Assessment and Characterization of Microbial Communities in Salt Affected Soils on Galveston Island.

In 2008, Hurricane Ike devastated Galveston Island and left behind elevated salt concentrations in the soils and groundwater, killing 80% of the live oak trees. In an effort to alleviate this situation, a project has been initiated to evaluate, introduce, and promote a wide range of salt- and hurricane- tolerant plants for Galveston Island. A research site has been established at Galveston’s Moody Gardens to study the growth of Hibiscus hamabo, and Quercus virginiana, and Taxidium distichum in salt-impacted soils. Because microbial species play an intricate role in the success of these plants, research included assessing indigenous microbial populations and activity at this site. The site contains 48 plots, half of which are bedded with nonnative bank sand soil. These soils were treated with one of the following amendments: 1) no additives; 2) gypsum; 3) pine bark mulch; 4) gypsum + pine bark mulch. Soil samples were collected in July and October 2016 to estimate total bacteria and fungi populations. These were determined by serial dilution plating on selective media using a spiral plating system. Soil respiration rates were determined using a Model EGM-4 Environmental Gas Monitor for CO₂ evolution. Bacteria populations ranged from 4.07 to 5.12 and 3.73 to 4.26 log CFU g^-1 in soils collected in July and October, respectively. Fungi ranged from 3.27 to 3.58 and 3.09 to 3.71 log CFU g^-1. Fungal populations were not significantly different between treatments. Bacteria populations were significantly higher only in control bedded and mulch flat treatments. Likewise soil respiration rates ranged from 0.873 to 3.07 g CO₂ m^-2 hr ^-2 but showed little response to soil amendments. These results indicate that there are relatively large and active soil microbial communities inhabiting soils at the field site. However, soil amendments had little effect on microbial populations and activities.