Award: OCE-1061823

Seagrass meadows create diverse and productive ecosystems in shallow seas through the world. Our ability to predict their response to climate change, however, remains elusive. Eelgrass (Zostera marina L.) populations of the Chesapeake region lie near the southern limit of their range in the Western North Atlantic, exposing them to increasing temperature stress as the climate warms. However, ocean acidification may offset some of the negative effects of temperature by stimulating photosynthesis of these carbon-limited aquatic plants. We explored the response of Chesapeake Bay eelgrass to carbon dioxide availability and climate warming using manipulative experiments and mathematical modeling. In our experiments, carbon dioxide enrichment increased eelgrass photosynthesis, growth, sugar production, shoot survival and flower production, even under warm temperatures that typically cause plants to die. The experimentally determined effects of temperature and carbon dioxide were translated into a mathematical model we call GrassLight, that provided a predictive environment for evaluating the interaction of multiple stressors on eelgrass distribution and density in the sea. Model predictions were verified against the experimental data and validated against field observations of eelgrass distribution in the Chesapeake Region. The model accurately reproduced the submarine light environment from measured water quality parameters, and predicted their impacts on eelgrass distribution. It also reproduced the negative effects of warm summer temperatures on eelgrass distributions in the absence of ocean acidification, and demonstrated that carbon dioxide increases projected for the next century should stimulate photosynthesis sufficiently to offset the negative effects of temperature stress on eelgrass growing in the Chesapeake Region. Thus, improved water quality should facilitate the survival of eelgrass populations in Chesapeake region, even in the face of a warming climate. The model is now being used to provide options regarding bay wide strategies for managing eelgrass and other aquatic plants in the face of a changing climate. This project provided training in plant physiology, oceanography and marine ecology opportunities for one postdoctoral associate, five graduate students, two undergraduate students and two high school interns. Results were disseminated through peer-reviewed publications in major scientific journals, numerous oral and poster presentations given at scientific conferences, in several publications by ODU, by Virginia Sea Grant, and the Virginian Pilot newspaper. We held several open-house days in association with Virginia Aquarium public events, making our experimental facility and scientists available for public inspection, often talking to more than 100 visitors on any given day. We worked with the Mentoring Young Scientists Program at the Virginia Aquarium, teaching students from local middle schools about the importance of eelgrass for the Chesapeake Bay, and the potential impacts of climate change on their survival, using hands-on experiments and demonstration projects. Experimental data created by this project are available from the Biological and Chemical Oceanography Data Management Office (BCO-DMO): Impact of Climate Warming and Ocean Carbonation on Eelgrass (Zostera marina L.) (link: http://www.bco-dmo.org/project/2141) The GrassLight Bio-Optical model is available free-of-charge via e-mail request to rzimmerm@odu.edu Last Modified: 05/16/2016 Submitted by: Richard C Zimmerman