On July 14th, 2023, from 12:30 to 13:30, in Amphitheater 9.1.1 (DEMaC), another edition of “Ocean Break,” a seminar series related to marine research conducted at CESAM, will take place.

This time, researcher Elisabet Cruz (CESAM/DFis) will address the topic: Transport Routes of Dinophysis acuta: From Portuguese Coasts to Galician Rias.

Blooms of Dinophysis acuta are common every year in the waters of the Northwestern Iberian Peninsula, from late summer to early autumn, and are associated with outbreaks of diarrhetic shellfish poisoning (DSP) that prohibit the harvesting of mussels in Europe’s most important production area, the Galician Rias Baixas (GRB). In this area, two hypotheses are considered for the presence of D. acuta, one due to local growth and the other related to the transport northwards of blooms originating on the Portuguese coast. The combination of these two processes can result in high cell concentrations within the GRB.

Based on D. acuta cell counts collected weekly by the Galician Monitoring Program (INTECMAR) and the Portuguese Monitoring Program (IPMA), two years, 2015 and 2017, were selected. In these two years, D. acuta cells were detected in the waters of both Galicia and Portugal, but in 2017, cells were not observed in two transit areas from Portugal to Galicia. To understand if there was D. acuta cell transport, under which conditions this transport was favored, and on what time scales it occurred, we used a Lagrangian model, ROMSPath v1.0.1. Ocean current fields every two hours were used to run ROMSPath, obtained through the execution of a bidirectional nesting hydrodynamic model, CROCO (a new version of ROMS-AGRIF). The model configuration has three nested domains, with horizontal resolutions of 1.6 km, 500 m, and 180 m, with the highest resolution domain covering the Galician Rias Baixas. These two analyzed years show contrasting results. In 2015, southerly winds blew in late August, allowing some particles to reach the Galician Rias Baixas and circulate internally. In contrast, in 2017, northerly winds prevailed during August, preventing the transport of D. acuta from Aveiro (Portugal) to the Galician Rias Baixas.

Lagrangian models are useful tools for studying the paths followed by these cells in places where weekly sampling is not available and for selecting better locations to sample D. acuta cells.

This seminar is a joint organization between three research groups from CESAM: CDEC (Ecology and Conservation of Coastal and Deep-Sea Ecosystems), MBA (Marine Biotechnology and Aquaculture), and POMG (Physical Oceanography and Marine Geology). Entry is free for all interested parties.