Global gene expression of Prochlorococcus ecotypes in response to changes in nitrogen availability

Nitrogen (N) often limits biological productivity in the oceanic gyres where Prochlorococcus is the most abundant photosynthetic organism. The Prochlorococcus community is composed of strains, such as MED4 and MIT9313, that have different N utilization capabilities and that belong to ecotypes with different depth distributions. An interstrain comparison of how Prochlorococcus responds to changes in ambient nitrogen is thus central to understanding its ecology. We quantified changes in MED4 and MIT9313 global mRNA expression, chlorophyll fluorescence, and photosystem II photochemical efficiency (F(v)/F(m)) along a time series of increasing N starvation. In addition, the global expression of both strains growing in ammonium-replete medium was compared to expression during growth on alternative N sources. There were interstrain similarities in N regulation such as the activation of a putative NtcA regulon during N stress. There were also important differences between the strains such as in the expression patterns of carbon metabolism genes, suggesting that the two strains integrate N and C metabolism in fundamentally different ways

Marsh macrophyte responses to inundation anticipate impacts of sea-level rise and indicate ongoing drowning of North Carolina marshes

In situ persistence of coastal marsh habitat as sea level rises depends on whether macrophytes induce compensatory accretion of the marsh surface. Experimental planters in two North Carolina marshes served to expose two dominant macrophyte species to six different elevations spanning 0.75 m (inundation durations 0.4–99 %). Spartina alterniflora and Juncus roemerianus exhibited similar responses—with production in planters suggesting initial increases and then demonstrating subsequent steep declines with increasing inundation, conforming to a segment of the ecophysiological parabola. Projecting inundation levels experienced by macrophytes in the planters onto adjacent marsh platforms revealed that neither species occupied elevations associated with increasing production. Declining macrophyte production with rising seas reduces both bioaccumulation of roots below-ground and baffle-induced sedimentation above-ground. By occupying only descending portions of the parabola, macrophytes in central North Carolina marshes are responding to rising water levels by progressive declines in production, ultimately leading to marsh drowning

Exchange of nutrients and oxygen across the sediment-water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea

