US EPA

3349581 

Journal Article 

Seston dynamics in two Texas prairie streams 

Hill, BH; Gardner, TJ 

1987 

Yes 

American Midland Naturalist
ISSN: 0003-0031
EISSN: 1938-4238 

118 

1 

85-93 

10.2307/2425631 

Particulate organic matter (seston) was sampled at weekly to monthly intervals between October 1984 and November 1985 in two Texas prairie streams. Discharge in these two streams ranged from 0-1,350 l/s at Site 1 (2nd order) and 0-3,310 l/s at Site 2 (3rd order). Seston concentration at Site 1 averaged 10.55±4.10 mg AFDW/l (Ash free dry weight) and ranged from 0.81-232 mg AFDW/l. At Site 2 mean seston concentration was 15.09±4.28 mg AFDW/l, and ranged from 0.81-203 mg AFDW/l. Seasonally, highest seston concentrations were measured in autumn, averaging 45.8 mg AFDW/l at Site 1 and 40.8 mg AFDW/l at Site 2. Lowest seston concentrations and transport were measured in winter at both sites. Minimum seston concentrations averaged 2.9 and 6.6 mg AFDW/l, respectively, for Sites 1 and 2. Total seston concentrations at both sites were moderately to highly correlated with discharge, both seasonally and annually (r2 = .52-.95). Seston transport averaged 1583±1037 mg AFDW/s (range 0-313,794 mg AFDW/s) at Site 1 and 2177±1188 mg AFDW/s (range 0-673,850 mg AFDW/s) at Site 2. Transport was significantly greater (t-test, p < .05) at Site 2, even when adjusted to transport per unit discharge and watershed area. Median seston particle size at Site 1 averaged 60.8±0.9 μ m, and ranged from 53.2-79.5 μ m. Median particle size at Site 2 averaged 57.1±0.3 μ m, with a range of 53.7-63.5 μ m. Median particle size was significantly larger (t-test, P < 0.05) at Site 1. There were no significant seasonal differences in median particle size at either site. Seston at both sites, and on most dates, was dominated by the ultrafine size fraction (0.45-41 μ m), averaging 83% of the seston at Site 1 and 91% at Site 2.