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16 results on '"Pozzato, Lara"'

1. Benthic oxygen dynamics and implication for the maintenance of chronic hypoxia and ecosystem degradation in the Berre lagoon (France)

Author

Rigaud, Sylvain, Deflandre, Bruno, Grenz, Christian, Cesbron, Florian, Pozzato, Lara, Voltz, Baptiste, Grémare, Antoine, Romero-Ramirez, Alicia, Mirleau, Pascal, Meulé, Samuel, Faure, Vincent, Mayot, Nicolas, Michotey, Valérie, Bonin, Patricia, Pascal, Ludovic, Cordier, Marie-Ange, Lamarque, Bastien, Tenório, Márcio, and Radakovitch, Olivier

Published
2021
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2. Polimeri superassorbenti all'impianto: una nuova risorsa per migliorare la tolleranza del vigneto alla carenza idrica

Author

Ripa, Clara, Giorgio Bonicelli, Pier, Frioni, Tommaso, Pozzato, Lara, Clara Ripa, Tommaso Frioni (ORCID:0000-0002-8663-3022), Ripa, Clara, Giorgio Bonicelli, Pier, Frioni, Tommaso, Pozzato, Lara, Clara Ripa, and Tommaso Frioni (ORCID:0000-0002-8663-3022)

Abstract

I risultati delle prove sperimentali, condotte all’interno del Progetto IN+VITE, in laboratorio, in ambiente controllato e in campo, in relazione a condizioni idriche limitanti – carenze e/ stress multipli estivi ad esempio -per lo sviluppo delle viti

Published
2024

9. Carbonate chemistry in sediment porewaters of the Rhône River delta driven by early diagenesis (northwestern Mediterranean)

Author

Rassmann, Jens, Lansard, Bruno, Pozzato, Lara, Rabouille, Christophe, Rassmann, Jens, Lansard, Bruno, Pozzato, Lara, and Rabouille, Christophe

Abstract

The Rhône River is the largest source of terrestrial organic and inorganic carbon for the Mediterranean Sea. A large fraction of this terrestrial carbon is either buried or mineralized in the sediments close to the river mouth. This mineralization follows aerobic and anaerobic pathways, with a range of impacts on calcium carbonate precipitation and dissolution in the sediment near the sediment–water interface. This study focuses on the production of dissolved inorganic carbon (DIC) and total alkalinity (TA) by early diagenesis, consequential pH variations and the effect on calcium carbonate precipitation or dissolution. The sediment porewater chemistry was investigated along a transect from the Rhône River outlet to the continental shelf. TA and concentrations of DIC, SO42− and Ca2+ were analyzed on bottom waters and extracted sediment porewaters, whereas pH and oxygen concentrations were measured in situ using microelectrodes. The average oxygen penetration depth into the sediment was 1.7 ± 0.4 mm close to the river mouth and 8.2 ± 2.6 mm in the continental shelf sediments, indicating intense respiration rates. Diffusive oxygen fluxes through the sediment–water interface ranged between 3 and 13 mmol O2 m−2 d−1. In the first 30 cm of the sediment, TA and DIC porewater concentrations increased with depth up to 48 mmol L−1 near the river outlet and up to 7 mmol L−1 on the shelf as a result of aerobic and anaerobic mineralization processes. Due to aerobic processes, at all stations pH decreased by 0.6 pH units in the oxic layer of the sediment accompanied by a decrease of the saturation state regarding calcium carbonate. In the anoxic layer of the sediments, sulfate reduction was the dominant mineralization process and was associated with an increase of porewater saturation state regarding calcium carbonate. Ultimately anoxic mineralization of organic matter caused calcium carbonate precipitation demonstrated by a large decrease in Ca2+ concentration with depth in the

Published
2016
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12. Impacts of Ocean Acidification on Sediment Processes in Shallow Waters of the Arctic Ocean

Author

Gazeau, Frederic, van Rijswijk, Pieter, Pozzato, Lara, and Middelburg, Jack J.

Abstract

Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.

