THE EFFECTS OF MAGNESIUM HYDROXIDE FOR THE MICROBIAL COMMUNITY IN THE SEDIMENTS OF A EUTROPHIC CLOSED BAY

Abstract

Bench scale laboratory experiments were carried out to evaluate the effects of magnesiumm hydroxide (Mg(OH)2) on the sediment quality and on the bacterial communities composition of the sediments collected from a eutrophic inner bay. The pH of sediments in Mg(OH)2 addition treatment group has risen up from the initial value of 7.19 to 8.68 after the 10-day incubation, meanwhile the pH of the control group has stayed around 7.16. The acid volatile sulfides (AVS) content of the treatment group was reduced from initial
value of 1.28 mg dry-g-1 to 1.11 mg dry-g-1, though in the control group it raised to 1.34 mg dry-g-1. The dissolved organic carbon (DOC) content increased from 125.3 mg L-1 to 136.5 mg L-1 and 183.9 mg L-1 in control group and treatment group sediments, respectively. Using a next-generation sequencing (NGS) method, it was revealed that the bacterial communities in sediments of the Mg(OH)2 addition treatment group were different from those of the control group sediments. The number of sulfate-reducing bacteria (SRB) such as genus Desulfobulbus in the treatment group sediments has significantly lessened whereas it is elevated in the control group sediments. Redundancy analysis showed that the decrease of AVS in the treatment group was correlated to the reduction of SRB, and the pH increase accelerated the growth of alkaliphilic bacteria (Fusibacter and Alkaliphilus). Moreover, it was speculated that the increase of DOC in the treatment group was due to the up rise of alkaliphilic bacteria and a decline of SRB.