The aggregation of clay minerals and marine microalgal cells : physicochemical theory and implications for controlling harmful algal blooms

In recent years, the use of clay minerals has emerged as one of the most promising strategies for directly controlling harmful algal blooms (HABs). Its principle is based on the mutual aggregation of algal cells and mineral particles, leading to the formation of large flocs that rapidly settle to the ocean floor. This work investigated the effectiveness of various domestic clays against a number of bloom-forming species from the United States. Twenty-five clays were tested against the dinoflagellate, Karenia brevis (formerly Gymnodinium breve), and the chrysophyte, Aureococcus anophagefferens. In general, the highest removal efficiencies (RE>90% at 0.25 g l-1 of clay) against K brevis were found using montmorillonite, bentonite and phosphatic clays (i.e. a product of phosphate mining containing large amounts of montmorillonite). The RE of phosphatic clays remained high (>80%) even at 0.03 g l-1. Kaolinite and zeolite were mostly ineffective against K brevis. Removal with clay exceeded those for alum, polyaluminum chloride (PAC) and several other polymeric flocculants by a factor of two. However, the combination of phosphatic clay and PAC (at 5 mg l-1) decreased the amount of clay needed to maintain 80% RE by one order of magnitude. Cell viability and recovery remained high when clay loading stayed below 0.03 g l-1 with or without resuspension of the sediment. However, cell mortality approached 100% with 0.50 g l-1 even with daily resuspension. Between 0.10 and 0.25 g l-1, K brevis survival and recovery depended on the interplay of clay loading, the frequency of resuspension, and duration of contact prior to the first resuspension event.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Sengco, Mario Rhuel

Advisor dc:contributor.advisor

• Donald M. Anderson.

• Biology.
• Joint Program in Oceanography.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29050

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29050