Dynamic Characteristics of Prochlorococcus and Synechococcus Consumption by Bacterivorous Nanoflagellates

Abstract

We compared the characteristics of ingestion of Prochlorococcus and Synechococcus by the marine heterotrophic nanoflagellate Pseudobodo sp. and by a mixed nanoflagellate culture (around 3 microm in size) obtained from an open sea oligotrophic area. Maximum ingestion rate on Synechococcus (2.7 Syn flagellate(-1) h(-1)) was reached at concentrations of 5 x 10(5) Syn mL(-1) and decreased between 6 x 10(5) and 1.5 x 10(6) Syn mL(-1). In order to validate laboratory data, one set of data on Synechococcus grazing was obtained during a field study in the oligotrophic northeastern Mediterranean Sea. Ingestion rates by heterotrophic nanoflagellates were related to Synechococcus abundance in the water, and the feeding rate showed a clear diel rhythm with consumption being highest during the night, declining during the day hours, and being lowest at dusk. Ingestion rates on Prochlorococcus increased linearly for the whole range of prey density used (i.e., from 1 x 10(3) to 3 x 10(6) Proc mL(-1)), with maximum ingestion of 6.7 Proc flagellate(-1) h(-1). However, for prey concentrations in the range of 10(3)-10(5), which are usually encountered in aquatic systems, ingestion rates were significantly less than on Synechococcus. In our experiments, both Prochlorococcus and Synechococcus proved to be poor food items for support of nanoflagellate growth.

Population dynamics and diversity of Synechococcus on the New England Shelf

“…This may indicate a grazer saturation concentration for which grazers (if only ingesting Synechococcus) are no longer food-limited and can achieve their maximum division rates. For nanoflagellates observed in other studies, these end-bloom concentrations appear to be just slightly below ingestion saturation concentrations [20,109].…”

“…This broad term encompasses the heterotrophic nanoflagellates, ciliates, and dinoflagellates, all which have been reported to feed on Synechococcus [21,15,85,20,44] and may be important classes of grazers at MVCO. These organisms can quickly react to and take advantage of an increase in prey cells as their own cell division rates can match or exceed those of Synechococcus [52].…”

“…If losses primarily result from grazers, then loss rate will mostly be determined by prey availability, number of grazers present, and temperature. While division rate is decreasing, cell concentrations are still within the range for which ingestion rate can be relatively high [20], such that the Synechococcus population could still be experiencing heavy grazing losses. From September through December, we also find a relationship between loss rate and temperature (Fig.…”

Importance of the Viral Shunt in Nitrogen Cycling in Synechococcus Spp. Growth in Subtropical Western Pacific Coastal Waters

“…Furthermore, during warm seasons, Synechococcus spp. shows distinct diel changes in abundance, with higher division rates at dusk (Dolan and Šimek 1999;Christaki et al 2002;Tsai et al 2009) and maximum abundances at night (Christaki et al 2002;Tsai et al 2008Tsai et al , 2009). Therefore, Synechococcus spp.…”

“…abundance is less than 1 × 10 4 cells mL -1 during low temperatures when there are no clear diel variations in abundance (Tsai et al 2008). Christaki et al (2002) reported that heterotrophic nanoflagellate (HNF) grazing on Synechococcus spp. is the highest at night and declines during the daytime in oligotrophic open-sea areas.…”