Effects of copper on production of periphyton, nitrogen fixation and processing of leaf litter in a Sierra Nevada, California, stream

Abstract

SUMMARY. 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 10μg 1‐1 CuT [total filtrable copper]; approximately 12, 25 and 50 ng 1‐1 Cu2+) were determined. 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. Autotrophic productivity was reduced by 57–81% at 2.5μg 1‐1 CuT, 55–96% at 5μg 1‐1 CuT, and 81–100% at 10μg 1‐1 CUT, Heterotrophic productivity (based on dark 35S‐sulphate uptake) was inhibited to a lesser extent (28–63% at 2.5μg 1‐1 CuT, 24–84% at 5μg 1‐1 CuT, and 67–92% at 10μg 1‐1 CuT), The inhibition of autotrophic and heterotrophic productivity persisted through the year of exposure. Production in stream sections previously exposed to 2.5 and 5μg 1‐1CuT increased to control levels within 4 weeks after dosing, but remained depressed for more than 7 weeks after exposure to 10μg 1‐1 CuT. The specific rate of photosynthesis (mg C mg chlorophyll a‐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. Achrtanthes minutissima and Fragilaria crotonensis were the primary replacement species on newly‐colonized surfaces. 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 10μg 1‐1 CuT. However, after 9 months of exposure, control and copper‐treated sections did not differ. 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.

Genes Conferring Copper Resistance in Sinorhizobium meliloti CCNWSX0020 Also Promote the Growth of Medicago lupulina in Copper-Contaminated Soil

“…Sinorhizobium meliloti CCN-WSX0020 and copper-sensitive mutants were precultured in TY medium at 28°C with shaking at 150 rpm for 48 h, and 1% of the cultures was added to TY medium (pH ϭ 7.0) supplemented with four different metals at the following concentrations: CuSO 4 DNA manipulations and sequence analysis. Copper-sensitive mutants were incubated for 2 days at 28°C in TY broth with shaking at 150 rpm.…”

“…Complementation constructs were sequence verified with the corresponding primers, transformed into E. coli donor strain JM109, and delivered into mutants via triparental mating. Single colonies carrying the complementation plasmids were selected on YMA plates with gentamicin and assayed for growth in medium supplemented with different concentrations of CuSO 4 .…”

“…To isolate copper-sensitive mutants, Tn5-1063a was used to mutate S. meliloti CCNWSX0020. A total of 14,000 Km r transconjugants were analyzed, of which five mutants, named SXa-1, SXa-2, SXc-1, SXc-2, and SXn, were unable to grow on TY agar plates supplemented with 0.8 mM CuSO 4 . Probing the total genomic DNA of these mutants (digested with BglII) with a labeled Tn5 DNA fragment established that each strain carried a single Tn5-luxAB insertion (data not shown) (23).…”

“…Copper is usually cytotoxic at high concentration, it persists in the environment, and it is risky to living organisms (2,3). Copper may reduce biodiversity and significantly limit reproduction, growth, and activity of bacteria, i.e., nitrogen fixation in diazotrophs (4). Transport systems for regulating copper homeostasis play a crucial role in tolerating copper toxicity in most organisms.…”

Efeitos da irradiância e da composição espectral da luz sobre o estabelecimento e desenvolvimento de comunidades de macroalgas lóticas em substratos artificiais

“…Exemplos de estudos ecológicos envolvendo a análise de comunidades de produtores associadas a substratos artificiais em ambientes lóticos são relativamente comuns na literatura mundial (Biggs, 1988;Liaw & Maccrimmon, 1978;Leland & Carter, 1985;Clifford et al, 1992;Barbee, 2005). Vários estudos semelhantes são encontrados para rios e riachos brasileiros (Lobo & BuselatoToniolli, 1985;Oliveira et al, 2002;Mendes & Barbosa, 2002;Fernandes & Esteves, 2003;Skinner & Coutinho, 2005;Lobo et al, 2004).…”