Abstract

Different combinations and intensities of physical (e.g. thermal) and biological (e.g. competition or predation)
stress operate on organisms in different locations. Variation in these stresses can occur over small tomediumspatial
scales (cm to 10s of metres) in heterogeneous environments such as rocky shores, due to differences in sun
and wave exposure, shore topography and/or recruitment. In this study we demonstrate how simple measurements
can be taken that represent physical and biological stresses (stress profiles) in a given location. Using a
bootstrapped principal component analysis, we identified significantly different stress profiles at four sites separated
by only 10s to 100s of metres on the Shek O peninsula in Hong Kong.We then measured response to thermal
stress, as determined by detachment temperature, in the limpet Cellana grata (which is known to be a
sensitive indicator species to thermal stress) from each location. Significant differences in stress profile between
locations were also seen in thermal stress tolerance of limpets fromthose locations. At locationswhere the major
stresses are likely to be more physical or less biological in nature (e.g. southerly facing aspect or lower density of
grazers), the mean detachment temperature was higher, whereas detachment temperature was lower at sites
with more biological or less physical stress. This method is, therefore, able to determine biologically meaningful
differences in stress profiles over small to mediumspatial scales, and demonstrates that localised adaptation (i.e.
post planktonic settlement) or acclimation of species may occur in response to these different stress profiles. The
technique can be adapted to different environments and smaller or larger spatial scales as long as the stress
experienced by the study species is relevant to these scales.