Study On Bioremediation Ability Of Several Seaweeds On Heavy Metal Contamination In Seawater

In the study, heavy metals contamination (seven kinds) were remidiated byfour kinds of seaweed (Gracilaria verrucosa, Ulva pertusa, Sargassumthunbergii and Rhodomela confervoides), in order to screen a seaweed whichhad strong ability for bioremediation of combined contamination of heavymetals (Cu, Pb, Zn, Cd, Cr, Ni, Mn). The heavy metal concentrations in the testwere setted up according to seawater quality standard of Chinese, from the firstclass to the twice of the four class national seawater quality standard.After15days of mixed heavy metals treatment, the relative growth rate(RGR) of seaweeds decreased with heavy metal concentrations increasing. In therange of experimental concentration, the RGR of U. pertusa decreased from1.46%/d to1.18%/d, smallest in four algae；the RGR of R. confervoides had abigger decline than others, from0.86%/d to0.46%/d.All of large algae had certain accumulation ability of heavy metals, and theaccumulatted content of heavy metals in algae increased with heavy metalconcentrations increasing. Different kinds of algae showed different storageability to heavy metals: G. verrucosa for copper and manganese (23.64mg/kg,51.62mg/kg), U. pertusa for the lead (43.55mg/kg), S. thunbergii for zinc,cadmium and chromium (152.69mg/kg,6.96mg/kg,9.29mg/kg), R. confervoidesfor nickel (55.24mg/kg) respectively, had high accumulation.Three kinds of algae, U. pertusa, S. thunbergii and R. confervoides, hadcertain removal ability of heavy metals in seawater, and the removal efficiencyincreased with the cultured time increasing. U. pertusa for cadmium, nickel andmanganese (0.76,0.69,0.74), S. thunbergii for zinc and chromium (0.80,0.70),and R. confervoides for copper and lead (0.75,0.76) respectively, had highremoval ability. Besides, three kinds of algae had similar removal ability oncopper, nickel and manganese. In addition, effect of mixed heavy metals on physiological indexes of fourmacroalgae were launched. With the concentration of heavy metals increasing,the changes of physiological indexes as follows: the contents of chlorophyll aascended at first and descended at last, indicating the metabolism of chlorophylla inhibitted by the high concentration of heavy metals; the contents of solublesugar decreased firstly and then increased, and soluble protein showed a downtrend on the whole, reflecting the heavy metals pollution influenced negativilyon physiological metabolism of cells; the contents of malondialdehyde (MDA)displayed overall an up trend; the activity of superoxide dismutase (SOD),showed an increasing tendency in G. verrucosa and U.pertusa, and increasedfirst and then decreased in S. thunbergii and R. confervoides; the activity ofcatalase (CAT), rose preliminarily and declined afterwards in G. verrucosa, S.thunbergii and R. confervoides, and increased overall in U. pertusa; and theactivity of peroxidase (POD) increased initially and then decreased in four algae.In the results, algae showed resistance and physiological adaptations in heavymetals pollution.At last, the removal capacity of macroalgae with nitrogen and phosphoruswas studied. The results showed that, U. pertusa, S. thunbergii and R.confervoides had removal ability of ammonia nitrogen and phosphate inseawater, and U. pertusa had a best removel effect of nitrogen and phosphorus inthree kinds of algae. In treatment of ammonia nitrogen, phosphate and mixedheavy metals, the removal efficiency on phosphate of U. pertusa decreased,comparing with the treatment without heavy metals.