James L. Carter Harry V. Leland 1985 <ul id="l1" class="custom"><li><span class="bullet">1</span>Production of periphyton, nitrogen fixation and processing of leaf litter were examined in an oligotrophic Sierra Nevada stream and the responses of these processes to copper (2.5, 5 and 10<i>μ</i>g 1^-1 Cu_T [total filtrable copper]; approximately 12, 25 and 50 ng 1^-1 Cu²⁺) were determined.</li><li><span class="bullet">2</span>Autotrophic and total production were estimated from 3-week accumulations of biomass on artificial substrates. Mean autotrophic production in the control ranged from 0.22 to 0.58 mg C m^-2 h^-1 in summer-autumn 1979, but declined to 0.08–0.28 mg C m ² h^-1 after peak discharge in summer 1980, apparently due to phosphorus-limited growth. Total production in the control ranged from 0.30 to 0.82 mg C m^-2 h ^-1 in summer-autumn 1979 and from 0.16 to 0,68 mg C m ^-2 h ^-1 in 1980. Mean autotrophic productivity, estimated by ^l4C-bicarbonate uptake in daylight, ranged from 0.30 to 2.8 mg C m^-2 h^-1.</li><li><span class="bullet">3</span>Autotrophic productivity was reduced by 57–81% at 2.5<i>μ</i>g 1^-1 Cu_T, 55–96% at 5<i>μ</i>g 1^-1Cu_T, and 81–100% at 10<i>μ</i>g 1^-1 CU_T, Heterotrophic productivity (based on dark ³⁵S-sulphate uptake) was inhibited to a lesser extent (28–63% at 2.5<i>μ</i>g 1^-1 Cu_T, 24–84% at 5<i>μ</i>g 1^-1 Cu_T, and 67–92% at 10<i>μ</i>g 1^-1 Cu_T), The inhibition of autotrophic and heterotrophic productivity persisted through the year of exposure. Production in stream sections previously exposed to 2.5 and 5<i>μ</i>g 1^-1Cu_T increased to control levels within 4 weeks after dosing, but remained depressed for more than 7 weeks after exposure to 10<i>μ</i>g 1^-1 Cu_T.</li><li><span class="bullet">4</span>The specific rate of photosynthesis (mg C mg chlorophyll <i>a</i>^-1 h^-1) of mature periphyton communities declined at all test concentrations of copper, but the rate for periphyton on newly-colonized surfaces did not change. The species composition of benthic algae shifted during exposure to an assemblage more tolerant of copper. <i>Achrtanthes minutissima</i> and <i>Fragilaria crotonensis</i> were the primary replacement species on newly-colonized surfaces.</li><li><span class="bullet">5</span>The nitrogenase activity of blue-green algae was low. with controls ranging from 2.4 to 12 nmol C₂H₂ m^-2 h^-1. Nitrogenase activity was inhibited during the initial weeks of exposure by 5 and 10<i>μ</i>g 1^-1 Cu_T. However, after 9 months of exposure, control and copper-treated sections did not differ.</li><li><span class="bullet">6</span>The rate of processing of leaf litter, estimated by microbial respiration and nutrient quality of litter of resident riparian woodland taxa, was inhibited at all test concentrations of copper.</li></ul> application/pdf 10.1111/j.1365-2427.1985.tb00189.x en Wiley Effects of copper on production of periphyton, nitrogen fixation and processing of leaf litter in a Sierra Nevada, California, stream article