People | Mark E. Warner

• B.S., Zoology, University of Georgia, 1992.
• Ph.D., Ecology, University of Georgia, 1998.

The physiological ecology of marine algae, algal-invertebrate symbioses, and the biochemical and molecular maintenance and regulation of photosynthesis in relation to changing environmental conditions.

Coral bleaching

Many reef-building corals contain endosymbiotic algae of the genus Symbiodinium, commonly called zooxanthellae. These algae provide a substantial amount of energy to the coral from translocation of photosynthetically fixed carbon. The past two decades has been a time of unprecedented coral bleaching, when corals loose significant numbers of these algae during physical stress. Cellular mechanisms that lead to bleaching are now currently investigated in my laboratory, with an emphasis on understanding how thermal stress effects the light reactions of photosynthesis. Current analyses include investigating the stability and repair of photosystem II (PSII), from measurements that probe a number of indices from gene transcription to protein stability and the biophysics of energy transfer via chlorophyll fluorescence.

Comparing algal diversity to physiology

Our current knowledge of the phylogeny and distribution of symbiotic dinoflagellates is growing rapidly, yet much less is known with regards to the physiological forces that may influence the ecological distribution of these algae within a single species of coral as well as across an entire reef system. We are currently investigating the physiology of several lineages of symbiotic dinoflagellates in the context of photosynthetic productivity and maintenance as well as the stability of their symbiotic relationship with particular host coral species. Currently funded research projects are underway in the Florida Keys, Bahamas, western Caribbean, and the eastern Pacific.

Photobiology of harmful algal blooms

There has been a dramatic rise in the marine phenomena known commonly as harmful algal blooms (HABs) in coastal waters of the US. While anthropogenic influence has been postulated as a major factor involved in many HABs (e.g. coastal eutrophication), a thorough understanding of what causes the formation and resilience of many blooms has remained elusive. My laboratory is investigating the photobiology of several species of microalgae found in Delaware waters in order to understand how changes in several factors including light, temperature, and nutrient status may affect the balance between photosynthesis, growth, and potential photon damage. Such alterations could lead to significant shifts in the competitive ability of these algae.

The Influence of rising CO₂ on the physiological ecology of microalgae

Atmospheric carbon dioxide is predicted to more than double in the next 100 years, and CO₂ emissions are thus rapidly acidifying the surface ocean with unknown consequences for many marine organisms. At the same time, over the next 50-100 years greenhouse warming is predicted to increase average sea surface temperatures by as much as 4°C. In collaboration with several other researchers, we are currently investigating the physiological impact of future increases in CO₂ and temperature in a wide array of microalgae, including local harmful blooming dinoflagellates and raphidophytes in Delaware, as well as the globally important cyanobacteria, Synechococcus, Prochlorococcus, and Trichodesmium and the coccolithophorid Emiliania huxleyi.

• Charles Tilney, Ph.D. student (M.S. University of Southampton, 2010) 
• Kenny Hoadley, Ph.D. student (M.S. University of North Carolina, Wilmington, 2010)
• Tye Pettay, Postdoctoral fellow (Ph.D., Penn State University, 2011)

MAST 442/642: Ecology and Evolution of Coral Reefs
MAST 441/641: Algal Ecological Physiology
MAST 821: Marine Biosciences Seminar

McGinley, M.P., Suggett, D.J., and M.E. Warner. 2013. Transcript patterns of chloroplast encoded genes in cultured Symbiodinium spp. (Dinophyceae): Testing the influence of a light shift and diel periodicity. Journal of Phycology. In press.

Hennige, S., Coyne, K., MacIntyre, H., Liefer, J., and M. Warner. 2012. The photobiology of Heterosigma akashiwo. Photoacclimation, diurnal periodicity and its ability to rapidly exploit exposure to high light. Journal of Phycology. 49: 349-360.

McGinley, M.P., Aschaffenburg, M.D., Pettay, D.T., Smith, R.T., LaJeunesse, T.C., and M.E. Warner. 2012. Transcriptional response of two core photosystem genes in Symbiodinium spp. exposed to thermal stress. PLoS One. 7: e50439.

Pokrzywinksi, K.L., Place, A.R., Warner, M.E., and K.J. Coyne. 2012. Investigation of the algicidal exudate produced by Shewanella sp. IRI-160 and its effect on dinoflagellates. Harmful Algae. 19: 23–29.

