Project: Impact of Climate Warming and Ocean Carbonation on Eelgrass (Zostera marina L.)

Project abstract from the NSF proposal:
The past few decades have accumulated mounting evidence of profound anthropogenic effects on fundamental biogeochemical processes across the planet, especially in coastal environments that support a diverse array of highly productive ecosystems including coral reefs, seagrass meadows, and estuaries. The ecological significance of seagrasses is largely due to the remarkable degree of adaptation they exhibit to a submerged aquatic existence. Despite numerous successful adaptations, however, seagrasses have high light requirements that make them vulnerable to anthropogenic disturbances. The paradoxical vulnerability results largely from their high reliance on dissolved aqueous CO2 for photosynthesis. The potential for rising atmospheric CO2 concentrations to have significant warming impacts on the global climate has long been recognized, but the potential impacts of the "other CO2 problem", also known as ocean acidification, have only recently begun to be appreciated. As with other impacts of climate change, the increased concentrations of dissolved aqueous CO2 [CO2 (aq)] in the oceans of the world will elicit both negative and positive responses among organisms, ultimately potentiating ecological losers and winners. This project will explore the response of eelgrass to increased CO2 (aq) within the context of a warming coastal ocean using a combination of manipulative experiments, physiological/biochemical investigations and mathematical modeling. The investigators hypothesize that rising CO2(aq) will increase the high temperature tolerance of plants by improving the Q10 response of photosynthesis relative to respiration, thereby leading to higher growth rates, improved survival of vegetative shoots at high temperature, and even flowering output and seed production. This project will investigate the key relationships between environmental parameters that have both negative (ocean warming) and positive (ocean carbonation) impacts on the light requirements and dynamics of carbon balance in these critically important marine angiosperms. By focusing on Chesapeake populations growing near the southern limit of eelgrass distribution on the Atlantic coast, the investigators will gain predictive insight into how climate change may alter the geographic distribution of this critically important species in other coastal environments that may be subjected to less temperature stress but similar levels of ocean carbonation.

Objectives: The overall goal of the proposed research will be to develop a predictive mechanistic understanding of the simultaneous impacts of water temperature, [CO_2(aq)] and [HCO^3-] on the photosynthetic metabolism, vegetative growth and reproductive success of Zostera marina L. We will address the following questions, (1) To what extent is the upper thermal limit of eelgrass controlled by CO_2(aq) availability, (2) Will prolonged CO_2(aq) enrichment affect the ability of eelgrass to utilize HCO^3- for photosynthesis, (3) Does prolonged CO_2(aq) enrichment increase seed production and viability, and (4) Does CO_2(aq) enrichment affect nutritional quality of seagrass tissue, particularly C:N ratios and protein content?

These experiments will be carried out at an experimental CO_2(aq) enrichment facility which is being constructed at the Virginia Aquarium & Marine Science Center, adjacent to Owl Creek and Rudee Inlet, in Virginia Beach, VA.

Data Inventory

1) Weather and hydrographic data for Owl Creek Experimental Facility. Metadata and time series observations of irradiance, water temperature, pH, salinity, alkalinity, CO₂ and dissolved nutrients will be posted on our web site, and final version data will be supplied to NODC for permanent archive.
2) Experimental metadata from the tanks (pH, temperature, eelgrass abundance and survival, growth rates, metabolic rates, etc.) will also be posted on our website listed above. Final data will be supplied to NODC and/or other databases as appropriate and as they become available.

Project data will also be contributed to thematic databases, including SeaBASS operated by NASA, WOOD operated by ONR, as well as NODC.

Preliminary results may be posted at the group's Web site hosted at ODU:
http://sci.odu.edu/oceanography/directory/faculty/zimmerman/researchpage/index.shtml