Award: OCE-1537807

This award supported a multi-institutional and interdisciplinary research expedition and subsequent analyses, designed primarily to increase our understanding of the physiological ecology of Lau Basin fauna and the processes that govern the ecological patterns observed in vent ecosystems, and to effectively communicate the findings to a broad audience. State-of-the-art equipment and analyses were used to characterize the physico-chemicalenvironment and obtain time-seriesobservations of natural changes in the geological setting and animal communities found on the Eastern Lau Spreading Center. Specifically, we used the ROV ROPOS to conduct multibeam seafloor surveys to examine potential geological changes in each vent field, revisited the community assessment sites we established in 2006 to acquire images for photomosaics, and made spatially explicit in situ temperature and chemistry measurements to define the realized niches of the fauna and document natural changes in diffuse flow chemistry and the communities over time. Although there were changes detected at the sites associated with some growth in ventstructures and inone case, chimney collapse, the study sites were remarkably similar both geologically and biologically to their state as far back as 2005. Similarly, the temperature and chemistry data collected from the diffuse-flow sites and high-temperatureorifices indicatesvery little change in the geochemical composition of fluids at the primary study sites over the decade of study. Together this data indicates that the vent sites themselves and the individual biological communities around discrete patches of active flow on this back-arcspreading center are considerably more stable than the more extensively studied hydrothermal vents and communities on mid-oceanridges spreading at a similar rate. This finding has important implications for many countries in this region because hydrothermal vents in this back-arc basin region are being targetedfor mining of copper, silver andgold in the polymetallic sulfidedeposits. Early environmental impact assessments written to address concerns associated with deep-seamining of active hydrothermal vents had assumed that the Lau Basin fauna wereadapted to catastrophic disruptions on the same time scales as those of the East Pacific Rise where tectonic and volcanic events disrupt sites on sub-decadal time scales. Resource managers should now be aware that this is unlikely to be the case in this region, and that the local vent fauna may not be as resilient to repeated anthropogenic impact as previously assumed. Last Modified: 05/25/2018 Submitted by: Charles R Fisher