Muestreo de fitoplancton para extracción de PUA (Aldehídos Volatiles Poliinsaturados)

Metodología para obtener muestras de fitoplancton para posterior extracción, caracterización y cuantificación de Aldehídos volátiles insaturados

Types and Distribution of Bioactive Polyunsaturated Aldehydes in a Gradient from Mesotrophic to OligotrophicWaters in the Alborán Sea (Western Mediterranean)

Polyunsaturated aldehydes (PUAs) are bioactive molecules suggested as chemical defenses and infochemicals. In marine coastal habitats, diatoms reach high PUA production levels during bloom episodes. Two fractions of PUA can usually be analyzed: pPUA obtained via artificial breakage of collected phytoplankton cells and dissolved PUA already released to the environment (dPUA). In nature, resource supply arises as a main environmental controlling factor of PUA production. In this work, we monitored the vertical distribution and daily variation of pPUA associated with large-size phytoplankton and dPUA, at three sites located in the Alboran Sea from mesotrophic to oligotrophic waters. The results corroborate the presence of large-size PUA producers in oligotrophic and mesotrophic waters with a significant (58%-85%) diatom biomass. In addition to diatoms, significant correlations between pPUA production and dinoflagellate and silicoflagellate abundance were observed. 2E,4E/Z-Heptadienal was the most abundant aldehyde at the three sites with higher values (17.1 fg center dot cell(-1)) at the most oligotrophic site. 2E,4E/Z-Decadienal was the least abundant aldehyde, decreasing toward the oligotrophic site. For the first time, we describe the daily fluctuation of pPUA attributable to cellular physiological state and not exclusively to taxonomical composition. Our results demonstrate the persistence of threshold levels of dPUA deep in the water column, as well as the different chromatographic profiles of dPUA compared with pPUA. We propose different isomerization processes that alter the chemical structure of the released PUAs with unknown effects on their stability, biological function, and potential bioactivity

A Lagrangian approach to the Atlantic Jet entering the Mediterranean Sea: Physical and biogeochemical characterization

The temporal evolution of the physical and biogeochemical properties of the Atlantic Jet (AJ) along the first similar to 75 m of the water column during a 4-day journey was analysed by following the trajectory of a drifter dragged by the jet from the Strait of Gibraltar towards the Alboran Sea. Three stages were differentiated based on the evolution of several variables (e.g., velocity, temperature, nutrients, fluorescence). (i) Within the Strait of Gibraltar, the water column was primarily influenced by the tidal cycle, leading to a nutrient-enrichment of surface waters. However, due to the short residence time, the phytoplankton community that was mainly dominated by diatoms, did not demonstrate significant changes. (H) Once outside the Strait, the drifter trajectory was mainly influenced by the frontal dynamics associated with the AJ. The drifter moved forward along the jet but also laterally across it and was continuously attracted to the mainstream (maximum current speed) or detached to its southern edge (minimum current speed). Due to the associated upwelling processes induced by the intensification of the current along the mainstream, the water column was characterized by colder, nutrient-richer water and lower fluorescence values. Conversely, along the southern edge of the jet, the water column was characterized by higher temperature, low nutrient concentration, and higher fluorescence. Along the first stations of this stage, diatom total abundance and biovolume continuously increased, reaching values similar to 12-times higher than the initial concentrations. (Hi) In the last stage, the water parcel was still influenced by the frontal dynamics but with less intensity. Additionally, the colder and denser water of the AJ and the associated phytoplankton community subducted progressively as it moved into the region surrounded by warmer waters. Concomitantly, fluorescence and diatoms total abundance and biovolume decreased and were influenced by the decline of nutrient availability and the increase of mesozooplankton. Our results reveal the coupled processes induced by the entrance of the AJ in the Alboran Sea and highlight the strong control of the physical environment over the ecological processes in this region.The authors gratefully acknowledge the officers, crew and technical staff of the R.V. Sarmiento de Gamboa for their altruistic help during the cruise, all the scientific team that participated in the MEGAN campaign collecting the different datasets, Manuel Arjonilla for nutrient sample measurements, and Reyes Garcia for her collaboration in the treatment of plankton samples. They also thank the Copernicus Marine Environmental Monitoring Service for providing access to satellite data. Neural network analyses were performed in the facilities of the Area de Sistemas de Informacion de la Universidad de Cadiz (https://supercomputacion.uca.es).Finally, the authors acknowledge Sara Soria Piriz (@nautillustrations) for the drawing of the conceptual diagram in Fig. 10. Comments provided by two anonymous reviewers substantially improved subsequent versions of the manuscript. The Spanish National Research Plan through project CTM2013-49048 has supported this work. Iria Sala and Marina Bolado-Penagos were supported by a grant of the FPI fellowship program, Spain. To accomplish this work, Iria Sala carried out a short-term stay with the research group Dinamica del Ecosistema Planctonico at the Instituto Espanol de Oceanografia de Gijon, under the supervision of Dr Angel Lopez-Urrutia, supported by a grant of the FPI fellowship program