营养盐浓度对中肋骨条藻优势种群富集多溴联苯醚的影响

以中肋骨条藻（Skeletonema costatum）和东海原甲藻（Prorocentrum donghaiense）组成中肋骨条藻优势种群的海洋微藻为研究对象，以我国近海水体中存在的3种丰度较高的多溴联苯醚同系物为代表，包括2,4,4＇-三溴联苯醚（BDE-28）、2,2’,4,4’-四溴联苯醚（BDE-47）和2,2＇,4,4＇,5-五溴联苯醚（BDE-99），研究了硝酸盐浓度（0、128、512μmol·L-1）和磷酸盐浓度（0、8、32μmol·L-1）对中肋骨条藻优势种群生化成分和富集3种多溴联苯醚的影响，分析了中肋骨条藻优势种群对多溴联苯醚的富集量与生化成分的关系。结果表明，随着营养盐浓度的升高，单位藻细胞的富集量呈现降低趋势，硝酸盐浓度为0μmol·L-1时，3种多溴联苯醚同系物每106cells的富集量为3.93-5.01 ng，而硝酸盐浓度为512μmol·L-1时，每106cells富集量为3.53-3.94 ng，降低了10%-23%；不同硝酸盐浓度下单位体积藻液富集量差异较小，随硝酸盐浓度的升高，BDE-99和47富集量分别从0.180和0.179 ng·mL^-1降低到0.167和0.150 ng·mL^-1，BDE-28没有出现明显差异。与硝酸盐相似，多溴联苯醚单位藻细胞富集量也随着磷酸盐浓度的升高而呈现出降低的趋势，每106cells的富集量从磷为0μmol·L-1的3.04-3.28 ng降低到32μmol·L-1时的2.27-2.73 ng；不同磷酸盐浓度下单位体积藻液的富集量差异不显著，其中BDE-99富集量范围在0.188-0.190 ng·mL^-1，随磷酸盐浓度的升高，BDE-47和28富集量略有降低，从0.20 ng·mL^-1降低到约0.16 ng·mL^-1。中肋骨条藻优势种群单位细胞对多溴联苯醚富集随着营养盐浓度的增加而降低，其原因是营养盐浓度影响了其细胞生化成分，其中脂类含量与富集量存在正相关关系。对3种同系物富集量的比较发现，随多溴联苯醚同系物的Kow降低，富集量总体上呈现降低的趋势。

Effect of nutrient concentrations on the bioaccumulation of polybrominated diphenyl ethers by Skeletonema costatum dominant population

The Skeletonema costatum dominant population, consisting of Skeletonema costatum and Prorocentrum donghaiense, as subject in this study. Three PBDEs congeners which had higher concentration in marine water, including 2,4,4′-tribromodiphenyl ether （BDE-28）, 2,2′,4,4′-tetrabromodiphenyl ether （BDE-47） and 2,2′,4,4′,5-pentabromodiphenyl ether （BDE-99）, were bioaccumulated by Skeletonema costatum dominant population under different nitrate and phosphate concentrations. Nitrate concentration was set as 0, 128 and 512 μmol·L-1 and phosphate was 0, 8 and 32 μmol·L-1. The bioaccumulated quantity and biochemical contents in Skeletonema costatum dominant population were measured, and correlation between bioaccumulated quantity and biochemical contents was analyzed. The results showed that the bioaccumulation content per cell decreased with the increasing of nutrient concentrations. When the nitrate was 0 μmol·L-1, the bioaccumulated PBDEs congeners per cell were 3.93-5.01 ng·（106cells）-1;while the nitrate was 512μmol·L-1, they were 3.53-3.94 ng·（106cells）-1, decreasing by 10-23%. There was no significant difference in bioaccumulated PBDEs contents per algal volume among nitrate concentrations. With the increasing of nitrate, the BDE-99 and 47 contents per algal volume decreased from 0.180 and 0.179 ng·mL^-1to 0.167 and 0.150 ng·mL^-1 respectively; and BDE-28 did not present obvious change. Similar with nitrate, the bioaccumulated PBDEs contents per cell decreased with the rising of phosphate concentration. It declined from 3.04-3.28 ng·（106cells）-1 in 0μmol·L-1 phosphate to 2.27-2.73 ng·（106cells）-1 in 32μmol·L-1 phosphate. There was no significant difference in bioaccumulated PBDEs contents per algal volume among phosphate concentrations. The bioaccumulated BDE-99 contents per algal volume were in the range of 0.188-0.190 ng·mL^-1and BDE-47 and 28 slightly decreased from 0.20 ng·mL^-1to 0.16 ng·mL^-1 The change of bioaccumulated PBDEs contents per cell resulted from the biochemical contents in microalgae induced by nutrient concentration and the positive correlation was found between lipid and bioaccumulated PBDEs content. By comparison, the bioaccumulated PBDEs content presented decline trend with the decreasing of the octanol/water partition coefficient （Kow） of PBDEs.