TITLE:    Palmer LTER: Hydrogen peroxide in the Palmer-LTER region: IV.
Photochemical interactions with dissolved organic matter
AUTHORS:  DM Karl, J Resing
Palmer LTER Contribution No. 22

There is a new 20th-century challenge to southern oceans
microbial assemblages in the form of an increased flux of
ultraviolet (UV) light caused by an erosion of the amtospheric
ozone layer (Frederick and Snell 1988).  Smith et al. (1992)
and Helbling et al. (1992) recently documented growth inhibitory,
UV-dependent effects on antarctic marine phytoplankton populations.
We hypothesized that UV radiation might also play a role in micro-
heterotrophic microbial processes by direct interactions with DOM.
Two independent pathways are proposed: (1) partial photolytic
degradation or alteration of refractory DOM resulting in a supply of
readily available organic substrates for bacterial metabolism and (2)
complete photolytic degradation of DOM.  The former pathway would
enhance heterotrophic bacterial processes; the latter would effectively
constitute a form of competition for the availability of organic nutrients
and, perhaps, provide an independent nonbiological pathway for DOM
decomposition.