Experimental Enrichment of a Coastal Stream in British Columbia: Effects of Organic and Inorganic Additions on Autotrophic Periphyton Production

Abstract

Periphyton accumulation rates and alkaline phosphatase activity were examined in reaches of the Keogh River, British Columbia, following additions of grain and inorganic fertilizer as separate treatments during spring–summer 1981. Two different levels of N and P addition were used: one to attain ambient N and P concentrations of 200 and 15 μg∙L−1, respectively, and the other to attain 400 and 20 μg∙L−1, respectively. Grain (rolled barley) was added monthly at 280 g∙m−2. N and P additions increased chlorophyll a accrual rates by more than an order of magnitude. Diatoms dominated the periphyton community until midsummer. In July and most of August, the relative importance of chlorophytes increased and biomass levels declined markedly in spite of continued nutrient additions. Grain additions resulted in no detectable change in periphyton accrual, but alkaline phosphatase activity increased by 35% over control levels. These results suggest that additions of labile organic matter to nutrient-deficient coastal streams can increase autotrophic P deficiency. Based on responses of juvenile salmonids, additions of inorganic nutrients to increase autotrophic production can maximize trophic enhancement in nutrient-deficient streams.

N and P limitation of benthos abundance in the Nechako River, British Columbia

“…A typical event during time-course accrual of periphyton in rivers augmented with nutrients is a massive decline in biomass shortly after a logarithmic increase in biomass has occurred (Perrin et al 1987) despite continuous enrichment. Results from the mesocosm were consistent with this process: biomass from the N + P addition declined from a peak chlorophyll a concentration of 62.4 mg⋅m -2 to reach 10.5 mg⋅m -2 within the final week of the experiment.…”

“…There are also many conditions under which such coupling of the productivities of producer and consumer may not keep pace with each other (e.g., Murdoch and McCauley 1985). For example, in the whole-river fertilization of the Keogh River (Perrin et al 1987) and the Nechako River (Slaney et al 1994), algal biomass increased by several times during the first few weeks of fertilization in spite of increased densities of grazing insects. In the Keogh River, the increase in algal biomass was followed Contrast (probability) Note: Critical a for statistical significance was 0.005 after the Bonferroni correction for multiple comparisons (not including total numbers, which is a composite measure of all the others).…”

“…This section provided substrata for the colonization and growth of benthic invertebrates. Downstream of the gravel was a 0.32-m section that was fitted with a sheet (1.2-cm thickness) of open-cell styrofoam (as reported by Perrin et al 1987) that provided a surface for the sampling of periphyton biomass. The gravel and styrofoam sections were separated with a 7-cm-high baffle that produced a water depth of 7 cm over the gravel and a surface current velocity of 5 cm⋅s -1 .…”

“…Peterson et al (1983), Perrin et al (1987), and Bothwell (1989) showed that additions of P to P-deficient streams can increase the growth and biomass of periphytic algae. The concentration of added PO 4 -P that saturates Pdeficient growth can be <1 µg⋅L -1 (Bothwell 1989), but the concentration that saturates the accrual of areal biomass is higher due to diffusion effects within the algal mat (Bothwell 1989;Stevenson and Glover 1993).…”

Water quality, chlorophyll, and periphyton responses to nutrient addition in the Kootenai River, Idaho

“…Two 30 × 30-cm cement tiles with 4 sections of 2.5-cm-thick Styrofoam ® glued to their upper surfaces were placed on the substrate at each site to estimate chlorophyll biomass (μg/cm 2 ) and accrual rate (μg cm -2 d -1 ) using methods published by Perrin et al (1987) and Bothwell (1989 Algal community composition Algal taxonomic composition was estimated from randomly selected, fixed-area (645.2 mm 2 ) periphyton scrapes from rocks. One sample was collected per site per sampling date.…”