Two species of marine phytoplankton, Platymonas helgolandica var. tsingtaoensis and Heterosigma akashiwo, were cul- tivated in bi-algal cultures to investigate the effect of anthracene （ANT） on the interaction betwe...Two species of marine phytoplankton, Platymonas helgolandica var. tsingtaoensis and Heterosigma akashiwo, were cul- tivated in bi-algal cultures to investigate the effect of anthracene （ANT） on the interaction between them. Without ANT, H. akashiwo out-competed P. helgolandica at low initial biomass ratios （P. helgolandica （P）： H. akashiwo （H） = 1：4 and 1 ： 1）, but not at the highest （P：H=4：I）. This observation was consistent with the description in Lotka-Volterra two species competition model. It was found that P. helgolandica was excluded at low initial biomass ratios, while the unstable equilibrium between two species was predicted at the highest. For both species, carrying capacity and maximal specific growth rate decreased in bi-algal cultures compared to those in monocultures. H. akashiwo exhibited a higher sensitivity to ANT than P helgolandica. This resulted markedly in a reduced cell den- sity of H. akashiwo but an increased cell density ofP. helgolandica. Carrying capacity ofP. helgolandica was consistently higher in bi-algal cultures with ANT than those without ANT, suggesting that ANT, through the elimination of H. akashiwo, generated the dominance of P helgolandica independently of initial biomass ratios. This study showed a density-dependent effect of harmful alga （H. akashiwo） on dietary alga （P helgolandica）, and indicated that ocean pollutant ANT could induce the succession of marine phytoplankton.展开更多
Ectomycorrhizal(EM) fungi could form symbiosis with plant roots and participate in nutrient absorption; however, many EM species commonly found in forest soils, where phosphorus(P) concentration and availability are u...Ectomycorrhizal(EM) fungi could form symbiosis with plant roots and participate in nutrient absorption; however, many EM species commonly found in forest soils, where phosphorus(P) concentration and availability are usually very low, particularly in tropical and subtropical areas, have not yet been investigated for their efficiencies to mobilize soil P. In this study, fungal growth, P absorption,efflux of protons and organic acids, and soil P depletion by four isolates of EM fungi isolated either from acidic or calcareous soils were compared in pure liquid culture using soil as a sole P source. Boletus sp. 7(Bo 7), Lactarius deliciosus 3(Ld 3), and Pisolithus tinctorius 715(Pt 715) from acidic and P-deficient soils of southwestern China showed higher biomass and P concentration and accumulation than Cenococcum geophilum 4(Cg 4) from a calcareous soil of Inner Mongolia, northern China, after 4 weeks of liquid culture. Oxalate, malate, succinate, acetate, and citrate concentrations in the culture solutions varied significantly with fungal species,and oxalate accounted for 51.5%–91.4% of the total organic acids. Organic acids, particularly oxalate, in the culture solutions may lead to the solubilization of iron-bound P(Fe-P), aluminum-bound P(Al-P), and occluded P(O-P) from soil phosphates. Fungal species also varied greatly in proton efflux, which decreased the culture solution pH and may dissolve calcium-bound P(Ca-P) in soil.This could be the reason for the increment of both inorganic P in the culture solutions and Olsen P in the soil when EM fungi were present. Total inorganic P, the sum of Al-P, Fe-P, O-P, and Ca-P, in the culture solutions was positively correlated with the total concentration of organic acids in the culture solutions(r = 0.918*, n = 5), but negatively with both the total inorganic P in soil(r =-0.970**, n = 5) and the culture solution pH(r =-0.830*, n = 5). These suggested variable efficiencies of EM fungal species to mobilize inorganic P fractions from soil, which could make EM trees to utilize inorganic P in the same way like EM fungi and adapt to the soils with various P concentrations and availabilities.展开更多
基金supported by the Ocean Public Welfare Scientific Research Projects, State Oceanic Administration People’s Republic of China (Grant Nos. 200905020, 2010225007, and 201305009)the National Natural Science Foundation of China (Grant No. 31070458)
文摘Two species of marine phytoplankton, Platymonas helgolandica var. tsingtaoensis and Heterosigma akashiwo, were cul- tivated in bi-algal cultures to investigate the effect of anthracene （ANT） on the interaction between them. Without ANT, H. akashiwo out-competed P. helgolandica at low initial biomass ratios （P. helgolandica （P）： H. akashiwo （H） = 1：4 and 1 ： 1）, but not at the highest （P：H=4：I）. This observation was consistent with the description in Lotka-Volterra two species competition model. It was found that P. helgolandica was excluded at low initial biomass ratios, while the unstable equilibrium between two species was predicted at the highest. For both species, carrying capacity and maximal specific growth rate decreased in bi-algal cultures compared to those in monocultures. H. akashiwo exhibited a higher sensitivity to ANT than P helgolandica. This resulted markedly in a reduced cell den- sity of H. akashiwo but an increased cell density ofP. helgolandica. Carrying capacity ofP. helgolandica was consistently higher in bi-algal cultures with ANT than those without ANT, suggesting that ANT, through the elimination of H. akashiwo, generated the dominance of P helgolandica independently of initial biomass ratios. This study showed a density-dependent effect of harmful alga （H. akashiwo） on dietary alga （P helgolandica）, and indicated that ocean pollutant ANT could induce the succession of marine phytoplankton.
基金Supported by the National Basic Research Program(973 Program)of China(No.2013CB27405)the National Natural Science Foundation of China(Nos.40771112 and 41171215)the Technology Innovation Program of Southwest University of China(No.Ky2009022)
文摘Ectomycorrhizal(EM) fungi could form symbiosis with plant roots and participate in nutrient absorption; however, many EM species commonly found in forest soils, where phosphorus(P) concentration and availability are usually very low, particularly in tropical and subtropical areas, have not yet been investigated for their efficiencies to mobilize soil P. In this study, fungal growth, P absorption,efflux of protons and organic acids, and soil P depletion by four isolates of EM fungi isolated either from acidic or calcareous soils were compared in pure liquid culture using soil as a sole P source. Boletus sp. 7(Bo 7), Lactarius deliciosus 3(Ld 3), and Pisolithus tinctorius 715(Pt 715) from acidic and P-deficient soils of southwestern China showed higher biomass and P concentration and accumulation than Cenococcum geophilum 4(Cg 4) from a calcareous soil of Inner Mongolia, northern China, after 4 weeks of liquid culture. Oxalate, malate, succinate, acetate, and citrate concentrations in the culture solutions varied significantly with fungal species,and oxalate accounted for 51.5%–91.4% of the total organic acids. Organic acids, particularly oxalate, in the culture solutions may lead to the solubilization of iron-bound P(Fe-P), aluminum-bound P(Al-P), and occluded P(O-P) from soil phosphates. Fungal species also varied greatly in proton efflux, which decreased the culture solution pH and may dissolve calcium-bound P(Ca-P) in soil.This could be the reason for the increment of both inorganic P in the culture solutions and Olsen P in the soil when EM fungi were present. Total inorganic P, the sum of Al-P, Fe-P, O-P, and Ca-P, in the culture solutions was positively correlated with the total concentration of organic acids in the culture solutions(r = 0.918*, n = 5), but negatively with both the total inorganic P in soil(r =-0.970**, n = 5) and the culture solution pH(r =-0.830*, n = 5). These suggested variable efficiencies of EM fungal species to mobilize inorganic P fractions from soil, which could make EM trees to utilize inorganic P in the same way like EM fungi and adapt to the soils with various P concentrations and availabilities.
