Sarah DeVaul & Bob Sanders present at Ocean Sciences Meeting in New Orleans

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Sarah presented some of her Ph.D. work on mixotrophy at the winter meeting (February 21-26) of the Association for the Sciences of Limnology and Oceanography (ASLO) . Bob presented work from his last ocean voyage in the Antarctic with Rebecca Gast of Woods Hole Oceanographic Institution. There are also a number of graduate students from the Cordes lab that presented at the meeting.

New pubs: DeVaul et al. in J. Phycol.; Mitra et al. in Protist

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Temperature-dependent phagotrophy and phototrophy in a mixotrophic chrysophyte by Sarah DeVaul Princiotta, Brian T. Smith and Robert W. Sanders has been published in the Journal of Phycology (52:432-440) and can be found here.

Defining planktonic protist functional groups on mechanisms for energy and nutrient acquisition: incorporation of diverse mixotrophic strategies by Aditee Mitra and 22 co-authors (including R.W. Sanders) was published in Protist (167:106-120) and is available online at  http://www.sciencedirect.com/science/article/pii/S1434461016000043

Sarah DeVaul Awarded Best Grad Student Talk at PSA

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At the 2015 Annual Meeting of the Phycological Society of America, which happened to be in Philadelphia this year, Sarah was awarded the Bold Award for the best graduate student talk during the conference. Her talk was entitled “Striking a Balance between Phototrophy and Heterotrophy in the Mixotrophic Chrysophyte Dinobryon sp.” Congrats to Sarah!

Three presentations from the lab at PSA Annual Meeting

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The lab will have three presentations at the Phycological Society of America annual meeting that is taking place in Philadelphia this month.

Sarah DeVaul has an oral presentation entitled: Striking a balance between phototrophy and heterotrophy in the mixotrophic chrysophyte Dinobryon sp.;

Grier Sellers talk with Rebecca Gast (Woods Hole Oceanographic Institution is entitled: Dark survival and recovery of a foreign organelle-retaining dinoflagellate and its haptophyte prey and plastid source following a simulated austral winter

and Bob Sanders will present a poster by Zaid McKie-Krisberg, Rebecca Gast and Bob Sanders entitled:  Gene expression and gene ontology in two species of mixotrophic Antarctic phytoplankton.

Papers published in ‘Limnology & Oceanography’ and ‘Freshwater Biology’

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Sanders, R.W., S.L. Cooke, J.M. Fischer, S.B. Fey, A.W. Heinze*, W.H. Jeffrey, A.L. Macaluso*, R.E. Moeller, D.P. Morris, P.J. Neale, M. Olson, J.D. Pakulski, J.A. Porter, D.M. Schoener*, C.E. Williamson. 2015. Shifts in microbial food web structure and productivity after additions of naturally occurring dissolved organic matter: results from large-scale lacustrine mesocosms. Limnology & Oceanography. 60: 2130-2144. DOI: 10.1002/lno.10159

Cooke, S.L., J.M. Fischer, K. Kessler, Craig E. Williamson, R.W. Sanders, D.P. Morris, J.A. Porter, W.H. Jeffrey, S.B. DeVaul*, J.D. Pakulski. 2015. Direct and indirect effects of additions of chromophoric dissolved organic matter on zooplankton during large-scale mesocosm experiments in an oligotrophic lake. Freshwater Biology. 60:2362-2378.  DOI:10.1111/fwb.12663

*Current or former graduate students in the lab.

Graham paper published in JEMBE

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Erin’s final paper from her Ph.D. work was published: Graham, E.R., A. Parekh, R.K. Devassy and R.W. Sanders. 2015. Carbonic anhydrase activity changes in response to increased temperature and pCO2 in Symbiodinium-zoanthid associations.Journal of Experimental Marine Biology and Ecology 473:218-226.  Here’s a link.

Amy Parekh and Roni Devassy were undergraduate researchers in the lab.

Congrats to them all!

