The continuous addition of built structures to the seabed, such as shipwrecks, energy platforms, and pipelines, is contributing to ocean sprawl in coastal and offshore regions. These structures, typically composed of steel or wood, are substrates for microbial attachment and biofilm formation. Success of biofilm growth depends on substrate characteristics and local environmental conditions, though it is unclear which feature is dominant in shaping biofilm microbiomes. The goal of this study was to understand substrate- and site-specific impacts of built structures on short-term biofilm composition and functional potential. Seafloor experiments containing steel and wood surfaces were deployed for four months at distances extending up to 115 m away from three historic (>50 years old) shipwrecks in the Gulf of Mexico. DNA from biofilms on steel and wood was extracted and metagenomes were sequenced on an Illumina NextSeq. Bioinformatics analysis revealed taxonomic composition was significantly different between substrates and sites, with substrate being the primary determining factor. Regardless of site, steel biofilms had a higher abundance of genes related to biofilm formation, and sulfur, iron, and nitrogen cycling, while wood biofilms showed a higher abundance of manganese cycling and methanol oxidation genes. This study demonstrates how substrate composition shapes biofilm microbiomes and suggests marine biofilms may contribute to nutrient cycling at depth. Analyzing the marine biofilm microbiome is a first step to understanding the ecological consequences of ocean sprawl.

Primary Presenter: Rachel Mugge, United States Naval Research Laboratory (rachel.mugge.ctr@nrlssc.navy.mil)

Authors:

Rachel Mugge, United States Naval Research Laboratory  (rachel.mugge.ctr@nrlssc.navy.mil)

Rachel Moseley, University of Southern Mississippi  (rachel.moseley@usm.edu)

Leila Hamdan, University of Southern Mississippi  (leila.hamdan@usm.edu)