The Research Of Inhibitory Effect On Red Tide Skeletonema Costatum By Macroalgae And Nanomaterials

The present study investigated the inhibitory effects of 8 macroalgaes Ulva pertusa, Enteromorpha clathrata, Porphyra tenera, Grateloupia filicina, Laminaria japonica, Undaria pinnatifida, Sargassum fusiforme, Sargassum pathen on the growth of one typical algae-blooming Skeletonema costatum. Then the next work is to extract, isolate and identify the chemicals in the extracts of the macroalgae which has displayed a strong inhibition of the growth of S. costatum in order to find out the mechanism of allelopathic inhibition of macroalgae on Skeletonema costatum and to develop a new and safe algicide from high efficient allelochemicals.The growth inhibition was evaluated by analyzing inhibition rate (IR), 50% effective concentrations (EC50) after adding the seawater extracts of 8 macroalgaes, respectively. Antialgal allelochemical was isolated from E. clathrata by liquid-liquid extract and silica gel column chromatography and identified by gas chromatograph-mass spectrometry (GC-MS) so that we can know the chemical data in the antialgal allelochemicals. The mechanism of allelopathic inhibition of macroalgae on Skeletonema costatum was used by analyzing the superoxide dismutase (SOD), Malondialdehyde (MDA), K ion and chlorophyl a in algae cells after adding the ethyl acetate extract B into the culture media. 6 nanoscale metal oxides inhibitory tests are investigated by analyzing IR and EC50.The EC(50, 120h) of the 8 macroalgae on S. costatum was Ulva pertusa 1.0g/L, Enteromorpha clathrata 1.0g/L, Porphyra tenera 0.6g/L, Grateloupia filicina 1.5g/L, Laminaria japonica 0.9g/L, Undaria pinnatifida 4.7g/L, Sargassum fusiforme 1.1g/L, Sargassum pathen 1.4g/L, with the growth IR results, among the 8 macroalgaes, E. clathrata and U. pertusa demonstrated the strongest inhibition on the algal growth. And the E. clathrata is the fist time to report. Among the four solvent extract: petroleum ether (A), ethyl acetate (B), double distilled water (C), n-butanol (D), ethyl acetate (B) showed the strongest inhibitory effect with the EC50 was only 0.08mg/L. The silica gel column chromatography inhibition results showed that hexanaphthene (1A) and hexanaphthene/acetone (1B) extracts have inhibitory effect on S. costatum with the EC50 of them are 3.81 and 4.09 mg/L, respectively. The GC-MS results showed that there are 16 chemicals in the ethyl acetate (B) isolated from E. clathrata. The inhibitory effect test of 4 possible possible substitutes of allelochemicals showed that only: tetradecanoic acid has strong inhibitory effect with that the EC50 is 8.43mg/L at 72 h. The red tide alga cells exhibit activity of SOD decrease, the content of MDA and the leakage K+ increase, the content of chl-a decrease.The macroalgae E. clathrata can inhibit the growth of S. costatum. etradecanoic acid is a possible allelochemical in E. clathrata. The inhibitory mechanism of allelochemical is likely to decrease the activity of SOD and resulted in an increasing production of reactive oxygen species (ROS). Reactive oxygen species caused lipid peroxidation with the content of MDA increase. As a result, the metal ions, K~+ leaked from the algal cells following with the algal cells died finally. E. clathrata contained high effective inhibitory allelochemicals.Besides, the effect of 6 nanomaterials TiO2 (anatase, HR3 and rutile, DJ3), SiO2 (spherical, SS1 and porous, SP1) and Al2O3 (αphase, MC2A andγphase, MC2R)on the growth of one typical algae-blooming Skeletonema costatum were also studied to search after the new method of applying the new nanomaterials into the red tide prevention and cure. The experimental results showed that HR3, DJ3 and MC2R had inhibitory impact on S. costatum, HR3 had the lowest EC50 value of 250 mg/L at 144 h. SS1 had stimulative growth effect especially when concentrations were below 500 mg/L, the IR could be lower than -70 % at day 5. Chlorophyll a measurements showed that HR3 DJ3 and MC2R can reduce the chlorophyll a content in algal cells, showing the same inhibitory trend the growth inhibition results.The future research is to isolate the allelochemicals, open the inhibitory mechanism.