From Microcosm to the Ocean

Protists have long been used as model species in various biological disciplines from cell to molecular biology. However, to this day they aren’t commonly used in marine ecology.

Protists are found in all marine habitats and are important components of all processes and food webs. They occupy every position from primary producers to parasites. Moreover, they are generally easy to cultivate and new molecular methods ease the in depth study of protists. Yet, most studies focus on bacteria to study macro ecological theories on microbes. In their review based on presentations at the VII ECOP/ISOP meeting in 2015, Weisse et al. (2016) outline the framework and methods for macro ecological studies on protists and advocate to revive aquatic protists as model organisms in conceptual studies. 

The focus of the review lies on functional ecology of aquatic phagotrophic protists, both heterotrophic and mixotrophic. Weisse et al. define functional ecology as the functions of a species in an ecosystem or community and the application of ecological models from the organism to whole ecosystems. As protists are important grazers in aquatic environments, their study is vital to understand the impact of various intensities of grazing due to seasonal, horizontal and vertical variability. Nevertheless, the transfer from laboratory to the ocean is very challenging. Research is usually carried out under controlled and very specific conditions, using one species in a microcosm. This approach is problematic in as it selects for species which are able to survive in specific environments and in situ conditions are notoriously difficult to mimic. Furthermore, prolonged captivity is shown to cause changes in feeding rhythms and in behaviour under stress. Also, single strain cultures eliminate intra- and interspecific interactions. Weisse at al. stress the importance for more detailed data on phagotrophic protists and outline possible methods to standardize future research.

While the review is said to focus on phagotrophic protists, Weisse et al. often use more general descriptors such as heterotrophic, autotrophic and mixotrophic. Thus most of the review could presumably also be applied to other types of protists. Interestingly, Weisse et al. refer to an online repository on methods for conceptual studies on protists (Altermatt et al. (2015)), but only to acknowledge that interest in protists as model organisms in ecology has been revived recently. Even though they strongly encourage fellow scientists to expand their research on protists, they do not further refer to the open access archive on various methods.

Reviewed Paper:

Weisse, T., Anderson, R., Arndt, H., Calbet, A., Hansen, P. J., & Montagnes, D. J. (2016). Functional ecology of aquatic phagotrophic protists–Concepts, limitations, and perspectives. European journal of protistology. Link: http://www.sciencedirect.com/science/article/pii/S0932473916300189

Further Reading:

Altermatt, F., Fronhofer, E. A., Garnier, A., Giometto, A., Hammes, F., Klecka, J., ... & Plebani, M. (2015). Big answers from small worlds: a user's guide for protist microcosms as a model system in ecology and evolution. Methods in Ecology and Evolution, 6(2), 218-231. Link: http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12312/full

Schmoker, C., Hernández-León, S., & Calbet, A. (2013). Microzooplankton grazing in the oceans: impacts, data variability, knowledge gaps and future directions. Journal of Plankton Research, 35(4), 691-706. Link: http://plankt.oxfordjournals.org/content/35/4/691.full.pdf+html