Paradox of classical food chain in pelagic ecosystem

The classical food chain traditionally refers to the widely held concept of a trophic linkage between diatom spring bloom, copepod production and important fisheries. During the last 6 years, the evidences on the failure of copepod reproduction with diatom diets were accumulated. In Centropages typicus, Temora stylifera and Calanus helgolandicus, it was found that in situ egg viability was highly variable and that the fecundity and/or hatching success were reduced when the copepods were fed on a diatom in the laboratory. Further study on the diatom effects using 16 species of copepods from fresh water, estuarine and marine environments in Northern and Southern Hemispare showed that except for one combination among the 37 diatom-copepod combinations examined, where there was no negative effect, diatoms supported either lower copepod fecundity or hatching success or both, when compared to non-diatom diets. One laboratory experiment shows that fecundity and hatching success of copepods is related to amount and composition of unsaturated fatty acid inalgal diets. Another one demonstrates that diatom cells contain an as yet unidentified inhibitory compound that blocks copepod embryogenesis. These findings on the dark side of the diatoms address the revision of the traditional concept in the pelagic ecosystems and relative importance of microbial food chain