Papers by Francesc Peters
Aquesta obra és d'ús lliure, però està sotmesa a les condicions de la llicència pública de Creati... more Aquesta obra és d'ús lliure, però està sotmesa a les condicions de la llicència pública de Creative Commons. Es pot reproduir, distribuir i comunicar l' obra sempre que se'n reconegui l'autoria i l' entitat que la publica i no se'n faci un ús comercial ni cap obra derivada. Es pot trobar una còpia completa dels termes d'aquesta llicència a l'adreça:
Aquatic Microbial Ecology, 2002
In the oligotrophic sea, phytoplankton and bacteria compete for nutrients. Turbulence changes the... more In the oligotrophic sea, phytoplankton and bacteria compete for nutrients. Turbulence changes the outcome of this competition by means of an increase in the nutrient flux to cells by the shear fields, which is cell-size dependent. This effect is insignificant for small cells such as natural bacteria. The hypothesis is that turbulence will increase the phytoplankton competition-capability for nutrients and reduce the organic matter utilisation by bacteria. Consequently, the composition of particulate organic matter should change. To test this hypothesis, we studied the response of natural plankton communities to turbulence enclosed in 15 l microcosms. We evaluated the response in terms of the ratio of heterotrophic:total biomass and the stoichiometry of particulate organic matter. Results under turbulent and still conditions were compared in 3 nutrient-induced conditions: nitrogen surplus (N, with initial addition of an excess of nitrogen, N:P ratio = 160), nitrogen:phosphorus ratio balanced (NP, with initial addition of nitrogen and phosphorus as Redfield ratio, N:P ratio = 16) and control (C, no nutrient addition). In N and NP conditions, turbulence decreased the heterotrophic:total biomass ratio up to 2-fold, and induced changes in the stoichiometry of the particulate organic matter. We found higher values of carbon:phosphorus and nitrogen:phosphorus ratios in turbulent than in still treatments. The magnitude of these responses to turbulence depended on the induced nutrient conditions. In the control microcosms, we found the maximum differences of carbon:phosphorus ratio between turbulence and still treatments. In terms of biomass, the response to turbulence was clear in the enriched conditions and insignificant in the control microcosms.
XXXII Trobades Científiques de la Mediterrània, Planeta Oceà - Planet Ocean, celebradas del 5 al ... more 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
XXXII Trobades Científiques de la Mediterrània, Planeta Oceà - Planet Ocean, celebradas del 5 al ... more 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 Mediterranean Sea is a low‐nutrient, low‐chlorophyll region, characterized by a marine planktonic community limited predominantly by phosphorus (P), or P along with nitrogen (N) in the northwestern basin (NW). In this context, the deposition of nutrients from the atmosphere may play an important role, especially during the stratification period, when thermocline prevents mixing of nutrient‐rich deep waters into the photic zone. Two main sources of atmospheric particles have been identified in the NW Mediterranean: continuous antropogenically‐derived emissions from Europe and local sources, and episodic Saharan dust events. We provide data of atmospheric fluxes of inorganic nutrients and total organic carbon (TOC) in an urban coastal location of the NW Mediterranean. Bulk deposition of nitrate, nitrite, ammonium, phosphate, silicate, and TOC was measured from May, 2011 to January, 2016, using passive collectors. Nitrate and nitrite followed opposite seasonal patterns, nitrate deposition flux being higher during the spring‐summer period and nitrite during autumn. TOC deposition was also higher during spring, whereas the other nutrients did not follow any seasonal pattern but large peaks were associated to point events, as Saharan intrusions. Mean deposition fluxes were 127, 14, 175, 5, 7, and 521 µmol m-2 d-1, for nitrate, nitrite, ammonium, phosphate, silicate and TOC, respectively. Both N and P fluxes were much higher than values reported in more pristine areas of the Mediterranean (e.g., Markaki et al. 2010), but a similar N:P ratio was determined, whereas very low Si:N and Si:P ratios were determined. These results provide evidence of a higher anthropogenic footprint for N and P than for silicate. A principal component analysis revealed that silicate deposition was highly correlated with the presence of atmospheric particles from the Saharan desert and with wind speed, mainly associated to dryfall. On the other hand, nitrate, phosphate, TOC, and in a lesser extend, nitrate and ammonium, were more correlated with accumulated rainfall, suggesting that wet deposition is more common for these nutrients. Although ecological implications are difficult to estimate for larger spatial and temporal scales, these results suggest that an increasing trend in anthropogenic atmospheric inputs (rich in N, P and TOC) could drive the planktonic coastal system to an increase in primary production of non‐siliceous phytoplankton cells, concomitant with an increase in bacterial production, at certain times of the year, with the consequent risk of eutrophicationPeer Reviewe
Limnology and Oceanography, 1994
Nitrogen uptake in the plume of the Chesapeake Bay estuary and its by size-fractionated phytoplan... more Nitrogen uptake in the plume of the Chesapeake Bay estuary and its by size-fractionated phytoplankton populations in regulation by large heterotrophs. Limnol. Oceanogr.
Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 pageIn aquatic s... more Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 pageIn aquatic systems phytoplankton and bacteria compete for inorganic nitrogen and phosphorus. It has been shown that the outcome of this competition will be in favour of diatoms when silicate (Si) is in excess and in favour of bacteria when Si is depleted [Havskum et al, 2003; Thingstad et al 2007]. We postulate that turbulence could change this competition interaction. Shear derived from turbulence increases nutrient flux to large cells, thus it should increase the phytoplankton competition capability for nutrients and reduce the organic matter utilisation by bacteria. Then, when Si is in excess diatom growth should be further enhanced by turbulence. We evaluated the effect of turbulence on the competition between bacteria and diatoms in experiments with natural plankton communities enclosed in microcosms. The response of plankton to turbulence versus still conditions was evaluated in four different nutrient conditions: C (glucose addition), Si (silicate addition), CSi (glucose and silicate addition), and B (no addition). In general, turbulence increased both heterotrophic and autotrophic biomass under all nutrient addition conditions, and enhanced the diatom competition for nutrients when Si was available. However turbulence did not change the ratio between autotrophic and heterotrophic biomass. We discuss the discrepancy between these results and previous data in terms of the level and frequency of nutrient additions, trophic interactions and initial conditions. References HAVSKUM, H, TF THINGSTAD, R SCHAREK, F PETERS, E BERDALET, MM SALA, M ALCARAZ , JCBANSGHOLT, UL ZWEIFEL, Å HAGSTRÖM, M PEREZ AND JR DOLAN (2003) Silicate and labile DOC interfere in structuring food web via algal-bacteria competition for mineral nutrients: Results of a mesocosm experiment. Limnol. Oceanogr. 48(1): 129-140. THINGSTAD TF, H HAVSKUM, UL ZWEIFEL, E BERDALET, MM SALA, F PETERS, M ALCARAZ, R SCHAREK, M PEREZ, S JACQUET, GA FONNES FLATEN, JR DOLAN, C MARRASE, F RASSOULZADEGAN, ÅHAGSTRØM, D VAULOT (2007). Ability of a minimum microbial food web model to reproduce response patterns observed in mesocosms manipulated with N and P, glucose and Si. Journal of Marine systems. 64: 15-3
Treballs de la Societat Catalana de Biologia, 2019
La recerca que hem presentat en aquest article ha estat finançada pel Leverhulme Trust a través d... more La recerca que hem presentat en aquest article ha estat finançada pel Leverhulme Trust a través del projecte «Form and function in a microbial world» atorgat a Stuart Humphries. Bibliografia Bartlett, T. M. [et al.] (2017). «A periplasmic polymer curves Vibrio cholerae and promotes pathogenesis». Cell, 168: 172-185. e15. Bennett, R. R. [et al.] (2016). «Species-dependent hydrodynamics of flagellum-tethered bacteria in early biofilm development».
Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 pageThe changes ... more Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 pageThe changes induced by small-scale turbulence on the grazing rates of metazoan microzooplankton on the different components of a natural microplankton community were studied by laboratory experiments. Eight, 15 L Perspex cylindrical microcosms containing coastal water were incubated during three days under controlled temperature, light and turbulence conditions. In four of the microcosms the metazoans had been excluded by reverse-flow filtration through 50 µ m mesh (m- microcosms). In the remaining four microcosms the “in situ” community of metazoan microzooplankton 50-150 µ m size organisms) had been concentrated three times, also by reverse-flow filtration (M- microcosms). Four microcosms, two duplicates from each trophic manipulation, were maintained in still conditions (S- microcosms), whereas the remaining four microcosms were subjected to the turbulence generated by vertically oscillating grids (ε = 0.055 cm2 s-3, T- microcosms). The grazing rates were estimated by comparing the changes occurred along the incubation in the microplankton community of SM, Sm, TM and Tm microcosms. Turbulence enhanced clearance and ingestion rates of metazoan microzooplankton. This community, dominated by meroplanktonic invertebrate larvae, exerted a strong trophic impact on ciliates, flagellates and especially on dinoflagellates. Similarly, the microcosms under turbulence illustrate clear examples of trophic cascade effect
Mediterranean Marine Science, 2021
The southern Alboran Sea is a highly dynamic region in the Mediterranean. However, there is few ... more The southern Alboran Sea is a highly dynamic region in the Mediterranean. However, there is few data on microphytoplankton which is, an important component of the marine ecosystem. We therefore collected microphytoplankton samples and related the biomass and diversity patterns to ambient variability, considering cross-shore and longitudinal gradients. There was a general eastward decrease in both species richness and biomass, with Cape Three Forks as a transitional point. Diversity increased in coastal areas and decreased with depth. High chlorophyll-a concentrations corresponded to low temperature and low-salinity waters, indicating the Atlantic origin. Microphytoplankton biomass was low in comparison with total chlorophyll, suggesting a dominance of nano- and picophytoplankton. Biomass values increased in the stretch between Cape Three Forks and Al Hoceima Bay, an area highly influenced by upwelled water originating from the northern Alboran Sea. We suggest that the Western Albo...
