Studies were undertaken to investigate the suitability of several molecular and physiological
responses as biomarkers of UV-B exposure in several marine macroalgal species.
Investigations into the sensitivity of mature plants and the reproductive unicells were also
carried out. Furthermore, experiments were conducted to determine the interaction between
UV-B radiation and the antifouling compound Irgarol 1051 in both a fouling alga and two
non-target algal species.
Chlorophyll fluorescence, in vivo thallus absorptance and ion leakage were investigated for
their suitability as physiological biomarkers of UV -B exposure in the intertidal alga
Enteromorpha intestinalis and the subtidal alga Palmaria palmata. DNA damage (measured
by Random Amplification Polymorphic DNA fingerprinting, RAPD) and the cellular stress
response (measured by induction of the heat shock 70 protein, HSP 70) were evaluated as
molecular biomarkers of UV-B exposure. Measurements of thallus growth were used as a
measure of adverse biological effects. Fv/Fm ratio showed potential as a sensitive, nonspecific
general biomarker of UV-B exposure in both E. intestinalis and P. palmata. In vivo
absorptance at wavelengths corresponding to chlorophyll a, phycoerythrin and/or carotenoids,
as well as phycoerythrobilin and phycocyanin decreased in a dose-response dependent manner
with UV-B exposure. These changes were associated with decreases in growth rate in P.
palmata. The RAPD technique used for measuring DNA damage, showed potential as a tool
for assessing UV -induced toxicity. These results illustrated that utilising several responses
from different levels of biological organisation offer greater possibilities for detecting UV-B
induced effects than do single responses.
Experiments with 12 h old reproductive unicells of E. intestinalis demonstrated that asexual
zoospores were up to 6 times more sensitive to UV-B exposure than mature thalli (measured
as variable fluorescence). After 1 hour exposure to elevated UV-B (equivalent to 27% ozone
depletion) reproductive unicells experienced decreases in variable fluorescence, accompanied
by a 50 % inhibition of germination success and 16.4 % reduction in growth rates. Moreover,
consistent patterns of greater sensitivity in the sexual reproductive part of the life cycle
compared to the asexual part of the life cycle emerged throughout the experiments.
The interactive relationship between UV-B radiation and the s-triazine Irgarol 1051 was
investigated in multi-factorial experiments. Inhibitions in optimal quantum yield of
approximately 20% were found after exposure to UV-B or Irgarol 1051 (applied singly).
When these two stressors were applied simultaneously, however, an additive effect resulting
in further reductions of up to 19.6 % compared to a single treatment occurred.
These decreases in Fv/Fm were accompanied by up to a 38.5 % reduction in growth rates.
Simultaneous exposure of the same stressors to two non-target macroalgae, P. palmata and
P. umbilicalis, revealed that these algae were less sensitive to Irgarol 1051 compared to E.
intestinalis. However, similar additive effects measured as reductions in both Fv/Fm ratio and
growth rates occurred after simultaneous exposure. These results underline the importance of
investigating combination effects between UV-B radiation and xenobiotic compounds, if an
under-estimation of the ecological implications of elevated UV-B exposure in the marine
environment is to be avoided
