Eutrophication and acidification: Do they induce changes in the dissolvedorganic matter dynamics in the coastal Mediterranean Sea?

Original research paperTwo mesocosms experiments were conducted in winter 2010 and summer 2011 to examine how increased pCO2and/or nutrient concentrations potentially perturbate dissolved organic matter dynamics in natural microbialassemblages. Thefluorescence signals of protein- and humic-like compounds were used as a proxy for labileand non-labile material, respectively, while the evolution of bacterial populations, chlorophylla(Chla) anddissolved organic carbon (DOC) concentrations were used as a proxy for biological activity. For both seasons,the presence of elevated pCO2did not cause any significant change in the DOC dynamics (p-valueb0.05). Theconditions that showed the greatest changes in prokaryote abundances and Chlacontent were those amendedwith nutrients, regardless of the change in pH. The temporal evolution offluorophores and optical indices re-vealed that the degree of humification of the organic molecules and their molecular weight changed significantlyin the nutrient-amended treatment. The generation of protein-like compounds was paired to increases in theprokaryote abundance, being higher in the nutrient-amended tanks than in the control. Different patterns inthe magnitude and direction of the generation of humic-like molecules suggested that these changes dependedon initial microbial populations and the availability of extra nutrient inputs. Based on our results, it is expected that in the future projected coastal scenarios the eutrophication processes will favor the transformations of labile and recalcitrant carbon regardless of changes in pCO2.MINECO, European Union, Generalitat de Catalunya, CSICVersión del editor3,25

Seasonal dynamics and net production of disolved organic carbon in an oligotrophic coastal environment

To understand dissolved organic carbon (DOC) seasonal dynamics in a coastal oligotrophic site in the north-western Mediterranean Sea, we monitored DOC concentrations monthly over 3 yr, together with the meteorological data and the food-web-related biological processes involved in DOC dynamics. Additional DOC samples were taken in several inshore−offshore transects along the Catalan coast. We found DOC concentrations of ~60 µmol C l−1 in winter, with increasing values through the summer and autumn and reaching 100 to 120 µmol C l−1 in November. There was high inter-annual variability in this summer DOC accumulation, with values of 36, 69 and 13 µmol C l−1 for 2006, 2007 and 2008, respectively. The analysis of the microbial food-web processes involved in the DOC balance did not reveal the causes of this accumulation, since the only occasion on which we observed net DOC production (0.3 ± 1 µmol C l−1 d−1 on average) was in 2007, and the negative DOC balance of 2006 and 2008 did not prevent DOC accumulating. The DOC accumulation episodes coincided with low rates of water renewal (average 0.037 ± 0.021 d−1 from May to October) compared with those of winter to early spring (average 0.11 ± 0.048 d−1 from November to April). Indeed, the amount of DOC accumulated each year was inversely correlated with the average summer rainfall. We hypothesize that decreased DOC turn-over due to photochemical or biological processes mostly active during the summer and low water renewal rate combine to determine seasonal DOC accumulation and influence its inter-annual variability

Preferences of phytoplankton groups for waters of different trophic status in the northwestern Mediterranean Sea

We examined the preferences of phytoplankton groups for waters of different trophic status by comparing the distribution of 8 main phytoplankton groups during the spring bloom, post-bloom, and late stratification periods in the northwestern Mediterranean. Pigment chemotaxonomy (using the CHEMTAX computer program) was applied to estimate the contribution of Prymnesiophyceae, Pelagophyceae, Synechococcus spp., Prochlorococcus spp., Prasinophyceae, Cryptophyceae, Dinophyceae, and Bacillariophyceae to the chlorophyll a (chl a) stock. Particulate organic nitrogen (PON) concentration was used as an indicator of trophic status. PON at the surface was 1.7 ± 1.4, 0.57 ± 0.02, and 0.37 ± 0.04 µmol l 1 in the bloom, post-bloom, and stratification periods, respectively. During the bloom period, there was a weak stratification and a large chl a biomass. Bacillariophyceae dominated during the bloom period, with a substantial contribution of Prasinophyceae. Prymnesiophyceae and Synechococcus spp. dominated during post-bloom and stratification periods, and Prochlorococcus spp. was a major contributor to biomass in the deep chlorophyll maximum (DCM) during the stratification period. Vertical segregation was also evident for Pelagophyceae, Prymnesiophyceae, and Cryptophyceae, which preferred the DCM to surface layers in non-bloom conditions. The relative distribution of each group combined with PON concentrations in these 3 periods allowed us to calculate a group-specific trophic preference index, which showed its highest values (more eutrophic) for Bacillariophyceae, Prasinophyceae, Cryptophyceae, and Dinophyceae; medium values (mesotrophic) for Prymnesiophyceae, Pelagophyceae, and Synechococcus spp.; and a very low value (oligotrophic) for Prochlorococcus spp. The pigment-group diversity (Shannon index) and evenness were lower during the bloom period

