【作者】 李娟；

【导师】 黄凌风；

【作者基本信息】 厦门大学 ， 海洋生物学， 2007， 硕士

【摘要】 随着国民经济和城市化进程的高速发展,我国的水域富营养化与赤潮问题不断加剧。目前,利用大型海藻清除水中营养盐防治赤潮的技术已得到普遍重视和研究,但这方面的研究多数开展于富营养化程度相对较低（Ⅳ类海水水质以下）的海湾和浅海区域,而对于高度富营养化（Ⅳ类海水水质以上）的城市水体（如厦门市筼筜湖）的研究还比较少。由于大型海藻在高度富营养化的水域环境中不一定具备良好的生长和环境修复能力,所以有必要研究大型海藻在相应的高浓度营养盐状态下的生长和对营养盐的吸收利用特征。本课题研究了龙须菜（Gracilariopsis lemaneiformis）、细基江蓠繁枝变种（Gracilaria tenuistipitata var.liui）和石莼（Ulva luctuca）等大型海藻在不同温度以及高浓度营养盐下的生长情况、营养盐吸收特征和对牟氏角毛藻（Chaetoceros muelleri）的生长抑制作用,并从营养盐竞争的角度探讨了大型海藻对赤潮发生的抑制作用机理。主要研究结果如下:在15℃、20℃和25℃下,使用筼筜湖中营养盐污染最严重的3#站点的过滤海水来培养三种大型海藻,测定其生长速率及Chlα含量变化情况。结果显示,三种大型海藻在20℃和25℃生长较快;海藻的Chlα含量与生长没有明显关系。结合其他研究者的研究结果,细基江蓠繁枝变种的适温范围为20℃～30℃,龙须菜和石莼的适温范围为15℃～25℃。另,同样的培养条件下,两种红藻的生长都没有受到影响,而石莼在3个温度下从第5天开始都出现漂白现象。可见,高浓度营养盐并没有改变这三种大型海藻的适温范围,但是石莼不能在NH₄⁺浓度极高的筼筜湖3#站点生长,而龙须菜和细基江蓠繁枝变种则可以。N:P为30:1的条件下,三种大型海藻在2μmol/L～500μmol/L的NH₄⁺浓度中培养12天,测定其生长速率、干重百分含量、C、N、P含量及培养始末对营养盐移除效率的变化。结果显示,龙须菜虽然是生长最慢的,但生长速率随着NH₄⁺浓度的升高而升高;细基江蓠繁枝变种在超过50μM的NH₄⁺浓度后生长速率就随着浓度的升高而减慢,干重百分含量相反;石莼在2μmol/L～100μmol/L中的生长速率是三种大型海藻中最快的,但在500μmol/L的NH₄⁺浓度下出现了漂白现象。三种大型海藻的C、N、P含量基本都随着NH₄⁺浓度的增加而增加,其中,龙须菜最高,石莼最低;NH₄⁺浓度为100μmol/L时,三种大型海藻在第1天和第12天,营养盐移除效率都能达到100%,而在其他NH₄⁺浓度时,龙须菜和细基江蓠繁枝变种在第12天对营养盐的移除效率比第1天稍有降低,石莼的移除效率则大幅降低。龙须菜和细基江蓠繁枝变种不经饥饿处理,只在实验前适应一天,即进行营养盐吸收速率的测定(该吸收速率反应了这两种大型海藻在原高NO₃^-、PO₄^3-和缺NH₄⁺的富营养水体中的吸收情况),结果显示,龙须菜和细基江蓠繁枝变种分别在5 min和25 min内完成快速吸收,她们在3个时间段里的吸收都符合米氏方程;对NO₃^-和PO₄^3-的吸收容易达到饱和,吸收速率较低。两种红藻的α值(=V_max/K_s)都较低,说明对低浓度营养盐耐受性较差;龙须菜对NH₄⁺的V_max比细基江蓠繁枝变种要大,说明龙须菜在高浓度状态中有竞争优势。把细基江蓠繁枝变种和石莼分别与牟氏角毛藻混合培养,结果显示,在DIN初始浓度为69μmol/L,赤潮爆发前添加细基江蓠繁枝变种,细基江蓠繁枝变种即使没有分泌克生物质,只需要通过竞争营养盐就足以抑制赤潮爆发,而赤潮爆发后再添加细基江蓠繁枝变种,只通过竞争营养盐则无法完全抑制赤潮发展的势头,此时抑制赤潮可能主要是通过分泌克生物质;DIN初始浓度为140μmol/L,在赤潮爆发前添加石莼,微藻生长受抑制程度与石莼的密度成正相关,可能与水体剩余营养盐浓度或者分泌克生物质的含量有关;DIN初始浓度为500μmol/L,在赤潮爆发前添加细基江蓠繁枝变种,细基江蓠繁枝变种抑制赤潮主要是通过克生作用,但在赤潮爆发后添加细基江蓠繁枝变种,如果分泌克生物质的量不足以抑制微藻生长,微藻还是会被营养盐刺激继续生长。所以,分泌克生物质跟竞争营养盐是防治赤潮的双保险。最后,根据以上研究结果,结合厦门市筼筜湖的基本环境特征,探讨了将龙须菜、细基江蓠繁枝变种和石莼等三种大型海藻应用于筼筜湖富营养化和赤潮防治的适宜栽培位点、栽种季节和可能达到的修复效果。更多还原

