Fractal dimensions of flocs between clay particles and HAB organisms

• Published in: Chinese journal of oceanology and limnology Vol. 29; no. 3; pp. 656 - 663
• Main Author: 王洪亮 俞志明 曹西华 宋秀贤
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science Press 01.05.2011; Springer Nature B.V
• Subjects: Alexandrium tamarense; Algae; Algal blooms; Algal growth; Cells; Clay; Coastal zone; Earth and Environmental Science; Earth Sciences; Eutrophication; Flocculation; Fractal geometry; Growth stage; Heterosigma akashiwo; Impact analysis; Marine; Marine ecology; Morphology; Oceanography; Organisms; Physical characteristics; Physiological effects; Plankton blooms; Public health; Removal; Sedimentation & deposition; Skeletonema costatum; 分形维数; 塔玛亚历山大藻; 改性粘土; 粘土颗粒; 絮凝体; 藻细胞; 赤潮异弯藻; 赤潮生物; modified clay; harmful algal blooms; fractal dimensions
• DOI: 10.1007/s00343-011-0065-z
• ISSN: 0254-4059; 2096-5508

The impact of harmful algal blooms （HABs） on public health and related economics have been increasing in many coastal regions of the world. Sedimentation of algal cells through flocculation with clay particles is a promising strategy for controlling HABs. Previous studies found that removal efficiency （RE） was influenced by many factors, including clay type and concentration, algal growth stage, and physiological aspects of HAB cells. To estimate the effect of morphological characteristics of the aggregates on HAB cell removal, fractal dimensions were measured and the RE of three species of HAB organism, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema eostatum, by original clay and modified clay, was determined. For all HAB species, the modified clay had a higher RE than original clay. For the original clay, the two-dimensional fractal dimension （D2） was 1.92 and three-dimensional ffactal dimension （D3） 2.81, while for the modified clay, D2 was 1.84 and D3 was 2.50. The addition of polyaluminum chloride （PAC1） lead to a decrease of the repulsive barrier between clay particles, and resulted in lower D2 and D3. Due to the decrease of D3, and the increase of the effective sticking coefficient, the flocculation rate between modified clay particles and HAB organisms increased, and thus resulted in a high RE. The fractal dimensions of flocs differed in HAB species with different cell morphologies. For example, Alexandrium tamarense cells are ellipsoidal, and the D3 and D2 of flocs were the highest, while for Skeletonema costatum, which has filamentous cells, the D3 and D2 of flocs were the lowest.