Rhodoliths are free-living calcareous red algae with a global distribution from the Artic to the tropics and the widest depth range of any marine algae. As ecosystem engineers, they form extensive beds in shallow marine environments that provide important habitats and nurseries for marine organisms and contribute to carbonate sediment accumulation. There is growing concern that these organisms are sensitive to rising carbon dioxide levels, yet little is known about their physiology. Therefore, the main goal of this project was to establish a better understanding of how rhodoliths obtain the carbon they need for photosynthesis and calcification, and how these mechanisms are affected by different environmental conditions. I found that the carbon uptake mechanisms of rhodoliths in the northeast Atlantic are flexible and depend on environmental conditions, mainly dissolved inorganic carbon concentrations in the seawater. Arctic rhodoliths have unique physiological mechanisms that facilitate calcification and reduce the loss of inorganic carbon during long periods of darkness. Some rhodoliths are even able to take up organic carbon and nitrogen to supplement their energy demands. High carbon dioxide levels did not have a strong effect on photosynthesis, and the algae were able to maintain a chemical microenvironment on their surface conducive to calcification. The results of this project show that rhodoliths are robust organisms that optimize the use of available dissolved inorganic and organic compounds through flexible physiological mechanisms. This is an important first step in understanding the physiology of rhodoliths and why they have such an extensive biogeographical distribution. Additionally, the results suggest that some rhodoliths may be less sensitive to high carbon dioxide levels than previously thought. Results from this project and other researchers working on coralline algae will be published in a special issue on coralline algae in the open access journal Frontiers in Marine Science.

The broader impacts of the project include the establishment of the Coralline Algae Network. The network is a platform on the Research Gate website where researchers and students around the world that are interested in coralline algae can ask questions, share results, discuss failures, and establish new collaborations. The project website, blog, facebook page and public talks increased awareness about the world wide importance of rhodolith beds. Additionally, the research conducted during this project resulted in the L'Oreal Germany For Women in Science award that established financial support for female researchers needing child care during field trips and travel for conferences. The project had a strong international network, including bachelor and masters students from Germany, Serbia, Spain, Latvia and the USA. A collaboration was also established with partners from Brazil, where resources for marine research are limited, to provide them with access to new technology and methods for investigating rhodolith beds in the north and south Atlantic. Future projects stemming from this project are planned, including investigating whether rhodoliths can be used as biofilters for fish aquaculture, physiological investigations of south Atlantic rhodoliths, and a diversity assessment of Cuban coralline algae, where little is known about the species present.

Last Modified: 03/09/2018
Modified by: Laurie C Hofmann