McGinley, M.P., Aschaffenburg, M.D., Pettay, D.T., Smith, R.T., LaJeunesse, T.C., and M.E. Warner. 2012. Symbiodinium spp. in colonies of eastern Pacific Pocillopora spp. are highly stable despite the prevalence of low-abundance background populations. Marine Ecology Progress Series. 462:1–7.

Suggett, D.J., Hall-Spencer, J.M., Rodolfo-Metalpa, R., Boatman, T.G., Payton, R., Pettay, D.T., Johnson, V.R., Warner, M.E., and T. Lawson. 2012. Sea anemones thrive in a high CO₂ world. Global Change Biology. 18:3015–3025.

Thornhill, D.J., Rotjan, R.D., Todd, B.D., Chilcoat, G.C., Iglesias-Prieto, R., Kemp, D.W., LaJeunesse, T.C., MaCabe Reynolds, J., Schmidt, G.W., Shannon, T., Warner, M.E., and W.K. Fitt. 2011. A connection between colony biomass and death in Caribbean reef-building corals. PLoS ONE. 6:e29535.

Steinke, M., Brading, P., Kerrison, P., Warner, M., Suggett, D.J. 2011. Concentrations of dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS) are strain-specific in symbiotic dinoflagellates (Symbiodinium sp., Dinophyceae). Journal of Phycology. 47:775–783.

Hennige, S.J., Smith, D.J., Walsh, S.J., McGinley, M., Warner, M.E., and D.J. Suggett. 2010. Acclimation and adaptation of scleractinian coral communities along environmental gradients within an Indonesian reef system. JEMBE. 391:143-152.

Portune, K., Cary, S.C., and M.E. Warner. 2010. Antioxidant enzyme response and reactive oxygen species production in marine raphidophytes. Journal of Phycology. 46:1161–1171.

LaJeunesse, T.C., Smith, R., Walther, M., Pinzón, J., Pettay, D.T., McGinley, M., Aschaffenburg, M., Medina-Rosas, P., Cupul-Magana, A., Pérez, A.L., Reyes-Bonilla, H., and M.E. Warner. 2010. Host-symbiont recombination versus natural selection in the response of coral-dinoflagellate symbioses to environmental disturbance. Proceedings of the Royal Society B. 277:2925-2934.

Ragni, M., Airs, R.L., Hennige, S.J., Suggett, D.J., Warner, M.E., and R.J. Geider. 2010. PSII photoinhibition and photorepair of Symbiodinium (Pyrrhophyta) differs between thermally tolerant and sensitive phylotypes. Marine Ecology Progress Series. 406:57-70.

Warner, M.E., Lesser, M.P., and P.J. Ralph. 2010. Chlorophyll fluorescence in reef building corals. In: Chlorophyll Fluorescence in Aquatic Sciences: Methods and Applications. (eds. Suggett, D.J., Prasil, O., and M. Borowitzka). Springer, Berlin.

Finney, J.C., Pettay, D.T., Sampayo, E.M., Warner, M.E., Oxenford, H.A. and T.C. LaJeunesse. 2010. On the relative significance of host-habitat, irradiance, and dispersal in the ecological distribution and speciation of coral endosymbionts. Microbial Ecology. 60:250-263.

Manzello, D., Warner, M., Stabenau, E., Hendee, J., Lesser, M., and M. Jankulak. 2009. Remote monitoring of chlorophyll fluorescence in two reef corals during the 2005 bleaching event at Lee Stocking Island, Bahamas. Coral Reefs. 28: 209-214.

Hennige, S.J., Suggett, D.J., Warner, M.E., McDougall, K.E., and D.J. Smith. 2009. Photobiology of Symbiodinium revisited: bio-physical and bio-optical signatures. Coral Reefs. 28: 179–195.

Morgan-Kiss, R.M., Chan, L-K., Modla, S., Weber, T.S., Warner, M., Czymmek, K.J., and T.E. Hanson. 2008. Chlorobaculum tepidum regulates chlorosome structure and function in response to temperature and electron donor availability. Photosynthesis Research. 99: 11–21.

• Matt Aschaffenburg, (Ph.D., University of Delaware, Marine Studies, 2012)
• Mike McGinley, (Ph.D., University of Delaware, Marine Studies, 2012)
• Dr. Sebastian Hennige, (postdoctoral fellow from 2009–2010)
• Lauren Salvitti, (M.S., University of Delaware, College of Earth, Ocean, and Environment, 2010)
• Jennifer Robison, (M.S., University of Delaware, College of Marine and Earth Studies, 2006)
• Matilda Madden, (M.S., University of Delaware, College of Marine Studies, 2005)