title: The Genetic Diversity ofMesodiniumand Associated Cryptophytes.
abstract: Ciliates from the genusMesodiniumare globally distributed in marine and freshwater ecosystems and may possess either heterotrophic or mixotrophic nutritional modes. Members of theMesodinium major/rubrumspecies complex photosynthesize by sequestering and maintaining organelles from cryptophyte prey, and under certain conditions form periodic or recurrent blooms (= red tides). Here, we present an analysis of the genetic diversity ofMesodiniumand cryptophyte populations from 10 environmental samples (eight globally dispersed habitats including fiveMesodiniumblooms), using group-specific primers forMesodiniumpartial 18S, ITS, and partial 28S rRNA genes as well as cryptophyte large subunit RuBisCO genes (rbcL). In addition, 22 new cryptophyte and four newM. rubrumcultures were used to extract DNA and sequencerbcLand 18S-ITS-28S genes, respectively, in order to provide a stronger phylogenetic context for our environmental sequences. Bloom samples were analyzed from coastal Brazil, Chile, two Northeastern locations in the United States, and the Pribilof Islands within the Bering Sea. Additionally, samples were also analyzed from the Baltic and Barents Seas and coastal California under non-bloom conditions. Most blooms were dominated by a singleMesodiniumgenotype, with coastal Brazil and Chile blooms composed ofM. majorand the Eastern USA blooms dominated byM. rubrumvariant B. Sequences from all four blooms were dominated byTeleaulax amphioxeia-like cryptophytes. Non-bloom communities revealed more diverse assemblages ofMesodiniumspp., including heterotrophic species and the mixotrophicMesodinium chamaeleon. Similarly, cryptophyte diversity was also higher in non-bloom samples. Our results confirm thatMesodiniumblooms may be caused byM. major, as well as multiple variants ofM. rubrum, and further implicateT. amphioxeiaas the key cryptophyte species linked to these phenomena in temperate and subtropical regions.
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Johnson
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beaudoin
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country Leioa, Spain.
authors.forename: Aitor
authors.initials: A
authors.lastname: Laza-Martinez
authors.affiliation: Department of Earth and Environmental Science, Lamont Doherty Earth Observatory, Columbia University, Palisades NY, USA.
authors.forename: Sonya T
authors.initials: ST
authors.lastname: Dyhrman
authors.affiliation: North Carolina Division of Water Quality, Raleigh NC, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Fensin
authors.affiliation: Marine Sciences, University of Connecticut, Groton CT, USA.
authors.forename: Senjie
authors.initials: S
authors.lastname: Lin
authors.affiliation: IGAP Coordinator, St. George Traditional Council, St. George Island AK, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Merculief
authors.affiliation: National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency Yokohama, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nagai
authors.affiliation: Departamento de Oceanografia Biológica, Instituto Oceanográfico da USP, University of São Paulo São Paulo, Brazil.
authors.forename: Mayza
authors.initials: M
authors.lastname: Pompeu
authors.affiliation: SYKE Marine Research Centre Helsinki, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Setälä
authors.affiliation: Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge MD, USA.
authors.forename: Diane K
authors.initials: DK
authors.lastname: Stoecker
keywords: Mesodinium; Teleaulax; acquired phototrophy; ciliate genetic diversity; ciliates; cryptophytes; mixotrophy; red tides