title: Environmental effects of modified clay flocculation on Alexandrium tamarense and paralytic shellfish poisoning toxins (PSTs).
abstract: Among various mitigation strategies for harmful algal blooms (HABs), the flocculation of algal cells by using modified clay (MC) has been widely applied in the field, particularly in Japan, Korea and China. However, to examine the long-term effects and the environmental safety of this method, we investigated alterations in macronutrients and paralytic shellfish poisoning toxins (PSTs) induced by the application of MC treatment to a toxic bloom, Alexandrium tamarense. The control, algal cells grew in nature condition (A1), was compared to the only MC flocculation (A2) and the MC-sediment co-matrix systems of A. tamarense (A3). The low-dosage of 0.25 g L(-1) MC could efficiently remove >90% of the A. tamarense cells within 3.5h. The mechanisms underlying the effects elicited by MC flocculation on nutrient cycling, PSTs and Chl-a degradation were also discussed. This study demonstrated that MC treatment was able to significantly remove the macronutrients (43-60% TP removal and 17-30% TN removal) and scavenge most of the PSTs from seawater, thereby speeding up the nutrient settling and the transformation and degradation of PSTs (83% decreasing in A2). Simultaneously, the study firstly demonstrated the potential detoxification of PSTs by using MC treatment, from the high toxicity of gonyautoxin 1 and 4 (GTX1 and GTX4) to the lower toxicity decarbamoyl gonyautoxins (dcGTX3) and gonyautoxin 2 (GTX2), particularly within the water-sediment environment during the two month incubation.
authors.affiliation: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, IOCAS, Qingdao 266071, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China; School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, PR China. Electronic address: luguangyuan09@mails.gucas.ac.cn.
authors.forename: Guangyuan
authors.initials: G
authors.lastname: Lu
authors.affiliation: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, IOCAS, Qingdao 266071, PR China. Electronic address: songxx@qdio.ac.cn.
authors.forename: Xiuxian
authors.initials: X
authors.lastname: Song
authors.affiliation: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, IOCAS, Qingdao 266071, PR China. Electronic address: zyu@qdio.ac.cn.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, IOCAS, Qingdao 266071, PR China. Electronic address: caoxh@qdio.ac.cn.
authors.forename: Xihua
authors.initials: X
authors.lastname: Cao
authors.affiliation: Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, IOCAS, Qingdao 266071, PR China. Electronic address: yqyuan@qdio.ac.cn.
authors.forename: Yongquan
authors.initials: Y
authors.lastname: Yuan
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D002681:China; D000077215:Clay; D002980:Climate; D004141:Dinoflagellida / Q000254:growth & development* / Q000378:metabolism; D005427:Flocculation; D057097:Harmful Algal Bloom; D006801:Humans; D012530:Saxitoxin / Q000031:analogs & derivatives* / Q000032:analysis; D012623:Seawater / Q000737:chemistry; D057096:Shellfish Poisoning / Q000517:prevention & control*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D000538:Aluminum Silicates; D012530:Saxitoxin; C013007:gonyautoxins; D000077215:Clay
keywords: Alexandrium tamarense; Environmental effect; HABs mitigation; Modified clay; Paralytic shellfish poisoning toxin (PSTs)