Effects of deposit-feeder gut passage and fecal pellet encapsulation on germination of dinoflagellate resting cysts

Abstract

Many species of dinoflagellates spend much of their lives buried in sediments as resting cysts. While on the bottom, cysts may pass through the guts of deposit feeders before conditions become favorable for germination. Little is known, however, about how dinoflagellate cysts are affected by deposit-feeder digestion, fecal pellet formation, and translocation within the sediment column. To answer the question of whether gut passage or pelletization reduces cyst germination, we fed cysts of the dinoflagellate Scrippsiella lachrymosa to 3 polychaete deposit feeders, Capitella sp., Streblospio benedicti, and Polydora cornuta. Fecal pellets of these species have different morphologies and represent a wide range of pellet robustness. To examine the effects of longer gut-passage times, cysts were incubated in the digestive fluids of the polychaete Arenicola marina for up to 24 h, and monitored to determine germination success. Cysts were remarkably resistant to digestion by deposit-feeding polychaetes, and were capable of germinating even within the robust fecal pellets of Capitella. In fact, cysts were more likely to germinate within fecal pellets of Capitella than outside those pellets. Thus, pellets may be favorable environments for germination of resting cysts. Our data suggest that deposit-feeder gut passage and pelletization do not substantially reduce germination of dinoflagellate cysts in the field, and may even enhance it.