Water column

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

Natural iron enrichment around the Antarctic Peninsula in the Southern Ocean

Abstract: . As part of the US-AMLR program in January-February of 2006, 99 stations in the South Shetland Islands-Antarctic Peninsula region were sampled to understand the variability in hydrographic and biological properties related to the abundance and distribution of krill in this area. Concentrations of dissolved iron (DFe) and total acid-leachable iron (TaLFe) were measured in the upper 150 m at 16 of these stations (both coastal and pelagic waters) to better resolve the factors limiting primary production in this area and in downstream waters of the Scotia Sea. The concentrations of DFe and TaLFe in the upper mixed layer (UML) were relatively high in Weddell Sea Shelf Waters (~0.6 nM and 15 nM, respectively) and low in Drake Passage waters (~0.2 nM and 0.9 nM, respectively). In the Bransfield Strait, representing a mixture of waters from the Weddell Sea and the Antarctic Circumpolar Current (ACC), concentrations of DFe were ~0.4 nM and of TaLFe ~1.7 nM. The highest concentrations of DFe and TaLFe in the UML were found at shallow coastal stations close to Livingston Island (~1.6 nM and 100 nM, respectively). The ratio of TaLFe:DFe varied with the distance to land: ~45 at the shallow coastal stations, ~15 in the high-salinity waters of Bransfield Strait, and ~4 in ACC waters. Concentrations of DFe increased slightly with depth in the water column, while that of TaLFe did not show any consistent trend with depth. Our Fe data are discussed in regard to the hydrography and water circulation patterns in the study area, and with the hypothesis that the relatively high rates of primary production in the central regions of the Scotia Sea are partially sustained by natural iron enrichment resulting from a northeasterly flow of iron-rich coastal waters originating in the South Shetland Islands-Antarctic Peninsula region.

Cycling of dissolved rare earth elements in Chesapeake Bay

Abstract: The measurement of dissolved rare earth elements (REE) in the surface waters, water column of anoxic basins, and pore waters in Chesapeake Bay has provided new insights to the biogeochemistry and estuarine chemistry of REE. All dissolved REE from the riverine source show large-scale removal in the lower salinity zone (0-10‰). The shale-normalized pattern of dissolved Susquehanna River water is opposite in form to that of surface sediments in the Bay. The former is enriched in heavy REE (HREE) while the latter are enriched in light REE (LREE). Neither component has a flat pattern normally assumed for river- transported REE to the ocean. The dissolved LREE (i.e., La, Ce, Nd, Sm, and Eu) are enriched 3 to 9 times) in the oxygen-depleted deep waters over their concentrations in the oxic surface waters. In contrast, HREE (Er, Yb, and Lu) are slightly depleted. All REE concentrations in the two surface (0-2 cm) pore waters are greatly enriched (8-17 times; 43 times for Ce) relative to oxygen-depleted bottom waters and have relative abundances opposite to those of their sediments. While Ce has a positive anomaly in the pore waters, negative anomalies exist in the oxygen-depleted bottom waters. The REE are participating in a set of complex biogeochemical cycles within the water column and surface sediments. Fractionation of REE during these cycles leads to the preferential enrichment of LREE in the seasonally oxygen-depleted bottom waters. It is proposed that this fractionation is coupled to redox cycles of Mn and Fe and the interaction of dissolved REE with suspended particles and surficial sediments.