The role of abiotic and biotic mechanisms controlling the dynamics of the dissolved organic matter in pelagic ecosystem (NW Mediterranean)

Memoria de tesis doctoral presentada por Elvia Denisse Sánchez Pérez para obtener el título de Doctora en Oceanographie por la Université Pierre et Marie Curie (UPMC), realizada bajo la dirección del Dr Pascal Conan de la Université Pierre et Marie Curie (UPMC) y de la Dra. Celia Marrasé Peña del Institut de Ciències del Mar (ICM-CSIC).-- 156 pages[EN] Chromophoric dissolved organic matter (CDOM) is a major fraction of dissolved organic matter (DOM). CDOM absorbs light over a broad range of ultraviolet (UV-R) and visible wavelengths. A small fraction of CDOM can emit fluorescence when excited by ultraviolet radiation; so called fluorescent dissolved organic matter (FDOM). CDOM plays a key role in regulating light penetration into the ocean, absorbing high-energy electromagnetic spectrum (visible and ultraviolet light) waves. On one hand, it protects aquatic organisms of potential photo-damage; in the other hand it induces a negative effect by reducing light for photosynthesis. [...][FR] La matière organique dissoute chromophorique (CDOM) est une fraction significative du pool global de matière organique dissoute (MOD) dans les océans. La CDOM absorbe une partie de la lumière dans le domaine du rayonnement ultraviolet (UV-R) et du visible. Une fraction de cette CDOM peut émettre une fluorescence lorsqu'elle est excitée par un UV-R. Cette fraction est alors appelée matière organique dissoute fluorescente (FDOM). La CDOM a donc d'une part, un effet positif, en protégeant les cellules contre les dommages causés par les UV-R, mais d'autre part, un effet négatif en réduisant la quantité de radiation disponible pour la photosynthèse. [...]Peer Reviewe

Los aportes de aerosoles afectan las propiedades ópticas de la materia orgánica disuelta en las aguas costeras del Mediterráneo Noroccidental

10 pages, 6 figures, 1 table[EN] Aeolian inputs of organic and inorganic nutrients to the ocean are important as they can enhance biological production in surface waters, especially in oligotrophic areas like the Mediterranean. The Mediterranean littoral is particularly exposed to both anthropogenic and Saharan aerosol depositions on a more or less regular basis. During the last few decades experimental studies have been devoted to examining the effect of inorganic nutrient inputs from dust on microbial activity. In this study, we performed experiments at two different locations of the NW Mediterranean, where we evaluated the changes in the quality and quantity of dissolved organic matter due to atmospheric inputs of different origin (Saharan and anthropogenic) and its subsequent transformations mediated by microbial activities. In both experiments the humic-like and protein-like substances, and the fluorescence quantum yield increased after addition. In general, these changes in the quality of dissolved organic matter did not significantly affect the prokaryotes. The recalcitrant character of the fluorescent dissolved organic matter (FDOM) associated with aerosols was confirmed, as we found negligible utilization of chromophoric compounds over the experimental period. We framed these experiments within a two-year time series data set of atmospheric deposition and coastal surface water analyses. These observations showed that both Saharan and anthropogenic inputs induced changes in the quality of organic matter, increasing the proportion of FDOM substances. This increase was larger during Saharan dust events than in the absence of Saharan influence[ES] Los aportes atmosféricos de nutrientes orgánicos e inorgánicos al océano son importantes ya que pueden aumentar la producción biológica en aguas superficiales, especialmente en las zonas oligotróficas como el Mediterráneo. El litoral del Mediterráneo está particularmente expuesto a aportes de origen antropogénico y a deposiciones de polvo sahariano de forma más o menos regular. Durante las últimas décadas los estudios experimentales se han dedicado, sobre todo, a examinar el efecto de la entrada de nutrientes inorgánicos atmosféricos sobre la actividad microbiana. En este estudio, se realizaron experimentos con comunidades microbianas procedentes de dos zonas del Mediterráneo noroccidental. Se evaluaron los cambios en la calidad y cantidad de la materia orgánica disuelta debido a aportes atmosféricos de distinto origen y sus posteriores transformaciones mediadas por actividades microbianas. En ambos experimentos las sustancias orgánicas fluorescentes y el rendimiento cuántico de fluorescencia aumentaron después de la adición de material atmosférico. En general, estos cambios en la calidad de la materia orgánica no afectaron significativamente a los organismos procariotas. El carácter recalcitrante de la materia orgánica disuelta fluorescente (FDOM) contenida en los aerosoles se confirmó ya que la utilización de compuestos cromóforos durante el período experimental fue insignificante. Los resultados obtenidos se contextualizan en relación con una serie temporal de dos años de datos adquiridos de deposición atmosférica y análisis de agua superficial costera. La variabilidad temporal de estas dos variables mostró que tanto los aportes saharianos como antropogénicos provocaron cambios en la calidad de la materia orgánica disuelta en aguas superficiales, incrementando la fracción fluorescente. Éste aumento resultó ser mayor durante eventos de polvo sahariano que en ausencia de ellosThis study was supported by the projects 1179-1198. ADEPT (CTM2011-23458), DOREMI (CTM2012-342949) and ANIMA (CTM2015-65720-R MINECO/FEDER, UE). E.D. Sánchez-Pérez would like to thank the Consejo Nacional de Ciencia y Tecnologia (CONACyT) for their financial support through a PhD fellowship. I. Marín thanks the FPI Spanish scholarship programme for its support (BES 2012-052976)Peer Reviewe

