The baldcypress tree (Taxodium distichum) is a key species in southeastern Louisiana, acting as a buffer against storm damage and as an important player in Gulf Coast restoration efforts. Little is known about the symbionts of baldcypress, namely the endophytes- microscopic fungi and bacteria that live within the tissues of all plants. Endophytes are known to confer advantages to their host plants, including increased resilience to stress. Our study compares the community composition of baldcypress root endophytes in four sites where they occur naturally to the endophytes found in trees that were planted in a wetland being treated with disinfected, secondarily-treated sewage effluent. Within this assimilation wetland, we further assessed the abundance and diversity of both leaf and root endophytes along a nutrient gradient created by distance from the wastewater outfall pipe.
In June 2014, we sampled the roots and leaves of 18 baldcypress trees across the nutrient gradient. In October of 2014, we sampled the roots of 48 baldcypress trees in four sites (12 trees/site) where they occur naturally in southeastern Louisiana. We isolated endophytes from roots and leaves using culture-dependent methods and made preliminary identifications (operational taxonomic units or OTUs) based on the 16S and ITS-LSU regions for bacteria and fungi, respectively.
Results/Conclusions
Among sites, root bacterial communities were more abundant and diverse in the assimilation wetland, with Fisher’s alpha diversity values more than twice that of natural sites. These results suggest that endophyte community composition is diversified in the nutrient-augmented environment. Within the assimilation wetland site, the bacterial to fungal ratio increased with distance from the outfall pipe. Because nutrients decrease with distance from the outfall pipe, this suggests that bacterial and fungal endophytes respond differently to nutrient levels.