Temperature Profiles of Settling Larvae+

Satoshi Mitarai

06/26/06

LARVAL DISPERSAL IN SIMULATIONS

DATA REQUESTED

• Characteristic profiles that captures variability– Find rapid temperature shift, and explain physics behind the

big jump wind? – e.g., wind, upwelling events, etc...

• Magnitude of temperature shift– Larger or smaller than diel change?

• Provide several scenarios to be tested in lab

(From our previous meeting)

LARVAL TRAJECTORIES ON SST

• Larvae mostly move along SST contours, due to Geostrophic balance– Temperature change

should be mainly due to mixing and diffusion

– Warmed up offshore, cooled down nearshore

• But, sometimes larvae cross temp contours– Geostrophic balance does

not always hold– Leads to significant jump in

temperature

SAMPLE TEMP PROFILE

Release location

Released in rather cold water (~12.2 C)

The larvae warms up as it goes offshore, but does not cool down as much when it comes back…

TRAJECTORY ON SST

Warms up as it goes offshore, come back before it really gets cooled down

Released in rather cold waters

ANOTHER EXAMPLE

Release location

Released in rather warm water (~13.3 C)

The larvae undergoes pretty much same temperature throughout its PLD (20 to 40 d)

TRAJECTORY ON SST

Released in warm spots Stay in warm zone throughout PLD

AND ANOTHER

Release location

Released in not warm not cold water (~13 C)

The larvae undergoes a big temperature jump (about 1.5 degree C within one day)

TRAJECTORY ON SST

Released in average temperature

Larvae goes across the region with large temperature gradient

TEMPERATURE CHANGE DURING PLD

Summer Winter

Moose: is this large or small? It looks small to me compared to the drifter data that you showed me

(Temperature change that each settler undergoes during its PLD)

Temperature change during PLD (C) Temperature change during PLD (C)

TEMPERATURE CHANGE PER DAY

Summer Winter

Moose: is this large or small? It looks small to me compared to the drifter data that you showed me

SUMMARY

• Temperature change that each settlers undergoes during PLD is less than 3 degree C in summer and 1.5 degree C in winter– This seems small to me

• The rate of temperature change (per day) is generally much smaller than 1 degree C / d – This seems small to me

• A big temperature jump can occur when a larva goes across temperature front – Can increase (or decrease) surrounding temperature

more than 1 degree C within a day

MODELING OF TEMP PROFILES?

• It seems difficult to mimic temperature profiles shown here because it is not a statistically stationary process– Released in colder region (nearshore); travel warmer region

(offshore); and come back colder region (nearshore)

• Simplest way may be to take the time series obtained from the simulations…

• Beyond this, we should discuss if the temperature change obtained from the simulations would significantly affect the growth rate of sea urchin larvae

• What do you think?