Feeding on dissolved organic matter by some marine animals

Abstract

The uptake of dissolved organic matter (DOM) by various marine invertebrates was determined using 14C-labelled algal hydrolysate and compared with the uptake of particulate (algae and bacteria) organic matter. Uptake was maximal in those forms having a large active epithelial surface exposed to the aqueous medium. Enteropneust and echinoderm larvae, bivalve molluscs, pteropods, sponges, coelenterate medusae and chaetognaths (in descending order) all exhibited significant capacity for uptake (10–40% of the total metabolic requirements) when exposed to 0.50 mg C/1 of DOM ∗ ∗ See explanation of symbols with equation (1). . Animals with chitinous exoskeletons (various crustaceans) had a considerably reduced capacity, DOM accounting for 2–5% of their total intake of organic matter. Uptake, at least in certain forms (bivalves, pteropods), bears a relationship with the environmental DOM concentration. That part of the DOM taken up by the animals entered into their metabolic pool could be demonstrated by the recovery of labelled CO 2 released by the animals for a considerable period after their return to unlabelled water. The importance of this phenomenon in the nutrition of marine animals and the need to consider it as a significant factor in evaluating energy flow in the ecosystem are emphasized.