The research is based on data obtained from the Remedios project, led by Beatriz Mouriño. Understanding phytoplankton dynamics is key to improving the prediction and management of harmful algal blooms
The Marine Research Centre (CIM) of the University of Vigo collaborated with the Vigo Oceanographic Centre of the Spanish Institute of Oceanography (IEO, CSIC) and the French Research Institute for Exploitation of the Sea (Ifremer) on a study that defines the ecological niche —the set of environmental conditions, biotic relationships and functions that determine the role each species plays within an ecosystem— of several phytoplankton species responsible for harmful algal blooms (HABs) in the Rías Baixas.
Specifically, the work stems from the PhD thesis of Esther Velasco Senovilla, presented in 2025 במסגרת the DoMar Programme at the University of Vigo, and used data from the Remedios project, led by CIM researcher Beatriz Mouriño from the Biological Oceanography group.
The study, recently published in the journal Harmul Algae, focuses on microalgae species frequently forming harmful algal blooms in the area, with potential impacts on public health and shellfish harvesting: Alexandrium minutum, Dinophysis acuminata and Pseudo-nitzschia spp., which produce paralytic (PSP), diarrhetic (DSP) and amnesic (ASP) toxins, respectively.
High-resolution observations
The study uses high-resolution vertical observations, including phytoplankton samples collected using the “Fine-Scale Sampler” designed at Ifremer. This system allows 15 samples to be taken simultaneously at 20 cm intervals without disturbing their natural distribution, enabling real-time targeted sampling of layers of interest. This technology made it possible to detect oceanic structures and organism aggregations that go unnoticed in conventional monitoring programmes, where water samples are collected at intervals of several metres.
The results provide a detailed description of the specific microhabitats of the target species. While D. acuminata and Pseudo-nitzschia spp. proliferate closely linked to coastal upwelling circulation dynamics —a process in which deep, nutrient-rich waters rise to the surface— and to the formation of thermoclines (thermal stratification), A. minutumpredominates in sheltered areas or “upwelling shadows” and proliferates following periods of heavy spring rainfall and the formation of a thin (5–6 m) warmer, lower-salinity surface layer (thermohaline stratification), with properties markedly different from the underlying water. However, these species do not exist in isolation and must compete with accompanying species that have their own adaptive strategies.
“The description of the vertical microstructure of the water column and the formation of multiple microhabitats separated by just a few tens of centimetres is key to understanding the coexistence of phytoplankton species with different adaptations for exploiting shared resources,” explains Velasco Senovilla, researcher at the Vigo Oceanographic Centre of the IEO and lead author of the study.
It was observed that Pseudo-nitzschia spp. and A. minutum may occur simultaneously but occupy different water layers where they exploit their specific traits. These findings provide a fundamental scientific basis for improving early warning systems and the management of precautionary closures of shellfish harvesting, by more precisely identifying the conditions that favour each type of bloom. “This work highlights the importance of integrating multiple scales —temporal, spatial and functional— in phytoplankton studies, with particular emphasis on adaptive strategies and physico-biological interactions of species that pose a significant natural risk to the sustainable exploitation of marine resources in the Rías Baixas,” the author concludes.
Institutional collaboration
The study also highlights the value of collaboration between institutions and the role of oceanographic campaigns, such as that conducted במסגרת the Remedios project, in generating knowledge for the sustainable management of marine ecosystems.
The campaign was carried out in 2018 over three weeks aboard the oceanographic vessel Ramón Margalef. The international team, led by CIM researcher Beatriz Mouriño, conducted several research lines to analyse the factors triggering phytoplankton growth and the importance of mixing between different ocean layers.
The CIM holds the CIGUS recognition from the Xunta de Galicia, certifying the quality and impact of its research, and its activities are co-funded by the European Union through the ERDF 2021–2027 Programme.
Source: DUVI
