First published online June 15, 2006
Journal of Experimental Biology 209, 2420-2431 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02258
Thermal stress on intertidal limpets: long-term hindcasts and lethal limits
Mark W. Denny1,*,
Luke P. Miller1 and
Christopher D. G. Harley1,2
1 Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,
USA
2 Department of Zoology, University of British Columbia, Vancouver, BC, V6T
1Z4, Canada
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Fig. 2. Measured survivorship of L. gigantea as a function of temperature.
The curve is drawn according to Eqn 4. Error bars are 95% confidence
limits.
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Fig. 3. Five years of predicted body temperatures (A,B) and measured air (C) and
sea-surface (D) temperatures. (A) A horizontal surface 1.5 m above mean lower
low water (MLLW), protected from waves. Note that the temperature spike near
day 1400 is actually two spikes on sequential days. (B) A wave-exposed
horizontal surface 0.5 m above MLLW.
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Fig. 4. Maximum body temperature as a function of shoreline elevation and
substratum orientation on (A) wave-exposed and (B) wave-protected shores.
MLLW, mean lower low water.
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Fig. 5. The predicted fraction of limpets surviving the acute maximum temperatures
shown in Fig. 4 for (A)
wave-exposed and (B) wave-protected shores. Survivorship is low on horizontal
and west-facing angled surfaces, but high elsewhere. MLLW, mean lower low
water.
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Fig. 6. Exposure to waves reduces the time spent out of water for shoreline
elevations between 0 and +3 m. The difference in emersion fraction (closed
circles) is greatest at +1.25 m, whereas the difference in maximum
temperatures (open circles, horizontal surfaces; open squares, angled,
west-facing surfaces) is greatest lower on the shore. MLLW, mean lower low
water.
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Fig. 7. Five-year cumulative survivorship as a function of shoreline elevation and
substratum orientation on (A) wave-exposed and (B) wave-protected shores.
MLLW, mean lower low water.
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Fig. 8. Environmental characteristics of the three potentially lethal days (A+B,
C+D, E+F) in the 5-year time series. Tb, body temperature;
Ta, air temperature; To, ocean
temperature.
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Fig. 9. (A) Daily maximal air temperature (Ta) accurately
predicts daily maximal body temperatures (Tb), including
the three potentially lethal body temperatures (circled). (B) Daily maximal
solar irradiance also predicts maximal body temperature, but with less
accuracy.
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Fig. 10. Low in the intertidal zone (+0.5 m; A,B), maximal body temperature is
typically reached at the end of a heating interval (Type A). Higher in the
intertidal zone (+1.5 m; C,D), maximal body temperature may occur at the end
of a heating interval, but occurs commonly near the middle of the interval
(Type G). Potentially lethal temperatures are circled.
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Fig. 11. Maximal body temperature increases with the length of time a limpet is
exposed to temperatures above 20°C. (A) High in the intertidal zone (+1.5
m). (B) Low in the intertidal zone (+0.5 m).
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© The Company of Biologists Ltd 2006
) and azimuth (
) angles. N, north. (B) For a limpet on a
vertical planar substratum, lines of sight (depicted by the broken arrow)
within arc S end at the sky, whereas lines of sight within arc
O end at the ocean (which in this hypothetical case extends to
infinity in a horizontal plane). Because arc S and arc O
each account for half the `visual field' of the limpet, each has a view factor
of 0.5. The fraction of the view factor allocated to sky and ocean depends on
the altitude angle of the substratum (see text, Eqn 1 and 2).