Data from: Nutrient deficiencies and the restriction of compensatory mechanisms in copepods

1.The flexible regulation of feeding behaviour and nutrient metabolism is
a prerequisite for consumers to grow and survive under variable food
conditions. Thus, it is essential to understand the ecological trade-offs
that restrict regulatory mechanisms in consumers to evaluate the
consequences of nutrient limitations for trophic interactions. 2.Here, we
assessed behavioural and physiological adjustments to nutrient
deficiencies in copepods and examined whether energy limitation, food
digestibility or co-limitation with a second nutrient restricted
compensatory mechanisms. 3.A combination of 13C-labelling and
compound-specific stable isotope measurements revealed that copepods
compensated nitrogen deficiencies by raising retention efficiencies of
amino acids. The costs of higher retention efficiencies were reflected in
the doubling of structural fatty acids, probably required for
morphological adaptations of the gut. A depletion of highly unsaturated
fatty acids in storage lipids and their selective retention suggested that
these fatty acids became co-limiting and restricted a further increase in
amino acids retention efficiencies. 4.Copepods feeding on
phosphorus-limited algae showed a marked increase of ingestion rates but
were not fully able to compensate dietary deficiencies. The increase of
ingestion rates was thereby not restricted by higher foraging costs
because energy storage in copepods increased. Instead thicker cell walls
of nutrient limited algae indicated that algal digestion resistance
restricted the extent of surplus feeding. 5.The strongly nutrient-specific
response of copepods had large implications for recycling rates, growth
efficiencies and the potential top-down control at the plant-animal
interface. Compensatory mechanisms to mitigate nutrient deficiencies are,
therefore, an essential aspect of trophic interactions and have the
potential to alter the structure of food-web.