Photosynthetically Available Radiation (PAR) Measurements - 2
Part 2. Measure available radiation at your water testing site

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Background
The amount of solar radiation reaching earth captured by photosynthesizing organisms is estimated to be approximently .0757%. When thinking about photosynthetically available light (PAR) and ecosystems, several factors need to be presented to students. Calculations suggest that for equivalent latitudes, the Southern Hemisphere receives approximently 15%moreUV than in the Northern Hemisphere. The impact of ozone depletion causes a greater increase in UV-B(280-320nm) than UV-A(320-400nm) than PAR(400 – 700nm). The level of UV-B in the Southern Hemisphere can exceed that of the Northern Hemisphere in comparable latitudes in Europe by as much as 50%. (UV radiation in polar regions by Greg Bodeker, National Institute of Water and Atmospheric Research Ltd. New Zealand) According to Ellis, Evans and Laybourn, in their studies of the effects of UV radiation on photosynthesis of phytoplankton in the MDV, both Antarctic and temperate organisms experienced inhibition of photosynthesis caused by increases in UV-B and UV-A. They also found that photosynthesis was inhibited by increases in PAR for the Antarctic organisms, but not for the temperate organisms. Phytoplankton in Bonny Lake, sampled below the 4 meter ice cover were very sensitive to photoinhibition by both UV and PAR increases. (Antarctic Research Series, 1994, p.125 – 142)

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