Dr. Hargreaves' research interests include eco-physiology and bio-optics in aquatic ecosystems, with a special focus on developing new electronic field instruments and new research applications for instruments. One research focus has been measuring and modeling the factors controlling penetration of ultraviolet radiation (UVR) into lakes in North and South American and also within stream networks and coastal waters. His work in Crater Lake, OR, established this alpine caldera lake as clearest in the world for the penetration of UVR, with attenuation near the surface controlled largely by water molecules (Hargreaves, 2003). By measuring how the diffuse attenuation of different wavelengths varied with depth in Crater Lake, Hargreaves established the role of phytoplankton as strong attenuators of light and also showed that phytoplankton use natural sunscreen compounds (known as mycosporine-like amino acids) to protect their cells from UV-B radiation in proportion to the average intensity of UV-B between the surface and the ocean-like deep chlorophyll maximum at 120 meters (Hargreaves et al., 2007). By developing several intercalibrated measurements (proxies) for UV transparency, Hargreaves also established that over the past 100 years there has been no decline in water clarity in Crater Lake, only decadal cycles in algal abundance and occasional short-lived turbidity from rain. However, one surprising outcome from an analysis of Satellite and Crater Lake data was a decline in algal biomass (estimated by chlorophyll-a) during summers when stratospheric ozone levels were low, which would allow the penetration of UV-B radiation deep into the clear waters. One focus of Hargreaves' current research project focuses on the spatial and temporal relationships between phytoplankton, colored dissolved organic matter (CDOM), and sunlight within the water column of clear deep lakes in Oregon and California, and shallower and more humic lakes in Pennsylvania. Another focus is the application of a new instrument for measuring the spectral absorption of sunlight by phytoplankton, both in lakes and as part of a Southern Ocean project (GASEX-III). In the case of GASEX-III, the project objective is to quantify the role of phytoplankton photosynthesis in the exchange of carbon dioxide between the ocean and the atmosphere. Another focus is the exploration of how Pennsylvania lakes are changing in response to climate change using a combined watershed-watercolumn approach (accounting for flux of water and CDOM from the watershed and from the lake sediments as well as microbial respiration and production of CDOM and photochemical bleaching in surface waters). References Web site: http://www.lehigh.edu/~brh0 2003 Hargreaves, B.R. Water Column Optics and Penetration of UVR, pp.59-105 IN: UV Effects in Aquatic Organisms and Ecosystems, E.W. Helbling & H. E. Zagarese (eds), Comprehensive Series in Photochemical and Photobiological Sciences, Royal Society of Chemistry, Cambridge, UK, 575 2007 Hargreaves, B.R., S. F. Girdner, M. W. Buktenica, R.W.Collier, E. Urbach, G. L. Larson, Ultraviolet Radiation and Bio-optics in Crater Lake, Oregon. Hydrobiologia 574:107-140