Latitudinal trends in stable isotope signatures and carbon-concentrating mechanisms of northeast Atlantic rhodoliths

• Published in: Biogeosciences
• Main Authors: Hofmann, Laurie, Heesch, Svenja
• Other Authors: Max Planck Institute for Marine Microbiology, Max-Planck-Gesellschaft, Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Northeast Atlantic; Spitsbergen
• Online Access: https://hal.sorbonne-universite.fr/hal-01913143; https://hal.sorbonne-universite.fr/hal-01913143/document; https://hal.sorbonne-universite.fr/hal-01913143/file/bg-15-6139-2018.pdf; https://doi.org/10.5194/bg-15-6139-2018

International audience Rhodoliths are free-living calcifying red algae that form extensive beds in shallow marine benthic environments (<250 m), which provide important habitats and nurseries for marine organisms and contribute to carbonate sediment accumulation. There is growing concern that these organisms are sensitive to global climate change, yet little is known about their physiology. Considering their broad distribution along most continental coastlines, their potential sensitivity to global change could have important consequences for the productivity and diversity of benthic coastal environments. The goal of this study was to determine the plasticity of carbon-concentrating mechanisms (CCMs) of rhodoliths along a latitudinal gradient in the northeast Atlantic using natural stable isotope signatures. The δ 13 C signature of macroalgae can be used to provide an indication of the preferred inorganic carbon source (CO 2 vs. HCO − 3). Here we present the total (δ 13 C T) and organic (δ 13 C org) δ 13 C signatures of northeast Atlantic rhodoliths with respect to changing environmental conditions along a latitudinal gradient from the Canary Islands to Spitsbergen. The δ 13 C T signatures (−11.9 to −0.89) of rhodoliths analyzed in this study were generally higher than the δ 13 C org signatures, which ranged from −25.7 to −2.8. We observed a decreasing trend in δ 13 C T signatures with increasing latitude and temperature, while δ 13 C org signatures were only significantly correlated to dissolved inorganic carbon. These data suggest that high-latitude rhodoliths rely more on CO 2 as an inorganic carbon source, while low-latitude rhodoliths likely take up HCO − 3 directly, but none of our specimens had ∂ 13 C org signatures less than −30, suggesting that none of them relied solely on diffusive CO 2 uptake. However, depth also has a significant effect on both skeletal and organic δ 13 C signatures, suggesting that both local and latitudinal trends influence the plasticity of rhodolith inorganic carbon ...