The size distribution of benthic nematodes was investigated along different gradients of food availability in various regions of the NE Atlantic: I. across the continental margin and II. with increasing distance from the continental rise. An overall trend for miniaturization with increasing distance from the food source was found. However, a series of physical, chemical and biological factors clearly lead to variations in nematode size structure. Moreover, our results indicate that seasonally varying food supply or a periodically pulsed input of organic matter to the sea floor affects nematode size spectra. The hypothesis is proposed that the life cycle of deep-sea nematode species and hence the size structure of their populations are related to seasonal energy availability. This dependence might result in one-year life spans of deep-sea nematodes and probably other meiofauna.