Trophic cascade pond mesocosm experiment at Brackenridge Field Lab. Photo by C. Rakowski (2017)

Trophic cascades

Trophic cascades are effects that stem from predators and propagate down through food webs (Ripple et al. 2016 Trends in Ecology and Evolution). Included in this definition are many indirect effects other than the classic trophic cascade where predator addition or removal alters the biomass of a low trophic level. For example, a change in predator diversity, composition, traits, or interactions could alter prey biomass, which in turn could alter the central tendency or stability of basal processes such as primary production and nutrient uptake. Such cascading effects are relevant to global change and ecosystem management, since 1) predator communities are heavily threatened by anthropogenic forces and 2) reliable basal ecosystem functions are vital for ecosystems and human well-being. However, some of these potential trophic cascades have scarcely been studied, especially those relating to stability.

I have found that some of these understudied trophic cascades can indeed occur — for example, predator diversity can suppress the variability of phytoplankton biomass without affecting its central tendency (Rakowski et al. 2021 Ecology). I am also working on understanding more complex interactions, such as how intraguild predation strength mediates the aforementioned cascade. I use an integrative approach, combining field experiments, laboratory experiments, and theory, using freshwater pond food webs as a model system.

Also, while fish normally get most of the attention in freshwater predator research, I am giving insect predators some love. After all, they are found in essentially every freshwater body, including small and temporary ones where the lack of fish often grants insects the role of top predator!

Check out my talk on the ESA 2021 website for more:

Relevant publications (see Publications page for abstracts and DOI links):

Rakowski, C. J., C. E. Farrior, S. R. Manning, and M. A. Leibold (2021). Predator complementarity dampens variability of phytoplankton biomass in a diversity-stability trophic cascade. Ecology, 102(12):e03534.

C. J. Rakowski and M. A. Leibold (2021). Beyond the fish-Daphnia paradigm: testing the potential for Neoplea striola (Hemiptera: Pleidae) to cause a trophic cascade in subtropical ponds. bioRxiv.

R. W. El-Sabaawi, R. D. Bassar, C. Rakowski, M. C. Marshall, B. L. Bryan, S. N. Thomas, C. Pringle, D. N. Reznick, and A. S. Flecker (2015). Intraspecific phenotypic differences in fish affect ecosystem processes as much as bottom–up factors. Oikos, 124(9):1181-1191.

Chase Rakowski
PhD Candidate