Nature of Phosphorus Limitation in the Ultraoligotrophic Eastern Mediterranean
by T. F. Thingstad et al in Science 12 August 2005 vol. 309 pg. 1063-1071
Journal abstract: Phosphate addition to surface waters of the ultraoligotrophic, phosphorus-starved eastern Mediterranean in a Lagrangian experiment caused unexpected ecosystem responses. The system exhibited a decline in chlorophyll and an increase in bacterial production and copepod egg abundance. Although nitrogen and phosphorus colimitation hindered phytoplankton growth, phosphorous may have been transferred through the microbial food web to copepods via two, not mutually exclusive, pathways: (i) bypass of the phytoplankton compartment by phosphorus uptake in heterotrophic bacteria and (ii) tunnelling, whereby phosphate luxury consumption rapidly shifts the stoichiometric composition of copepod prey. Copepods may thus be coupled to lower trophic levels through interactions not usually considered.
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
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".