Toxic Effects And Mechanisms Of Petroleum Hydrocarbon On Marine Microalgae

Petroleum hydrocarbon caused marine environment pollution is one of the mostimportant global environment problems; petroleum hydrocarbon toxicity affect on themarine ecosystem is obviously. Marine microalgae are the base of marine food chainand are the main marine primary productivity. Marine microalgae drive the marineecosystem energy and matter cycle and global environmental change. The dynamicchange of marine phytoplankton populations and communities once damaged willendanger the other sea creatures and the whole marine ecosystem. Many studiesplaced emphasis on cell density data show that the oil pollutants have significantlyeffects on marine microalgae growth, data to illustrate the mechanism of thepetroleum hydrocarbons in marine microalgae on relationship between populationdynamics and species of quantitative, photosynthetic characteristics and cellper-oxidation and antioxidant research the was lack. Research on marine microalgaeshort-term acute toxicity and long-term sub-acute toxicity effects response differencesand mechanism of action under the condition of petroleum hydrocarbon is necessary.In lab, short-term acute toxicity and long-term sub-acute toxicity affects onPlatymonas helgolandica var. tsingtaoensis, Isochrysis galbana and Nitzschiaclosterium f. minutissima, competitive relation between the marine microalgae,photosynthesis characteristics, cell per-oxidation, antioxidase enzyme activities andantioxidant content changes were studied, in which the marine microalgae responsemechanism under the condition of petroleum hydrocarbon was found out.1Petroleum hydrocarbon acute toxicity effects on marine microalgae（1）Petroleum hydrocarbon had significant inhibition of the marine microalgaegrowth, only the0.5mg/L petroleum hydrocarbon had inapparent stimulated effect.96h EC50of the Platymonas helgolandica var. tsingtaoensis was13.84mg/L（12.11-18.14mg/L）, Isochrysis galbana was18.83mg/L（17.22-22.39mg/L）,Nitzschia closterium f. minutissima was6.73mg/L（2.76-14.11mg/L）. The level ofPetroleum hydrocarbon sensitivity was Nitzschia closterium f. minutissima＞Platymonas helgolandica var. tsingtaoensis＞Isochrysis galbana. （2）Chlorophyll-a content was inhibited. Isochrysis galbana content changes weremore sensitive than Platymonas helgolandica var. tsingtaoensis and Nitzschiaclosterium f. minutissima.（3）Petroleum hydrocarbon acute toxicity effects on chlorophyll fluorescenceparameter were different. Platymonas helgolandica var. tsingtaoensis’s in0.5mg/Lincreased significantly. Fv/Fm，ETR and qP were inhibited.（4）In the lower concentration （0.5mg/L） condition, chlorophyll fluorescenceparameter changes sensitive was more obvious than the chlorophyll-a content’s,except the Isochrysis galbana Fv/Fm and qP. Chlorophyll fluorescence parameter ismore suitable for oil pollution acute toxicity biological monitoring.2Petroleum hydrocarbon effects on marine microalgae populations dynamic（1）Petroleum hydrocarbon sub-acute toxicity had significant effect on Logisticmodel. In Platymonas helgolandica var. tsingtaoensis and Isochrysis galbana groupsenvironment capacity K decreased with the petroleum hydrocarbon concentrationincreasing was obvious lower than in the blank control, and so was the instantmaximum growth r. They needed more time than in the blank control to arrive at thegrowth curve inflexion point.（2） In the same petroleum hydrocarbon concentration condition, Nitzschiaclosterium f. minutissima K decreased the most. The Logistic model and the growthcurve inflexion point showed that Nitzschia closterium f. minutissima could arrive atthe population stability earlier and more quickly than the Platymonas helgolandicavar. tsingtaoensis and Isochrysis galbana, and which was the basis of populationrelative dominance.3Petroleum hydrocarbon effects on interspecific competition（1）Mixed cultivation had obvious effects on the Logistic mode and growth curveinflexion point. K decreased significantly in the condition of mixed cultivation ofPlatymonas helgolandica var. tsingtaoensis-Nitzschia closterium f. minutissima andIsochrysis galbana-Nitzschia closterium f. minutissima. In the two groups theNitzschia closterium f. minutissima instant maximum growth and growth curveinflexion point privilege over the other.（2）Different had significant effects on interspecific competition. In the blank controlgroups, the initial biomass advantage was not the determine factor of dominance inlong term marine microalgae cultivation. In the condition of petroleum hydrocarbon toxicity, the higher proportion of initial biomass privilege over the other.4Petroleum hydrocarbon effects on photosynthesis（1）Chlorophyll-a content reduced for the petroleum hydrocarbon of sub-acutetoxicity concentration, and chlorophyll-a content changes were largely in line with thetrend of the higher petroleum hydrocarbon concentration and the longer of the time,the lower chlorophyll-a content. Nitzschia closterium f. minutissima chlorophyll-awas effected the most.（2） Petroleum hydrocarbon effects on the Platymonas helgolandica var.tsingtaoensis, Isochrysis galbana and Nitzschia closterium f. minutissima chlorophyllfluorescence parameters were different. The Fm/Fv、Yield、ETR、qP、NPQ changesshowed that the Platymonas helgolandica var. tsingtaoensis and Isochrysis galbanawere inhibited smaller than the Nitzschia closterium f. minutissima.（3）In the Petroleum hydrocarbon condition, Nitzschia closterium f. minutissimaRuBPCase activity was lower than in the blank control. Isochrysis galbana andPlatymonas helgolandica var. tsingtaoensis RuBPCase activity changes were notobvious in the beginning and decreased significantly in the late.5Petroleum hydrocarbon Petroleum hydrocarbon effects on per-oxidation, antioxidantenzyme and antioxidant content（1）Petroleum hydrocarbon had effects on MDA content increase and lipidperoxidation. The Platymonas helgolandica var. tsingtaoensis MDA content rose themost, and Nitzschia closterium f. minutissima MDA content rose the lest in the threekinds.（2）In the condition of petroleum hydrocarbon the SOD, GPx and GR activityshowed a trend of decrease after the first rise in roughly. It showed the antioxidantenzyme protection was activated and antioxidant enzyme activity was destroyed in thelong term petroleum hydrocarbon toxicity condition, microalgae were hurt by thepetroleum hydrocarbon.（3）Lower Petroleum hydrocarbon concentration had little effects on Platymonashelgolandica var. tsingtaoensis and Nitzschia closterium f. minutissima GSH content.In the condition of1/596h EC50, Isochrysis galbana GSH content increasedobviously during the experimental middle.（4）In the long-term and sub-acute toxicity petroleum hydrocarbon concentrationcondition, the marine microalgae cell per-oxidation; antioxidase and antioxidant were significantly affected. The antioxidase activity increased and the antioxidant contentdecreased in the beginning, the antioxidase activity decreased and the antioxidantcontent fluctuated in the late, and the lipid peroxide content increased with theexperiment. Nitzschia closterium f. minutissima MDA and SOD indexes were betterthan the Platymonas helgolandica var. tsingtaoensis, and were similar to theIsochrysis galbana, which was the cause of the interspecific dominance.