Response of Calcified and Fleshy Macroalgae to Warming and Ocean Acidification: From Single Species to Community Interactions

Though researchers generally expect terrestrial plants to grow larger with rising atmospheric carbon dioxide levels, it is more difficult to predict how marine algae, kelp, and seaweeds may respond to climate change. This project is exploring the physiological responses of coralline (calcified) algae and fleshy seaweeds (red and brown) to an ocean that is both warming and more corrosive. In work to date, research teams deployed collecting trays (i.e. sets of settlement tiles) off Carmel and La Jolla and allowed these to be colonized with natural assemblages of seaweeds and invertebrates for a year. Researchers are exposing the organisms on these settlement tiles to ocean conditions predicted for 2100 and tracking changes in growth, calcification and species composition for two to three months. The idea is to better understand how rocky reef communities may respond to climate change. Researchers will also look at whether climate change may interfere with the chemical cues that help red abalone larvae find coralline algae— their preferred settlement habitat. The scientists hypothesize that weaker, more fragile coralline algae may emit different chemical signals and that abalone larvae reared at elevated pCO2 levels may have impaired sensory abilities to detect settlement cues. Results further both state and federal goals of managing marine ecosystems in the face of climate change. In addition, scientists plan to develop K-12 classroom curricula about climate change in marine ecosystems.