The Science of the total environment, 2017
The atmosphere of the northwestern (NW) Mediterranean Sea is affected by continuous inputs of ant... more The atmosphere of the northwestern (NW) Mediterranean Sea is affected by continuous inputs of anthropogenic aerosols and episodic Saharan dust events. These atmospheric inputs deliver to the surface waters high amounts of macronutrients and trace metals that can constitute their main source at certain times of the year. The effect of both anthropogenic and crustal particles over the autotrophic and heterotrophic planktonic community assembles was evaluated through three microcosm experiments carried out in the summer of 2013 and in the winter and spring of 2014 at an urban coastal location of the NW Mediterranean (Barcelona, Spain). Particles were added to seawater at a concentration of 0.8mgl(-1). The results showed that (i) a greater stimulation of the whole community was observed in summer and spring than in winter; (ii) both kinds of aerosols produced an increase in the growth of phytoplankton, although the stimulation of nanoeukaryotes was significantly larger with anthropogeni...
The atmosphere of the Northwestern Mediterranean Sea is mainly affected by continuous inputs of a... more The atmosphere of the Northwestern Mediterranean Sea is mainly affected by continuous inputs of aerosols from Europe and episodic Saharan dust events. The effect of both crustal and anthropogenic aerosols was evaluated through four microcosm experiments carried out during 2014 in the NW Mediterranean coast. Six containers were incubated 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) collected on quartz filters. The remaining two microcosms were amended with blank filters and served as control (K). Results show that anthropogenic aerosols are a major source of nitrogen, a limiting nutrient during spring and summer in the western Mediterranean waters, usually resulting in a higher increase of chlorophyll a in A containers respect to S and K ones. Changes in the abundance of picoplanktonic communities were also observed during...
Science of The Total Environment, 2021
COVID-19 has led to global population lockdowns that have had indirect effects on terrestrial and... more COVID-19 has led to global population lockdowns that have had indirect effects on terrestrial and marine fauna, yet little is known on their effects on marine planktonic communities. We analysed the effect of the spring 2020 lockdown in a marine coastal area in Blanes Bay, NW Mediterranean. We compared a set of 23 oceanographic, microbial and biogeochemical variables sampled right after the strict lockdown in Spain, with data from the previous 15 years after correcting for long-term trends. Our analysis shows a series of changes in the microbial communities which may have been induced by the combination of the decreased nitrogen atmospheric load, the lower wastewater flux and the reduced fishing activity in the area, among other factors. In particular, we detected a slight decrease beyond the long-term trend in chlorophyll a, in the abundance of several microbial groups (phototrophic nanoflagellates and total prokaryotes) and in prokaryotic activity (heterotrophic prokaryotic production and β-glucosidase activity) which, as a whole, resulted in a moderate increase of oligotrophy in Blanes Bay after the lockdown.
Bonnet et al. (2005). Effect of atmospheric nutrients on the autotrophic communities in a low nut... more Bonnet et al. (2005). Effect of atmospheric nutrients on the autotrophic communities in a low nutrient, low chlorophyll system.
