Evidence for Absorption of Kelp Detritus by the Ribbed Mussel Aulacomya ater Using a New 51Cr-Labelled Microsphere Technique

Abstract

A modification of the 51Cr:'4C twin-labelling technique is described in which the food source is labelled with 14C but the 51Cr is enclosed in a polymeric resin membrane and presented as microspheres of a similar diameter to the food particles. This eliminates the major uptake of 5 1 ~r which is transferred to the ctenidia and palps of the suspension-feeding mussel Aulacomya ater(Mo1ina) from detritus labelled with 51Cr. The results suggest that although bacterial cultures based on isolates of kelp bacteria can be absorbed with an efficiency of 67 to 70 %, the debris itself is also absorbed with an efficiency of approximately 50 %. The kelp debris, which forms an important component of the particulate matter potentially available for consumers, may thus represent an important source of carbon for the filter feeding community adjacent to kelp beds. In contrast to the results obtained in other studies with artificial food sources, the data for kelp debris suggest that A. ateris able to maintain a positive scope for growth at the concentrations of suspended organic matter which occur under natural conditions in the kelp bed environment.