Marta Estrada - Academia.edu (original) (raw)

Papers by Marta Estrada

Life, 2020

We explored how changes of viral abundance and community composition among four contrasting regio... more We explored how changes of viral abundance and community composition among four contrasting regions in the Southern Ocean relied on physicochemical and microbiological traits. During January–February 2015, we visited areas north and south of the South Orkney Islands (NSO and SSO) characterized by low temperature and salinity and high inorganic nutrient concentration, north of South Georgia Island (NSG) and west of Anvers Island (WA), which have relatively higher temperatures and lower inorganic nutrient concentrations. Surface viral abundance (VA) was highest in NSG (21.50 ± 10.70 × 106 viruses mL−1) and lowest in SSO (2.96 ± 1.48 × 106 viruses mL−1). VA was positively correlated with temperature, prokaryote abundance and prokaryotic heterotrophic production, chlorophyll a, diatoms, haptophytes, fluorescent organic matter, and isoprene concentration, and was negatively correlated with inorganic nutrients (NO3−, SiO42−, PO43−), and dimethyl sulfide (DMS) concentrations. Viral communi...

Atmosphere, 2020

Isoprene is a biogenic trace gas produced by terrestrial vegetation and marine phytoplankton. In ... more Isoprene is a biogenic trace gas produced by terrestrial vegetation and marine phytoplankton. In the remote oceans, where secondary aerosols are mostly biogenic, marine isoprene emissions affect atmospheric chemistry and influence cloud formation and brightness. Here, we present the first compilation of new and published measurements of isoprene concentrations in the Southern Ocean and explore their distribution patterns. Surface ocean isoprene concentrations in November through April span 1 to 94 pM. A band of higher concentrations is observed around a latitude of ≈40 ∘ S and a surface sea temperature of 15 ∘ C. High isoprene also occurs in high productivity waters near islands and continental coasts. We use concurrent measurements of physical, chemical, and biological variables to explore the main potential drivers of isoprene concentration by means of paired regressions and multivariate analysis. Isoprene is best explained by phytoplankton-related variables like the concentration...

Deep Sea Research Part I: Oceanographic Research Papers, 2019

The relationships between taxonomy and distribution of the phytoplankton and environmental parame... more The relationships between taxonomy and distribution of the phytoplankton and environmental parameters were studied in four contrasting zones (North of the South Orkney Islands= NSO, Southeast of the South Orkney Islands = SSO, Northwest of South Georgia = NSG and West of Anvers = WA) of the Atlantic sector of the Southern Ocean, during the PEGASO cruise of the BIO Hespérides (January-February 2015). The structure of the phytoplankton community was determined by microscopic examination and by pigment analyses using high-performance liquid chromatography (HPLC) followed by application of the CHEMTAX algorithm,. Overall, a statistically significant association was found between fluorometric and HPLC determinations of chlorophyll a, and between chemotaxonomic and microscopy-derived estimates of the contribution of diatoms, dinoflagellates and cryptophytes, although the latter appeared to be underestimated by the microscopic observations. The highest average levels of fluorometric chlorophyll a (517 mg m-2) were found at NSG, followed by WA (132 mg m-2), NSO (120 mg m-2) and SSO (34 mg m-2). The phytoplankton community at NSG was dominated by diatoms like Eucampia antarctica and Thalassiosira spp. Cryptophytes and diatoms (mainly Corethron pennatum, small Thalassiosira spp. and Fragilariopsis spp.) were the most abundant chemotaxonomic groups at NSO, followed by haptophytes types 6 + 7, Phaeocystis-like (haptophytes type 8) and, especially in the deeper levels of the euphotic zone, pelagophytes. At SSO, the most important groups were haptophytes types 6 + 7, followed by diatoms (with a combination of taxa similar to that of NSO), Phaeocystis-like and pelagophytes. The main CHEMTAX groups at WA were cryptophytes (between surface and about 40 m depth), haptophytes types 6 + 7 and diatoms. The ratio between the photoprotective pigment diadinoxanthin and the sum of the light harvesting pigments of diadinoxanthin-containing phytoplankton

Scientia Marina, 2016

Minidiscus comicus is a marine centric diatom that has cells with diameters as small as 1.9 µm, w... more Minidiscus comicus is a marine centric diatom that has cells with diameters as small as 1.9 µm, which brings it close to the lower limit of diatom cell size and also near to the lower limit of photosynthetic eukaryote cells. One of the questions that this raises is whether the cycle of size decline and size restoration used by most diatoms to time their life cycle can operate in such small cells. In samples collected from the western Mediterranean during 2009, M. comicus cells were found with diameters ranging from 1.9 to 6.0 µm. The larger cells were initial cells after size restoration, and these still had the valves of their parent cells attached, making it possible to determine the diameter of the threshold below which size restoration could be induced (3.1 µm). During size decline, M. comicus cell shape changed from discoid to spherical. This adaptation helped to reduce and even halt the rate of cell volume decrease, allowing cells to continue to use diameter decline as a clocking mechanism. The results show how adaptable the diatom cell wall can be, in spite of its rigid appearance.

