Researchers from the Marine Research Center of the University of Vigo, the Spanish Institute of Oceanography and the Spanish Council for Scientific Research are developing the scientific project Remedios (RolE of Mixing on phytoplankton bloom initiation, maintEnance and DIssipatiOn in the Galician estuaries, ) which aims to determine the role of turbulence in the growth of toxic phytoplankton that causes red tides in Galician estuaries. The study, funded by the Ministry of Economy and Competitiveness, started at the beginning of 2017 and will be carried out until the end of 2019, coordinated by researchers Beatriz Mouriño, from the University’s Biological Oceanography Group, and Enrique Nogueira, from the IEO-Vigo. Together with these organizations, the Technological Institute for the Control of the Marine Environment of Galicia (Intecmar), the University of Southampton (United Kingdom), Ifremer (France) and the Scripps Institution of Oceanography (USA) are part of the project..
The Remedios project was born as a multidisciplinary initiative that brings together more than twenty scientists who, over the next three years, will make observations in the Galician estuaries, analyze databases and use mathematical models in order to investigate the role of mixing in the growth of phytoplankton. Special attention will be paid to the genera Dinophysis and Pseudo-nitzschia and their aggregation in the form of thin layers of phytoplankton. The experts are confident that their results will contribute to the prediction and early warning of toxicity events in the region and, consequently, to mitigating their socioeconomic impact.
Thin layers of phytoplankton, a challenge for toxicity detection
The Galician estuaries are one of the most productive coastal regions on the planet, being responsible for 95% of the national mussel production and 50% of the European production. This is mainly a consequence of the nutrient input associated with the Iberian outcrop, which stimulates the growth of phytoplankton, composed of microalgae. The researcher Bea Mouriño-Carballido, responsible for one of the two parts of the study, explains that “the growth of these microscopic algae is determined by the amount of light and nutrients they receive, which, in turn, depends on the mixing of the water column”. However, quantifying the intensity of mixing in the natural environment is extremely complex, “and requires specific equipment that was not available until recently”, she adds. But although they are responsible for this natural wealth, the researchers remember that not all phytoplankton species are favorable for the productivity of the estuaries. For example, “species of the genera Dinophysis and Pseudo-nitzschia, due to the production of diarrheal (DSP) and amnesic (ASP) toxins, respectively, are responsible for prolonged closures in mussel extraction,” says Enrique Nogueira, a researcher at the Spanish Institute of Oceanography who is coordinating the other part of the study. Frequently, the expert explains, these species aggregate to form “thin layers,” which are less than 5 meters thick and can reach a horizontal extension of several kilometers. According to Nogueira, “the formation of these structures poses a challenge for toxicity detection programs, since, due to their small thickness, they very easily go unnoticed.” For this reason, the study of these thin layers will be one of the central parts of the REMEDIOS project, whose ultimate purpose will be to understand the processes of formation of red tides caused by toxic phytoplankton, in order to be able to develop prediction and warning systems in order to reduce their impact.
Sample collection and laboratory work
The project is divided into several parts, one of which focuses on the collection and analysis of samples and the other on the study of existing databases. From the beginning of the year until next spring, the team has been carrying out weekly sampling at a central station in the Vigo estuary aboard the Kraken, an ECIMAT vessel. Part of the samples collected are analysed at the IEO in Vigo, which coordinates the biological part of the study, and another part in the laboratories of the Biological Oceanography Group, in Citexvi, which focuses on the more physical part. Once this first year of sampling is over, a specific three-week campaign will start in the spring to study the thin layers of phytoplankton, in which they will use a larger boat that will carry out sampling in the Vigo and Pontevedra estuaries. Once the sampling period is over, the researchers will focus on the analysis of the samples and the processing of the data.
In parallel, the project also includes the analysis of existing databases, including the set of hydrographic data obtained by Intecmar, which collects samples every week at 43 stations spread across the estuaries to monitor water quality. Thanks to these data, the researchers of the Remedios project were able to determine that in the period 2012-2015 a total of 215 thin layers were observed in the four Rías Baixas, with the highest incidence in the Pontevedra estuary, which is also the one that suffers the longest periods of closure of mussel extraction due to the presence of diarrheal toxins.
I work with ocean models
One of the objectives of the project is to investigate the mechanisms responsible for the formation of thin phytoplankton layers (TPL). To do this, researchers from the University of Vigo use the ROMS ocean circulation model, coupled with the Pisces biogeochemical model, to represent the Vigo and Pontevedra estuaries at a high spatial resolution (150 m). In this way, the conditions of the ocean are reproduced before, during and after a moment in which observations made from the boat detected a TPL. For example, if on a given date several TPL were detected in both estuaries, the model allows scientists to investigate what conditions were common to both that could have led to the formation of the TPL. In other words, thanks to these validated models, scientific teams can understand what is happening in the sea without going to sea.
Source: duvi
