Variation of bioaccumulation ability of 2,2′,4,4′-tetrabromodiphenyl ether by marine diatom Skeletonema costatum under different N:P ratios

Abstract

The growth, biochemical content and bioaccumulation quantity of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in Skeletonema costatum were studied under different N:P ratios (1, 4, 16, 64 and 128). All cellular biochemical contents of S. costatum presented decreasing trend over cultivation time. At early stage of cultivation, the cellular protein, carbohydrate and lipid in S. costatum presented higher values in treatments of N:P=4 and 16. However, they were lower in these treatments at the late stage, but higher in treatments N:P=1 and 128. Similarly, BDE-47 levels per cell of S. costatum were higher in treatments of N:P=4 and 16 at early stage of cultivation, which were 3.8 and 3.7 ng (106 cells)−1, respectively. At the middle stage of cultivation, the BDE-47 level per S. costatum cell lowered; and it further reduced in the treatments of N:P=4 and 16 at the late stage with the values 0.6 and 0.5 ng (106 cells)−1, respectively. However, it rose in N:P=128, reaching up to 2.3 ng (106 cells)−1. Compared with BDE-47 per cell, BDE-47 per algal volume under different N:P ratios did not present obvious difference. The quantity BDE-47 accumulated per cell of S. costatum was positively correlated with protein, carbohydrate and lipid per cell; meanwhile, the BDE-47 per volume had a positive correlation with biochemical content per volume. The variation of bioaccumulation ability of BDE-47 in S. costatum can be explained by biochemical changes due to N:P ratios.