 

McKie-Krisberg paper published in Microbial Ecology

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McKie-Krisberg, Z.M., R.J. Gast and R.W. Sanders. 2015. Physiological responses of three species of Antarctic mixotrophic phytoflagellates to changes in light and dissolved nutrients. Microbial Ecology 70:21-29.

Abstract: Antarctic phototrophs are challenged by extreme temperatures, ice cover, nutrient limitation and prolonged periods of darkness. Yet this environment may also provide niche opportunities for phytoplankton utilizing alternative nutritional modes. Mixotrophy, the combination of photosynthesis and particle ingestion, has been proposed as a mechanism for some phytoplankton to contend with the adverse conditions of the Antarctic. We conducted feeding experiments using fluorescent bacteria-sized tracers to compare the effects of light and nutrients on bacterivory rates in three Antarctic marine photosynthetic nanoflagellates representing two evolutionary lineages: Cryptophyceae (Geminigera cryophila), and Prasinophyceae (Pyramimonas tychotreta and Mantoniella antarctica). Only G. cryophila had previously been identified as mixotrophic. We also measured photoautotrophic abilities over a range of light intensities (P vs. I) and used dark survival experiments to assess cell population dynamics in the absence of light. Feeding behavior in these three nanoflagellates was affected by either light, nutrient levels, or a combination of both factors in a species-specific manner that was not conserved by evolutionary lineage. The different responses to environmental factors by these mixotrophs supported the idea of tradeoffs in the use of phagotrophy and phototrophy for growth.

Sarah DeVaul receives PSA Fellowship

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Sarah had a busy week. While she was at the Northeast Algal Society Symposium giving a talk and winning awards, she learned that she had received the Hannah T. Coasdale Fellowship from the Phycological Society of America to cover some of her costs toward attending a workshop on Molecular Methods for Algae Research offered by The Scottish Association for Marine Science in Oban, Scotland.

Sarah DeVaul receives NEAS awards

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Sarah attended the Northeast Algal Society Symposium in Syracuse, NY and received an NEAS Travel Award plus the Robert T. Wilce Award for Best Graduate Student Presentation. Her talk was: “Temperature-Dependent Phagotrophy and Phototrophy in a Mixotrophic Chrysophyte.”

Ocean Acidification pub by Erin Graham accepted

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“Species-specific photosynthetic responses of symbiotic zoanthids to thermal stress and ocean acidification” by Erin R. Graham and Robert W. Sanders is accepted for publication in Marine Ecology.

ABSTRACT: Increasing sea surface temperatures and ocean acidification (OA) are impacting physiological processes in a variety of marine organisms. Many sea anemones, corals, and jellies in the phylum Cnidaria, form endosymbiotic relationships with the dinoflagellate Symbiodinium spp., which supplies the hosts with fixed carbon from photosynthesis. Much work has focused on the generally negative effects of rising temperature and OA on calcification in Symbiodinium-coral symbioses, but has not directly measured symbiont photosynthesis in hospite or fixed carbon translocation from symbiont to host. Symbiodinium species or types vary in their environmental tolerance and photosynthetic capacity, therefore, primary production in symbiotic associations is directly related to symbiont type. However, symbiont type has not been identified in a large portion of Symbiodinium-cnidarian studies. Future climate conditions and OA may favor non-calcifying, soft-bodied cnidarians, including zoanthids, over coral species. Here we show that two zoanthid species, Palythoa sp. and Zoanthus sp., harboring different symbiont types (C1 and A4), had very different responses to increased temperature and increased pCO2/low pH. Thermal stress did not affect carbon fixation or fixed carbon translocation in the Zoanthus sp./A4 association, and high pCO2/low pH increased carbon fixation. In contrast, both thermal stress and high pCO2/low pH greatly inhibited carbon fixation in the Palythoa sp./C1 association. However, the combined treatment of high temperature and high pCO2 increased carbon fixation relative to the treatment of high temperature alone. Our observations support the growing body of evidence that demonstrates that the response of symbiotic cnidarians to thermal stress and OA must be considered on a host-specific and symbiont-specific basis. In addition, we show that the effects of increased temperature and pCO2 on photosynthesis may change when these two stressors are combined. Understanding how carbon fixation and translocation varies among different host-symbiont combinations is critical to predicting which Symbiodinium associations may persist in warm, acidified oceans.

