Water column

About: Water column is a research topic. Over the lifetime, 13706 publications have been published within this topic receiving 496626 citations.

Transfer of hydrocarbons from natural seeps to the water column and atmosphere

Abstract: Results from surface geochemical prospecting, seismic exploration and satellite remote sensing have documented oil and gas seeps in marine basins around the world. Seeps are a dynamic component of the carbon cycle and can be important indicators for economically significant hydrocarbon deposits. The northern Gulf of Mexico contains hundreds of active seeps that can be studied experimentally with the use of submarines and Remotely Operated Vehicles (ROV). Hydrocarbon flux through surface sediments profoundly alters benthic ecology and seafloor geology at seeps. In water depths of 500‐2000 m, rapid gas flux results in shallow, metastable deposits of gas hydrate, which reduce sediment porosity and affect seepage rates. This paper details the processes that occur during the final, brief transition — as oil and gas escape from the seafloor, rise through the water and dissolve, are consumed by microbial processes, or disperse into the atmosphere. The geology of the upper sediment column determines whether discharge is rapid and episodic, as occurs in mud volcanoes, or more gradual and steady, as occurs where the seep orifice is plugged with gas hydrate. In both cases, seep oil and gas appear to rise through the water in close proximity instead of separating. Chemical alteration of the oil is relatively minor during transit through the water column, but once at the sea surface its more volatile components rapidly evaporate. Gas bubbles rapidly dissolve as they rise, although observations suggest that oil coatings on the bubbles inhibit dissolution. At the sea surface, the floating oil forms slicks, detectable by remote sensing, whose origins are laterally within � 1000 m of the seafloor vent. This contradicts the much larger distance predicted if oil drops rise through a 500 m water column at an expected rate of � 0.01 m s � 1 while subjected to lateral currents of � 0.2 m s � 1 or greater. It indicates that oil rises with the gas bubbles at speeds of � 0.15 m s � 1 all the way to the surface.

Abundance and distribution of planktonic Archaea and Bacteria in the waters west of the Antarctic Peninsula

Abstract: Polyribonucleotide probes targeting planktonic archaeal (Group I and II) and bacterial rRNA revealed that Ar- chaea comprised a significant fraction of total prokaryote cell abundance in the marine waters west of the Antarctic Peninsula. Determinations of Archaea and Bacteria cell abundances were made during two research cruises to the Palmer Long-Term Ecological Research region during the austral winter and summer of 1999. During the austral summer, surface water abundances of Group I (GI) Archaea were generally low, averaging 4.7 3 10 3 cells ml 21 and comprising 9-39% of the total picoplankton abundance in the meso- (150-1,000 m) and bathypelagic (1,000-3,500 m) circumpolar deep water (CDW). Relative to summertime distri- butions, GI cells were more evenly distributed throughout the water column during the winter, averaging 10% of the picoplankton in the surface waters and 13% in the CDW. Surface water GI abundance increased 44% between the summer and winter, coincident with a fivefold decrease in GI abundance in the deeper waters. The abundance of Group II (GII) Archaea was persistently ,2% of the total picoplankton throughout the water column in both summer and winter. Bacterial abundance was greatest in the upper water column (0-100 m) during the summer, averaging 3.9 3 10 5 cells ml 21 and comprised 89% of the total picoplankton assemblage. Generally, GI Archaea varied seasonally in the deeper waters, whereas bacterial abundance varied more in the upper waters. The observed variability in bacterial and archaeal abundance suggests that these two groups of marine picoplankton are dynamic components of Southern Ocean microbial food webs.

The influence of physical stability on spring, summer and autumn phytoplankton blooms in the Celtic Sea

Abstract: The Celtic Sea extends from the south of Ireland and the St Georges Channel across the continental shelf, with the Bristol and English Channels as its eastern limits (Fig. 1) (Cooper, 1967). Although various investigations of the physical oceanography (Matthews, 1914; Cooper, 1967) and zooplankton (Russell, 1934, a, b, 1936; Corbin, 1947; and more recently Southward, 1962; Bary, 1963) of this area have been carried out, there is little or no information on seasonal changes in levels of chlorophyll ‘a’ and inorganic nutrients, and on the importance of tidal mixing in determining these distributions. Since the speeds of the tidal streams range from weak (∼ 0.5 knot) in the northern part of the Celtic Sea to strong (∼ 3 knots) around the Scilly Isles and Ushant (Fig. 2), the vertical stability of the water column as well as the duration of the seasonal thermocline (Pingree, 1975) are likely to be important factors in determining spatial and temporal variations of phytoplankton production. In this paper the influence of water-column stability on phytoplankton distributions (in spring, summer and autumn) in the Celtic Sea is described, using data for temperature, salinity, chlorophyll ‘a’ and inorganic nutrients obtained during seven cruises in 1975. An account of the red tide conditions that occurred in late July to the north-west of Ushant has already been published (Pingree, Pugh, HoUigan & Forster, 1975).

Characteristics of dissolved organic matter in Baltic coastal sea ice: allochthonous or autochthonous origins?

Abstract: The origin of dissolved organic matter (DOM) within sea ice in coastal waters of the Baltic Sea was investigated using parallel factor (PARAFAC) analysis of DOM fluorescence. Sea ice DOM had distinctly different fluorescence characteristics than that of the underlying humic-rich waters and was dominated by protein-like fluorescence signals. PARAFAC analysis identified five fluorescent components, all of which were present in both sea ice and water. Three humic components were negatively correlated to salinity and concluded to be terrestrially derived material. Baltic Sea ice DOM was found to be a mixture of humic material from the underlying water column incorporated during ice formation and autochthonous material produced by organisms within the ice. Dissolved organic carbon (DOC) and nitrogen (DON) concentrations were correlated to the humic fluorescence, indicating that the majority of the organic carbon and nitrogen in Baltic Sea ice is bound in terrestrial humic material trapped within the ice. This has implications for our understanding of sea ice carbon cycling in regions influenced by riverine input (e.g., Baltic and Arctic coastal waters), as the susceptibility of DOM to degradation and remineralization is largely determined by its source.