Sanders Lab

“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.

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

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Kyle, a graduate student in Engineering, designed a project in Biology 5436 (Freshwater Ecology) that was expanded to result in a recently published paper:  Gilroy, K.D., S. Neretina and R.W. Sanders. 2014. Behavior of gold nanoparticles in an experimental algal-zooplankton food chain. Journal of Nanoparticle Research 16:2414. Link

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Zaid’s paper “Phagotrophy by the picoeukaryotic green alga Micromonas: implications for Arctic Oceans” (McKie-Krisberg, Z.M. and R.W. Sanders) is now on line at ISME Journal (Nature Publishing Group). Here’s the link

Abstract: Photosynthetic picoeukaryotes (PPE) are recognized as major primary producers and contributors to phytoplankton biomass in oceanic and coastal environments. Molecular surveys indicate a large phylogenetic diversity in the picoeukaryotes, with members of the Prymnesiophyceae and Chrysophyseae tending to be more common in open ocean waters and Prasinophyceae dominating coastal and Arctic waters. In addition to their role as primary producers, PPE have been identified in several studies as mixotrophic and major predators of prokaryotes. Mixotrophy, the combination of photosynthesis and phagotrophy in a single organism, is well established for most photosynthetic lineages. However, green algae, including prasinophytes, were widely considered as a purely photosynthetic group. The prasinophyte Micromonas is perhaps the most common picoeukaryote in coastal and Arctic waters and is one of the relatively few cultured representatives of the picoeukaryotes available for physiological investigations. In this study, we demonstrate phagotrophy by a strain of Micromonas (CCMP2099) isolated from Arctic waters and show that environmental factors (light and nutrient concentration) affect ingestion rates in this mixotroph. In addition, we show size-selective feeding with a preference for smaller particles, and determine P vs. I (photosynthesis vs. irradiance) responses in different nutrient conditions. The widespread distribution and frequently high abundances of Micromonas suggest that these green algae may have significant impact on prokaryote populations in several oceanic regimes.

Scott Fay, a former post-doc in the lab has had some of the work he did at Temple University published in Aquatic Microbial Ecology:  Fay, S.A., R.J. Gast, and R.W. Sanders. accepted. Linking bacterivory and phyletic diversity of protists with a marker gene survey and experimental feeding with BrdU-labeled bacteria. Here’s a link to the open access paper: Fay, Gast, Sanders AME

Adam Heinze, along with other graduated and current members of the Sanders Lab, authored a paper in Aquatic Microbial Ecology. The paper is entitled: “The role of temperature in growth, feeding and the vertical distribution of the mixotrophic chrysophyte Dinobryon.” Link to Paper

A book review by Bob Sanders (doi:10.1111/jeu.12061) of “The Biology and Ecology of Tintinnid Ciliates – Models for Marine Plankton” edited by J.R. Dolan, et al. was published in the Journal of Eukaryotic Microbiology (link)