High Summer Temperatures Amplify Functional Differences Between Coral‐ and Algae‐Dominated Reef Communities

Photo 1: Typical examples of coral- (A) and algae-dominated (B) reef communities in the central Red Sea. The distance between the two sites is only 500 m. Changes from coral to algal dominance are observed globally, often as a result of local and/or global anthropogenic disturbances leading to the loss of live coral cover and the subsequent establishment of fast-growing algae. The consequences of these community changes for key ecosystem functions, such as primary productivity, calcification, organic matter, and nutrient recycling mediated by the underlying benthic communities are poorly understood. The alterations of these processes remain particularly uncertain with regard to the combined effects of environmental change. Photo credit: Florian Roth. Photo 2: Experiments were carried out at Abu Shosha reef located in the central Red Sea on the west coast of Saudi Arabia. The reef is characterized by a heterogeneous mosaic of patches of coral- and algae-dominated communities. Thus, this site allowed for the quantification of the functionality of both communities under identical environmental conditions. The detailed composition of benthic communities used for this experiment was assessed multiple times during the study period by benthic surveys and modern photogrammetry tools to account for the reef's structural complexity. Photo credit: Florian Roth. Photo 3: We used in situ incubations of natural coral- and algae-dominated reef communities to measure fluxes of oxygen, dissolved inorganic carbon, total alkalinity, dissolved organic carbon, and dissolved inorganic nitrogen. This non-invasive approach provides reproducible measurements of biogeochemical processes of structurally complex benthic communities. Thereby, it also accounts for the components of the carbon and nitrogen pool that are remineralized by microbial communities or cryptic fauna within the reef matrix. Photo credit: Holger Anlauf. Photo 4: A total of 2520 syringes with water drawn from the incubations chambers were collected to monitor changes in water chemistry and biological variables during the experiments; (A) a researcher collecting water samples from an algae-dominated reef community; (B) custom-made syringe-holders were used to stop the syringes from floating away; and (C) on the boat, water samples were filtered and/or processed directly for the highest quality in water chemistry measurements in the laboratory later on. Photo credit: (A) Holger Anlauf; (B) Florian Roth; (C) Luis Silva. These photographs illustrate the article “High summer temperatures amplify functional differences between coral- and algae-dominated reef communities” by Florian Roth, Nils Rädecker, Susana Carvalho, Carlos M. Duarte, Vincent Saderne, Andrea Anton, Luis Silva, Maria Ll. Calleja, Xosé Anxelu G. Morán, Christian R. Voolstra, Benjamin Kürten, Burton H. Jones, and Christian Wild published in Ecology. https://doi.org/10.1002/ecy.3226.