我国赤潮频发现象分析与海藻栽培生物修复作用

In this paper,the history,main events and present status of red tide（HAB,harmful algal blooms） along China coast in recent years were reviewed and presented.It showed that the HAB's frequency and scale,number of HAB species,percentage of toxic HAB events and the degree of damages to marine environment and economy have sharply increased in China since 1960's.Eutrophication was key factor for high occurrence of red tide.In this paper,main causes of frequent HAB occurrence along China coast was discussed.Many factors might influence the occurrence of red tide,which included weather,climate,coastal current,tidal current,water temperature,salinity,hydrodynamic and nutrient conditions,trace metals and the variation of biological environment.Numerous evidences from all over the world revealed the linkage between the increases in nutrient loading and the occurrences of high biomass blooms.Eutrophication was one of the important causes that involved in high occurrence of HAB.The main sources of nutrients potentially stimulating HABs included terrestrial runoff,aquaculture self-pollution,atmospheric deposition,sea projects and other pollution events in the ocean.Studies showed that the input from land contaminations and the self-pollution of marine aquaculture accelerated eutrophication in coastal waters and were also important impact factors on red tide.Researches suggested that nutrient composition could affect the species composition of phytoplankton as well as the development of some HABs.The changes in nutrient supply ratios,primarily N∶P,often resulted in shifts in red tide species composition.The correlation between cysts and formation of HAB was discussed from the viewpoint of transformation of cyst and vegetative cell,the effects of trace elements and other organic substances on the occurrence of HAB were presented also.It indicated that the nutrient control could be an effective way to reduce the risk of red tide occurrence.Seaweed would play an important role for decreasing marine eutrophication.Among the different methods of red tide controlling studied,seaweed biomass has received much attention due to the cost saving,low sensitivity to environmental and impurity factors,the possible contaminant recovery from the biomaterial and its elevated adsorption capacity.Cultivated seaweeds have very high rates of productivity higher than that of seaweed in its natural habits and grow well in water bodies with higher nitrogen and other nutrients.Seaweeds are able to absorb large quantities of nitrogen,phosphorus and carbon dioxide,produce large quantities of oxygen,and have excellent effect on decreasing eutrophication.Large amounts of C,N and P are accumulated into seaweed tissues as they accumulate considerable biomass over a period of months or years depending on the cultivation season.When seaweeds are harvested,nutrients are removed from the sea area.An investigation was carried out for inorganic nitrogen and inorganic phosphorus concentration at Lusi Coast,Qidong County,Jiangsu Province in China,where there were about 270 hm2 for Porphyra yezoensis cultivation with eutrophic seawater in recent years.While during Porphyra yezoensis cultivation,from Sep 2003 to May 2004,the concentration of ammonium nitrogen declined form 0.511-0.778 mg·L-1 to 0.006-0.057 mg·L-1,nitrite nitrogen concentration declined from 0.010-0.040 mg·L-1 to 0.001-0.009 mg·L-1,and nitrate nitrogen concentration declined from 0.466-0.549 mg·L-1 to 0.286-0.0568 mg·L-1,the average concentration of inorganic phosphorus declined from 0.024 mg·L-1 to 0.019 mg·L-1. Furthermore,during five hours,the concentration of ammonium nitrogen in the seawater declined form 220.88 μmol·L-1 to 8.59 μmol·L-1 by cultivated Gracilaria lemanaiformis,and the concentration of ammonium nitrogen declined form 213.84 μmol·L-1 to zero by cultivated Enteromorpha clathrata.Other bioremediation mechanisms of seaweed inhibiting the red tide microalgae such as nutrients competition and allelopathic effects were also discussed.