改性粘土治理有害藻华的生态环境效应研究

As we all know, harmful algal blooms (HABs) have been becoming in an increasing trend both in the frequency and range accompany with the more serious coastal eutrophication. But so far HABs still cannot be forecasted accurately. So some cases HABs need to deal with emergencies or prevention and control if it occurs in some special coastal waters (such as culture areas, scenic areas, some important international and domestic competitions waters etc.). Now it is confirmed and has been used successful in coastal areas several times that modified clay is the preferred and effective method to coagulation HABs. Although modified clays have been proved friendly to the environment and is safe to the aquatic organism in the concentration of effective removal of HABs. However, as for the eco-environmental effects by using modified clays coagulation HABs could not give a clear answer up to now. In this project comparative research will be conducted between the natural death and modified clay flocculation for HABs systems. Both aquatic and benthic environment, including the important water and depositional parameters, will be studied with the comparative research. The biological tolerance and response mechanisms of some typical aquatic and benthic organism on modified clay flocculation HABs will be pay more attention. The eco-environmental effects by using modified clays to control HABs will be expected to clarify according to the above researches and field experiment on benthic community composition between the natural death and modified clay flocculation systems. Results produced by this project will provide a scientific basis for the effective and reasonable prevention and control HABs in the coastal areas in China.

随着近海富营养化程度呈日趋严重，有害藻华发生频率和面积均呈增加态势。但迄今有害藻华尚不能准确预测预报，针对发生在近海特殊海域（如养殖区、风景区、重要国内外赛事水域等）的有害藻华需要应急处置或防控。目前，改性粘土技术已在近海有害藻华治理中得到多次成功应用。虽然在粘土材料选择、改性处理及制备等各环节均已充分考虑了对环境和生物的安全性，以往研究也表明改性粘土在有效去除藻华生物的浓度下对水生生物无毒副作用等，但关于改性粘土治理有害藻华对生态环境的影响尚未开展系统的研究。本项目将针对有害藻华自然消亡和利用改性粘土絮凝沉降两种不同体系，从水质环境和底质环境两方面入手，开展对比研究，重点考察改性粘土絮凝对典型水生和底栖生物生长繁殖的影响以及生物的耐受力和响应机制，通过现场实验对比研究两种体系底栖生物群落组成的变化情况，阐明改性粘土治理有害藻华的生态环境效应，为我国近海有害藻华的合理有效防控提供科学依据。

改性粘土技术作为有害藻华应急处置的首选方法，已在我国沿海多个水域成功应用。改性粘土治理有害藻华的过程，相当于在水体中添加具有较强絮凝作用的悬浮物，系统阐释其生态环境效应对藻华治理具有重要的指导意义。本项目研究了利用改性粘土治理我国近海两种典型甲藻（海洋原甲藻Prorocentrum micans、东海原甲藻Prorocentrum donghaiense）和一种典型硅藻（中肋骨条藻Skeletonema costatum）藻华过程中海水环境主要营养元素氮、磷、硅的变化特征。对比有害藻华自然消亡和改性粘土絮凝两种体系的实验结果显示，改性粘土絮凝沉降甲藻及硅藻藻华后，减缓了氮、磷、硅等营养物质从沉积环境向水体的快速转化，在实验周期内能有效的降低水环境中的营养盐浓度。考察了改性粘土对典型有毒甲藻—塔玛亚历山大藻（Alexandrium tamarense）毒素的影响，结果显示，改性粘土可以有效降低沉积环境及贝类体内的毒素（PSTs），且毒素呈现由高毒性组分向低毒性组分转化的现象。同时关注了改性粘土絮凝沉降过程对塔玛亚历山大藻（Alexandrium tamarense）、锥状斯氏藻（Scrippsiella trochoidea）孢囊形成及萌发的影响，实验结果表明，改性粘土在絮凝去除上述两种能产生孢囊的甲藻过程并不会为沉积环境埋下更多“种源”。另外，研究了改性粘土絮凝体系对典型敏感期水生生物的影响，结果表明，采取适当的策略和适当用量的改性粘土不仅可效去除有害藻华，而且对仿刺参（Apostichopus japonicas Selenka）稚参、虾夷扇贝(Patinopectenyessoensis)稚贝、大菱鲆（Scophthalms maximus）胚胎等的敏感期养殖生物无害。借助改性粘土现场应急处置有害赤潮的实际应用，考察了改性粘土对底栖生物群落组成的影响，对现场喷洒海域和对照海域各调查站位的分析结果显示，各站位底栖生态环境均为“优良”以上，沉积物重金属含量均符合海洋沉积物质第一类标准，改性粘土对环境无不良影响。另外，针对近年来我国黄海频繁爆发的绿潮种—浒苔（Ulva prolifera），重点考察了不同体系改性粘土对浒苔生活史早期阶段微观繁殖体的去除效果及萌发影响，结果表明，适当浓度的改性粘土对实验室内及自然丰度下的微观繁殖体均具有显著的去除和萌发抑制效果。