Scientia Marina, 2016

We carried out monthly photosynthesis-irradiance (P-E) experiments with the 14 C-method for 12 ye... more We carried out monthly photosynthesis-irradiance (P-E) experiments with the 14 C-method for 12 years (2003-2014) to determine the photosynthetic parameters and primary production of surface phytoplankton in the Blanes Bay Microbial Observatory, a coastal sampling station in the NW Mediterranean Sea. Our goal was to obtain seasonal trends and to establish the basis for detecting future changes of primary production in this oligotrophic area. The maximal photosynthetic rate P B max ranged 30-fold (0.5-15 mg C mg Chl a-1 h-1), averaged 3.7 mg C mg Chl a-1 h-1 (±0.25 SE) and was highest in August and lowest in April and December. We only observed photoinhibition twice. The initial or light-limited slope of the P-E relationship, α B , was low, averaging 0.007 mg C mg Chl a-1 h-1 (μmol photons m-2 s-1)-1 (±0.001 SE, range 0.001-0.045) and showed the lowest values in spring (April-June). The light saturation parameter or saturation irradiance, E K , averaged 711 μmol photons m-2 s-1 (± 58.4 SE) and tended to be higher in spring and lower in winter. Phytoplankton assemblages were typically dominated by picoeukaryotes in early winter, diatoms in late autumn and late winter, dinoflagellates in spring and cyanobacteria in summer. Total particulate primary production averaged 1.45 mg C m-3 h-1 (±0.13 SE) with highest values in winter (up to 8.50 mg C m-3 h-1) and lowest values in summer (summer average, 0.30 mg C m-3 h-1), while chlorophyllspecific primary production averaged 2.49 mg C mg Chl a-1 h-1 (±0.19, SE) and peaked in summer (up to 12.0 mg C mg Chl a-1 h-1 in August). 14 C-determined phytoplankton growth rates varied between ca. 0.3 d-1 in winter and 0.5 d-1 in summer and were within 60-80% of the maximal rates of growth, based on P B max. Chlorophyll a was a good predictor of primary production only in the winter and autumn. Seasonality appeared to explain most of the variability in the studied variables, while phytoplankton composition played a minor role. Daily integrated primary production was fairly constant throughout the year: similar to previous oxygen-based estimates in winter but considerably lower than these in summer. The difference between 14 C-and oxygen-based estimates of primary production could be explained by community respiration. Annually integrated primary production amounted to a rather modest 48 g C m-2 yr-1 (equivalent to 130 mg C m-2 d-1). Although no interannual patterns were detected, our work soundly establishes the seasonal trends for the coastal NW Mediterranean, therefore setting the basis for future detection of change.

Author's personal copy Climatic forcing on hydrography of a Mediterranean bay (Alfacs Bay)

Continental Shelf Research, Apr 9, 2009

Effect of reversed light gradients on phytoplankton composition in marine microcosms

Margalef’s hypothesis. Experimental approaches

Surface distribution of dissolved trace metals in the oligotrophic ocean and their influence on phytoplankton biomass and productivity

Global Biogeochemical Cycles, 2015

Meso and microzooplankton feeding rates on toxic and non-toxic dinoflagellates cultured at different N/P ratios

Photosynthetic gene expression responses of the oceanic ubiquitous cyanobacterium Prochlorococcus due to changes of environmental variables

The cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on E... more The cyanobacterium Prochlorococcus is the smallest and most abundant photosynthetic organism on Earth [1]. Being a main global primary producer and ubiquist in the tropical and subtropical regions of the world’s oceans [2], it constitutes a good sentinel species for evaluating the effect of environmental stressors on oceanic photosynthesis. We developed a sensitive method to monitor the expression of two genes responsible of photosynthesis in Prochlorococcus , rbc L (RuBisCO) and psb A (D1 protein), using rnp B as reference gene [3,4]. We applied the method to samples from 63 stations of the Malaspina circumnavigation cruise (December 2010 - July 2011), sampled at three depths. In addition, natural communities of nano-and picoplankton were experimentally exposed to organic pollutant mixtures. Expression of Prochlorococcus rbcL and psbA genes correlated with several physical variables and other biological measurements, and were sensitive to low levels of organic pollutant mixtures. W...

