The effects of macrobenthic deposit-feeding on the degradation of chloropigments in sandy sediments

Abstract

Microcosms with sediments containing either the bivalve Macoma balthica (surface deposit-feeder), the polychaete Leitoscoloplos fragilis (subsurface deposit-feeder), or both animals were maintained in a flow-through seawater system. Two different plant-derived food sources (Ulva rotundata or Zostera marina) were added (weekly) to the microcosms. The conversion of chlorophyll a to phaeophorbide a was significantly higher in microcosms containing macrofauna than in the controls with no macrofauna. Microbenthos in the controls were only capable of converting chlorophylls a and b to phaeophytins. The highest production of phaeophorbide a was in isolated deposit-feeder treatments with U. rotundata as the food source. Even though the total macrofaunal biomass was greater in the treatments with the two deposit-feeders together, more phaeophorbide was produced in the isolated treatments. Because M. balthica has a different feeding mode than L. fragilis, feeding interference between surface and subsurface deposit-feeding activities may have occurred in the combined treatments, thus producing less phaeophorbides. Phaeophorbides may represent good feeding markers for macrobenthic deposit-feeding processes. The amount of ingested chlorophyll that is converted to phaeopigments is dependent upon the quality of plant source materials and the interactions between coexisting species. © 1988.