Water column

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

The biology of soft shores and estuaries

Abstract: 1: Introduction: organisms, sediments, and water movements 2: The world of particles: a variety of habitats 3: The coarse extreme: life on sandy beaches 4: A fine option: life on mudflats and in seagrass beds 5: Salt marshes and mangrove swamps 6: Life at the bottom: sublittoral sediments and community structure 7: Estuarine habitats and coastal lagoons 8: The estuarine benthos and its distribution 9: Life in the estuarine water column 10: Estuarine ecosystems 11: Uses and abuses: human impact and counter-measures.

Effects of low oxygen waters on Chesapeake Bay zooplankton

Abstract: The bottom waters of the mesohaline portion of Chesapeake Bay become depleted in oxygen in summer. We found that copepods and nauplii were in low abundance or absent from bottom waters when oxygen concentrations were <1 mg O2 liter−1. In contrast, when oxygen concentrations were higher in bottom waters in spring or summer due to episodic mixing events, the highest copepod abundances were often found in bottom waters. Laboratory experiments confirmed that oxygen concentrations <1 mg O2 liter−1 resulted in reduced survival of the copepods Acartia tonsa and Oithona colcarva and inhibited the hatching of A. tonsa eggs. The decrease in Chesapeake Bay copepods in May–June parallels the decline of oxygen in bottom waters. Our field and laboratory data suggest that this decline in copepods could result from reduced recruitment as a consequence of egg mortality in the low-oxygen bottom waters. In summer this source of mortality would be reduced because warmer water temperatures would allow the eggs to hatch in the upper water column above the low-oxygen bottom waters.

Role of bottom sediments in the secondary pollution of aquatic environments by heavy metal compounds

Abstract: The results of long-term investigations into the concentrations of some heavy metals (Fe, Mn, Cu, Zn, Pb, Cr, and Cd) in the bottom sediments of the Dnieper reservoirs and the Dnieper–Bug estuary are considered. Maximum quantities of the metals studied are characteristic of southern water bodies located within industrial zones (the Zaporozh’e and Kakhovka reservoirs as well as the Dnieper–Bug estuary). The highest concentrations of the metals studied occurred in the clay silts (Fe, 11 600–32 400; Mn, 1504–3450; Cu, 38.9–85.5; Zn, 89.8–186.5; Cr, 48.6–193.0; and Cd, 1.9–4.4 mg kg-1 dry weight). Accumulation of heavy metals in the bottom sediments is an important factor in the self-purification of aquatic environments. However, this process is reversible and therefore provides a constant threat of secondary water pollution. Secondary water pollution is observed in summer and autumn when water consumption increases. The concentrations of heavy metals increase by a factor of 1.5–3 after the drawdown of the water level. The main reason for the rise in the concentrations of metals is exchange between the bottom sediments and the water column. The rate of heavy metal migration is connected with the forms of occurrence in solid substrates and pore solutions in the bottom sediments, as well as with physico-chemical conditions arising at the sediment/water boundary. Therefore, our investigations concentrated on the study of the fractional distribution of heavy metals among solid substrates and their forms of occurrence in interstitial solutions. This distribution depends, most of all, on the chemical properties of metals as well as the chemical and mineralogical composition of the sediments and the chemical properties of pore solutions. Most of the supply of Mn, Zn, Fe, and Cd is associated with oxides and hydroxides of iron and manganese (Mn, 74–93%; Zn, 43–70%; Fe, 27–59%; and Cd, 28–41%). Most copper and chromium is bound to organic matter and to scarcely soluble minerals. In the interstitial solutions studied, metals (except manganese) are found mainly as complex compounds with dissolved organic matter of a different molecular weight. Nevertheless, the fraction of complexes with a relatively low molecular weight (500–5000 Da) prevailed (40–70%). Dissolved manganese in the pore solutions consists chiefly of free (hydrated) ions Mn2+ (80–95%). The results obtained were used for a comparative evaluation of heavy metal mobility and the exchange ability of their associated compounds in the bottom sediment–water system.