OCE-PRF Track 2 (International) - Plasticity of Inorganic Carbon Use in Marine Calcifying Macroalgae Across a Latitudinal Gradient and Consequences of Global Change

Hofmann Laurie C, 28195 Bremen

Investigators

Abstract

Crustose coralline algae (CCA) are calcifying algae that are important to coastal stability, beach formation, and coral reef structure. There is growing concern that these organisms are sensitive to global climate change, which will have important consequences for coastal and reef stability. Despite their significance and sensitivity, their basic photosynthetic and calcification mechanisms are not well understood. In this project, the fellow will establish a better understanding of these mechanisms by studying CCA specimens along a latitudinal gradient in the Northeast Atlantic. The research will be conducted at the Max Planck Institute for Marine Microbiology in Bremen, Germany within the Microsensor Research Group led by Dr. Dirk de Beer. The activities and results of this project will be shared on a Blog and Facebook page to enhance public awareness of the project. Furthermore, the fellow will facilitate development of a Virtual CCA Research Group to foster communication among scientists world-wide working with CCA which will elevate the impacts of this project to a global scale. Both field sampling and laboratory experiments are used to pursue the goals of the project, which are: 1) to determine the environmental factors influencing the stable carbon isotope signatures of Lithothamnion spp. along a latitudinal gradient, 2) to determine the plasticity of dissolved inorganic carbon (DIC) uptake mechanisms in response to light and temperature and 3) to determine how photosynthesis and calcification are linked to DIC uptake mechanisms. The latitudinal gradient consists of eight sampling locations in the North Atlantic from Svalbard to Cape Verde in the east and from Florida to the Caribbean in the west. The stable carbon isotope signatures of collected samples are measured to determine the plasticity of DIC uptake along the latitudinal gradient in relation to environmental conditions measured at long-term monitoring stations. In the lab, microsensors are used to measure pH, oxygen and calcium fluxes within the diffusive boundary layer (DBL) at the surface of the algae. Because DIC uptake depends heavily on the DBL, microsensors provide a unique method for determining the effects of temperature and light on photosynthesis and calcification within the microenvironment at the interface between the external seawater and the algal surface. Successful completion of the project will provide the first study on latitudinal patterns and the flexibility of DIC uptake mechanisms in a calcifying macroalga and will improve the scientific knowledge of the relationship between DIC uptake, photosynthesis and calcification under changing environmental conditions and across biogeographical ranges.