Purpose: This study analyzes the effects of aquaculture activities in open seawater in the north-western coastal waters of the Mediterranean Sea. It is the first of its kind to be based on benthic flux data gathered in situ below fish farms for this particular area. Materials and methods: Samples were collected on four sampling campaigns over a 1-year cycle under a Sparus aurata fish farm facility where benthic fluxes were measured in situ using light and dark benthic chambers. Bottom water and sediment samples were also collected. Data were compared to those for a nearby control station. Results and discussion: Significant differences were found (ANOVA, p < 0. 05) between concentrations of organic matter (OM), total phosphorus and redox potentials in sediments located under the cages and those of the control station. The consumption of dissolved oxygen (DO) by sediment and positive ammonium (NH4 +) fluxes was stimulated by OM content, with correlations of r = -0. 60 (p < 0. 01) and r = 0. 70 (p < 0. 01), respectively. The OM content of sediments was found to be consistently higher under the cages than at the control station, with the highest value (1. 8 ± 0. 7 %) under the cages observed during the early summer; values of DO and NH4 + fluxes were -64 ± 17 and 12. 7 ± 1. 0 mmol m-2 day-1, respectively. PO4 3- fluxes were consistently higher in the fish farm sediments (between 0. 58 and 0. 98 mmol m-2 day-1) than those observed at the control station. Nitrate (NO3 -) fluxes were found to be consistently negative due to denitrification occurring in the sediments and were related to the concentration of NO3 - in bottom waters (r = 0. 92, p < 0. 01). Si fluxes were shown to be associated with water temperature (r = 0. 59, p < 0. 05). Conclusions: The results imply that sediments located below cages accumulate organic matter originating from aquaculture activities, especially during summer months when this activity increases. Sediments undergo biogeochemical changes that mainly affect fluxes of DO, NH4 + and soluble reactive phosphorus, although these do not seem to have a significant impact on the quality of the water column due to the hydrodynamic characteristics of the area. © 2012 Springer-Verlag.We would like to thank the Caja del Mediterraneo for a predoctoral fellowship fund for this research and Antonio Asuncion Acuigroup Maremar manager for the facilities and support in conducting the study. The translation of this paper was funded by the Universidad Politecnica de Valencia, Spain. We are grateful for the valuable comments of the anonymous reviewers on previous versions of the manuscript.Morata Higón, T.; Sospedra, J.; Falco Giaccaglia, SL.; Rodilla Alama, M. (2012). Exchange of nutrients and oxygen across the sediment-water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea. Journal of Soils and Sediments. 12(10):1623-1632. doi:10.1007/s11368-012-0581-2S162316321210APHA, AWWA, and WEF (2005) Standard methods for the examination of water wastewater, 21st edn. American Public Health Association, WashingtonAksu M, Kocatas A (2007) Environmental effects of the three fish farms in Izmir Bay (Aegean Sea-Turkey) on water column and sediment. Rapport du 38e Congrés de la Commission Internationale Pour L’exploration Scientifique de la Mer Méditerranée 38, 414Aminot A, Chaussepied M (1983) Manuel des analyses chimiques en milieu marin. Centre National pour l’Explotation des Oceans, BrestArocena R, Conde D (1999) Sedimento. Métodos en ecología de aguas continentales. Universidad de la República, Montevideo, pp 40–52Asociación Empresarial de Productores de Cultivos Marinas (APROMAR) (2010) La Acuicultura Marina de Peces en España, pp. 69Baumgarten MGZ, Rocha JM, Niencheski LFH (1996) Manual de análises em oceanografia química, Rio GrandeBelias C, Dassenakis M, Scoullos M (2007) Study of the N, P and Si fluxes between fish farm sediment and seawater. Results of simulation experiments employing a benthic chamber under various redox conditions. Mar Chem 103:266–275Berelson WM, McManus J, Coale KH, Johnson KS, Burdige D, Kilgore T, Colodner D, Chavez F, Kudela R, Boucher J (2003) A time series of benthic flux measurements from Monterey Bay, CA. Cont Shelf Res 23:457–481Black KD, McDougall N (2002) Hydrography of four Mediterranean marine cage sites. J Appl Ichthyol 18:129–133Borja A, Rodríguez JG, Black K, Bodoy A, Emblow C, Fernandes TF, Forte J, Karakassis I, Muxika I, Nickell TD, Papageorgiou N, Pranovi F, Sevastou K, Tomassetti P, Angel D (2009) Assessing the suitability of a range of benthic indices in the evaluation of environmental impact of fin and shellfish aquaculture located in sites across Europe. Aquaculture 293:231–240Cermelj B, Ogrinc N, Faganeli J (2001) Anoxic mineralization of biogenic debris in near-shore marine sediments (Gulf of Trieste, northern Adriatic). Sci Total Environ 266:143–152Dell’Anno A, Mei