Effects of Ocean Acidification on Trophic Interactions Across a Natural pH Gradient

Polychaetes are a class of segmented worms that live under a wide range of oceanic conditions. Often, they are the dominant organisms found living in the sea floor, but they also thrive in the open ocean. According to Ricevuto et al. (2015), although knowledge of the potential response of these organisms to ocean acidification is growing, much remains to be learned, including “how their trophic behavior might change in response to low [less basic, or more acidic] pH.” In an effort to fill this informational void, Ricevuto et al. thus set out to examine food-chain interactions of three polychaete species (Platynereis dumerilii, Polyophthalmus pictus and Syllis prolifera) and their organic matter (food) sources (macroalgae, seagrass and epiphytes) in a naturally acidified region of the Mediterranean Sea.

The location for their study was a shallow water reef area on the north-eastern coast of Ischia, an island off the coast of Italy known for volcanic features, including underwater vents that release copious quantities of CO2. The vents produce a pH gradient in the area that provides “a natural laboratory for ocean acidification studies,” which the researchers further describe as “an ideal model system to conduct experiments investigating the effect of climate changes (particularly ocean acidification) on benthic community composition and structure, as well as on functional aspects, such as tropic interactions,” which was the focus of this study. And what did the study show?

After collecting data and conducting a series of complex analyses, the three Italian researchers report “increased pCO2 did not alter the trophic interactions dramatically,” adding “there seems to be a resilience in the trophic pattern, possibly due to the tolerance of the target species to acidification and potential local acclimatization and/or adaptation (see Calosi et al., 2013).” Such “phenotypic plasticity” (the ability to alter biochemical reactions based on environmental changes such as increasing temperature or acidity) observed in the three polychaete species studied, according to Ricevuto et al., “may allow them to respond well to alterations in the environment and eventually offset near-future ocean acidification scenarios.” Thus, as the researchers ultimately conclude, “for some species, like the ones considered in this study, ocean acidification may not represent a dramatic stress.” And that’s good news worth reporting.



Calosi, P., Rastrick, S.P.S., Lombardi, C., de Guzman, H.J., Davidson, L., Jahnke, M., Giangrande, A., Hardege, J.D., Schulze, A., Spicer, J.I. and Gambi, M.C.  2013.  Adaptation and acclimatization to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow CO2 vent system. Philosophical Transactions of the Royal Society of London B Biological Sciences 368: 20120444.

Ricevuto, E., Vizzini, S. and Gambi, M.C. 2015. Ocean acidification effects on stable isotope signatures and trophic interactions of polychaete consumers and organic matter sources at a CO2 shallow vent system. Journal of Experimental Marine Biology and Ecology 468: 105-117.