My commentary: Ultra-oligo-tropic means extremely-sparce-nutrient, i.e. this part of the Meteriterranean Sea, about 100 km South of Cyprus, has few nutrients. In this case this means low total nitrogen and phosphorus. The experiment consisted of releasing, i.e. dumping, a large amount of phosphate (compared to what was already present) in a 16 square km area of sea and following the growth of several classes of organisms for about 10 days. The somewhat surprizing finding was that the chlorophyl concentration (an index of phytoplankton) decreased, while the concentration of bacteria and the amount of eggs carried by copepods increased.
My diagram on the left is an illustrated (and perhaps idiosyncratic) version of Fig. 4 in this paper; first some definitions:
phagotrope- eats other organisms
osmotroph- adsorbs nutrients through cell wall
heterotroph- requires complex organic compounds to live, e.g. amino acids.
phytoplankton- small (just a few microns in diameter) organisms that can use inorganic minerals and sunlight to grow.
P- inorganic phosphorous, e.g. the phosphoric acid that was dumped into the sea by the experimenters (the "P" is large because the concentration is large).
N- inorganic nitrogen, e.g. ammonia, nitrate (the "N" is small because the concentration is very low.
DOC- dissolved organic carbon, e.g. amino acids, fats, carbohydrates.
DON- dissolved organic nitrogen, e.g. amino acids
The knee jerk guess of what would happen to the added phosphate was that the phytoplankton would absorb most of it and grow like crazy; they in turn would be eaten by those higher on the food chain. However, the phytoplankton can't use organic nitrogen, thus they are starving in the midst of the phosphate feast. However, bacteria can use both phosphate and organic nitrogen, so they grow and pass the phosphate up the food chain.
In addition to this "bypass" theory, both bacteria and phytoplankton may accumulate phosphate quickly even before they start to multiply (phytoplankton never do). This increase in quality of the prey may trigger increased egg production by copepods before the mass of food increases; a kind of trophic "tunneling".