What is the name for the principle that brings floating crust into gravitational balance?

Correct Isostasy

Isostasy is the state of gravitational equilibrium between the mantle and the earth's crust. It tries to explain how different topographic heights exists on the earth surface.

It tries to balance all large portions of the earth's lithosphere. It controls the regional elevations of oceans and continents according to the density of rocks.

above statement is not a true statement about the open ocean because the open ocean has low levels of nutrients. most of the photosynthetic activity on earth occurs in the open ocean within the photic zone. organisms in the deep ocean are exposed to frigid temperatures and total darkness but it does not begin at the low-tide mark.