Zaid awarded his Ph.D.

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Zaid McKie-Krisberg successfully defended his Ph.D. dissertation, entitled “Phagotrophy in Photosynthetic Eukaryotic Microbes from Polar Environments” on 20 November 2014. Congratulations, Zaid.

Graham et al. published in BMC Research Notes

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Erin Graham (Ph.D. 2014) had another paper published.

Graham, E.R., Z.M. McKie-Krisberg and R.W. Sanders. 2014. Photosynthetic carbon from algal symbionts supplements Ambystoma maculatum embryos during the later stages of embryonic development. BMC Research Notes 7:764 [link]

ABSTRACT:

Background: It was recently discovered that symbiotic algae in the eggs of the salamander Ambystoma maculatum translocate fixed carbon from photosynthesis to developing embryos. Fixed carbon translocation was shown in embryos at one time point during development however, it was unknown if fixed carbon translocation occurs throughout all developmental stages.  Findings: In this study, fixed carbon translocation was measured in salamander eggs at six time points over the latter half of development. Fixed carbon translocation did not occur until the middle tailbud portion of development (stages 26-30), and translocation was measured in 20% or less of eggs sampled. Peak carbon translocation occurred during the late tailbud phase of development (stages 31-35), where as much as 87% of eggs sampled showed translocation, and average percent translocation was 6.5%. During the final stages of development, fixed carbon translocation declined, and translocation was not detected in embryos five days prior to hatching.  Conclusions: The onset of fixed carbon translocation from Oophila to A. maculatum embryos during the second half of embryonic development is likely due to the corresponding settlement and concentration of Oophila in the inner egg envelope. In addition, carbon translocation ceases in late stage embryos as the inner egg envelope thins and ruptures in preparation for hatching.

Grier Sellers publishes paper and completes his Ph.D.

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Grier graduated in August and had one of the chapters of his dissertation accepted for publication in Journal of Phycology. Here’s the link.

Abstract

The peridinin-containing plastid found in most photosynthetic dinoflagellates is thought to have been replaced in a few lineages by plastids of chlorophyte, diatom, or haptophyte origin. Other distinct lineages of phagotrophic dinoflagellates retain functional plastids obtained from algal prey for different durations and with varying source species specificity. 18S rRNA gene sequence analyses have placed a novel gymnodinoid dinoflagellate isolated from the Ross Sea (RSD) in the Kareniaceae, a family of dinoflagellates with permanent plastids of haptophyte origin. In contrast to other species in this family, the RSD contains kleptoplastids sequestered from its prey, Phaeocystis antarctica. Culture experiments were employed to determine whether the RSD fed selectively on P. antarctica when offered in combination with another polar haptophyte or cryptophyte species, and whether the RSD, isolated from its prey and starved, would take up plastids from P. antarctica or from other polar haptophyte or cryptophyte species. Evidence was obtained for selective feeding on P. antarctica, plastid uptake from P. antarctica, and increased RSD growth in the presence of P. antarctica. The presence of a peduncle-like structure in the RSD suggests that kleptoplasts are obtained by myzocytosis. RSD cells incubated without P. antarctica were capable of survival for at least 29.5 months. This remarkable longevity of the RSD’s kleptoplasts and its species specificity for prey and plastid source is consistent with its prolonged co-evolution with P. antarctica. It may also reflect the presence of a plastid protein import mechanism and genes transferred to the dinokaryon from a lost permanent haptophyte plastid.

New faces in the lab

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Several undergraduate researchers started working in the lab during the summer and fall. Tiffany Nguyen and Lydia Adnane were supported as Presidential Scholars, and Brian Smith and Jessica Wyatt with Undergraduate Research Awards.