B.A.S., 1987, Biological Sciences and Anthropology, Stanford University
M.S., 1987, Biological Sciences, Stanford University
Ph.D., 1995, Marine Biology, Scripps Institution of Oceanography (U.C. San Diego)
Postdoc, Hopkins Marine Station of Stanford Unversity
NSP 210. Genetically Modified Organisms
BIO 325. Marine Biology
BIO 334. Metabolic Biochemistry
BIO 374. Tropical Biology
BIO 390/490. Independent Research
Coral Bleaching and Biochemical Temperature Adaptation
The work in our lab focuses on biochemical adaptations of marine organisms to extreme environments. Over the past several years, my students and I have focused on the relationship between tropical corals and their algal symbionts, exploring potential biochemical causes of coral bleaching, a devastating phenomenon that is harming reefs at an ever increasing rate. Reef-building corals throughout the tropical oceans depend on a relationship with single-celled algae (Symbiodinium) that live within coral tissue and that provide the coral most of its energy. However, during times of environmental stress, and especially high temperature, corals expel these algal symbionts, a process termed "coral bleaching." Unfortunatley, bleaching often leads to the death of the coral and damage to the reef. In fact, many scientists are concerned that much of the Earth's coral reef habitat will be lost in the next fifty years due to the impacts of ocean warming and coral bleaching. Through work in our lab, we are aiming to extend our understanding of why bleaching occurs, by comparing the temperature sensitivity of important enzymes in corals to those of different types of Symbiodinium.
In our current project we are testing two specific hypotheses: First, that there is a mismatch in adaptation temperature between the corals and the algae, leading to a loss of metabolic function in Symbiodinium at higher temperatures. To test this hypothesis, my students and I are recombinantly expressing metabolic enzymes of both corals and Symbiodinium, and measuring molecular thermal stability and temperature sensitivity of enzyme function. A second hypothesis is that Symbiodinium types differing in thermal tolerance are biochemically adapted to different temperatures. Researchers have shown that different clades (kind of like species) of Symbiodinium have varying thermal sensitivities, providing the coral-algae symbiosis different levels of resistance to heat-induced bleaching. We are testing this second hypothesis by examining enzymes from different Symbiodinium types. In addition, because Symbiodinium orthologs are structurally similar, we are creating 3D models of our study enzymes and examining them to determine the extent, location, and types of amino acid substitutions that lead to changes in thermal sensitivity. We hope that the results of the study will help researchers better predict the likely extent of future bleaching events, and the possibility that corals and algae may be able to adapt to withstand increasing water temperatures.
If you are an F&M student, and you are interested in the interface between biochemistry and marine biology, I encourage you to contact me about research opportunities in my lab.
Selected Publications (* denotes undergraduate author)
Fields PA, EM Burmester*, KM Cox* and KL Karch*. 2016. Rapid proteomic responses to a near-lethal heat stress in the salt marsh mussel Geukensia demissa. Journal of Experimental Biology. doi: 10.1242/jeb.141176 PubMed
Fields PA, YW Dong, XL Meng and GN Somero. 2015. Adaptations of protein structure and function to temperature: there is more than one way to “skin the cat.” Journal of Experimental Biology 218: 1801-1811. PubMed free article
Fields PA, C Eurich, WL Gao* and B Cela*. 2014. Changes in protein expression in the salt marsh mussel Geukensia demissa: evidence for a shift from anaerobic to aerobic metabolism during prolonged aerial exposure. Journal of Experimental Biology 217: 1601-1612. PubMed free article
Fields PA, KM Cox* and KR Karch*. 2012. Latitudinal variation in protein expression after heat stress in the salt marsh mussel Geukensia demissa. Integrative and Comparative Biology 52: 636-647. PubMed free article
Fields PA, MJ Zuzow and L Tomanek. 2012. Proteomic responses of blue mussel (Mytilus) congeners to temperature acclimation. Journal of Experimental Biology 215: 1106-1116. PubMed free article
Eurich C, PA Fields and E Rice. 2012. Proteomics: Protein Identification Using Online Databases. Amer. Biol. Teacher 74: 250-255. Link to abstract
Fields PA, CM Strothers* and MA Mitchell. 2008. Function of muscle-type lactate dehydrogenase and citrate synthase of the Galapagos marine iguana, Amblyrhynchus cristatus, in relation to temperature. Comparative Biochemistry and Physiology. B 150: 62-73. PubMed
Fields PA, EL Rudomin* and GN Somero. 2006. Temperature sensitivities of cytosolic malate dehydrogenases from native and invasive species of marine mussels (genus Mytilus): sequence-function linkages and correlations with biogeographic patterning. Journal of Experimental Biology 209: 656-667. PubMed free article
Fields PA and DA Houseman*. 2004 Decreases in activation energy and substrate affinity in cold-adapted A4-lactate dehydrogenase: Evidence from the Antarctic notothenioid fish Chaenocephalus aceratus. Molecular Biology and Evolution 21: 2246-2255. PubMed free article
Fields PA, Y-S Kim, JF Carpenter and GN Somero 2002. Temperature adaptation in Gillichthys (Teleost: Gobiidae) A4-lactate dehydrogenases: identical primary structures produce subtly different conformations. Journal of Experimental Biology 205: 1293-1303. PubMed free article
Fields PA, BD Wahlstrand* and GN Somero. 2001. Intrinsic vs. extrinsic stabilization of enzymes: the interaction of solutes and temperature on A4-lactate dehydrogenase orthologs from warm-adapted and cold-adapted marine fishes. European Journal of Biochemistry. 268: 4497-4505. PubMed free article
Fields PA. 2001. Protein function at thermal extremes: Balancing stability and flexibility. Comparative Biochemistry and Physiology A 129: 417-431. PubMed
Fields PA and GN Somero. 1998. Hot spots in cold adaptation: Localized increases in conformational flexibility in A4-lactate dehydrogenase orthologs of Antarctic notothenioid fishes. Proc. Natl. Acad. Sci. USA 95: 11476-11481. PubMed free article
Fischer JM, PA Fields, PG Pryzbylkowski*, JL Nicolai* and PJ Neale. 2005. Sublethal exposure to UV radiation affects respiration rates of the freshwater cladoceran Daphnia catawba. Photochemistry and Photobiology 82: 547-550. PubMed
Lin J-J, T-H Yang, BD Wahlstrand*, PA Fields and GN Somero. 2002. Phylogenetic relationships and biochemical properties of the duplicated cytosolic and mitochondrial isoforms of malate dehydrogenase from a teleost fish, Sphyraena idiastes. Journal of Molecular Evolution 54:107-117. PubMed
Grants & Awards
P. A. Fields. Biochemical adaptation to temperature in the coral-dinoflagellate symbiosis. National Science Foundation RUI grant. 2017-2020.
P. A. Fields. A proteomic analysis of stress responses in the ribbed salt marsh mussel, Geukensia demissa. National Science Foundation RUI grant. 2009-2013.
P. A. Fields and L. Tomanek. Evolutionary and Ecological Physiology of Blue Mussels (genus Mytilus): Gene and Protein Expression and Molecular Evolution in Differently-adapted Congeners. National Science Foundation ROA grant. 2008.
P. A. Fields. Structure and Function in Enzymes Adapted to Extreme Cold. National Science Foundation RUI grant. 2003-2007.
P. A. Fields and G. N. Somero. Adaptation of Malate Dehydrogenases to Temperature and Hydrostatic Pressure: Complementary Changes in Amino Acid Sequence and Intracellular Milieu. National Science Foundation ROA grant. 2004.