SS4.09 Does Intentional Nutrient Fertilization (N,P And Fe) Foster C Sequestration and/or Increased Fish Fertilization?
Date: Tuesday, June 11, 2002
Time: 10:30:00 AM
Location: Colwood
 
DzialowskiAR, University of Kansas, Lawrence, USA, dzial@ku.edu
Smith, V, H, University of Kansas, Lawrence, USA, vsmith@ku.edu
 
EFFECTS OF VARYING NITROGEN : PHOSPHORUS SUPPLY RATIOS ON ZOOPLANKTON COMMUNITY STRUCTURE
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Variations in the ratios of growth-limiting nutrients can have profound effects on phytoplankton community structure. However, little is unknown about how these stoichiometric effects cascade into secondary aquatic consumers. Therefore, we conducted a preliminary mesocosm experiment to determine how variations in the supply ratios of nitrogen and phosphorus (N:P) affect zooplankton community structure. Nutrient levels were manipulated in a series of mesocosms to create a gradient of five N:P supply ratios ranging from 5:1 to 50:1 by mass. We found a strong effect of N:P supply ratio on zooplankton species composition, community size structure, and diversity. For example, most mesocosms receiving the lowest N:P ratio (5:1) were dominated by the small-bodied cladoceran Chydorus sphaericus; in contrast, mesocosms receiving the highest N:P ratio (50:1) were dominated by the larger cladoceran Diaphanasoma birgei. In addition, zooplankton diversity tended to be highest in mesocosms with intermediate N:P ratios. Overall, our results suggest that N:P supply ratios are potentially an important determinant of zooplankton community structure.