Seasonal dynamics and net production of disolved organic carbon in an oligotrophic coastal environment

To understand dissolved organic carbon (DOC) seasonal dynamics in a coastal oligotrophic site in the north-western Mediterranean Sea, we monitored DOC concentrations monthly over 3 yr, together with the meteorological data and the food-web-related biological processes involved in DOC dynamics. Additional DOC samples were taken in several inshore−offshore transects along the Catalan coast. We found DOC concentrations of ~60 µmol C l−1 in winter, with increasing values through the summer and autumn and reaching 100 to 120 µmol C l−1 in November. There was high inter-annual variability in this summer DOC accumulation, with values of 36, 69 and 13 µmol C l−1 for 2006, 2007 and 2008, respectively. The analysis of the microbial food-web processes involved in the DOC balance did not reveal the causes of this accumulation, since the only occasion on which we observed net DOC production (0.3 ± 1 µmol C l−1 d−1 on average) was in 2007, and the negative DOC balance of 2006 and 2008 did not prevent DOC accumulating. The DOC accumulation episodes coincided with low rates of water renewal (average 0.037 ± 0.021 d−1 from May to October) compared with those of winter to early spring (average 0.11 ± 0.048 d−1 from November to April). Indeed, the amount of DOC accumulated each year was inversely correlated with the average summer rainfall. We hypothesize that decreased DOC turn-over due to photochemical or biological processes mostly active during the summer and low water renewal rate combine to determine seasonal DOC accumulation and influence its inter-annual variability

Effect of viruses on marine stramenopile (MAST) communities in an oligotrophic coastal marine system

10 pages, 2 figures, 3 tablesViruses are the most abundant biological entities in aquatic systems, infecting from bacteria to mammals. However, there has been little study so far on their impact on marine heterotrophic flagellates (HFs). For this reason, four experiments were carried out between April 2006 and February 2007 in the Blanes Bay Microbial Observatory (NW Mediterranean coast). We investigated whether viruses could affect HF communities, and specifically two uncultured marine stramenopile groups (MAST-4 and MAST-1C). For each experiment, four microcosms containing 12 L of 5-µm filtered seawater were prepared, two received active viruses and the other two received heat-inactivated viruses. Microcosms were then incubated for 48 h in order to measure changes in the abundance of the target groups. In three of the four experiments, both the growth rates of HF and MAST-4 cells and the percentage of MAST-4 cells with respect to HF after 48 h were higher in the heat-inactivated treatment compared with the active viruses treatment. These results indicate that viruses can negatively affect the HF community either directly via lysis of protists or indirectly via lysis of bacteria, and highlight the interactions between, virus, bacteria and protistsThis work was supported by the projects funded by the Spanish Ministry of Sciences and Innovation (CTM2004-04404-CO2-01 and CTM 2007-62140 to D.V., CGL2010-16304 to R.M. and CTM2008-06261-CO3-01 to M.L.)Peer reviewe

Hydrographical structure and nutrient distribution during the 2005 spring phytoplankton bloom in NW Mediterranean: a tool for estimating the export production

