Ecophysiological response of marine copepods to dietary elemental imbalances

We assessed the effects of nutrient imbalanced diets on the feeding, reproduction and gross-growth efficiency of egg production of the copepod Paracartia grani. The cryptophyte Rhodomonas salina, cultivated under balanced (f/2) and imbalanced growth conditions (N and P limitation), served as prey. Copepod C:N and C:P ratios increased in the imbalanced treatments, particularly under P limitation. Feeding and egg production rates did not differ between the balanced and N-limited treatments but decreased under P limitation. We found no evidence of compensatory feeding in P. grani. C gross-growth efficiency averaged 0.34 in the balanced treatment and declined to values of 0.23 and 0.14 for the N-and P-limited treatments, respectively. Under N limitation, N gross -growth efficiency increased significantly to a mean value of 0.69, likely as a result of increasing the nutrient absorption efficiency. P gross-growth efficiency reached values > 1 under P limitation, involving the depletion of body P. Hatching success was >80%, with no differences among diets. Hatched nauplii, however, had lower size and slower development when the progenitor was fed a P-limited diet. This study highlights the effects of P limitation in copepods, which are more constraining than N, and the presence of maternal effects driven by prey nutritional composition that ultimately may affect population fitness.

Automated summary

This study assessed the effects of nutrient imbalanced diets on the feeding, reproduction, and gross-growth efficiency of the copepod Paracartia grani. The results showed that P limitation had a greater impact than N limitation on copepod growth and reproductive rates. The study also revealed the presence of maternal effects driven by prey nutritional composition, which potentially affects population fitness.