Water column

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

Significant Flux Of Atmospheric Nitrous-Oxide From The Northwest Indian-Ocean

Abstract: INTEREST in nitrous oxide (N2O) has increased considerably in the light of its deleterious effect on the ozone layer1, and contribution to the greenhouse effect2. There are many sources of atmospheric N2O, both anthropogenic (for example, combustion) and natural, but the global budget is still inadequately defined. Despite the fact that most of the world's oceans are close to equilibrium with the atmosphere3, water bodies depleted in oxygen have been identified as areas of N2O production4,5, and so the oceans represent a potential source of atmospheric N2O. Here we report elevated N2O concentrations in the northwest Indian Ocean, an area that exhibits upwelling and high oxygen consumption in the water column. We found that N2O was supersaturated in both oxygen-saturated surface waters (up to 246% N2O saturation) and oxygen-depleted sub-surface waters (1,264% N2O saturation). The calculated flux to the atmosphere indicated that upwelling in the northwest Indian Ocean (15–25° N) represents one of the most significant marine sources of N2O, contributing between 5 and 18% of the total marine flux from a surface area of only 0.43% of the world ocean. These data suggest that the oceanic flux of N2O to the atmosphere shows strong spatial heterogeneity which should be considered in global budgets and ocean–atmosphere models.

Arsenic, antimony, and germanium biogeochemistry in the Baltic Sea

Abstract: Arsenic, antimony, and germanium species concentrations have been determined from fivehydrographic stations along the central axis of the Baltic Sea from the Bornholm Basin to theGulf of Finland. Arsenic and antimony concentrations are lower than in the open oceans and inmost rivers. In the oxic waters, the pentavalent species of As and Sb predominate, while in theanoxic basins, the distribution shifts to the trivalent species and possibly some sulfo-complexes.Methylated arsenic species make up a large fraction of dissolved As in the surface waters, andmethylated species of As, Sb, and Ge are detectable throughout the water column. Germanicacid concentrations are about ten times higher than in the ocean and much higher than can beaccounted for by Ruvial input. The vertical distributions of arsenic, antimony, and germaniumwithin the Baltic Sea are controlled by biogeochemical cycling, involving biogenic uptake,particulate scavenging and partial regeneration. A mass balance including river and atmosphericinputs, exchange with the Atlantic through the Belt Sea, and removal by sediment depositionsuggests that anthropogenic inputs make a significant contribution to the budgets of all threeelements, with atmospheric fluxes dominating the input of Ge to the Baltic. DOI: 10.1111/j.1600-0889.1984.tb00232.x

Comparative accounts of biological productivity characteristics and estimates of carbon fluxes in the Arabian Sea and the Bay of Bengal

Abstract: The Arabian Sea and the Bay of Bengal are tropical basins experiencing monsoonal wind forcing that reverses semi-annually. This brings changes in physics, chemistry and biology of the upper water column on a seasonal scale and ultimately regulates the sinking fluxes of the region. An attempt is made here to focus on factors responsible for fluxes of carbon from the upper layers to the deep sea. Higher fluxes are observed during southwest and northeast monsoon season in both the regions. In contrast to the Arabian Sea, an immense quantity of freshwater runoff together with warmer SST (∼30 °C) makes the northern bay strongly stratified. The runoff also brings in billions of tonnes of fluvial matter as well. Stratification constrains subsurface nutrient input into the surface waters thereby reducing the primary production in the Bay of Bengal. The total living carbon content in the Bay of Bengal is much lower than in the Arabian Sea. Higher downward fluxes associated with deep mixed layer and high production in the Arabian Sea during summer and winter pinpoint importance of strong winds causing mixing and upwelling during summer and evaporative cooling and convection during winter. Inability of the low-speed winds to break the stratification in the Bay of Bengal keeps the region low productive throughout the year. Therefore, river water associated with the terrigenous material due to ballast effect appears to swipe off surface producers to the deep, thereby increasing the downward fluxes of total particulates, which are sometimes even higher than that of the more productive Arabian Sea.

Effects of Fish and Plankton and Lake Temperature and Mixing Depth

Abstract: A comparative study of small temperate lakes (<20 square kilometers) indicates that the mixing depth or epilimnion is directly related to light penetration measured as Secchi depth Clearer lakes have deeper mixing depths This relation is the result of greater penetration of incident solar radiation in lakes and enclosures with high water clarity Data show that light penetration is largely a function of size distribution and biomass of algae as indicated by a relation between the index of plankton size distribution (slope) and Secchi depth Larger or steeper slopes (indicative of communities dominated by small plankton) are associated with shallower Secchi depth In lakes with high abundances of planktivorous fish, water clarity or light penetration is reduced because large zooplankton, which feed on small algae, are reduced by fish predation The net effect is a shallower mixing depth, lower metalimnetic temperature and lower heat content in the water column Consequently, the biomass and size distribution of plankton can change the thermal structure and heat content of small lakes by modifying light penetration