Silicon Retention in River Basins

Silicon Retention in River Basins: Far-Reaching Effects on Biogeochemistry and Aquatic Food Webs in Coastal Marine Environments

Christoph Humborg, Daniel J. Conley, Lars Rahm, Fredrik Wulff, Adriana Cociasu and Venugopalan Ittekkot

Ambio, Vol. 29, No. 1 (Feb., 2000), pp. 45-50
(article consists of 6 pages)

Published by: Allen Press on behalf of Royal Swedish Academy of Sciences
Stable URL: http://www.jstor.org/stable/4314993

Silicon Retention in River Basins: Far-Reaching Effects on Biogeochemistry and Aquatic Food Webs in Coastal Marine Environments, by Christoph Humborg, Daniel J. Conley, Lars Rahm, Fredrik Wulff, Adriana Cociasu and Venugopalan Ittekkot © 2000 Royal Swedish Academy of Sciences.

Abstract

Regulation of rivers by damming as well as eutrophication in river basins has substantially reduced dissolved silicon (DSi) loads to the Black Sea and the Baltic Sea.

Whereas removal of N and P in lakes and reservoirs can be compensated for by anthropogenic inputs in the drainage basins, no such compensation occurs for DSi.
[ except for Nualgi ]

The resulting changes in the nutrient composition (DSi:N:P ratio) of river discharges seem to be responsible for dramatic shifts in phytoplankton species composition in the Black Sea.

In the Baltic Sea, DSi concentrations and the DSi:N ratio have been decreasing since the end of the 1960s, and there are indications that the proportion of diatoms in the spring bloom has decreased while flagellates have increased.

The effects on coastal biogeochemical cycles and food web structure observed in the Black Sea and the Baltic Sea may be far reaching, because it appears that the reductions in DSi delivery by rivers are probably occurring worldwide with the ever increasing construction of dams for flow regulation.