Search results for "UAT"
showing 10 items of 12350 documents
Deciphering carbon sources of mussel shell carbonate under experimental ocean acidification and warming.
2018
Abstract Ocean acidification and warming is widely reported to affect the ability of marine bivalves to calcify, but little is known about the underlying mechanisms. In particular, the response of their calcifying fluid carbonate chemistry to changing seawater carbonate chemistry remains poorly understood. The present study deciphers sources of the dissolved inorganic carbon (DIC) in the calcifying fluid of the blue mussel (Mytilus edulis) reared at two pH (8.1 and 7.7) and temperature (16 and 22 °C) levels for five weeks. Stable carbon isotopic ratios of seawater DIC, mussel soft tissues and shells were measured to determine the relative contribution of seawater DIC and metabolically gener…
Effect of Intensity and Mode of Artificial Upwelling on Particle Flux and Carbon Export
2021
Reduction of anthropogenic CO2 emissions alone will not sufficiently restrict global warming and enable the 1.5°C goal of the Paris agreement to be met. To effectively counteract climate change, measures to actively remove carbon dioxide from the atmosphere are required. Artificial upwelling has been proposed as one such carbon dioxide removal technique. By fueling primary productivity in the surface ocean with nutrient-rich deep water, it could potentially enhance downward fluxes of particulate organic carbon (POC) and carbon sequestration. In this study we investigated the effect of different intensities of artificial upwelling combined with two upwelling modes (recurring additions vs. on…
Ocean Circulation Model Applications for the Estuary-Coastal-Open Sea Continuum
2021
Coastal zones are among the most variable environments. As such, they require adaptive water management to ensure the balance of economic and social interests with environmental concerns. High quality marine data of hydrographic conditions e.g., sea level, temperature, salinity, and currents are needed to provide a sound foundation for the decision making process. Operational models with sufficiently high forecasting quality and resolution can be used for a further extension of the marine service toward the coastal-estuary areas. The Limfjord is a large and shallow water body in Northern Jutland, connecting the North Sea in the West and the Kattegat in the East. It is currently not covered …
Stochastic models for phytoplankton dynamics in Mediterranean Sea
2016
Abstract In this paper, we review some results obtained from three one-dimensional stochastic models, which were used to analyze picophytoplankton dynamics in two sites of the Mediterranean Sea. Firstly, we present a stochastic advection–reaction–diffusion model to describe the vertical spatial distribution of picoeukaryotes in a site of the Sicily Channel. The second model, which is an extended version of the first one, is used to obtain the vertical stationary profiles of two groups of picophytoplankton, i.e. Pelagophytes and Prochlorococcus, in the same marine site as in the previous case. Here, we include intraspecific competition of picophytoplanktonic groups for limiting factors, i.e.…
Coastal Oceanic climate change and variability from 1982 to 2009 around South Africa
2010
Changes and fluctuations in sea surface temperature (SST) around the South African coast are analysed at a monthly scale from 1982 to 2009. There is a statistically significant negative trend of up to 0.5 °C per decade in the southern Benguela from January to August, and a cooling trend of lesser magnitude along the South Coast and in the Port Elizabeth/Port Alfred region from May to August. The cooling is due to an increase in upwelling-favourable south-easterly and easterly winds. There is a positive trend in SST of up to 0.55 °C per decade in most parts of the Agulhas Current system during all months of the year, except for KwaZulu-Natal where warming is in summer. The warming was attri…
Mn/Ca in shells of Arctica islandica (Baltic Sea) – A potential proxy for ocean hypoxia?
2021
Oxygen depletion threatens an increasing number of shallow water environments, specifically habitats below the seasonal halocline in coastal settings of the Baltic Sea. To understand the natural variations of dissolved oxygen levels on seasonal and inter-annual time-scales prior to the instrumental era, high-resolution archives are urgently required. The present study evaluates the potential use of Mn/Ca values in shells of the bivalve, Arctica islandica to infer concentrations of past dissolved oxygen concentrations. This study is based on laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) data of six contemporaneous specimens and demonstrates that background varia…
Oxygen respiration rates of benthic foraminifera as measured with oxygen microsensors
2011
Abstract Oxygen respiration rates of benthic foraminifera are still badly known, mainly because they are difficult to measure. Oxygen respiration rates of seventeen species of benthic foraminifera were measured using microelectrodes and calculated on the basis of the oxygen fluxes measured in the vicinity of the foraminiferal specimens. The results show a wide range of oxygen respiration rates for the different species (from 0.09 to 5.27 nl cell−1 h−1) and a clear correlation with foraminiferal biovolume showed by the power law relationship: R = 3.98 10−3 BioVol0.88 where the oxygen respiration rate (R) is expressed in nl O2 h−1 and in μm3 biovolume (BioVol) (n = 44, R2 = 0.72, F = 114, p
Molecular composition of dissolved organic matter from a wetland plant (Juncus effusus) after photochemical and microbial decomposition (1.25 yr): Co…
2013
We hypothesized that microbial and photochemical processing of dissolved organic matter (DOM) determines its molecular formula composition in aquatic systems to a greater degree than does the original source of the DOM. To test this hypothesis, we exposed DOM from a leachate of a wetland plant (Juncus effusus) to solar radiation or incubated it in the dark for 1.25 yr. Analysis of the extracted DOM of the leachates via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) identified 2800 molecular formulae. Of the formulae in the initial DOM, 11% were lost during microbial decomposition in the dark and 54% under solar radiation. Solar radiation also produced a large number…
Are aquatic and semiaquatic true bugs (Hemiptera: Nepomorpha; Gerromorpha) distinct aquatic communities? A case study in homogeneous habitats
2019
We investigated the environmental factors influencing Nepomorpha and Gerromorpha in lentic, highly vegetated habitats from the Danube Delta. We collected 7032 individuals from 12 species from 23 ha...
Insights from sodium into the impacts of elevated pCO2 and temperature on bivalve shell formation
2017
Ocean acidification and warming are predicted to affect the ability of marine bivalves to build their shells, but little is known about the underlying mechanisms. Shell formation is an extremely complex process requiring a detailed understanding of biomineralization processes. Sodium incorporation into the shells would increase if bivalves rely on the exchange of Na+/H+ to maintain homeostasis for shell formation, thereby shedding new light on the acid-base and ionic regulation at the calcifying front. Here, we investigated the combined effects of seawater pH (8.1, 7.7 and 7.4) and temperature (16 and 22 °C) on the growth and sodium composition of the shells of the blue mussel, Mytilus edul…