Identifying sediment nutrients that further characterize the habitat associated with the endangered Texas wildrice (Zizania texana Hitch)
Date
1999-05
Authors
Pennington, Toni
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Abstract
Interstitial water samplers (peepers) were used to examine porewater nutrients associated with a particular stand of the endangered aquatic macrophyte, Texas wild rice (Zizania texana Hitchcock), in the San Marcos River in June, August, and November 1998. Peepers were oriented vertically down into the sediments to capture water in discrete chambers at 2.5 cm intervals from approximately 15 cm above the sediment-water interface and to a depth of 15 cm into the sediments. They were deployed under the leaf blades (inside the stand) and adjacent to or upstream of the stand (outside the stand). Samples were analyzed for NO3¯N and soluble reactive phosphorus (SRP). Water column concentrations were around 1.0 mg L-1 N03¯N and 10 µg L-1 SRP. Porewater concentrations were <0.4 mg L-1 N03¯N and between 10 and 58 µg L-1 SRP. Porewater phosphorus concentrations were highly patchy indicating a dynamic sediment structure in the river channel. Significant differences between nutrient concentrations were predominately observed between the water column and porewater and less common between inside and outside the stand. A nutrient limitation experiment using low P (500 µg L-1), high P (1000 µg L-1), and N+P (1.5 mg L-1 N + 500 µg L-1) showed a slight increase in plant mass between P treatments (p<0.10); however, the relationship between plant mass and enrichment concentration was weak (r=0.44). Only a slight effect on plant mass was observed in the N-enriched plants (p=0.08), but not leaf lengths. The lowest r:s ratio was observed in the N+P enrichment.
Description
Keywords
Zizania texana, wild rice, nutrition, habitats, interstitial nutrients, sediments
Citation
Pennington, T. (1999). Identifying sediment nutrients that further characterize the habitat associated with the endangered Texas wild rice (Zizania texana Hitch) (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.