Dissertation - HQ

144 Oceanography vs. behaviour
Figure 6.12 Development of critical speed throughout the larval period and
effect of temperature. Speed is zero before hatching. When larvae hatch (around
2.5 days here), the development of maximum U crit is deduced from Fisher 57
(solid curve). The effect of a 2ºC increase in water temperature on the pelagic
larval duration is computed from O’Connor et al. 37 and ontogeny of swimming
speed is re-calculated. In warmer temperatures, the pelagic stage is shorter and
swimming abilities develop faster (dashed curve).
Exponential decrease
of PLD when
temperature increases
Faster development
of swimming abilities
after a 2ºC increase
etc.). They attributed the wide applicability of this relationship to the
universal effect of temperature on metabolism. In all taxa, PLD decreases
exponentially with temperature
ln(P LD) = β 0 + β 1 ln(T/T c) + β 2(ln(T/T c)) 2 (6.10)
where β 0 is a species-specific constant, β 1 and β 2 are constants valid
for all species: β 1 = -1.368 and β 2 = -0.283, and T c = 15ºC (Figure 6.13).
Dividing by T c is equivalent to subtracting ln(T c) to each observation
on a log scale and is a form of centring, to improve the fit. For any
species, β 0 can be calculated by substituting the species’ PLD and the
water temperature in the environment where PLD was measured in
equation (6.10). Once the relationship is calibrated, it allows to predict
the variations of PLD in response to changes in temperature.
In our model, the effect of a 2ºC increase in water temperature is
simulated. 2ºC corresponds to the estimated mean variation expected
in most climate change scenarios over the next century (A. Clement
and C. Paris, pers. comm.). A 3ºC difference in rearing temperature was
found to decrease critical swimming speed of 7 days old Amphiprion
melanopus larvae from 17 cm s -1 to 12 cm s -1 , because larvae reared at
the lower temperature were smaller and less advanced in ontogeny 262 .
However, the same 3ºC difference in the temperature of the water in