It is due to a lack of providable energy to the next trophic level of the energy pyramid. Primary consumers only obtain around 10% of energy that producers have, and the energy depletes as you move further and further up the food chain, until you reach the tertiary consumers which have the least amount of energy at their disposal, meaning there are less of them than other organisms further down the energy pyramid.
The answer is "32.9 meq/liter". 1875ml = 1875 / 1000 = 1.875ml mass of magnesium = 24.305 g 0.750 g Mg²+ x 1 mole Mg²⁺/24.305 g x 2 equivalents/mole = 0.617 equivalents0.0617 eq x 1000 meq/eq = 61.7 meq37.4 meq/1.875 L = 32.9 meq/liter