Published
2014

15. Carbonate chemistry in sediment pore waters of the Rhône River delta driven by early diagenesis (NW Mediterranean).

Author

Rassmann, Jens, Lansard, Bruno, Pozzato, Lara, and Rabouille, Christophe

Subjects
CARBONATES, RIVER sediments, PH effect, WATER chemistry
Abstract

The Rhône River is the largest source of terrestrial organic and inorganic carbon for the Mediterranean Sea, and a large fraction thereof is buried or mineralized in the sediments close to the river mouth. The mineralization follows aerobic and anaerobic pathways with varying impacts on the carbonate chemistry in the sediment pore waters. This study focused on the production of dissolved inorganic carbon (DIC) and total alkalinity (TA) by early diagenesis at the sediment water-interface, consequential pH variations and the effect on calcium carbonate precipitation or dissolution. The sediment pore water chemistry was investigated during the DICASE cruise along a transect from the Rhône River outlet to the continental shelf. The concentrations of DIC, TA, SO42- and Ca2+ were analyzed on bottom waters and extracted pore waters, whereas pH and oxygen concentrations were measured in situ using microelectrodes. The average oxygen penetration depth into the sediment was 1.7 ± 0.4 mm in the proximal domain and 8.2 ± 2.6 mm in the distal domain, indicating intense aerobic respiration rates. Diffusive oxygen fluxes through the sediment water interface range between 3 and 13 mmol O2 m-2 d-1. The DIC and TA concentrations increased with depth in the sediment pore waters up to 48 mmol L-1 near the river outlet and up to 7 mmol L-1 on the shelf as a result of aerobic and anaerobic mineralization processes. Due to oxic processes, the pH decreased by 0.6 pH units in the oxic layer of the sediment accompanied by a decrease of the saturation state regarding calcium carbonate. In the anoxic part of the sediments, sulfate reduction was seen to be the dominant mineralization process and was associated to an increase of pore water saturation state regarding calcium carbonate. Ultimately anoxic mineralization of organic matter caused calcium carbonate precipitation as shown by large decrease in Ca2+ concentration with depth in the sediment. The saturation state and carbonate precipitation decreased in offshore direction, together with the carbon turnover and sulfate consumption in the sediments. [ABSTRACT FROM AUTHOR]

Published
2016
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16. Effects of Suspended Sediments on Seston Food Quality for Zebra Mussels in Lake Markermeer, The Netherlands

Author

Penning, Willemijntje E., Pozzato, Lara, Vijverberg, Thomas, Noordhuis, Ruurd, bij de Vaate, Abraham, Van Donk, Ellen, and Dionisio Pires, L. Miguel

Abstract

AbstractUntil 1992, zebra mussels (Dreissena polymorpha) were an important food source for diving ducks in Lake Markermeer (The Netherlands). After 1993, the mussel biomass sharply declined, and the current population is in poor condition (maximum shell length <15 mm) compared to populations from adjacent Lake IJsselmeer. Lake Markermeer is characterized by high concentrations of total suspended matter (TSM), including 70% inorganic suspended sediments (ISS) affected by wind-driven resuspension, which may influence the food uptake by the mussels. We assessed whether the poor condition of the zebra mussels in Lake Markermeer could be attributed to the high TSM concentrations, and especially the fraction of ISS. In situ measurements of near-bottom TSM concentrations were linked to wind-driven wave action, and experiments were carried out using increasing natural sediment (NS) concentrations combined with a fixed concentration of a green alga (Scenedesmus obliquus) to determine the clearance rates (CR) of adult and juvenile zebra mussels. CR on NS particles decreased with increasing NS concentrations. The CR on S. obliquus, however, increased with an increasing NS concentration up to 0.75 g L−1for adult mussels, indicating that zebra mussels can tolerate relatively high TSM concentrations and selectively graze on phytoplankton. Zebra mussels eventually reduce their CR at high TSM concentrations; the CR of juvenile mussels on S. obliquus collapsed at NS concentrations >0.5 g L−1. The NS concentrations used in this study are high, but analyses of the near-bottom TSM concentrations show that these values occur frequently and may be partly responsible for the poor mussel status in Lake Markermeer.

Published
2013
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