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Water column
About: Water column is a research topic. Over the lifetime, 13706 publications have been published within this topic receiving 496626 citations.
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TL;DR: Coliphage survived the longest of any group of organisms in the sediment and the least in the water column, and Giardia survived best in theWater column and least inThe sediment.
220 citations
TL;DR: The concentrations of nutrients, dissolved and particulate organic matter, salinity and chlorophyll-α in the water column were measured over the period of June 1989 to August 1990 at a network of 26 sampling locations across Florida Bay as discussed by the authors.
Abstract: The concentrations of nutrients, dissolved and particulate organic matter, salinity and chlorophyll-α in the water column were measured over the period of June 1989 to August 1990 at a network of 26 sampling locations across Florida Bay. Florida Bay was hypersaline during this time period, with an average salinity of 41·4. Dissolved organic phosphorus was the dominant form of P in the water column, while soluble reactive P was generally less than 5% of the total P. Organic nitrogen forms dominated the N pool, and NH + 4 was the dominant form of dissolved inorganic nitrogen. Many of the measured parameters were correlated. Principal Components Analysis extracted three composite variables that described 90·3% of the variation in the original data set. PC I was highly correlated with total organic N, total N, total organic C and salinity. PC II was correlated with all measures of P and chlorophyll-α. PC III was correlated with measures of inorganic N. The spatial distribution of factor scores for these principal components indicate three processes acting independently to control the composition of the water column of Florida Bay: the evaporation-driven concentration of dissolved material in Florida Bay; the delivery of P to Florida Bay through water exchange with the Gulf of Mexico; and the delivery of freshwater with an excess of N with respect to P to Florida Bay. The phytoplankton biomass in the water column of Florida Bay is shown to be P-limited.
219 citations
TL;DR: In this paper, the authors couple measurements of aqueous CO2 and CH4 partial pressures (pCO2, pCH4) and flux across the water-air interface with gas transfer models to calculate subbasin distributions of gas flux density.
Abstract: [1] Carbon dioxide (CO2) and methane (CH4) emissions are important, but poorly quantified, components of riverine carbon (C) budgets. This is largely because the data needed for gas flux calculations are sparse and are spatially and temporally variable. Additionally, the importance of C gas emissions relative to lateral C exports is not well known because gaseous and aqueous fluxes are not commonly measured on the same rivers. We couple measurements of aqueous CO2 and CH4 partial pressures (pCO2, pCH4) and flux across the water-air interface with gas transfer models to calculate subbasin distributions of gas flux density. We then combine those flux densities with remote and direct observations of stream and river water surface area and ice duration, to calculate C gas emissions from flowing waters throughout the Yukon River basin. CO2 emissions were 7.68 Tg C yr−1 (95% CI: 5.84 −10.46), averaging 750 g C m−2 yr−1 normalized to water surface area, and 9.0 g C m−2 yr−1 normalized to river basin area. River CH4 emissions totaled 55 Gg C yr−1 or 0.7% of the total mass of C emitted as CO2 plus CH4 and ∼6.4% of their combined radiative forcing. When combined with lateral inorganic plus organic C exports to below head of tide, C gas emissions comprised 50% of total C exported by the Yukon River and its tributaries. River CO2 and CH4 derive from multiple sources, including groundwater, surface water runoff, carbonate equilibrium reactions, and benthic and water column microbial processing of organic C. The exact role of each of these processes is not yet quantified in the overall river C budget.
219 citations
TL;DR: 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.
Abstract: Being a major cause of eutrophication and subsequent loss of water quality, the turnover of phosphorus (P) in lake sediments is in need of deeper understanding. A major part of the flux of P to eutrophic lake sediments is organically bound or of biogenic origin. This P is incorporated in a poorly described mixture of autochthonous and allochthonous sediment and forms the primary storage of P available for recycling to the water column, thus regulating lake trophic status. To identify and quantify biogenic sediment P and assess its lability, we analyzed sediment cores from Lake Erken, Sweden, using traditional P fractionation, and in parallel, NaOH extracts were analyzed using 31P NMR. The surface sediments contain orthophosphates (ortho-P) and pyrophosphates (pyro-P), as well as phosphate mono- and diesters. The first group of compounds to disappear with increased sediment depth is pyrophosphate, followed by a steady decline of the different ester compounds. Estimated half-life times of these compound groups are about 10 yr for pyrophosphate and 2 decades for mono- and diesters. Probably, these compounds will be mineralized to ortho-P and is thus potentially available for recycling to the water column, supporting further growth of phytoplankton. In conclusion, 31P NMR is a useful tool to asses the bioavailability of certain P compound groups, and the combination with traditional fractionation techniques makes quantification possible.
219 citations
TL;DR: In this article, a large seasonal change in the dissolved iron (dFe) concentration of surface waters in the Bermuda Atlantic Time-series Study region, from ∼1-2 nM in summer 2003, when aerosol iron concentrations were high (mean 10 nmol m−3), to ∼0.1-0.2 nm in spring 2004, when they were low (mean 0.64 nmolm−3).
Abstract: [1] We report iron measurements for water column and aerosol samples collected in the Sargasso Sea during July-August 2003 (summer 2003) and April-May 2004 (spring 2004). Our data reveal a large seasonal change in the dissolved iron (dFe) concentration of surface waters in the Bermuda Atlantic Time-series Study region, from ∼1–2 nM in summer 2003, when aerosol iron concentrations were high (mean 10 nmol m−3), to ∼0.1–0.2 nM in spring 2004, when aerosol iron concentrations were low (mean 0.64 nmol m−3). During summer 2003, we observed an increase of ∼0.6 nM in surface water dFe concentrations over 13 days, presumably due to eolian iron input; an estimate of total iron deposition over this same period suggests an effective solubility of 3–30% for aerosol iron. Our summer 2003 water column profiles show potentially growth-limiting dFe concentrations (0.02–0.19 nM) coinciding with a deep chlorophyll maximum at 100–150 m depth, where phytoplankton biomass is typically dominated by Prochlorococcus during late summer.
218 citations