 1990 showed D. acuta distribution in shelf waters within the 50 m and 130 m isobaths, delimited by the upwelling front. A joint review of monitoring data from Galicia and Portugal provided a mesoscale view of anomalies in SST and other hydroclimatic factors associated with a northward displacement of the center of gravity of D. acuta populations. At the microscale, re-examination of the vertical segregation of cell maxima in the light of current knowledge, improved our understanding of niche differentiation between the two species of Dinophysis. Results here improve local transport models and forecast of Dinophysis events, the main cause of shellfish harvesting bans in the most important mussel production area in Europe.

2019-01Journal article

Open access

Toward predicting Dinophysis blooms off NW Iberia: a decade of events

Publication . Moita, Maria Teresa; Pazos, Yolanda; Rocha, Carlos; Nolasco, Rita; Oliveira, Paulo B.

Dinophysis acuminata and Dinophysis acuta are recurrent species off NW Iberia but their outbreaks occur under different conditions. A decade (2004-2013) of weekly data for each species at two sentinel stations located at the entrance of Rias de Aveiro-AV (NW Portugal, 40 degrees 38.6' N) and Pontevedra-PO (Galicia, Spain, 42 degrees 21.5' N), were used to investigate the regional synchronism and mesoscale differences related to species detection, bloom (>200 cells L-1) initiation and development. Results highlight the high interannual variability of bloom events and summarize the associated meteorological/oceanographic conditions. D. acuta blooms were observed in 2004-2008 and 2013, and the species highest maxima at AV occurred after the highest maxima of its prey Mesodinium, with a time-lag of 2-3 weeks. D. acuminate blooms were observed every year at both stations. The cell concentration time series shows that the blooms generally present a sequence starting in March with D. acuminata in PO and three weeks later in AV, followed by D. acuta that starts at AV and three months later in PO. Exceptionally, D. acuminate blooms occurred earlier at AV than PO, namely in high spring upwelling (2007) or river runoff (2010) years. A four-year gap (2009-2012) of D. acuta blooms occurred after an anomalous 2008 autumn with intense upwelling which is interpreted as the result of an equatorward displacement of the population core. Numerical model solutions are used to analyze monthly alongshore current anomalies and test transport hypotheses for selected events. The results show a strong interannual variability in the poleward/equatorward currents associated with changes in upwelling forcing winds, the advection of D. acute blooms from AV to PO and the possibility that D. acuminata blooms at AV might result from inocula advected southward from PO. However, the sensitivity of the results to vertical position of the lagrangian tracers call for more studies on species distribution at the various bloom stages. (C) 2015 Elsevier B.V. All rights reserved.

2016-07Journal article

Open access