Effects of ocean acidification on the performance and interaction of fleshy macroalgae and a grazing sea urchin

When predicting the response of marine ecosystems to climate change, it is increasingly recognized that understanding indirect effects ocean acidification on trophic interactions as important studying direct organism physiology. Furthermore, comprehensive studies examine these simultaneously are needed identify and link underlying mechanisms driving changes in species interactions. Using an onshore simulator system, we investigated elevated seawater pCO2 physiology interaction fleshy macroalgae grazing sea urchin Lytechinus variegatus. Macroalgal (Dictyota spp.) biomass increased despite decreased photosynthetic rates after two-week exposure pCO2. Algal tissue carbon content remained constant, suggesting use alternative acquisition pathways beneficial growth under acidification. Higher C:N ratios driven by a slight reduction N algae exposed suggest decrease nutritional Urchin (L. variegatus) respiration, biomass, righting time did not change significantly six-week pCO2, indicating physiological stress metabolism through which was impacted. Correspondingly, consumption untreated (Caulerpa racemosa) were affected In contrast, urchins reduced number correct foraging choices for ambient spp.), impairment chemical sensing However, returned similarly levels, alongside higher algal altered way detectable These results highlight importance with Together, quality behind surprisingly unaltered behavior joint Consistent between L. variegatus may be sustained future increases macroalgal opportunistic strategies have potential cause ecological depending how grazer populations respond. Additional field research determine outcome over wider range environmental conditions.