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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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Journal ArticleDOI
TL;DR: A robust comparative phylogenetic framework for inferring systems metabolism of nitrogen, carbon and sulfur cycling within oxygen-deficient oceanic waters is provided and Saanich Inlet is established as a tractable model for studying the response of microbial communities to changing levels of water column hypoxia.
Abstract: Summary Dissolved oxygen concentration plays a major role in shaping biotic interactions and nutrient flows within marine ecosystems. Throughout the global ocean, regions of low dissolved oxygen concentration (hypoxia) are a common and expanding feature of the water column, with major feedback on productivity and greenhouse gas cycling. To better understand microbial diversity underlying biogeochemical transformations within oxygen-deficient oceanic waters, we monitored and quantified bacterial and archaeal community dynamics in relation to dissolved gases and nutrients during a seasonal stratification and deep water renewal cycle in Saanich Inlet, British Columbia, a seasonally anoxic fjord. A number of microbial groups partitioned within oxygen-deficient waters including Nitrospina and SAR324 affiliated with the δ-proteobacteria, SAR406 and γ-proteobacteria related to thiotrophic gill symbionts of deep-sea clams and mussels. Microbial diversity was highest within the hypoxic transition zone decreasing dramatically within anoxic basin waters and temporal patterns of niche partitioning were observed along defined gradients of oxygen and phosphate. These results provide a robust comparative phylogenetic framework for inferring systems metabolism of nitrogen, carbon and sulfur cycling within oxygen-deficient oceanic waters and establish Saanich Inlet as a tractable model for studying the response of microbial communities to changing levels of water column hypoxia.

214 citations

OtherDOI
01 Jan 1984
TL;DR: In this paper, the authors present a broad overview of the physical and chemical factors that govern the concentration and distribution of trace metals associated with bottom and suspended sediments, including grain size, surface area, surface charge, cation exchange capacity, composition and so forth.
Abstract: In most aquatic systems, concentrations of trace metals in suspended sediment and the top few centimeters of bottom sediment are far greater than concentrations of trace metals dissolved in the water column. Consequently, the distribution, transport, and availability of these constituents can not be intelligently evaluated, nor can their environmental impact be determined or predicted solely through the sampling and analysis of dissolved phases. This Primer is designed to acquaint the reader with the basic principles that govern the concentration and distribution of trace metals associated with bottom and suspended sediments. The sampling and analysis of suspended and bottom sediments are very important for monitoring studies, not only because trace metal concentrations associated with them are orders of magnitude higher than in the dissolved phase, but also because of several other factors. Riverine transport of trace metals is dominated by sediment. In addition, bottom sediments serve as a source for suspended sediment and can provide a historical record of chemical conditions. This record will help establish area baseline metal levels against which existing conditions can be compared. Many physical and chemical factors affect a sediment's capacity to collect and concentrate trace metals. The physical factors include grain size, surface area, surface charge, cation exchange capacity, composition, and so forth. Increases in metal concentrations are strongly correlated with decreasing grain size and increasing surface area, surface charge, cation exchange capacity, and increasing concentrations of iron and manganese oxides, organic matter, and clay minerals. Chemical factors are equally important, especially for differentiating between samples having similar bulk chemistries and for inferring or predicting environmental availability. Chemical factors entail phase associations (with such sedimentary components as interstitial water, sulfides, carbonates, and organic matter) and ways in which the metals are entrained by the sediments (such as adsorption, complexation, and within mineral lattices). INTRODUCTION The basic goal of most chemically oriented water-quality studies is to describe or evaluate existing environmental conditions and to attempt to identify the source or sources of the constituents under investigation. An equally important goal is to attempt to predict or determine potential impacts. This heading could accommodate such subjects as bioavailability, amount of constituent transport, location of chemical sinks, ultimate fate, and potential toxic effects. Historically, the U.S. Geological Survey has attempted to assess trace metals in aquatic systems by analyzing water samples. This assessment has entailed determining concentrations of total and dissolved elements and compounds through the collection and analysis, respectively, of unfiltered and filtered water. Concentrations associated with suspended sediment (particulates, seston) are determined indirectly by the difference between total and dissolved concentrations. It is recognized that this approach casts doubt on the reliability of reported suspended-sediment chemical analyses. As a result, water quality tends to be evaluated on the kinds and concentration of various constituents found in solution (Feltz, 1980). However, in most aquatic systems, the concentration of trace metals in suspended sediment and the top few centimeters of bottom sediment is far greater than the concentration of trace metals dissolved in the water column. The strong association of numerous trace metals (for example, As, Cd, Hg, Pb, Zn) with seston and bottom sediments means that the distribution, transport, and availability of these constituents can not be intelligently evaluated solely through the sampling and analysis of the dissolved phase. Additionally, because bottom sediments can act as a reservoir for many trace metals, they must, for several reasons, be given serious consideration in the planning and design of any water-quality study. First, an undisturbed sediment sink contains a historical record of chemical conditions. If a sufficiently large and stable sink can be found and studied, it will allow the investigator to study changes over time and, possibly, to establish area baseline levels against which existing conditions can be compared and contrasted. Second, under changing environmental or physicochemical conditions (like pH, Eh, dissolved oxygen, bacterial action), sediment-bound trace metals can dissolve into the water column, possibly enter the food chain, and have a significant environmental impact. Third, several relatively inert or otherwise environmentally harmless inorganic constituents can degrade, or react with others, to form soluble and potentially toxic forms (for example, the conversion of elemental mercury to methyl-mercury). Finally, bottom sediments should be regarded as a major, if not the major, source of suspended sediment. Therefore, they must be investigated to determine transport potential. Under changing hydrologic conditions (such as a heavy storm or spring runoff), a localized pollution problem can suddenly become widespread and result in significant environmental impact. The foregoing discussion indicates that data on suspended and bottom sediments, as well as on the dissolved phase, are a requisite for the development of a comprehensive understanding of the impact of trace metals on water quality. Through the use of such additional data, it may be possible to begin to identify sources and sinks and the fate and potential effects of toxic or environmentally necessary metals. Similarly, sediment-chemical data are a requisite for transport modeling, for estimating geochemical cycles, and for inferring the availability of various trace metals in an ecological system.

