Dissolved organic carbon as a potential food source for marine nematodes: myth or missing link?

Functional classifications of marine nematodes usually work with feeding types or trophic guilds. These guilds link feeding behavior to mouth morphology, and in turn to different potential particulate food sources. However, over the past four decades, the suggestion has been raised several times that dissolved organic carbon (DOC) compounds could also be important contributors to nematode diets. DOC concentrations in coastal waters and interstitial pore water can be considerable, rendering DOC a significant carbon reservoir potentially available to a variety of consumers. Various lines of evidence point at the ability of nematodes to obtain dissolved organic carbon, but there is no clear evidence that such uptake could be important under field conditions. One line of reasoning, for instance, is that nematodes cannot compete with bacteria for uptake of dissolved compounds. On the other hand, since nematodes cannot efficiently be axenized, experiments of DOC-uptake in complete absence of bacteria are hard to establish, rendering unequivocal proof of DOC-utilization by nematodes difficult to obtain. In the present study, we aim at assessing the uptake of different types of DOC (from simple sugars over exopolymer secretions from diatom biofilms to more complex and refractory molecules) by nematodes in stable-isotope labeling experiments. We will model the uptake kinetics in both bacteria and nematodes to estimate to what extent any uptake by nematodes can be considered direct uptake or is more likely to be indirect uptake through bacteria.

ISCED Categories

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0511 - Biology", "0521 - Ecology