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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
10 Apr 2003-Nature
TL;DR: The anammox reaction is shown to be a globally significant sink for oceanic nitrogen in the anoxic waters of Golfo Dulce, a 200-m-deep coastal bay in Costa Rica, where it accounts for 19–35% of the total N2 formation in the water column.
Abstract: In oxygen-depleted zones of the open ocean, and in anoxic basins and fjords, denitrification (the bacterial reduction of nitrate to give N2) is recognized as the only significant process converting fixed nitrogen to gaseous N2. Primary production in the oceans is often limited by the availability of fixed nitrogen such as ammonium or nitrate1, and nitrogen-removal processes consequently affect both ecosystem function and global biogeochemical cycles. It was recently discovered that the anaerobic oxidation of ammonium with nitrite—the ‘anammox’ reaction, performed by bacteria—was responsible for a significant fraction of N2 production in some marine sediments2. Here we show that this reaction is also important in the anoxic waters of Golfo Dulce, a 200-m-deep coastal bay in Costa Rica, where it accounts for 19–35% of the total N2 formation in the water column. The water-column chemistry in Golfo Dulce is very similar to that in oxygen-depleted zones of the oceans—in which one-half to one-third of the global nitrogen removal is believed to occur3,4. We therefore expect the anammox reaction to be a globally significant sink for oceanic nitrogen.

623 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of land use (forested, agricultural, urban) on water quality and aquatic biota was evaluated in three streams in the Piedmont ecoregion of North Carolina.
Abstract: Three streams in the Piedmont ecoregion of North Carolina were studied to evaluate the effect of land use (forested, agricultural, urban) on water quality and aquatic biota. In comparison with the forested stream, there were few changes in water quality at the agricultural and urban streams. Suspended-sediment yield was greatest for the urban catchment and least at the forested catchment. Suspended-sediment concentrations during storm events followed this same pattern, but at low-moderate flows suspended-sediment concentrations were greatest at the agricultural site. Most nutrient concentrations were highest at the agricultural site, and the amount of ‘available’ dissolved nitrogen was elevated at both the urban and agricultural sites. High concentrations of metals (totals) in the water column were sometimes observed at all sites, but maximum average concentrations were recorded at the urban site (especially Cr, Cu, and Pb). Maximum sediment metal concentrations, however, were not found at the urban site, but were usually recorded at the forested site. Only minor differences were noted between fish communities of the forested and agricultural sites, although both abundance and average size of some species increased at the agricultural site. The fish community at the urban site was characterized by low species richness, low biomass, and the absence of intolerant species. Invertebrate taxa richness, a biotic index, and the number of unique invertebrate species (found at only one site) indicated moderate stress (Fair water quality) at the agricultural site and severe stress (Poor water quality) at the urban site. At the agricultural site, declines in taxa richness within intolerant groups were partially offset by increases within tolerant groups. The agricultural stream had the highest abundance values, indicating enrichment. The urban site, however, was characterized by low species richness for most groups and very low abundance values. Analysis of seasonal patterns suggested detritus was the most important food source for invertebrates in the forested stream, while periphyton was of greater importance in the agricultural stream. Dominant macroinvertebrate groups shifted from Ephemeroptera at the forested site, to Chironomidae at the agricultural site, and Oligochaeta at the urban site. There was little between-site overlap in dominant species (8–7%), indicating that land use strongly influenced the invertebrate community. Chemical and physical parameters measured at the three sites did not seem sufficient to account for all of the observed differences in the invertebrate communities, suggesting some unmeasured toxicity. Biological measurements, especially macroinvertebrates community structure, consistently indicated strong between-site differences in water and habitat quality.

605 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that biochemical processes are involved in the formation of the BaSO4 mineral in the water column, rather than purely chemical processes, which would not be anticipated for purely chemical interactions.

605 citations

Journal ArticleDOI
01 Jan 1982-Nature
TL;DR: In an East Mediterranean marine core, the upper sapropel begins soon after the start of a global event, a very heavy precipitation which occurred in the equatorial latitudes during the late Glacial-early Holocene as discussed by the authors.
Abstract: In an East Mediterranean marine core, the upper sapropel begins soon after the start of a global event—a very heavy precipitation which occurred in the equatorial latitudes during the late Glacial–early Holocene. This heavy precipitation in Africa, channelled by the Nile River across 35° of latitude, produced a low-salinity surface layer in the East Mediterranean. In this confined basin, with high bottom salinity, the steep salinity gradient stratified the water column. The stagnant bottom waters triggered the sapropel formation. Cretaceous sapropels in the tropical oceans may result from the same chain of events in warm, humid climates, with contrasting wet-and-dry seasonal rhythm.

588 citations

Journal ArticleDOI
TL;DR: In this article, the water column and the sediments of the Cariaco Trench were measured and the results showed that CH4 is non-conservative in both environments, and the concentrations of CH4 were found to be non-consistency.

557 citations


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