题目

Peter lived in a village. He was sad recently because he thought that he had nothing left. One day，Peter went to ask a wise man for help. He said to the wise man，I have nothing left，so I don't want to live. ”The wise man smiled sympathetically（同情地）. The wise man took out a piece of paper and drew a straight line down the middle. He explained that he would write down the things Peter had lost on the left side and the things Peter still had on the right side. The wise man asked，“When did your family leave you？”“What do you mean？They haven't left me. They love me！氮、磷等无机营养物质大量排入水体，会造成水体富营养化，严重时可引发蓝藻爆发，使水域生态遭到破坏。控制蓝藻疯长，同时“变废为宝”是减轻“绿色灾害”的有效途径。请回答下列有关问题：（1）从细胞结构分析，蓝藻属于        生物，蓝藻与其他水生生物构成了该水域生态系统中的           ，由于某些蓝藻具有气囊，在水域中有趋表聚集的现象，从              的角度看，这些蓝藻处于其上层。（1）      下表为某湖泊不同营养状态的各种藻类种群组成情况。营养状态[[来源:学&科&网]藻类种群组成铜绿微囊藻鱼腥藻斜生栅藻汉氏菱形藻薄甲藻小定鞭金藻重度富营养中度富营养轻度富营养贫营养50%5%0025%40%25%0.5%14%42%60510%10%12%14%11.5%0.5%0.5%0.5%10%0.5%0.5%0.5%68%        据表分析，检测水中重度富营养化的指示生物是         ，在中度富营养化水体环境中，竞争最激烈的是         。（3）采用浮床生态工艺法（如右图所示）可治理水体污染，改善水质。其机理正确的是（  ）①植物吸收水中悬物  ②植物吸收水中的NO3-、PO3-等，降低水中氮、磷等含量  ③浮床遮光，抑制浮游藻类的生长繁殖，防止水华发生  ④浮床下方水体氧浓度升高，减少微生物种类和数量A．①④B．②④C．②③D．①③