TY - JOUR

T1 - Feeding on copepod fecal pellets

T2 - a new trophic role of dinoflagellates as detritivores.

AU - Poulsen, Louise

AU - Moldrup, Morten

AU - Berge, Terje

AU - Hansen, Per Juel

PY - 2011

Y1 - 2011

N2 - Recent field studies indicate that dinoflagellates are key degraders of copepod fecalpellets. This study is the first to publish direct evidence of pellet grazing by dinoflagellates. Feedingand growth on copepod fecal pellets were studied for both heterotrophic (4 species) and mixotrophicdinoflagellates (3 species) using a combination of classic incubation experiments and videorecordings of feeding behavior. Fecal pellets were produced by adult Acartia tonsa feeding onRhodomonas salina. Two mixotrophic species (Karlodinium armiger, a gymnodinoid dinoflagellate,Gy1) and all heterotrophic dinoflagellates (Gyrodinium dominans, Gyrodinium spirale, Diplopsalislenticula, Protoperidinium depressum) studied fed on fecal pellets. Using natural concentrations ofdinoflagellates and copepod fecal pellets, average ingestion rates of 0.2 and 0.1 pellets cell-1 d-1 andclearance rates of between 0.2 and 0.3 ml cell-1 d-1 were obtained for G. spirale and P. depressum, respectively.Pellet feeding resulted in average growth rates of 0.69 and 0.08 d-1 with growth yields of0.58 and 0.50 for G. spirale and P. depressum. Important factors for the grazing impact of the dinoflagellateson fecal pellets in this study were: dinoflagellate concentration, the dinoflagellate-to-pelletsize ratio, the feeding mechanism, pellet food source, and pellet age. This study reveals a new trophicrole for dinoflagellates as detritivores, and shows that large (>20 µm) heterotrophic dinoflagellatesalone can account for reported pellet degradation rates in field studies. Thus, dinoflagellates canfunction as an effective ‘protozoan filter’ for fecal pellets in the water column.

AB - Recent field studies indicate that dinoflagellates are key degraders of copepod fecalpellets. This study is the first to publish direct evidence of pellet grazing by dinoflagellates. Feedingand growth on copepod fecal pellets were studied for both heterotrophic (4 species) and mixotrophicdinoflagellates (3 species) using a combination of classic incubation experiments and videorecordings of feeding behavior. Fecal pellets were produced by adult Acartia tonsa feeding onRhodomonas salina. Two mixotrophic species (Karlodinium armiger, a gymnodinoid dinoflagellate,Gy1) and all heterotrophic dinoflagellates (Gyrodinium dominans, Gyrodinium spirale, Diplopsalislenticula, Protoperidinium depressum) studied fed on fecal pellets. Using natural concentrations ofdinoflagellates and copepod fecal pellets, average ingestion rates of 0.2 and 0.1 pellets cell-1 d-1 andclearance rates of between 0.2 and 0.3 ml cell-1 d-1 were obtained for G. spirale and P. depressum, respectively.Pellet feeding resulted in average growth rates of 0.69 and 0.08 d-1 with growth yields of0.58 and 0.50 for G. spirale and P. depressum. Important factors for the grazing impact of the dinoflagellateson fecal pellets in this study were: dinoflagellate concentration, the dinoflagellate-to-pelletsize ratio, the feeding mechanism, pellet food source, and pellet age. This study reveals a new trophicrole for dinoflagellates as detritivores, and shows that large (>20 µm) heterotrophic dinoflagellatesalone can account for reported pellet degradation rates in field studies. Thus, dinoflagellates canfunction as an effective ‘protozoan filter’ for fecal pellets in the water column.

U2 - 10.3354/meps09357

DO - 10.3354/meps09357

M3 - Journal article

VL - 441

SP - 65

EP - 78

JO - Marine Ecology - Progress Series

JF - Marine Ecology - Progress Series

SN - 0171-8630

ER -