Award: OISE-1515267

Ocean acidification and coastal nutrient enrichment may have synergistic effects on the physiological responses of macroalgae in todayÆs changing ocean environment. Understanding the biological impacts of these environmental changes has become increasingly important within the past few decades as carbon dioxide (CO2) continues to be released into the atmosphere, absorbed in the oceans, and decreasing oceanic pH. This EAPSI project aimed to quantify the effects of nutrient enrichment and ocean acidification on the green macroalga Ulva sp. using a state-of-the-art ocean acidification incubation station with a full cross of three levels of CO2 enrichment and two levels of nutrient enrichment. Ulva sp. were incubated for one week. Measurements of growth rates, nutrient uptake rates, and photosynthetic parameters were measured at the end of the experiment. Growth rates were positively affected by nutrient enrichment, but not CO2 enrichment. Photosynthetic rates were unaffected by nutrient and CO2 enrichment. Nutrient uptake was different among nutrient treatments, and there was an interactive effect of CO2 enrichment and nutrient enrichment. The interaction increased the differences between nutrient uptake rates in the ambient and enrichment nutrient treatments at the intermediate level on CO2 enrichment. In summary, nutrient enrichment will continue to be the primary driver of green macroalgae blooms. The research on the effects of CO2 enrichment (ocean acidification) should be studied under different environmental variables to better understand physiological processes in macroalgae under CO2 enrichment. This project used a non-calcifying macroalga Ulva sp., to provide a basis for understanding how ocean acidification and eutrophication will affect oceanic primary producers, such as opportunistic macroalgae species, which informs our knowledge on the future of coastal ecosystems. Last Modified: 03/16/2016 Submitted by: Leah B Reidenbach