Increased anthropogenic aerosol emissions might disrupt marine microbial plankton communities

2nd International Ocean Research Conference, One planet one ocean, 17-21 November 2014, Barcelona... more 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... more 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

Microbial planktonic communities response to Saharan dust and anthropogenic atmospheric inputs in a low-nutrient low-chlorophyll region

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...

Zooplankton excretion and primary production: contribution of regenerated ammonia to nitrogen requirements of phytoplankton in the Catalan Sea (NW Mediterranean)

A combined field and modelling study to understand the modulation of phytoplankton variability by physical forcing in Alfacs Bay (NW Mediterranean)

Symposium on Integrating New Advances in Mediterranean Oceanography and Marine Biology, 26-29 Nov... more Symposium on Integrating New Advances in Mediterranean Oceanography and Marine Biology, 26-29 November 2013, Institut de Ciències del Mar (CSIC), Barcelona, Catalunya, SpainAlfacs Bay (Ebre delta) is a shallow microtidal estuary whose high productivity (compared to the adjacent oligotrophic Mediterranean waters) sustains a rich ecosystem and allows a valuable aquaculture activity. The appropriate management of the natural resources in the area requires a thorough understanding of the spatio-temporal variability of phytoplankton. Here we will summarize our main findings arisen from the field studies conducted between 2007 and 2012 combined with modeling approaches addressed to study the ecosystem of Alfacs Bay. Synoptic cruises were performed in different periods of the year in order to characterize the physico-chemical (water temperature and salinity, nutrient concentrations) and biological (phytoplankton biomass and community structure) parameters. Deployed sensors provided the continuous record of water temperature, salinity and velocities at a fixed central station. These data and concurrent meteorological data (wind intensity) were used to implement and validate a semi-implicit Three-Dimensional Circulation Model (Si3D) in the bay. The overall study showed the existence of a preferential phytoplankton accumulation area in the inner NE side of the Bay. Nutrient supply, mainly through the irrigation channels discharging into the northern coast, fuels phytoplankton biomass development, but does not explain the patchy distribution over the year. This is better understood by the physical forcing established by the wind conditions and freshwater input which control the stratification and water circulation patterns in Alfacs bay. Using the 3D hydrodynamic model, we simulated the particle distribution dynamics under different hydrodynamic scenarios. The simulation experiments suggest that the estuarine circulation dynamics operating in the bay would foster the observed phytoplankton confinement in the inner NE area in Alfacs bayPeer Reviewe

Progress in Oceanography, 2007

Microbial Components

The Mediterranean Sea, 2013

25 pages, 7 figures, 1 tableThis chapter presents an overview of the diversity, distribution and ... more 25 pages, 7 figures, 1 tableThis chapter presents an overview of the diversity, distribution and ecology of major groups of microbial plankton in the Mediterranean Sea, including phytoplankton, viruses, heterotrophic prokaryotes and flagellates, and ciliates. Some protists with hard structures like diatoms, thecate dinoflagellates, coccolithophorids and tintinnids have been relatively well studied from a morphological point of view, but in general microbial diversity is poorly known, in particular with respect to prokaryotes and the smallest eukaryotes. This situation is rapidly changing, in a large part due to the incorporation of molecular techniques. The general oligotrophy of the Mediterranean, which increases from west to east, is reflected in a strong contribution of the picoplankton and the microbial food web. However, a variety of nutrient enrichment mechanisms, including winter mixing, mesoscale hydrographic structures and land runoff, which operate at various spatio-temporal scales, may enhance primary production and result in the intermittent dominance of diatoms and the herbivorous food web. During the stratification period, a deep chlorophyll maximum is a general feature throughout the basin and plays a substantial role in the fertility of the MediterraneanWe acknowledge the support of grant 2009 SGR 588 of the Generalitat de Catalunya, and projects FAMOSO (CTM2008-06261-C03-01) and FLAME (CGL2010-16304) of the Spanish Ministry of Science and InnovationPeer reviewe

Marine Ecology Progress Series, 2013