Symposium GLOBEC-IMBER España celebrado del 28-30 marzo de 2007 en Valencia.-- 1 pageKnowing the export production is a primary goal of ocean sciences. This has been limited by the complex physical and biological controls and the high spatial and temporal variability (Fasham 2003). Many estimates are based on changes in nutrient concentrations. Consequently, awareness of nutrient distribution and fate during phytoplankton blooms is essential. Here we report on the dissolved inorganic, organic and particulate nutrient and carbon distribution in NW Mediterranean during the EFLUBIO-2 cruise (between March 25 and April 5 2005). The studied area in the Gulf of Lions is a major site of carbon export, since strong deep mixing provides nutrients for phytoplankton growth. The study included an area south of the Nor-Balearic Front outside the bloom area. We found equivalent vertical profiles of nitrate, phosphate and silicate in the north stations. In contrast, there was high variability in water T-S characteristics. Nutrient concentrations were low in surface waters, increasing to a maximum of 10.2 ± 0.25 µ M nitrate, 0.39 ± 0.01 µ M phosphate and 9.50 ± 0.11 µ M silicate at depth. Particulate organic carbon, nitrogen and phosphorus concentrations were around 30, 4 and 0.2 µ M, respectively, at the beginning, decreasing subsequently to values below 5, 1 and 0.05 µ M. In addition, there was a deepening of the peak concentrations and an increase in the contribution of dissolved organic nutrients in the total pool. These results are discussed in the frame of the export production of the region. Fasham, M. J. R. (ed.) 2003. Ocean biogeochemistry: a synthesis of the Joint Global Ocean Flux Study (JGOFS). Springe

Preferences of phytoplankton groups for waters of different trophic status in the northwestern Mediterranean Sea

We examined the preferences of phytoplankton groups for waters of different trophic status by comparing the distribution of 8 main phytoplankton groups during the spring bloom, post-bloom, and late stratification periods in the northwestern Mediterranean. Pigment chemotaxonomy (using the CHEMTAX computer program) was applied to estimate the contribution of Prymnesiophyceae, Pelagophyceae, Synechococcus spp., Prochlorococcus spp., Prasinophyceae, Cryptophyceae, Dinophyceae, and Bacillariophyceae to the chlorophyll a (chl a) stock. Particulate organic nitrogen (PON) concentration was used as an indicator of trophic status. PON at the surface was 1.7 ± 1.4, 0.57 ± 0.02, and 0.37 ± 0.04 µmol l 1 in the bloom, post-bloom, and stratification periods, respectively. During the bloom period, there was a weak stratification and a large chl a biomass. Bacillariophyceae dominated during the bloom period, with a substantial contribution of Prasinophyceae. Prymnesiophyceae and Synechococcus spp. dominated during post-bloom and stratification periods, and Prochlorococcus spp. was a major contributor to biomass in the deep chlorophyll maximum (DCM) during the stratification period. Vertical segregation was also evident for Pelagophyceae, Prymnesiophyceae, and Cryptophyceae, which preferred the DCM to surface layers in non-bloom conditions. The relative distribution of each group combined with PON concentrations in these 3 periods allowed us to calculate a group-specific trophic preference index, which showed its highest values (more eutrophic) for Bacillariophyceae, Prasinophyceae, Cryptophyceae, and Dinophyceae; medium values (mesotrophic) for Prymnesiophyceae, Pelagophyceae, and Synechococcus spp.; and a very low value (oligotrophic) for Prochlorococcus spp. The pigment-group diversity (Shannon index) and evenness were lower during the bloom period

Dret d'Internet, setembre 2010

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Dret d'Internet, setembre 2010

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Factors of importance when selecting sows as embryo donors

The improvement in porcine embryo preservation and non-surgical embryo transfer (ET) procedures achieved in recent years represents essential progress for the practical use of ET in the pig industry. This study aimed to evaluate the effects of parity, weaning-to-estrus interval (WEI) and season on reproductive and embryonic parameters at day 6 after insemination of donor sows superovulated after weaning. The selection of donor sows was based on their reproductive history, body condition and parity. The effects of parity at weaning (2 to 3, 4 to 5 or 6 to 7 litters), season (fall, winter and spring), and WEI (estrus within 3 to 4 days), and their interactions on the number of corpus luteum, cysts in sows with cysts, number and quality of viable and transferable embryos, embryo developmental stage and recovery and fertilization rates were evaluated using linear mixed effects models. The analyses showed a lack of significant effects of parity, season, WEI or their interactions on any of the reproductive and embryonic parameters examined. In conclusion, these results demonstrate that fertilization rates and numbers of viable and transferable embryos collected at day 6 of the cycle from superovulated donor sows are not affected by their parity, regardless of the time of the year (from fall to spring) and WEI (3 or 4 days).Funding Agencies|Centro para el Desarrollo Tecnologico e Industrial (CDTI/Seleccion Batalle), Madrid, Spain [IDI-20090686]; MINECO-FEDER, Madrid, Spain [AGL2012-38621, AGL2015-69735-R]; Fundacion Seneca, Murcia, Spain [19892/GERM/15]; MINECO [BES-2013-064087, BES-2013-064069]</p