Combinations of stresses showed an additive effect in comparison to the ind
ividual stress responses. It is apparent from these results that thermal, e
levated-light or osmotic stress increases the sensitivity of Halophila oval
is to any of the other stress factors. Photosynthetic stress was detected u
sing chlorophyll a fluorescence. Quantum yield was consistently the most ef
fective measure of photosynthetic stress from combination stress exposures.
Chlorophyll pigment analysis supported the general decline in photosynthet
ic capacity as indicated by the chlorophyll fluorescence; however, several
anomalies did occur. (C) 1999 Elsevier Science B.V. All rights reserved.