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  • 1
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    High grazing rates on cryptophyte algae in Chesapeake Bay (2018)
    Frontiers Media
    Details
    Publication Date: 2018-07-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 241, doi:10.3389/fmars.2018.00241.
    Description: Cryptophyte algae are globally distributed photosynthetic flagellates found in freshwater, estuarine, and neritic ecosystems. While cryptophytes can be highly abundant and are consumed by a wide variety of protistan predators, few studies have sought to quantify in situ grazing rates on their populations. Here we show that autumnal grazing rates on in situ communities of cryptophyte algae in Chesapeake Bay are high throughout the system, while growth rates, particularly in the lower bay, were low. Analysis of the genetic diversity of cryptophyte populations within dilution experiments suggests that microzooplankton may be selectively grazing the fastest-growing members of the population, which were generally Teleaulax spp. We also demonstrate that potential grazing rates of ciliates and dinoflagellates on fluorescently labeled (FL) Rhodomonas salina, Storeatula major, and Teleaulax amphioxeia can be high (up to 149 prey predator−1 d−1), and that a Gyrodinium sp. and Mesodinium rubrum could be selective grazers. Potential grazing was highest for heterotrophic dinoflagellates, but due to its abundance, M. rubrum also had a high overall impact. This study reveals that cryptophyte algae in Chesapeake Bay can experience extremely high grazing pressure from phagotrophic protists, and that this grazing likely shapes their community diversity.
    Description: The authors thank the National Science Foundation (OCE 1031718 and 1436169) for providing support for this research.
    Keywords: Cryptophytes ; Mixotrophy ; Grazing ; Chesapeake Bay ; Dinoflagellates ; Mesodinium rubrum
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Seasonal dynamics of Mesodinium rubrum in Chesapeake Bay (2013)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Journal of Plankton Research 35 (2013): 877-893, doi:10.1093/plankt/fbt028.
    Description: The photosynthetic ciliate Mesodinium rubrum is a common member of coastal phytoplankton communities that is well adapted to low-light, turbid ecosystems. It supports the growth of or competes with harmful dinoflagellate species for cryptophyte prey, as well as being a trophic link to copepods and larval fish. We have compiled data from various sources (n = 1063), on the abundance and distribution of M. rubrum in Chesapeake Bay and its tributaries. Because M. rubrum relies on obtaining organelles from cryptophyte algae to maintain rapid growth, we also enumerated cryptophyte algae in the portion of these samples that we collected (n = 386). M. rubrum occurred in oligohaline to polyhaline regions of Chesapeake Bay and throughout the year. Blooms (〉100 cells ml-1) of M. rubrum primarily occurred during spring, followed by autumn. When compared across all seasons, M. rubrum abundance was positively correlated to temperature and cryptophytes, and negatively correlated with salinity. However, more focused analyses revealed that M. rubrum abundance during spring was associated with surface layer warming and decreased salinity, while early autumn assemblages were associated with surface cooling. These results imply there are distinct seasonal niches for M. rubrum blooms. Blooms of M. rubrum were more common in tributaries than in the main stem Bay and tended to be restricted to salinities under 10 PSU. Despite the rarity of “red water” events, M. rubrum is a ubiquitous mixotroph in Chesapeake Bay and at times likely exerts a strong influence on cryptophyte algal abundance and hence planktonic food web structure.
    Description: MDJ and DKS would like to acknowledge funding from NSF 1031718 and 1031344.
    Description: 2014-04-05
    Keywords: Mesodinium rubrum ; Cryptophytes ; Chesapeake Bay ; Phytoplankton ; Red-tides
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 3
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    Insights into transcriptional changes that accompany organelle sequestration from the stolen nucleus of Mesodinium rubrum (2015)
    BioMed Central
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Genomics 16 (2015): 805, doi:10.1186/s12864-015-2052-9.
    Description: Organelle retention is a form of mixotrophy that allows organisms to reap metabolic benefits similar to those of photoautotrophs through capture of algal prey and sequestration of their plastids. Mesodinium rubrum is an abundant and broadly distributed photosynthetic marine ciliate that steals organelles from cryptophyte algae, such as Geminigera cryophila. M. rubrum is unique from most other acquired phototrophs because it also steals a functional nucleus that facilitates genetic control of sequestered plastids and other organelles. We analyzed changes in G. cryophila nuclear gene expression and transcript abundance after its incorporation into the cellular architecture of M. rubrum as an initial step towards understanding this complex system. We compared Illumina-generated transcriptomes of the cryptophyte Geminigera cryophila as a free-living cell and as a sequestered nucleus in M. rubrum to identify changes in protein abundance and gene expression. After KEGG annotation, proteins were clustered by functional categories, which were evaluated for over- or under-representation in the sequestered nucleus. Similarly, coding sequences were grouped by KEGG categories/pathways, which were then evaluated for over- or under-expression via read count strategies. At the time of sampling, the global transcriptome of M. rubrum was dominated (~58–62 %) by transcription from its stolen nucleus. A comparison of transcriptomes from free-living G. cryophila cells to those of the sequestered nucleus revealed a decrease in gene expression and transcript abundance for most functional protein categories within the ciliate. However, genes coding for proteins involved in photosynthesis, oxidative stress reduction, and several other metabolic pathways revealed striking exceptions to this general decline. Major changes in G. cryophila transcript expression after sequestration by M. rubrum and the ciliate’s success as a photoautotroph imply some level of control or gene regulation by the ciliate and at the very least reflect a degree of coordination between host and foreign organelles. Intriguingly, cryptophyte genes involved in protein transport are significantly under-expressed in M. rubrum, implicating a role for the ciliate’s endomembrane system in targeting cryptophyte proteins to plastid complexes. Collectively, this initial portrait of an acquired transcriptome within a dynamic and ecologically successful ciliate highlights the remarkable cellular and metabolic chimerism of this system.
