UTILIZATION OF C-14 FORMALDEHYDE TO INFER INGESTION RATES AND ABSORPTION EFFICIENCIES BY BENTHIC DEPOSIT-FEEDERS

Several experiments were carried out to provide new information on the use of the C-14 formaldehyde technique in deposit-feeding studies. Ou r results show that: (1) uptake and stability of labelling vary with s pecies and types of detritus, (2) there are significant differences be tween the labelling stabilities of uniformly and C-14 formaldehyde lab elled diatoms, (3) the use of uniformly and C-14 formaldehyde labelled detritus derived from Pavlova lutheri results in very similar ingesti on rates and absorption efficiencies by Abra ovata, (4) ingestion rate s and absorption efficiencies of Abra ovata fed on 11 macrophytobenthi c types of detritus labelled with C-14 formaldehyde are consistent wit h the Literature (negative relationship between ingestion and protein content, and between absorption and phenolic content), and (5) absorpt ion efficiencies recorded for C-14 formaldehyde labelled sediment trap materials collected at different periods of the year correlate negati vely with gross sedimentation rates. These results support the use of the C-14 formaldehyde technique with monospecific detritus. The relati ve values of absorption efficiencies recorded for heterogeneous detrit us also seem consistent. However, it is stressed that the exactitude o f the absolute values of these absorption efficiencies is yet to be pr oven.