A dominant consideration, when concerned with possible ozone-related UV-B
effects, is how laboratory and field results can be properly extrapolated
to longer time and larger spatial scales.
The work of numerous investigators,
beginning with Steemann Nielsen [1964]
[Steemann 1964]
and continuing until today, provides conclusive evidence that exposure to
UV-B decreases measured rates of algal productivity.
Much of this evidence is based upon comparison of rates of 
uptake in incubation bottles that transmit, or do not transmit, UV
radiation.
This subject continues to be explored
[Holm-Hansen 1990 primary production,
Mitchell 1990 diffuse,
Vernet pigments 1990,
El-Sayed Stephens Bidigare Ondrusek 1990,
Karentz Bothwell Coffin Hanson 1994,
Holm-Hansen Helbling Lubin 1993,
Vernet Brody Holm-Hansen Mitchell 1994,
Cullen Lesser 1991, Neale Lesser Cullen carbon 1994,
Gala Giesy 1991, Behrenfeld Hardy Lee 1992,
Behrenfeld Hardy Gucinski Hanneman Lee Wones 1993].
Further, there is convincing evidence that UV radiation, at levels
currently incident at the surface of the ocean, may have an influence
on phytoplankton productivity
[Worrest VanDyke Thomson 1978, Worrest Brooker VanDyke 1980,
Worrest Thomson VanDyke 1981 estuarine,
Worrest Wolniakowski Scott Brooks 1981,
Ray Smith Baker 1980 science, Calkins Thordardottir 1980,
Worrest 1982, Worrest 1983, Jokiel York 1982, Jokiel York 1984,
Dohler 1984, Dohler 1985,
Hader 1984, Hader 1985, Hader 1986, Hader 1987 phototaxis,
Ray Smith Prezelin macintyre 1992,
Behrenfeld Hardy Gucinski Hanneman Lee Wones 1993].
Consequently, there is now little dispute that UV damages phytoplankton
in laboratory and microcosm experiments.
On the other hand, extrapolation of this information to
natural populations and ecosystems continues to be controversial.
A recent Scientific Committee on Problems of the Environment (SCOPE)
workshop [SCOPE 1993] addressed and summarized issues associated
with UV impacts on global ecosystems.
The SCOPE report points out that we presently lack the necessary knowledge
and appropriate models to make use of laboratory results for quantitative
prediction of whole-system performance at the ecosystem level.
Currently, little information is available with which to infer long-term
ecological consequences from short-term observations.
Further, Bothwell and co-workers
[Bothwell Sherbot Roberge Daley 1993, Bothwell Sherbot Pollock 1994]
recently demonstrated that UV-B could potentially influence trophic structure,
via differential predator/prey sensitivity to UV-B, thus emphasizing the need
for long-term (multigeneration times) studies on both individual and
multiple organism populations in order to assess ecosystem structure.
In short, ecosystem level information with respect to enhanced levels of
UV-B is limited and in great need of further research, recognizing that
a variety of issues influence meaningful extrapolation of current results.