Spatial and temporal variability of CDOM fluorescence in a coastal station (NW Mediterranean)

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainWe performed a multi-parameter monitoring during 14 months from February 2013 through April 2014 in a coastal station (NW Mediterranean). We studied the temporal variability of dissolved organic matter (DOC) in relation to changes in abiotic and biotic variables. The production of fluorescent dissolved organic matter (FDOM) peaked in winter, and the highest concentrations of FDOM humic-like compounds coincided with decreases of salinity, indicating a notable fresh-water contribution to the organic matter pool. The significant linear relationship between humic-like FDOM peak and Silicate concentration (r2=0.72 n=60 p <0.05) also reveals the importance of ground water inputs in the quality of dissolved organic matter. DOC concentrations showed its maxima in late spring and summer (probably because of a low bacterial activity associated to nutrient limitation). These DOC maxima in warm periods did not coincide with the FDOM peaks maxima as we could anticipate due to the photolability of FDOM compounds. We discuss the relative importance of bacterial activity, light conditions and fresh water inputs on FDOM temporal variabilityPeer Reviewe

Variabilité saisonniere de la matière organique dissoute colorée en zone mediterranéenne côtière

40th CIESM Congress: The largest Forum on Mediterranean and Black Sea Research, 28 October - 1 November 2013, Marseille, France.-- 1 page, 1 figureUn suivi multiparamétrique de 8 mois sur une station côtière (golfe du Lion, Méditerranée Nord occidentale) permet de décrire la variabilité saisonnière de la matière organique dissoute colorée (CDOM) et de préciser son origine et son devenir. Au cours du cycle saisonnier, la concentration de la CDOM permet de montrer l'importance dominante des apports continentaux par rapport à la production autochtone de matière, même lors du développement d'efflorescences phytoplanctoniques et de montrer l'importance relative de l'exportation vis à vis des consommations par le compartiment bactérienPeer reviewe

Distribution of water masses in the tropical-subtropical convergence off Mexico, using an autonomous profiler (2017–2021)

8 pages, 1 table, 7 figuresData from an autonomous ARGO float launched on December 26, 2016, south of the entrance of the Gulf of California, reveal variations in the distribution of water masses in the tropical-subtropical convergence off Mexico. The float trajectory drifted through three areas of distinct characteristics: i) the southern Gulf of California in January 2017, ii) south of Cabo San Lucas from February 2017 to January 2018, when the float crossed an eddy, and iii) off Cabo Corrientes from February 2018 to April 2021. During the sampling, the vertical distribution of the water masses showed for the first time with “in situ” data a semiannual variability mainly in the salinity as response to poleward propagating semiannual Kelvin wave. The surface water masses had potential densities 25 kg m−3) at times extended up to only 20 m below surface in the three areas around the summer as part of a semiannual cycle. The intermittent presence of this oxygen-deficient water close to the surface (∼ 20 m depth) is consistent with the on-going expansion of the shallow oxygen minimum zone. Wavelet analysis highlighted a bimonthly spectral frequency in the StSsW lower limit when the float crossed the eddy in the south of Cabo San Lucas, showing the influence of the mesoscale features of the area, and therefore a possible interchange of properties between deep watersThis work was made possible thanks to financial support of IPN-CICIMAR Project no. 20220088 (LSV, Grupos del zooplancton, con énfasis en larvas de peces, en relación a gradientes de oxígeno)Peer reviewe