214 citations

Journal ArticleDOI
TL;DR: A realistic hydrodynamic model of the Texas-Louisiana shelf is configured with various simple oxygen respiration models to isolate the effects of stratification and circulation on the formation and maintenance of hypoxia as mentioned in this paper.

214 citations

Book ChapterDOI
TL;DR: San Francisco Bay, the largest bay on the California coast, is a broad, shallow, turbid estuary comprising two geographically and hydrologically distinct sub-estuaries: the northern reach lying between the connection to the Pacific Ocean at the Golden Gate and the confluence of the Sacramento-San Joaquin River system, and the southern reach (herein called South Bay) between the golden gate and the Southern terminus of the bay.
Abstract: San Francisco Bay, the largest bay on the California coast, is a broad, shallow, turbid estuary comprising two geographically and hydrologically distinct subestuaries: the northern reach lying between the connection to the Pacific Ocean at the Golden Gate and the confluence of the Sacramento-San Joaquin River system, and the southern reach (herein called South Bay) between the Golden Gate and the southern terminus of the bay. The northern reach is a partially mixed estuary dominated by seasonally varying river inflow, and the South Bay is a tidally oscillating lagoon-type estuary. Freshwater inflows, highest during winter, generate strong estuarine circulation and largely determine water residence times. They also bring large volumes of dissolved and particulate materials to the estuary. Tidal currents, generated by mixed semidiurnal and diurnal tides, mix the water column and, together with river inflow and basin geometry, determine circulation patterns. Winds, which are strongest during summer and during winter storms, exert stress on the bay’s water surface, thereby creating large waves that resuspend sediment from the shallow bay bottom and, together with the tidal currents, contribute markedly to the transport of water masses throughout the shallow estuary.

214 citations

Journal ArticleDOI
TL;DR: Results provide solid evidence for the major role of internal P loading in causing N limitation during the prebloom-bloom period.

214 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023458
2022969
2021497
2020502
2019502
2018466