locations (South Pole, McMurdo, and Palmer Stations), and a system is planned for 

 installation at Ushuaia, Argentina. Data from this network will be used to 

 determine the extent of ultraviolet radiation enhancement due to Antarctic ozone 

 depletion and to estimate the health and biological consequences of stratospheric 

 ozone depletion for Antarctic organisms and personnel. 



WORKSHOP SUMMARY: 



Because so little biological UV research has been conducted in Antarctica, 

 workshop speakers reviewed research results from lower latitudes. Where 

 possible, speakers and participants commented on the implications of UV trends 

 for Antarctic organisms; these insights are summarized below. 



Both Martyn Caldwell and Richard Setlow stressed that there are considerable gaps 

 in our knowledge of UV effects on organisms (and Antarctic organisms are 

 virtually unstudied at this time). Caldwell established the importance of 

 obtaining accurate and biologically relevant action spectra for UV damage. He 

 pointed out that different cellular processes have different action spectra and 

 that ozone reduction causes damage for a particular system or organism only if 

 the relevant biological action spectrum/spectra has certain characteristics, such 

 as increasing detrimental effect with decreasing wavelength over the ozone- 

 absorbing (UV-B) region. In addition to obtaining accurate dose-response curves, 

 Setlow urged Antarctic researchers to establish the relationship between UV dose, 

 dose rate, and biological effect. 



Arlin Krueger noted that in October 1987, ozone values in some areas were close 

 to zero at the altitude where the ozone maximum usually occurred. This implies 

 column ozone may not fall much below the 1987 ozone minimum (109 DU) unless it is 

 removed from other altitudes. Krueger and John Frederick pointed out that solar 

 elevation has a strong effect on UV-B penetration; solar elevation at midday 

 increases between June 21 and Dec. 21, and toward the equator. Therefore, even 

 if ozone levels are the same or higher than the October 1987 ozone minimum 

 values, increases in the size of the ozone hole or in its duration will 

 significantly increase the amount of UV-B penetrating to the earth's surface. 

 Because UV penetration varies so strongly with latitude, maximum UV penetration 

 in the Antarctic will not necessarily coincide with the ozone minimum. Because 

 photoperiod changes rapidly and dramatically between June and December in 

 Antarctica, it will be important to monitor organism responses to both the 

 maximum daily UV-B dose and the integrated daily UV-B dose. Frederick's model 

 calculations indicate that UV-B levels for the ozone minimum (October 5) were 

 comparable to summer solstice values at that location; Antarctic organisms 

 presumably have not experienced "record" UV-B levels, though spring UV-B levels 

 were higher than normal. 



Data on the motion of the ozone hole show changes in the position of the hole 

 relative to geographical locations. In a matter of days, a particular region may 

 experience dramatic changes in UV-B radiation (column ozone changes of more than 

 150 DU have already been observed over this time scale). Ray Smith coined the 

 term "Middle-UV front" for this phenomenon. Because it is so difficult to 

 reconstruct the solar UV-B spectrum with artificial light sources, the UV front 

 provides a unique opportunity to study the response of organisms to large changes 

 in solar UV-B. Smith noted that organisms adapted to gradual seasonal changes in 

 UV-B may not be able to respond equivalently to similar or greater changes 



