Salt of the Earth: A Biofilm's Ability to Withstand Varying Salinities And Implications For Barnacle Colonization

Title: SALT OF THE EARTH: A BIOFILM’S ABILITY TO WITHSTAND VARYING SALINITIES AND IMPLICATIONS FOR BARNACLE COLONIZATION

Authors: ^1,2Laurynn Thompson Torres, ¹Dr. Wei Xu, ¹Dr. Ioana Emilia Pavel, ¹Dr. Lin Zhang, ¹Dr. Yajuan Lin, and ¹Kyra Kaiser.

Affiliations: ¹Texas A&M Corpus Christi, ²NOAA Coastal & Marine Sciences

 

Abstract:

Current climate conditions in the Western Gulf of Mexico are undergoing significant water chemistry changes. Salinity levels rapidly fluctuate with varying seasonal conditions, inducing consistent variability of abiotic stressors in the water column. Marine biofilms support the settlement of marine sessile organisms by colonizing non-living Crassostrea virginica shells. Due to the fluctuating salinity levels, marine biofilms may no longer accumulate satisfactory extracellular polymeric substance (EPS) components. Marine biofilms allow for the detection, exploration, and potential permanent settlement of local barnacle species such as Amphibalanus amphitrite. Marine biofilms must meet certain morphological, chemical and functional standards to entice barnacle cypris larvae to ‘explore’ the biofilm and permanently settle. These microbial communities are highly adapted to these conditions and respond to any deviations in the water chemistry including salinity. The salinity alterations present in marine biofilms can harm local barnacle colonization. Thus, the main goals of this project are (a) to identify potential alterations in the morphology, composition, and bacterial community of the marine biofilm under varying salinity levels (10, 25, 36, 50 ppt), and (b) to investigate the effects of biofilm alteration by salinity on the larval settlement of barnacles and physiological/behavioral responses of settled adult barnacles. These will be achieved using three well-established chemical and biological characterization techniques. (i) In our preliminary work, Raman spectroscopy has confirmed the establishment of marine biofilms on oyster shell substrates through characteristic biochemical vibrational modes. Furthermore, Raman analysis will chemically fingerprint the microbial community encased in the biofilm EPS matrix. Raman spectroscopy is a well-established analytical chemistry technique that has yet to be utilized in the studying of marine biofilm establishment on oyster substrates and its ecological connection to foundational coastal species. (ii) Compound Stable Isotope Analysis of Amino Acids of Nitrogen (CSIAA-N) will identify the nitrogen ratios and the metabolic pathways in the biofilm leading to microbial functional identification and insight into bacterial functional diversity of the biofilm community. (iii) DNA sequencing will provide additional details on the biofilm microbial population's taxonomical diversity and the overall community composition. The results emerging from these analyses indicate that marine biofilms will change in 3-D architecture, bacterial composition, and community diversity will increase under varying salinity conditions. These biofilm changes will cause different settlement rates of cypris larvae and physiological responses in the adult barnacle. Overall, this study will provide insight into how salinity will change the microscape of a biofilm and its assisting role in the establishment of healthy and productive coastlines.