Turbulence‐mediated facilitation of resource uptake in patchy stream macrophytes

• Published in: Limnology and Oceanography
• Main Authors: Cornacchia, Loreta, Licci, Sofia, Nepf, Heidi, Folkard, Andrew, Wal, Daphne, Koppel, Johan, Puijalon, Sara, Bouma, Tjeerd
• Other Authors: Royal Netherlands Institute for Sea Research (NIOZ), Groningen Institute for Evolutionary Life Sciences Groningen (GELIFES), University of Groningen Groningen, Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS), Department of Civil and Environmental Engineering Cambridge (CEE), Massachusetts Institute of Technology (MIT), Lancaster Environment Centre, Lancaster University, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente Netherlands
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: submerged macrophytes; nutrient uptake; mass transfer; envir; info; Groenlandia
• Online Access: https://doi.org/10.1002/lno.11070; https://hal-univ-lyon1.archives-ouvertes.fr/hal-02071382/file/Cornacchia2019_L%26O_HAL.pdf; https://hal-univ-lyon1.archives-ouvertes.fr/hal-02071382

International audience Many landscapes are characterized by a patchy, rather than homogeneous, distribution of vegetation. Often this patchiness is composed of single-species patches with contrasting traits, interacting with each other. To date, it is unknown whether patches of different species affect each other’s uptake of resources by altering hydrodynamic conditions, and how this depends on their spatial patch configuration. Patches of two contrasting aquatic macrophyte species (i.e., dense canopy-forming Callitriche and sparse canopy-forming Groenlandia) were grown together in a racetrack flume and placed in different patch configurations. We measured 15NH4+ uptake rates and hydrodynamic properties along the centerline and the lateral edge of both patches. When the species with a taller, denser canopy (Callitriche) was located upstream of the shorter, sparser species (Groenlandia), it generated turbulence in its wake that enhanced nutrient uptake for the sparser Groenlandia. At the same time, Callitriche benefited from being located at a leading edge where it was exposed to higher mean velocity, as its canopy was too dense for turbulence to penetrate from upstream. Consistent with this, we found that ammonium uptake rates depended on turbulence level for the sparse Groenlandia and on mean flow velocity for the dense Callitriche, but Total Kinetic Energy was the best descriptor of uptake rates for both species. By influencing turbulence, macrophyte species interact with each other through facilitation of resource uptake. Hence, heterogeneity due to multi-specific spatial patchiness has crucial implications for both species interactions and aquatic ecosystem functions, such as nitrogen retention.