Fiona   Tomas Nash
Fiona   Tomas Nash

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seagrass ecology
invasive species
plant-herbivore interactions
climate change
trophic interactions
marine reserves
ocean acidification
Fiona Tomas Nash
Courtesy Assistant Professor

I study the impacts of anthropogenic activities (e.g. eutrophication, climate change, overfishing, invasive species) on the functioning of marine benthic communities. 

OSU Campus
Fisheries and Wildlife
Oregon State University
104 Nash Hall
Corvallis, OR 97331
United States


The theme of my research is to understand the processes and mechanisms that regulate the structure and functioning of marine benthic systems, with particular emphasis on how human activities transform them. My research focuses mainly on seagrasses and macroalgae which have a fundamental role as habitat-forming species and perform key ecological functions at the land-sea interface. A significant part of my work studies the ecological consequences of overfishing, eutrophication, climate change and the introduction of non-native species on modifying different aspects of trophic interactions (predator – prey, plant – herbivore), because these interactions are fundamental in determining ecosystem structure and function as well as species evolution.


FW 421/521 Aquatic Biological Invasions

FW 434/534 Estuarine Ecology



Ph.D. 2001 - 2004. Ecology, University of Barcelona, Barcelona, Spain.

M.S. 2000 - 2001.  Ecology, University of Barcelona, Barcelona, Spain.

B.S. 1994 - 1999. Biological Sciences, University of Barcelona, Barcelona, Spain

I accept graduate students for the Fisheries and Wildlife Department


JOURNAL ARTICLES OR BOOK CHAPTERS PUBLISHED (*indicates graduate or undergraduate students)

30. Hernan- Martinez G*., Ramajo L., Basso L., Delgado A., Terrados J., Duarte CM, F. Tomas. 2016. Seagrass (Posidonia oceanica) seedlings in a high-CO2 world: from physiology to herbivory. Scientific Reports. In press

29. Alos, J, F. Tomas, Terrados J., Verbruggen H., Ballesteros E . 2016. Fast-spreading green beds of recently introduced Halimeda incrassata (Bryopsidales, Chlorophyta) invade Mallorca island (NW Mediterranean Sea). Marine Ecology Progress Series (in press).  doi: 10.3354/meps11869

28. B. Martínez-Crego, P. Arteaga, F. Tomas, R. Santos. 2016. The role of seagrass traits in mediating Zostera noltei vulnerability to mesograzers. PlosONE 11(6): e0156848.

27. F. Tomas^, B. Martínez-Crego^, G. Hernan*, R. Santos. 2015. Responses of seagrass to anthropogenic and natural disturbance do not equally translate to its consumers. (^ equally contributing authors). Global Change Biology 21: 4021-4030

26. Sampeiro-Ramos, G*., Olsen Y., F. Tomas, Marbà N. 2015. Ecophysiological responses of three Mediterranean invasive seaweeds (Acrothamnion preissii, Lophocladia lallemandii and Caulerpa cylindracea) to experimental warming. Marine Pollution Bulletin 96 (1–2): 418-423  

25. J. Bernardeau-Esteller*, J.M. Ruiz, F. Tomas, J.M. Sandoval-Gil, L. Marín-Guirao. 2015. Photoacclimation of Caulerpa racemosa: light as a limiting factor in the invasion of native Mediterranean seagrass meadows. Journal of Experimental Marine Biology and Ecology 465: 130-141.

24. Vergés A. ^, Tomas, F. ^, Cebrian E., Ballesteros E., Kizilkaya Z., Dendrinos P., Karamanlidis A.A., Spiegel D., Sala E. 2014. Tropical rabbitfish and the deforestation of a warming temperate sea. (^ equally contributing authors). Journal of Ecology.   102(6): 1518-1527. (Editor’s choice for November 2014 Issue and selected for the special Virtual Issue on Marine Ecology published in October 2015, featuring the top 20 papers published in Journal of Ecology in the past 4 years;  

23. Vergés A., Steinberg P.D., Poore A.G., Hay M.E., Ballesteros E., Heck K., Booth D., Campbell A.H., Coleman M.A., Feary D:, Figueira W., Langlois T., Mizerek T., Marzinelli E., Mumby P., Nakamura Y., Roughan M., van Sebille E., Sen Gupta A., Smale D., Tomas, F. , Wernberg T., Wilson S.K. 2014. The tropicalisation of temperate marine ecosystems: climate-mediated changes in herbivory cause community phase shifts. Proceedings of the Royal Society B 281: 20140846. (Selected by Faculty of the 1000).

22. Ballesteros E., Alcoverro T., Sánchez-Lisazo L., Tomas F., Romero J. Els Alguers. In: Ballesteros E. (ed). Atles d’Ecologia, clima i evolució. Història Natural dels Països Catalans. Enciclopèdia Catalana, Barcelona, Spain., 2013.

21. Castejón-Silvo, I. *, Domínguez M., Terrados J.,  Tomas, F., Morales-Nin B. 2012. Invertebrate response to nutrient-driven epiphytic load increase in Posidonia oceanica meadows. Estuarine Coastal and Shelf Science 112: 225-235.

