1. A First Look at Temporal Change among Lau Basin megafauna June 2006—June 2009 Arunima Sen a , Elizabeth L. Podowski a , Erin L. Becker a , George W. Luther III b and Charles R. Fisher a Biology Department, Pennsylvania State University, 208 Mueller Building, University Park, PA 16802 b College of Marine and Earth Studies, University of Delaware, 700 Pilottown Road, Lewes, DE 19958 Early observations of the three foundation Lau megafauna, Alviniconcha hessleri, Ifrermeria nautliei and Bathymodiolus brevior indicated differentiation on a spatial scale. We combined high resolution imagery with in-situ physico-chemical measurements to tease apart species specific tolerances to temperature, oxygen concentration and sulphide concentrations. Based on these studies, we hypothesized temporal change and succession and both chimney and diffuse flow sites. Alviniconcha hessleri Highest temperature, Highest sulfide Lowest oxygen Ifremeria nautilei Medium temperautre Medium sulfide Medium oxygen Bathymodiolus brevior Lowest temperature Lowest sulfide Highest oxygen Spatial Differentiation of Lau megafauna Change in Diffuse Flow Sites Stability of Chimneys We returned to 7 diffuse flow sites in June 2009 for re-imaging and electrochemical measurements. We found both examples of more active and less active sites, giving us a glimpse of successional patterns in different directions. The following examples illustrate our findings. Unlike diffuse flow sites, chimneys displayed much more stability and less change over time. While diffuse flow sites are undergoing a process of replacement linked to changing flow regimes, chimneys communities displayed little difference in the past four years. Kilo Moana Site 1, 2006 Kilo Moana Site 1, 2009 This site is an example of an area becoming less active. Note the larger numbers of dead mussels, fewer anemones and the appearance of non vent endemic brisingids in the 2009 mosaic. The graphs show that the site is dying. ABE Site 2, 2006 Kilo Moana 2: Example of less active site ABE 2: Example of more active site Bugs Bunny, 2006 Tu’i Malila 62, 2006 Note the lack of change in fauna between the two years. At the Tu’I chimney, the chemistry has remained the same, whereas at Bugs Bunny, the chemistry has reversed. This indicates that faunal changes at chimneys is slow despite flow regime changes. Future Questions Acknowledgements Bugs Bunny, 2009 ABE Site 2, 2009 This is an example of a site undergoing succession. The graphs show little chemical difference, but note the lack of anemones and the higher dominance of B. brevior in the 2009 mosaic. Pioneering species--- Intermediate species--- Climax species This is a preliminary look at succession and temporal change among Lau Basin megafauna. Further analyses within a GIS framework will be conducted to quantify both faunal and chemical change at these sites. In addition to diffuse flow and chimney sites, we have collected data for peripheral sites which will further contribute to our understanding of temporal change of Lau megafauna. This project was funded by NSF grants ……………..to CRF? Many thanks to the ROV JASON II and R/V Thompson crews, without whom none of this work would have been possible. Thanks also to Jason Sylvan for use of his photographs, the e-chem team, Andrew Madison, Mustafa Yucel and Amy Gartman and Dominique Cowart for assembling mosaics.