Consumption of carrageenophyte Sarconema filiforme by Platynereis insolita (Polychaeta: Phyllodocida: Nereididae)—laboratory experiments and outplanting

Laboratory experiments and outplanting were conducted to understand the consumption of the economically important carrageenophyte Sarconema filiforme by the polychaete Platynereis insolita. When S. filiforme was outplanted, the harvested biomass reached its lowest value (0.56 ± 0.12 kg fresh wt m−2) when the polychaete density showed its highest abundance (10 individuals per g fresh wt of alga), indicating that the algae were under a high grazing pressure by P. insolita on the rafts. Laboratory feeding experiments showed that the specific food consumption rate (SFR) increases with the size of the polychaete reaching seaweed consumption values that varied between 73.86 and 215.00% of animal wet body weight. These consumption values suggest that up to 71 ± 2% of biomass yield on raft can be lost due to grazing. The present study demonstrated heavy crop loss of S. filiforme due to grazing by P. insolita.