    Description: The authors wish to acknowledge the support of NSF award 1354773.
    Keywords: Mesodinium rubrum ; Geminigera cryophila ; Karyoklepty ; Acquired phototrophy ; Transcriptome ; Differential gene expression ; Chimeric metabolism ; Organelle retention ; Mixotrophy
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/vnd.ms-excel
    Format: application/pdf
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  • 4
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    High grazing rates on cryptophyte algae in Chesapeake Bay (2019)
    Frontiers Media
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Johnson, M. D., Beaudoin, D. J., Frada, M. J., Brownlee, E. F., & Stoecker, D. K. High grazing rates on cryptophyte algae in Chesapeake Bay. Frontiers in Marine Science, 5, (2018): 241. doi:10.3389/fmars.2018.00241.
    Description: Cryptophyte algae are globally distributed photosynthetic flagellates found in freshwater, estuarine, and neritic ecosystems. While cryptophytes can be highly abundant and are consumed by a wide variety of protistan predators, few studies have sought to quantify in situ grazing rates on their populations. Here we show that autumnal grazing rates on in situ communities of cryptophyte algae in Chesapeake Bay are high throughout the system, while growth rates, particularly in the lower bay, were low. Analysis of the genetic diversity of cryptophyte populations within dilution experiments suggests that microzooplankton may be selectively grazing the fastest-growing members of the population, which were generally Teleaulax spp. We also demonstrate that potential grazing rates of ciliates and dinoflagellates on fluorescently labeled (FL) Rhodomonas salina, Storeatula major, and Teleaulax amphioxeia can be high (up to 149 prey predator−1 d−1), and that a Gyrodinium sp. and Mesodinium rubrum could be selective grazers. Potential grazing was highest for heterotrophic dinoflagellates, but due to its abundance, M. rubrum also had a high overall impact. This study reveals that cryptophyte algae in Chesapeake Bay can experience extremely high grazing pressure from phagotrophic protists, and that this grazing likely shapes their community diversity.
    Description: The authors thank the National Science Foundation (OCE 1031718 and 1436169) for providing support for this research.
    Keywords: cryptophytes ; mixotrophy ; grazing ; Chesapeake Bay ; dinoflagellates ; Mesodinium rubrum
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Acquired phototrophy stabilizes coexistence and shapes intrinsic dynamics of an intraguild predator and its prey (2016)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Ecology Letters 19 (2016): 393-402, doi:10.1111/ele.12572.
    Description: In marine ecosystems, acquired phototrophs|organisms that obtain their photo- synthetic ability by hosting endosymbionts or stealing plastids from their prey|are omnipresent. Such taxa function as intraguild predators yet depend on their prey to periodically obtain chloroplasts. We present new theory for the effects of acquired phototrophy on community dynamics by analyzing a mathematical model of this predator-prey interaction and experimentally verifying its predictions with a lab- oratory model system. We show that acquired phototrophy stabilizes coexistence, but that the nature of this coexistence exhibits a `paradox of enrichment:' as light increases, the coexistence between the acquired phototroph and its prey transitions from a stable equilibrium to boom-bust cycles whose amplitude increases with light availability. In contrast, heterotrophs and mixotrophic acquired phototrophs (that obtain 〈30% of their carbon from photosynthesis) do not exhibit such cycles. This prediction matches eld observations, in which only strict (〉95% of carbon from photosynthesis) acquired phototrophs form blooms.
    Description: HVM is supported by a United States National Science Foundation Postdoctoral Research Fellowship in Biology (Grant No. DBI-1401332). EP is supported by the Academy of Finland through research grant 276268. MDJ acknowledges NSF Grant No. IOS-1354773. MGN acknowledges support provided by the Independent Research and Development Program at the Woods Hole Oceanographic Institution.
    Description: 2017-02-01
    Keywords: Acquired metabolic potential ; Community ecology ; Intraguild predation ; Kleptoplastidy ; Mesodinium rubrum ; Mixotrophy
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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