Search results for "BIOGEOCHEMICAL"
showing 10 items of 105 documents
HR3DHG version 1: modeling the spatiotemporal dynamics of mercury in the Augusta Bay (southern Italy)
2020
The biogeochemical dynamics of Hg, and specifically of its three species Hg0, HgII, and MeHg (elemental, inorganic, and organic, respectively), in the marine coastal area of Augusta Bay (southern Italy) have been explored by the high-resolution 3D Hg (HR3DHG) model, namely an advection–diffusion–reaction model for dissolved mercury in the seawater compartment coupled with a diffusion–reaction model for dissolved mercury in the pore water of sediments in which the desorption process for the sediment total mercury is taken into account. The spatiotemporal variability of the mercury concentration in both seawater ([HgD]) and the first layers of bottom sediments ([HgDsed] and [HgTsed]), as well…
Seasonal benthic nepheloid layer in the Gulf of Riga, Baltic Sea: Sources, structure and geochemical interactions
2005
Abstract The sources of particles, as well as the geochemical structure and interfacial exchange were studied for the summer benthic nepheloid layer of the shallow (50 m) Gulf of Riga. The material was sampled at nine stations during three cruises of August 2001–2003 with a main focus on the deep waters. Suspended particulate matter (SPM) and its major (N, Si, P, Al, Fe, Mn, Ca) elements were determined as the principal parameters. The results indicate the summer benthic nepheloid layer as an important component of the environmental regime of the Gulf of Riga. The nepheloid layer develops as a result of the near-bottom hydrodynamics and a corresponding saline structure below the thermocline…
Possible impacts of volcanic ash emissions of Mount Etna on the primary productivity in the oligotrophic Mediterranean Sea: Results from nutrient-rel…
2013
Atmospheric deposition of volcanic ash has recently been recognized as an important nutrient source into the surface ocean. Mount Etna (Italy), one of the world's most active volcanoes, is located in the oligotrophic Mediterranean Sea (MedSea). Despite the active volcanism on Mount Etna, the biogeochemical impacts of volcanic ash fallouts on the marine primary productivity (MPP) remain largely unknown. Here we present the results of seawater nutrient release experiments with volcanic ash samples from Mount Etna that have been collected during different eruptive episodes between 2001 and 2007. Our results show that volcanic ash from Mount Etna releases significant amounts of fixed-N (35-855 …
Modeling the Response of the Planktonic Microbial Community to Warming Effects in Maritime Antarctic Lakes
2014
Abstract In this chapter, we describe the design and prognoses given by the simulation of an ecological model dealing with the functioning of the microbial community of a maritime Antarctic lake, whose main ecological features are also reported. The model is based on carbon fluxes through the planktonic community and the carbon subsides from the benthic mosses covering the lake bottom and microbial mats spread over the lake’s catchment. It describes the dynamics of the bacterioplankton, phytoplankton, and organic matter, both particulate and dissolved, during the austral summer, with temperature and solar radiation as the main forcing functions driving the response of the modeled state vari…
Impact of hydrologically driven hillslope erosion and landslide occurrence on soil organic carbon dynamics in tropical watersheds
2016
The dynamics of soil organic carbon (SOC) in tropical forests play an important role in the global carbon (C) cycle. Past attempts to quantify the net C exchange with the atmosphere in regional and global budgets do not systematically account for dynamic feedbacks among linked hydrological, geomorphological, and biogeochemical processes, which control the fate of SOC. Here we quantify effects of geomorphic perturbations on SOC oxidation and accumulation in two adjacent wet tropical forest watersheds underlain by contrasting lithology (volcaniclastic rock and quartz diorite) in the Luquillo Critical Zone Observatory. This study uses the spatially-explicit and physically-based model of SOC dy…
Spatial distribution of N-cycling microbial communities showed complex patterns in constructed wetland sediments.
2013
International audience; Constructed wetlands are used for biological treatment of wastewater from agricultural lands carrying pollutants such as nitrates. Nitrogen removal in wetlands occurs from direct assimilation by plants and through microbial nitrification and denitrification. We investigated the spatial distribution of N-cycling microbial communities and genes involved in nitrification and denitrification in constructed wetland sediments receiving irrigation water. We used quantitative real-time PCR (qPCR) to characterize microbial communities. Geostatistical variance analysis was used to relate them with vegetation cover and biogeochemical sediment properties. The spatial distributio…
Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy.
2014
The effects of increasing atmospheric CO2 on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO2 gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 mu atm, minimum Omega(arag) 3.77), moderately CO2-enriched (median pCO(2) 592 mu atm, minimum Omega(arag) 2.96), and highly CO2-enriched (median pCO(2) 1611 mu at…
Archaea in boreal Swedish lakes are diverse, dominated by Woesearchaeota and follow deterministic community assembly
2020
Despite their key role in biogeochemical processes, particularly the methane cycle, archaea are widely underrepresented in molecular surveys because of their lower abundance compared to bacteria and eukaryotes. Here, we use parallel high‐resolution small subunit rRNA gene sequencing to explore archaeal diversity in 109 Swedish lakes and correlate archaeal community assembly mechanisms to large‐scale latitudinal, climatic (nemoral to arctic), and nutrient (oligotrophic to eutrophic) gradients. Sequencing with universal primers showed the contribution of archaea was on average 0.8% but increased up to 1.5% of the three domains in forest lakes. Archaea‐specific sequencing revealed that freshwa…
Stable Copper Isotopes: A Novel Tool to Trace Copper Behavior in Hydromorphic Soils
2010
Copper is an essential micronutrient for all organisms but may also be a pollutant. We studied the natural abundance of stable Cu isotope ratios in four soils to test whether δ 65 Cu values can be used as a tracer for biogeochemical processes in hydromorphic soils. Two of the soils were affected by stagnant water and the other two by groundwater. We determined standard soil properties and Cu partitioning into seven fractions of a sequential extraction. Copper stable isotope ratios were measured in total soil digests with multicollector inductively coupled plasma mass spectrometry. Copper concentrations in the study soils were low to average (5-34 mg kg -1 ). The variation in Cu isotope rati…
Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean
2020
12 pages, 5 figures, supporting information https://doi.org/10.1073/pnas.1918943117.-- Data Availability. Our published databases are publicly accessible for readers, and they are deposited at the NOAA NCEI at https://data.nodc.noaa.gov/cgi-bin/iso?id=gov.noaa.nodc:0171017.-- Correction for Lebrato et al., Global variability in seawater Mg:Ca and Sr:Ca ratios in the modern ocean; Proceedings of the National Academy of Sciences of the USA 118(49): e2119099118 (2021); doi: 10.1073/pnas.2119099118; http://hdl.handle.net/10261/258054.-- This is Pacific Marine Environmental Laboratory contribution number 5046