Preprint volume - SIBM

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Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS
a similar recruitment success at all shore levels. However, F. serratus (low shore)
propagules exhibited a declining recruitment success with increasing shore height.
Conclusions - Closely related fucoid species demonstrate very different osmotic
strategies to optimise survival within natural shore position. The high shore fucoid,
Fucus spiralis, possesses a higher tolerance to hypo-osmotic stress through the
development of an intricate osmo-regulatory mechanism. This mechanism comes at a
price to growth and competitive ability likely to be responsible for its inability to
significantly colonise lower shore levels. The mid shore fucoid, F. vesiculosus, does
not seem to possess an osmo-regulatory mechanism; instead it is likely to rely on
structural reinforcement through thicker cell walls conferring tolerance. The low shore
fucoid, F. serratus, a passive osmometer, invests little energy into tolerating hypoosmotic
stress and as a result is less capable of recruiting outside its natural shore
position on higher shore levels. There is an indication that greater exposure on higher
shore levels contributes to a higher tolerance of fluctuations in the external osmotic
environment. Hypo-osmotic stress is a likely significant selective pressure acting
negatively on vulnerable early developmental stages in recruiting fucoid algae,
contributing to community composition.
References
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