In one square meter of open ocean, phytoplankton can generate 1,600,000 Calories of chemical “food” energy per year. Assuming that there is a 90% “loss” of usable chemical energy during transfers form one trophic level to the next, calculate the energy available at each trophic level for each of five trophic levels.

The question is asking us to say what organisms in the same ecosystem are.

Organisms in one ecosystem are all dependent on each other: they feed on each other or are dependent on the tissues of the other organisms when they die - this is called "interdependence" - dependence from each other.

So the answer is interdependent.