title: Factors controlling the abundance and size distribution of the phototrophic ciliate Myrionecta rubra in open waters of the North Atlantic.
abstract: Myrionecta rubra, a ubiquitous planktonic ciliate, has received much attention due to its wide distribution, occurrence as a red tide organism, and unusual cryptophyte endosymbiont. Although well studied in coastal waters, M. rubra is poorly examined in the open ocean. In the Irminger Basin, North Atlantic, the abundance of M. rubra was 0-5 cells/ml, which is low compared with that found in coastal areas. Distinct patchiness (100 km) was revealed by geostatistical analysis. Multiple regression indicated there was little relationship between M. rubra abundance and a number of environmental factors, with the exception of temperature and phytoplankton biomass, which influenced abundance in the spring. We also improve on studies that indicate distinct size classes of M. rubra; we statistically recognise four significantly distinct width classes (5-16, 12-23, 18-27, 21-33 microm), which decrease in abundance with increasing size. A multinomial logistic regression revealed the main variable correlated with this size distribution was ambient nitrate concentration. Finally, we propose a hypothesis for the distribution of sizes, involving nutrients, feeding, and dividing of the endosymbiont.
authors.affiliation: School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, United Kingdom. dmontag@liv.ac.uk
authors.forename: David J S
authors.initials: DJ
authors.lastname: Montagnes
authors.forename: John
authors.initials: J
authors.lastname: Allen
authors.forename: Louise
authors.initials: L
authors.lastname: Brown
authors.forename: Celia
authors.initials: C
authors.lastname: Bulit
authors.forename: Russell
authors.initials: R
authors.lastname: Davidson
authors.forename: Carlos
authors.initials: C
authors.lastname: Díaz-Avalos
authors.forename: Sophie
authors.initials: S
authors.lastname: Fielding
authors.forename: Mike
authors.initials: M
authors.lastname: Heath
authors.forename: Naomi P
authors.initials: NP
authors.lastname: Holliday
authors.forename: Jens
authors.initials: J
authors.lastname: Rasmussen
authors.forename: Richard
authors.initials: R
authors.lastname: Sanders
authors.forename: Joanna J
authors.initials: JJ
authors.lastname: Waniek
authors.forename: David
authors.initials: D
authors.lastname: Wilson
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D018533:Biomass; D002452:Cell Count; D016798:Ciliophora / Q000254:growth & development* / Q000302:isolation & purification*; D009566:Nitrates / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development; D012621:Seasons; D012623:Seawater / Q000737:chemistry / Q000469:parasitology*; D013696:Temperature
chemical_list: D009566:Nitrates