Increased anthropogenic aerosol emissions might disrupt marine microbial plankton communities

2nd International Ocean Research Conference, One planet one ocean, 17-21 November 2014, Barcelona, SpainThe effect of dust deposition of crustal origin over low-nutrient low-chlorophyll regions as the Mediterranean Sea has been the object of study during last decades. Our oceans are also exposed to atmospheric inputs of anthropogenic origin. We evaluated the effect of both crustal and anthropogenic aerosols through two microcosm experiments carried out during winter and spring of 2014 in the NW Mediterranean coast. We incubated six containers at the temperature and light cycle of the corresponding time of the year. Two of the containers were amended with 0.8 mg L-1 of Saharan dust (S) and two with 0.8 mg L-1 of aerosols of anthropogenic origin (A). The remaining two microcosms were left unamended and served as control (K). In the winter experiment, a slight increase in chlorophyll a concentration in A and S containers was observed with respect to the control, but the growth was soon phosphorous limited. On the other hand, while only a moderate increase in chlorophyll a was observed in S containers during the spring experiment, a larger increase was evident in A containers, owing mainly to an increase in nitrogen concentration. Changes in the relative abundance of pico and nanoeukaryotes and bacteria communities were also observed during both experiments. Thus, aerosols of anthropogenic origin may have a drastically different effect on marine ecosystems than naturally occurring aerosols, especially under certain environmental conditions or times of the yearPeer Reviewe

Phytoplankton response to atmospheric aerosol deposition in a coastal zone of the NW Mediterranean

2nd International Ocean Research Conference, One planet one ocean, 17-21 November 2014, Barcelona, SpainAtmospheric deposition of nutrients and contaminants may have particularly important consequences in a low nutrient – low chlorophyll marine system such as the Mediterranean Sea, which is exposed to aerosols of both local Anthropogenic and Saharan origin. The effect of atmospheric deposition on coastal phytoplankton of the NW Mediterranean was investigated by means of a stimulation experiment in microcosms. We filled six 15 L containers with coastal seawater pre-filtered through 150 μm. The microcosms were incubated at 12.7 ºC under an 11:13 h light: dark cycle. On the second day, atmospheric dust from Saharan and Anthropogenic origin collected in Barcelona was added to four of the containers. Two of the microcosms (SI and SII) were amended with 0.8 mg L-1 of Saharan dust and the other two (AI and AII) received the same amount of Anthropogenic dust. The two remaining containers (KI and KII) were left as controls. The experiment lasted for seven days and subsamples were taken daily for chlorophyll a, flow cytometry and phytoplankton biomass determinations. Saharan and Anthropogenic dust additions slightly induced chlorophyll a increases and stimulated Synechococcus growth during the 24 h after dust addition. The stimulation of chlorophyll a was on average 56% larger in S than in A. We will discuss these dynamics in relation to nutrient concentrations and additionsPeer Reviewe

Water masses and larval fish habitats in the Pacific tropical-subtropical convergence off Mexico

