Phytoplankton employ a wide variety of defense against grazers, and rely on chemical cues to assess the current grazing pressure. However, these signals are potentially vulnerable to environmental change, such as ocean acidification. In a collaboration with the Marine Chemical Ecology group at the University of Gothenburg, Sweden, Ocean Life researchers have tested if ocean acidification can alter the chemical signals released by copepod grazers.
Copepods are common grazers of phytoplankton, and release chemical cues, called copepodamides, into the water column. Many phytoplankton respond to these cues by upregulating defenses, such as toxin production and bioluminescence, and many chain-forming diatoms break up their chains. However, it is not known how these signals, and thus, how they influence the marine food web, are affected by climate-change related factors, such as ocean acidification. Ocean acidification is caused by increased atmospheric CO2 dissolving into surface waters, leading to a more acidic equilibrium of the ocean carbonate system. With atmospheric CO2 projected to increase in the near future, this will likely also affect our oceans.
We exposed four chain-forming diatoms and the toxin-producing dinoflagellate Alexandrium minutum to copepodamides in current (400 ppm) and projected (1000 ppm) pCO2 levels. Responses to elevated pCO2 were highly species specific, but the more acidic conditions did not interfere with the copepodamide signaling system. However, the variable responses of the different phytoplankton species suggests that ocean acidification may have structuring effects on phytoplankton communities.
Read the paper here: https://www.frontiersin.org/articles/10.3389/fmars.2022.875858/full
Rigby K, Kinnby A, Grønning J, Ryderheim F, Cervin G, Berdan EL and Selander E (2022) Species Specific Responses to Grazer Cues and acidification in Phytoplankton- Winners and Losers in a Changing World. Front. Mar. Sci. 9:875858. doi: 10.3389/fmars.2022.875858