【Abstract】 A great deal of sewage had been poured before sufficient treated due to the rapid urbanization,which makes the water become eutrophicated and red tide breaks out frequently.At present,lots of studies about removing nutrition in the water and prevention of red tide through macroalgae are carried on,and most of them focus on the bay or shallow sea（water quality under LevelⅣ）.How ever,the study of applying macroalgae in ultra-eutrophic lagoon（water quality above LevelⅣ）,such as Yundang lagoon,is rarely be carried.Macroalgae does not always grow well or have good capabilities of remediation in ultra-eutrophic lagoon;therefore,it is necessary to understand the growth and the nutrition absorption characteristics of macroalgae incubating in corresponding ultra-eutrophic water condition.This paper has studied the growth of Gracilariopsis lemaneiformis,Gracilaria tenuistipitata var.liui and Ulva luctuca under 3 different temperature and ultra-eutrophic environment respectively,also researched the prevention of outbreak of Chaetoceros muelleri by G. tenuistipitata var.liui or U.luctuca,and the mechanism of red tide prevention by seaweed through nutrition competition in ultra-eutrophic waters has been discussed. The results were as following:At 15℃,20℃and 25℃,the seaweeds were incubated in filtered water from Station 3# of Yundang lagoon,the growth rate and Chl a content of seaweeds were studied.The results have indicated that seaweeds grew faster at 20℃and 25℃obviously,and Chl a content has no clear relation with growth.Integrated with other’s results,the suitable temperature of G.tenuistipitata var.liui was 20℃-30℃, and that for G.lemaneiformis and U.luctuca were 15℃～25℃.Under the same circumstance,both G.lemaneiformis and G.tenuistipitata var.liui grew well,whereas U.luctuca bleached.Seaweeds were cultured in ultra-eutrophic media for 12 days,the N:P was around 30,and the concentration of ammonium was 2μmol/L～500μmol/L.The growth rate,C,N,P content and removal efficiency on the first and the last day of experiment were identified.Though the growth of G.lemaneiformis was the slowest, it has grown faster with higher concentration;over 50μmol/L NH₄⁺,G.tenuistipitata var.liui has grown slower with higher concentration;between 2μmol/L～100μmol/L NH₄⁺,U luctuca has grown fastest but bleached in 500μmol/L NH₄⁺ treatment.At the end of the experiment,C,N,P content of seaweeds were increased with increasing ambient concentration,and seaweeds have maintained 100%removal efficiency in the 100μmol/L NH₄⁺ treatment as they had on the first day.Except for 100μmol/L NH₄⁺ treatment,removal efficiencies of G.lemaneiformis and G.tenuistipitata vat.liui have dropped slightly and that of U.luctuca has reduced sharply on the last day.After one day’s adaptation,the uptake rates of G.lemaneiformis and G.tenuistipitata var.liui without hungry treatment were identified.These uptake rates represented the response of seaweeds living in ultra-eutrophic environment to the nutrition pulse.The NH₄⁺ surge uptake of G.lemaneiformis and G.tenuistipitata var. liui have accomplished within 5 min and 25 min respectively,and their uptake rate could be described by the Michaelis-Menten equation.The uptake saturation of NO₃^-and PO₄^3- were reached under low concentration,and the uptake rates were low.Thus, these two seaweeds were suitable for recovering the high NH₄⁺ concentration zone.αvalues(=V_max/K_s) of G.lemaneiformis and G.tenuistipitata vat.liui were low, which means the tolerance of low nutrition was extremely poor.The fact that V_max of G.lemaneiformis was higher than G.tenuistipitata var.liui means the former one has a more competitive advantage in the ultra-eutrophic zone.G.tenuistipitata var.liui and U.luctuca mixed cultured with C.muelleri respectively.In DIN=69μmol/L treatment,G.tenuistipitata var.liui was added before the red tide break out,seaweed could prevent the outbreak of C.muelleri just by competing for nutrition without excreting allelochemicals,whereas once G. tenuistipitata var.liui was added after the red tide outbreak,seaweed inhibited the redtide maily through excreting allelochemicals but not competing for nutrition.In DIN=140μmol/L condition and U.luctuca was added before the outbreak of red tide, the inhibition level on red tide was positively related to density of U.luctuca,due to the quantity of the remaining nutrition and allelochemicals.In DIN=500 caseμmol/L and G.tenuistipitata var.liui was added before the red tide outbreak,it inhibited red tide by excreting allelochemicals,while G.tenuistipitata var.liui was added after the outbreak of red tide,the quantity of allelochemicals must be sufficient,otherwise the growth of red tide could still be stimulated by remaining nutrition.Therefore,seaweed excreting allelochemicals and competing for nutrition are double insurance on prevention and inhibition of the red tide.Base the above results,seaweed cultivation site,cultivation period and possible remediation effect in Yundang lagoon were discussed.更多还原