Thalassa va dedicar un reportatge al gran naturalista català. Home cabdal en els estudis de la na... more Thalassa va dedicar un reportatge al gran naturalista català. Home cabdal en els estudis de la natura i dels oceans i un dels primers que va concebre el concepte d'ecologia. Reconegut arreu del món, Margalef va ser un científic creatiu que va obrir moltes línies d'investigacions vigents encara avui dia. Es diu que analitzava el que veia amb la curiositat d'un infant i amb la rigorositat d'un científic. A finals de l'any 2011 es va fer a la mar, a Vigo, un nou i modern vaixell de l'Institut Espanyol d'Oceanografia amb el nom de "Ramon Margalef". Un homenatge merescut al primer catedràtic d'Ecologia que va tenir l'estat espanyol. La seva tasca com a professor ha tingut una marcada influència en molts investigadors actuals, capdavanters en el camp de l'ecologia i l'oceanografia, que han estat alumnes seus i segueixen els camins que ell va obrirPeer reviewe
Science of The Total Environment, Dec 1, 2020
Coastal marine ecosystems are strongly influenced by different occasional events, such as intense... more Coastal marine ecosystems are strongly influenced by different occasional events, such as intense winds, mixing, rain and river discharges. These events can directly or indirectly cause changes in dissolved organic matter (DOM) quality through a cascade of different biotic and abiotic processes. Changes in DOM quality are often associated with changes in DOM optical properties. Thus, examining the dynamics of chromophoric DOM (CDOM) can provide valuable information about biological and physical processes that have occurred in the ecosystem. Episodic meteorological events, particularly in temperate areas, appear very abruptly and induce very rapid responses; therefore, high time-resolved measurements are needed to capture them. We used a weekly sampling scheme to characterize DOM and nutrient dynamics in the NW Mediterranean coastal station 'SOLA'. From February 2013 to April 2014, we measured several physical and chemical variables including temperature, salinity, inorganic nutrients, chlorophyll a dissolved organic carbon (DOC), CDOM and fluorescent DOM (FDOM). During this period, two extremely high fresh water intrusions greatly influenced the dynamics of some DOM fractions, in particular the FDOM. Inorganic nutrients and chlorophyll a showed seasonal patterns: A winter period characterized by a high nutrient concentration in surface waters favored the phytoplankton spring bloom; then, summer stratification extended until autumn. This stratification led to nutrient depletion and, consequently, lower chlorophyll a values in the photic zone. The CDOM and FDOM optical active fractions did not follow temporal trends similar to total DOC. This was likely because the potential sources and sinks of these DOM pools are microbial activity
XXXII Trobades Científiques de la Mediterrània, Planeta Oceà - Planet Ocean, celebradas del 5 al ... more 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 pageAnnual phytoplankton dynamics in the Mediterranean Sea are strongly driven by the seasonal overturning in winter‐spring when deep waters rich in essential nutrients are mixed with upper sunlit waters. Being in the subtropical highs zone, with relatively low wind energy and variability, only enhances the seasonal component. We have analyzed the seasonality of chlorophyll using 8‐d averaged 1 x 1 degree satellite data for the whole basin and higher spatial resolution in certain areas. We calculated the Seasonality Index (SI) as the proportion of the variance owing to annual recurrent trends with respect to total time series variance. The index is calculated either from spectral analysis or using a statistical cubic spline adjustment for multiyear data. The SI is high in general of 75% or more. Some areas influenced by large rivers (Rhone, Po, Nile) and other areas such as the Alboran Sea where Atlantic waters enter the Mediterranean, the northern Aegean Sea with the influence from the Black Sea through the Sea of Marmara or the Gulf of Gabes with a shallow shelf and coastal enrichment all show decreased seasonality and a larger annual chlorophyll signal. If the variability for frequencies larger than the annual can be interpreted as a results of disturbances to the system that force nutrients into the euphotic zone, there is room for addressing ecological hypotheses that relate disturbance to system diversity and production, and to use this information in the frame of global change scenariosPeer Reviewe
Treballs de la Societat Catalana de Biologia, 2020
1st Iberian Ecological Society Meeting (2019); XIV Congreso Nacional de la Asociación Española de... more 1st Iberian Ecological Society Meeting (2019); XIV Congreso Nacional de la Asociación Española de Ecología Terrestre (AEET), Ecology: an integrative science in the Anthropocene, 4-7 February 2019, Barcelona, SpainIn marine plankton ecosystems, diatoms and heterotrophic bacteria (HB) compete for inorganic nitrogen (N) and phosphorus (P). It has been shown that the outcome of this competition is in favor of diatoms when silicate (Si) is in excess and in favor of HB when Si is depleted. However, the supply of organic compounds, so pervasive in marine plankton ecosystems, could alter the outcome of these competitive interactions. Here, we evaluate the response of natural plankton communities to glucose addition, Si addition, and glucose plus Si addition in laboratory microcosms to which N and P were also added by default. The addition of glucose boosted the growth of HB, which prevented diatoms from thriving. We found that HB were superior competitors as long as labile organic compounds fuelled their metabolic activity, yet, once glucose was consumed, the biomass of diatoms increased conspicuously in the glucose plus Si addition treatment. These substrate-mediated competitive interactions contribute to regulating the structure and succession of marine plankton in nature and provide us with technical know-how to design highly efficient synthetic communities with applications in wastewater treatment and quality biomass productionPeer Reviewe
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Papers by Francesc Peters