Topic
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: In this paper, the authors investigated rare earth element and manganese distributions in Saanich Inlet, British Columbia, a seasonally anoxic basin, and proposed an annual redox cycle in which flushing causes extensive oxidative precipitation and scavenging of trace elements from the water column each autumn.
192 citations
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TL;DR: In this article, samples collected in surface waters of the Seine estuary (France) during a low discharge period were analyzed for dissolved and particulate trace metals (Cd, Co, Cu, Mn, Ni, Pb and Zn).
191 citations
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TL;DR: It is shown that a deepening of the thermocline accompanied the warming and increased the stratification of the water column, leading to a decrease in the supply of plant nutrients to the upper layers, which is the most likely mechanism for the observed plankton decline, and subsequent ecosystem changes.
Abstract: Among the least understood interactions between physics and biology in the oceans are those that take place on the decadal scale. But this temporal scale is important because some of the greatest ecological events take place on this time scale. More than 50 years of measurement in the California Current System have revealed significant ecosystem changes, including a large, decadal decline in zooplankton biomass, along with a rise in upper-ocean temperature. The temperature change was a relatively abrupt shift around 1976–77, concurrent with other basin-wide changes associated with an intensification of the Aleutian Low-pressure system. This intensification generates temperature anomalies in the ocean by altering the patterns of net surface-heat fluxes, turbulent mixing, and horizontal transport. Changes in the mean abundance of zooplankton in the southern California Current have been attributed to variations in the strength of coastal upwelling, variations in the horizontal transport of nutrient-rich water from the north, or increased stratification due to warming, all of which could be affected by fluctuations in the Aleutian Low. Here we show that a deepening of the thermocline accompanied the warming and increased the stratification of the water column, leading to a decrease in the supply of plant nutrients to the upper layers. This is the most likely mechanism for the observed plankton decline, and subsequent ecosystem changes. A global change in upper-ocean heat content, accompanied by an increase in stratification and mixed-layer deepening relative to the critical depth for net production, could lead to a widespread decline in plankton abundance.
191 citations
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TL;DR: The TEX86 is a temperature proxy which is based on the number of cyclopentane moieties in the Glycerol dialkyl glycerol tetraether (GDGT) lipids of Crenarchaeota that occur ubiquitously in oceans and shelf seas as mentioned in this paper.
Abstract: The TEX86 is a new temperature proxy which is based on the number of cyclopentane moieties in the
glycerol dialkyl glycerol tetraether (GDGT) lipids of the membranes of Crenarchaeota that occur ubiquitously in
oceans and shelf seas. This proxy was calibrated by core top sediments, but it is as yet not clear during which
season and at which depth in the water column the GDGT signal used for TEX86 paleothermometry is
biosynthesized. Here we analyzed >200 particulate organic matter (POM) samples from 11 different marine
settings for TEX86. This revealed that the GDGTs occur seasonally in surface waters and occur in higher
abundances during the winter and spring months. The depth distribution showed that GDGTs generally appeared
in higher amounts below 100 m depth in the water column. However, the TEX86 values for waters below the
photic zone (150–1500 m) did not correlate with the in situ temperature but rather correlated linearly with
surface temperature. The TEX86 for POM from the upper 100 m showed a linear correlation with in situ
temperature, which was nearly identical to the previously reported core top equation. The correlation of all POM
samples with surface temperature was also strikingly similar to the core top correlation. These findings
demonstrate that the GDGT signal which reaches the sediment is mainly derived from the upper 100 m of the
water column. This may be caused by the fact that GDGTs from the photic zone are much more effectively
transported to the sediment by grazing and repackaging in large particles than GDGTs from deeper waters.
191 citations
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TL;DR: It is shown that carbohydrate- and protein-like substances in the open Atlantic and Pacific oceans, though often significantly aged, comprise younger fractions of the DOM, whereas dissolved lipophilic material exhibits up to ∼90 per cent fossil character.
Abstract: Seawater dissolved organic matter (DOM) is the largest reservoir of exchangeable organic carbon in the ocean, comparable in quantity to atmospheric carbon dioxide. The composition, turnover times and fate of all but a few planktonic constituents of this material are, however, largely unknown. Models of ocean carbon cycling are thus limited by the need for information on temporal scales of carbon storage in DOM subcomponents, produced via the 'biological pump', relative to their recycling by bacteria. Here we show that carbohydrate- and protein-like substances in the open Atlantic and Pacific oceans, though often significantly aged, comprise younger fractions of the DOM, whereas dissolved lipophilic material exhibits up to approximately 90 per cent fossil character. In contrast to the millennial mean ages of DOM observed throughout the water column, weighted mean turnover times of DOM in the surface ocean are only decadal in magnitude. An observed size-age continuum further demonstrates that small dissolved molecules are the most highly aged forms of organic matter, cycling much more slowly than larger, younger dissolved and particulate precursors, and directly links oceanic organic matter age and size with reactivity.
191 citations