20. Prado, P. *, Tomas, F. , Pinna, S., Farina, S. *, Roca, G., Ceccherelli, G., Romero. J., Alcoverro, T. 2012. Habitat and scale shape the demographic fate of the keystone sea urchin Paracentrotus lividus in Mediterranean macrophyte communities. PLOS One. 7(4): e35170. doi:10.1371/journal.pone.0035170

19. Sala E., Ballesteros, E, Dendrinos P., DiFranco A., Ferretti F., Foley D., Fraschetti S., Friedlander A., Garrabou J., Güçlüsoy H., Guidetti P., Halpern B.S., Hereu B., Karamanlidis A.A., Kizilkaya Z., Macpherson E., Mangialajo L., Mariani S., Micheli F., Pais A., Riser K., Rosenberg A., Sales M., Selkoe K.A., Starr R., Tomas, F., Zabala M. 2012. The structure of Mediterranean rocky reef ecosystems across environmental and human gradients, and conservation implications. PLOS One. 7(2): e32742. doi:10.1371/journal.pone.0032742.

18. Verges, A.^, Tomas, F.^, Ballesteros, E. 2012. Interactive effects of depth and marine protection on predation and herbivory patterns. (^ equally contributing authors). Marine Ecology Progress Series 450: 55-65.

17. Tomas F., Abbott J.M., Steinberg C.S., Balk M.A., Williams S.L., Stachowicz J.J. 2011. Plant genotype and nitrogen loading influence seagrass (Zostera marina) productivity, biochemistry, and plant-herbivore interactions. Ecology 92(9): 1807-1817.

16. Sales, M., Cebrian E., Tomas F., Ballesteros E. 2011. Pollution impacts and recovery potential in three species of the genus Cystoseira (Fucales, Heterokonphyta). Estuarine Coastal and Shelf Science 92(3): 347-357.

15. Tomas, F., Cebrian, E., Ballesteros, E. 2011. Differential herbivory of invasive algae by native fish in the Mediterranean Sea. Estuarine Coastal and Shelf Science 92(1): 27-34, 2011. 

14. Manzanera, M., Alcoverro, T., Tomas, F., Romero, J. 2011. Response of Posidonia oceanica to burial dynamics. Marine Ecology Progress Series 423: 47-56.

13. Tomas, F., Box, A., Terrados, J. 2011. Effects of invasive seaweeds on feeding preference and performance of a keystone Mediterranean herbivore. Biological Invasions 13: 1559-1570.

12. Cebrian, E., Ballesteros, E., Linares, C., Tomas, F. 2011. Do native herbivores provide biotic resistance to Mediterranean marine bioinvasions? A seaweed example. Biological Invasions 13(6) 1397-1408.

11. Gacia, E., Costalago, D., Piorno, D., Prado, P. *, Tomas, F. 2009. Mesograzers in Posidonia oceanica meadows: an update on gastropod-epiphyte-seagrass interactions. Botanica Marina special issue on Mediterranean Seagrasses. 52 (5):439-447.

10. Ruiz, J.M., Pérez, M., Romero, J., Tomas, F. 2009. Importance of herbivory on seagrass (Posidonia oceanica) decline near a fish farm: an experimental approach. Botanica Marina special issue on Mediterranean Seagrasses. 52 (5): 449–458, 2009.

9. Farina, S*., Tomas, F., Prado, P., Alcoverro, T., Romero, J. 2009. Seagrass meadow structure alters interactions between the sea urchin Paracentrotus lividus and its predators. Marine Ecology Progress Series 377: 131-137.

8. Prado, P. *, Farina, S. *, Tomas, F., Alcoverro, T., Romero, J. 2008. Marine protection and meadow size alter fish herbivory in seagrass ecosystems. Marine Ecology Progress Series 371:11-21.

7. Prado, P. *, Tomas, F., Alcoverro, T., Romero, J. 2007. Extensive direct measurements of Posidonia oceanica defoliation confirm the importance of herbivory in temperate seagrass meadows. Marine Ecology Progress Series 340: 63-71.

6. Tomas, F., Álvarez-Cascos, D., Turon, X., Romero, J. 2006. Differential element assimilation by sea urchins Paracentrotus lividus in seagrass beds: implications for trophic interactions. Marine Ecology Progress Series 306:125-131.

5. Tomas, F., Turon, X., Romero, J. 2005. Seasonal and small–scale spatial variability of herbivore pressure on the temperate seagrass Posidonia oceanica (L.) Delile. Marine Ecology Progress Series 301: 95-107.

4. Tomas, F., Turon, X., Romero, J. 2005. Effects of herbivores on a Posidonia oceanica seagrass meadow: importance of epiphytes. Marine Ecology Progress Series 287: 115-125. 

3. Tomas, F., Romero, J., Turon, X. 2005. Experimental evidence that intraspecific competition in seagrass meadows reduces reproductive potential in the sea urchin Paracentrotus lividus (Lamarck). Scientia Marina 69 (4): 475-484.

2. Tomas, F., Romero, J., Turon, X. 2004. Settlement and recruitment of the sea urchin Paracentrotus lividus in two contrasting habitats in the Mediterranean. Marine Ecology Progress Series 282: 173 – 184.

1. Invers, O., Tomas, F., Pérez, M., Romero, J. 2002. Potential effect of increased CO2 availability on the depth distribution of the seagrass Posidonia oceanica (L.) Delile: a tentative assessment using a carbon balance model. Bulletin of Marine Science 71 (3): 1191-1198.  


Fun Fact

I enjoy music, backpacking, kayaking, scuba diving, and good food!