title: Size differences of Arctic marine protists between two climate periods-using the paleoecological record to assess the importance of within-species trait variation.
abstract: Mean body size decreases with increasing temperature in a variety of organisms. This size-temperature relationship has generally been tested through space but rarely through time. We analyzed the sedimentary archive of dinoflagellate cysts in a sediment record taken from the West Greenland shelf and show that mean cell size decreased at both intra- and interspecific scales in a period of relatively warm temperatures, compared with a period of relatively cold temperatures. We further show that intraspecific changes accounted for more than 70% of the change in community mean size, whereas shifts in species composition only accounted for about 30% of the observed change. Literature values on size ranges and midpoints for individual taxa were in several cases not representative for the measured sizes, although changes in community mean size, calculated from literature values, did capture the direction of change. While the results show that intraspecific variation is necessary to accurately estimate the magnitude of change in protist community mean size, it may be possible to investigate general patterns, that is relative size differences, using interspecific-level estimates.
authors.affiliation: Center for Macroecology, Evolution and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen Denmark.
authors.forename: Erik A
authors.identifier: 0000-0003-1663-2507
authors.initials: EA
authors.lastname: Mousing
authors.affiliation: Department of Glaciology and Climate Geological Survey of Denmark and Greenland (GEUS) Copenhagen Denmark.
authors.forename: Sofia
authors.identifier: 0000-0003-0672-9161
authors.initials: S
authors.lastname: Ribeiro
authors.affiliation: Center for Macroecology, Evolution and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen Denmark.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Chisholm
authors.affiliation: Department of Glaciology and Climate Geological Survey of Denmark and Greenland (GEUS) Copenhagen Denmark.
authors.forename: Antoon
authors.initials: A
authors.lastname: Kuijpers
authors.affiliation: Leibniz Institute for Baltic Sea Research Warnemünde (IOW) Warnemünde Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Moros
authors.affiliation: Department of Plant and Environmental Sciences University of Copenhagen Copenhagen Denmark.
authors.forename: Marianne
authors.identifier: 0000-0002-6032-3376
authors.initials: M
authors.lastname: Ellegaard
keywords: cell size; dinoflagellate cysts; interspecific; intraspecific; paleoecology; temperature