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|Title:||Effects of water chemistry on aquatic plants : interactive effects of inorganic carbon and nitrogen on biomass production and plant nutrition|
|Authors:||Aquatic Plant Control Research Program (U.S.)|
Smart, R. Michael.
Barko, John W.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Growth of the submersed aquatic plants Egeria densa, Hydrilla verticillata, and Myriophyllum spicatum was examined under two levels of inorganic carbon supply, at two sediment nitrogen (N) levels, in a solution containing moderate levels of major cations and inorganic carbon (CT). Levels of inorganic carbon supply were achieved by aeration with ambient air or CO2-enriched air. Sediment N levels consisted of a control sediment and the same sediment after fertilization with ammonium chloride. The primary objective of the study was to evaluate the interactive effects of inorganic carbon supply and sediment N availability on plant growth and nutrition. Results indicate that both inorganic carbon supply and sediment N availability can limit the growth of submersed aquatic plant populations. Of the species studied here, Egeria was more affected by inorganic carbon supply, Myriophyllum was more affected by sediment N availability, and Hydrilla was equally affected by both factors. Maximal plant growth of all species occurred under conditions of high inorganic carbon supply and high sediment N availability, indicating that suboptimal levels of either factor can depress growth. Myriophyllum, by virtue of its relatively greater root production, was more effective at N acquisition, and thus produced the most biomass under maximal growth conditions. Increased N availability led to increased accumulation not only of N, but of other nutrients (phosphorus and potassium) as well. Under N-limiting conditions, increased N availability also promoted an increased demand for inorganic carbon, resulting in depletion of C𝚝 from solution under the lower level of inorganic carbon supply. Depletion of solution C𝚝 resulted from both enhanced photosynthetic rates and the resultant increased rates of CaCO3 precipitation. Under inorganic carbon-limiting conditions, increased inorganic carbon availability increased the demand for both sediment and water nutrients. These results suggest the existence of a feedback loop regulating biomass production in submersed aquatic plants. Both inorganic carbon and sediment nitrogen may limit biomass production in field populations. Increases in the supply of either limiting factor may result in increased demand for the other factor, eventually resulting in low levels of both factors. For this reason, biomass production in natural populations of submersed aquatic plants may decline over the years as both inorganic carbon supply and sediment N availability approach limiting levels.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|
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