ML, Pusceddu A, Danovaro R (2002) Assessing the trophic state and eutrophication of coastal marine systems: a new approach based on the biochemical composition of sediment organic matter. Mar Pollut Bull 44:611–622Dosdat A (2001) Environmental impact of aquaculture in the Mediterranean: nutritional and feeding aspects. Environmental impact assessment of Mediterranean aquaculture farms. Cah Options Méditerr CIHEAM-FAO 55:23–36Ferrón S, Ortega T, Forja JM (2009) Benthic fluxes in a tidal salt marsh creek by fish farm activities: Río San Pedro (Bay of Cádiz, SW Spain). Mar Chem 113:50–62Freitas U, Niencheski LFH, Zarzur S, Manzolli RP, Vieira JPP, Rosa LC (2008) Influência de um cultivo de camaraô sobre o metabolismo béntico e a qualidade da agua. Rev Bras Eng Agríc Ambient 12:293–301Hall POJ, Holby O, Kollberg S, Samuelsson MO (1992) Chemical fluxes and mass balances in a marine fish cage farm: IV. Nitrogen. Mar Ecol Prog Ser 89:81–91Hargrave B (2005) Environmental effects of marine finfish aquaculture. The handbook of environmental. chemistry, vol. 5. Part M. Springer, BerlinHargrave BT, Phillips GA, Doucette LI, White MJ, Milligan TG, Wildish DJ, Cranston RE (1997) Assessing benthic impacts of organic enrichment from marine aquaculture. Water Air Soil Pollut 99:641–650Heilskov AC, Holmer M (2001) Effects of benthic fauna on organic matter mineralization in fish-farm sediments: importance of size and abundance. ICES J Mar Sci 58:427–434Herbert RA (1999) Nitrogen cycling in coastal marine ecosystems. FEMS Microbiol Rev 23:563–590Holby O, Hall POJ (1991) Chemical fluxes and mass balances in a marine fish cage farm. 11. Phosphorus. Mar Ecol Prog Ser 70:263–272Holby O, Hall POJ (1994) Chemical fluxes and mass balances in a marine fish cage farm. III. Silicon. Aquaculture 120:305–318Jackson C, Preston N, Thompson PJ (2004) Intake and discharge nutrient loads at three intensive shrimp farms. Aquacult Res 35:1053–1061Karakassis I, Tsapakis M, Hatziyanni E (1998) Seasonal variability in sediment profiles beneath fish farm cages in the Mediterranean. Mar Ecol Prog Ser 162:243–252Kaymakci A, Aksu M, Egemen O (2010) Impacts of the fish farms on the water column nutrient concentrations and accumulation of heavy metals in the sediments in the eastern Aegean Sea (Turkey). Environ Monit Assess 162:439–451Lorenti M, De Falco G (2004) Measurements and characterization of abiotic variables. In: Gambi MC, Diappiano M (eds) Mediterranean marine benthos: a manual of methods for its sampling and study. Societa Italiana di Biologia Marina, Genova, pp 1–37Maldonado M, Carmona MC, Echeverría Y, Riesgo A (2005) The environmental impact of Mediterranean cage fish farms at semi-exposed locations: does it need a re-assessment? Helgol Mar Res 59:121–135Mantzavrakos E, Kornaros M, Lyberatos G, Kaspiris P (2007) Impacts of a marine fish farm in Argolikos Gulf (Greece) on the water column and the sediment. Desalination 210:110–124Mazzola A, Mirto S, La Rosa T, Fabiano M, Danovaro R (2000) Fish-farming effects on benthic community structure in coastal sediments: analysis of meiofaunal recovery. ICES J Mar Sci 57:1454–1461Molina L, Vergara JM (2005) Impacto ambiental de jaulas flotantes: estado actual de conocimientos y conclusiones prácticas. Bol Inst Esp Oceanogr 21:75–81Morán XAG, Estrada M (2005) Winter pelagic photosynthesis in the NW Mediterranean Deep-Sea. Research I 52:1806–1822Neofitou N, Klaoudatos S (2008) Effect of fish farming on the water column nutrient concentration in a semi-enclosed gulf of the Eastern Mediterranean. Aquac Res 39:482–490Niencheski LF, Jahnke RA (2002) Benthic respiration and inorganic nutrient fluxes in the estuarine región of Patos Lagoon (Brazil). Aquat Geochem 8:135–152Nizzoli D, Bartoli M, Viaroli P (2007) Oxygen and ammonium dynamics during a farming cycle of the bivalve Tapes philippinarum. Hydrobiologia 587:25–36Pergent-Martini C, Boudouresque CF, Pasqualini V, Pergent G (2006) Impact of fish farming facilities on Posidonia oceanica meadows: a review. Mar Ecol 27:310–319Pitta P, Karakassis I, Tsapakis M, Zivanovic S (1999) Natural versus mariculture induced variability in nutrients and plankton in the Eastern Mediterranean. Hydrobiologia 391:181–194Redfield AC, Ketchum BH, Richards FA (1963) The influence of organisms on the composition of seawater. In: Hill MN (ed) The sea, vol 2. Interscience, New YorkRiise JC, Roos N (1997) Benthic metabolism and the effects of bioturbation in a fertilized polyculture fish pond in northeast Thailand. Aquaculture 150:45–62Rodríguez J (1999) Ecología. Ed. Pirámide. pp 411Sakamaki T, Nishimura O, Sudo R (2006) Tidal time-scale variation in nutrient flux across the sediment-water interface of an estuarine tidal flat. 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On-line estimation of O2 production, CO2 uptake, and growth kinetics of microalgal cultures in a gas-tight photobioreactor

Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO2, H2, and N2 were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively. The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO2 uptake was estimated from the addition of CO2 as acidic titrant and O2 evolution was estimated from titration by H2, which was used to reduce O2 over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O2 evolution and CO2 up-take rates. NH4+, NO2−, or NO3− was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH4+ as the nitrogen source and 1.3 when NO3− was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards 1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree of reduction of the biomass. When using the titrations of CO2 and H2 into the reactor headspace to estimate the up-take of CO2, the production of O2, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be estimated, and different growth phases could be identified

Abnormal shortened diastolic time length at increasing heart rates in patients with abnormal exercise-induced increase in pulmonary artery pressure

<p>Abstract</p> <p>Background</p> <p>The degree of pulmonary hypertension is not independently related to the severity of left ventricular systolic dysfunction but is frequently associated with diastolic filling abnormalities. The aim of this study was to assess diastolic times at increasing heart rates in normal and in patients with and without abnormal exercise-induced increase in pulmonary artery pressure (PASP). Methods. We enrolled 109 patients (78 males, age 62 ± 13 years) referred for exercise stress echocardiography and 16 controls. The PASP was derived from the tricuspid Doppler tracing. A cut-off value of PASP ≥ 50 mmHg at peak stress was considered as indicative of abnormal increase in PASP. Diastolic times and the diastolic/systolic time ratio were recorded by a precordial cutaneous force sensor based on a linear accelerometer.</p> <p>Results</p> <p>At baseline, PASP was 30 ± 5 mmHg in patients and 25 ± 4 in controls. At peak stress the PASP was normal in 95 patients (Group 1); 14 patients (Group 2) showed an abnormal increase in PASP (from 35 ± 4 to 62 ± 12 mmHg; P < 0.01). At 100 bpm, an abnormal (< 1) diastolic/systolic time ratio was found in 0/16 (0%) controls, in 12/93 (13%) Group 1 and 7/14 (50%) Group 2 patients (p < 0.05 between groups).</p> <p>Conclusion</p> <p>The first and second heart sound vibrations non-invasively monitored by a force sensor are useful for continuously assessing diastolic time during exercise. Exercise-induced abnormal PASP was associated with reduced diastolic time at heart rates beyond 100 beats per minute.</p

Iron and phosphorus co-limit nitrogen fixation in the eastern tropical North Atlantic

The role of iron in enhancing phytoplankton productivity in high nutrient, low chlorophyll oceanic regions was demonstrated first through iron-addition bioassay experiments1 and subsequently confirmed by large-scale iron fertilization experiments2. Iron supply has been hypothesized to limit nitrogen fixation and hence oceanic primary productivity on geological timescales3, providing an alternative to phosphorus as the ultimate limiting nutrient4. Oceanographic observations have been interpreted both to confirm and refute this hypothesis5, 6, but direct experimental evidence is lacking7. We conducted experiments to test this hypothesis during the Meteor 55 cruise to the tropical North Atlantic. This region is rich in diazotrophs8 and strongly impacted by Saharan dust input9. Here we show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus. Saharan dust addition stimulated nitrogen fixation, presumably by supplying both iron and phosphorus10, 11. Our results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic

Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea

Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA), a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp.) collected from different sites of the Catalan coast (NW Mediterranean Sea). As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20–23). The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical cycles