Abstract:
The coastal area forms one of the most biologically productive and undoubtedly one of the most complex ecosystems. A balance in the coastal ecosystem is fragile because biotic communities are affected by the numerous environmental factors from atmospheric, marine, and terrestrial processes, all interacting in the coastal area. Algae are responsible for the majority of the gross primary production in the coastal regions. However, despite the critical importance of algae for the global ecosystem, the biodiversity of many algal groups is understudied, partially due to the high complexity in identifying algal species according to their morphological structures. The current study aimed to take advantage of the recently developed technology for biotic community assessment through the high-throughput sequencing (HTS) of environmental DNA (eDNA) known as the “eDNA metabarcoding” to evaluate littoral algal communities in the Northern Gulf of Mexico (NGoM). As with other new procedures, the implementation of eDNA metabarcoding has potential unrevealed factors, which is particularly true for algal communities. Therefore, this study developed and tested the complete methodology, including the conception of new reference databases for assessing littoral algae via eDNA using the partial 28s rDNA (LSU) and 23S rDNA plastid (UPA) molecular markers. This study indicated that generally, UPA is a more efficient marker for studies interested primarily in algal communities. Also, the analysis of structure and composition between algal communities revealed that eDNA could be used to assess algal communities' variation between different littoral zones and geographical locations along the shoreline. Furthermore, 126 unique algal species were identified based on eDNA signals, among which 46 species have not been previously reported for the Gulf of Mexico. However, verification according to the morphology-based species identification might be required to confirm these non-indigenous algae species (NIS). Nevertheless, distribution and relative abundance of identified NIS had strongly positive and highly significant correlations and/or associations with the traffic of trading ships in NGoM. This dissertation research has provided a bioinformatics framework for future eDNA studies of algal communities.
