Periodic sulfide irruptions impact microbial community structure and diversity in the water column of a hypersaline lake

Abstract

The occurrence of hypoxia/anoxia and sulfide formation in productive lakes, enclosed seas, and the coastal ocean often results in catastrophic loss of plankton, benthic invertebrates, and fish populations. Sulfide formed in deeper waters is mixed upward due to storm events or currents, thereby removing oxygen from large portions of the water column. Although the deleterious effects of these events on many organisms are known, the effects on microbial communities have received less attention. Archaeal and bacterial community structure and diversity were investigated at 6 sta- tions along 2 intersecting transects passing through a sulfide-rich plume formed in the moderately hypersaline Salton Sea, California, USA. Community structure analysis clearly distinguished samples within and outside the sulfide plume, and multivariate analyses found these patterns to be correlated with sulfide concentration. Cloning and sequencing of 16S rRNA genes revealed that Actinobacteria, Gammaproteobacteria (purple sulfur bacteria), and Chlorobi (green sulfur bacteria) were more pre- valent at stations with higher sulfide concentration, and Synechococcus spp. was the most abundant bacterial lineage at most stations. Archaeal diversity was low, and sequences were affiliated with Methanohalophilus spp., Methanococcoides spp., Methanosarcinales spp., many of which are related to known methylotrophs, and Marine Benthic Group (MBG)-D sequences. Compositional differences detected between stations may reflect differential tolerances or utilization of sulfide and other reduced-sulfur compounds by the planktonic microbial community.