12 pages, 10 figures, 1 tableIn early summer (June 2010), we used zooplankton and hydrographic sampling to analyze relationships between larval fish habitats and converging water masses in the Pacific tropical-subtropical region off Mexico. Results showed an equatorward jet parallel to the Baja California Peninsula (the Tropical Branch of California Current) which was located northward of 25oC surface isotherm. In this area, a larval fish habitat indicated by Triphoturus mexicanus larvae was identified. The habitat had low larval abundance (17 larvae per 10 m2) with major larval concentration below the thermocline (∼ 20 Co and oligotrophic conditions, 1 mg m-3) waters of the shallow thermocline (∼30 m depth). The other larval fish habitat occupied an area of anticyclonic circulation in the offshore California Current Water, where the thermocline was depressed ∼ 70 m depth. Oligotrophic conditions (0.3 mg m-3) corresponded with the lowest mean larval abundance (14 larvae per 10 m2) of the study. The distribution of the larval fish habitats and their indicator species correspond with the water masses distributions in the Tropical-Subtropical convergence, which are modulated by mesoscale structures affecting the thermocline depth and the larval life-historyThe study was funded by the CONACyT Project no. 236864 (LSV, Influencia de remolinos de mesoscala sobre hábitats de larvas de peces en la zona de mínimo de oxígeno frente a México) and IPN-CICIMAR Project no. 20210789 (LSV, Grupos del zooplancton, con énfasis en larvas de peces, en relación a gradientes de oxígeno)Peer reviewe

Atmospheric inputs in the Mediterranean may modulate its colour

XXXII Trobades Científiques de la Mediterrània, Planeta Oceà - Planet Ocean, celebradas del 5 al 7 de octubre de 2016 en Maó, Menorca.-- Homenatge als Drs. Marta Estrada, Jordi Font i Jordi Salat, pioners de l'oceanografia mediterrània moderna. A tribute to Drs. Marta Estrada, Jordi Font and Jordi Salat, pioneers of modern Mediterranean oceanography.-- 1 pageThe dynamics of the coloured fraction of dissolved organic matter (CDOM) in marine systems is of high interest because this fraction is optically active. CDOM absorbs UV and visible light and thus affects the pelagic microorganisms in two ways: it reduces the light availability for photosynthesis and diminishes the cell damage induced by UV radiation. Major sources of CDOM are continental runoff and in situ production by microorganisms. Interestingly, Mediterranean waters exhibit exceptionally high values of CDOM to chlorophyll (Chl) ratio when comparing them with those of waters from other marine basins. We, in this study, explored the possible importance of atmospheric material deposition in modulating the amount of the CDOM in an area influenced by anthropogenic aerosols and also by episodic events of Sahara winds, which are associated with high dust deposition rates. To address this question we collected samples for atmospheric deposition (at the roof of the Institute of Marine Sciences (ICM‐CSIC) in Barcelona) and for seawater analyses (at 0.5 km offshore of Barcelona) over a two‐year period (September 2012 ‐ July 2014). We investigate, during this period, the dynamics of CDOM and also of a subfraction of this organic matter, the fluorescent dissolved organic matter (FDOM). Our observations indicate that DOM composition measured with optical techniques varied when Saharan wind events occurred and also evidence an increase in the FDOM flux during these events. We will discuss our findings in relation to organic matter remineralization in surface Mediterranean watersPeer Reviewe

Fluorescent organic matter dynamics induced by inputs of different types of dust. An experimental approach

2nd International Ocean Research Conference, One planet one ocean, 17-21 November 2014, Barcelona, SpainA small fraction of coloured dissolved organic matter (CDOM) can emit blue light when excited by ultraviolet radiation. This fraction is called fluorescent dissolved organic matter (FDOM). Optical spectrometry can be used to characterize this fraction and to study the distribution, and dynamics of dissolved organic matter. Using a combination of different pairs of excitation-emission (EX/EM) wavelengths we can determine different group of compounds: (340/440) peak-C terrestrial-humic, (220/410) peak-M marine-humic, (280/350) peak-T protein-like and (250/435) peak-A humic-like. We conducted three experiments to determine the impact of different type of atmospheric dust (urban and Sahara dust) in dynamics of FDOM in coastal seawaters. Water was collected 0.5 km offshore of Barcelona beach (NW Mediterranean Sea) and distributed in 6 microcosms, subject to experimental conditions in a light-dark and temperature during 8 days. Two microcosms contained Sahara dust (S), two other contained urban dust (A) and two were kept as controls (K). The S microcosms presented marked fluorescence at humic-like and protein-like peaks during the course of the incubation with maximum values of 2.8 and 2.3 QSU respectively. In contrast, the microcosm with urban dust showed lower values (1.9 and 1.3 QSU respectively). We will discuss the contrasting FDOM and CDOM dynamics in the different experimental conditions in relation to the plankton responsesPeer Reviewe