Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea

PeerJ

article

Denis B. Karcher¹  Florian Roth²  Susana Carvalho²  Yusuf C. El-Khaled¹  Arjen Tilstra¹  Benjamin Kürten²  Ulrich Struck⁶  Burton H. Jones²  Christian Wild¹ 

[1] Marine Ecology Department, Faculty of Biology and Chemistry, University of Bremen;Red Sea Research Center, King Abdullah University of Science and Technology;Baltic Sea Centre, Stockholm University;Tvärminne Zoological Station, Faculty of Biological and Environmental Sciences, University of Helsinki;Project Management Jülich, Jülich Research Centre;Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science;Department of Earth Sciences, Freie Universität Berlin

关键词: Coral reefs;    Nutrients;    Stable isotopes;    Nitrogen cycling;    Eutrophication;    Turf algae;    Zooxanthellae;    Phase shifts;   

DOI  :  10.7717/peerj.8737

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

While various sources increasingly release nutrients to the Red Sea, knowledge about their effects on benthic coral reef communities is scarce. Here, we provide the first comparative assessment of the response of all major benthic groups (hard and soft corals, turf algae and reef sands—together accounting for 80% of the benthic reef community) to in-situ eutrophication in a central Red Sea coral reef. For 8 weeks, dissolved inorganic nitrogen (DIN) concentrations were experimentally increased 3-fold above environmental background concentrations around natural benthic reef communities using a slow release fertilizer with 15% total nitrogen (N) content. We investigated which major functional groups took up the available N, and how this changed organic carbon (Corg) and N contents using elemental and stable isotope measurements. Findings revealed that hard corals (in their tissue), soft corals and turf algae incorporated fertilizer N as indicated by significant increases in δ15N by 8%, 27% and 28%, respectively. Among the investigated groups, Corg content significantly increased in sediments (+24%) and in turf algae (+33%). Altogether, this suggests that among the benthic organisms only turf algae were limited by N availability and thus benefited most from N addition. Thereby, based on higher Corg content, turf algae potentially gained competitive advantage over, for example, hard corals. Local management should, thus, particularly address DIN eutrophication by coastal development and consider the role of turf algae as potential bioindicator for eutrophication.

【 授权许可】

CC BY