Synergism of Nutrients and Humic Acid in Accrual of Periphytic Biomass in a Subalpine Stream, Colorado Front Range

Abstract

ABSTRACT Nutrient diffusing substrata were used to test for a three-way interaction between humic acid (HA), nitrogen (N) and phosphorus (P) nutrients in North Boulder Creek, Colorado. Biomass accrual was measured after three weeks as chlorophyll a (chl a). In 2001 the experimental design was a 2x2x2 factorial arrangement of treatments in a completely randomized design. Ethylene diamine tetraacetic acid (EDTA) was also tested as a possible growth stimulant in 2002. Analysis of variance procedures were used to reveal important interactions among the three factors. Higher chl a in HA+P and N+P treatments suggested strongest synergisms between P and HA and between P and N. EDTA failed to promote as much biomass accrual as HA when N and P were supplied. It is suggested that the synergism between P and HA may simply be due to dissolved organic matter that HA provides. Alternatively, HA may provide a microhabit free of UV-B radiation which is conducive to colonization by tube-forming chironomid larvae and their algal “gardens.”