crab have been migrating, en masse, to the antartic waters for some time now. the antartic landscape has small volcanic vents all over the place, creating 'ice chimneys' in the landscape.

dunno about effect on weather, but effect on sealevel might be significant if things start to melt:

[link to en.wikipedia.org] (en.wikipedia.org/wiki/Current_sea_level_rise#Glaciers_and_ice_caps)

[link to en.wikipedia.org] (en.wikipedia.org/wiki/West_Antarctic_Ice_Sheet#Potential_collapse)