Strong leaf surface basification and CO2 limitation of seagrass induced by epiphytic biofilm microenvironments

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DOI

  • Kasper Elgetti Brodersen, Københavns Universitet
  • ,
  • Klaus Koren
  • Niels Peter Revsbech
  • Michael Kühl, Københavns Universitet, Climate Change Cluster, University of Technology Sydney

Coastal eutrophication is a growing problem worldwide, leading to increased epiphyte overgrowth of seagrass leaves. Yet little is known about how epiphytes affect key biogeochemical conditions and processes in the seagrass phyllosphere. We used electrochemical microsensors to measure microgradients of O2, pH, and CO2 at the bare and epiphyte-covered leaf surface of seagrass (Zostera marina L.) to determine effects of epiphytes on the leaf chemical microenvironment. Epiphytes result in extreme daily fluctuations in pH, O2, and inorganic carbon concentrations at the seagrass leaf surface severely hampering the plant's performance. In light, leaf epiphyte biofilms and their diffusive boundary layer lead to strong basification, markedly reducing the CO2 and HCO3 - availability at the leaf surface, leading to reduced photosynthetic efficiency as a result of carbon limitation and enhanced photorespiration. With epiphytes, leaf surface pH increased to >10, thereby exceeding final pH levels (~9.62) and CO2 compensation points for active photosynthesis. In darkness, epiphyte biofilms resulted in increased CO2 and hypoxia at the leaf surface. Epiphytes can lead to severe carbon limitation in seagrasses owing to strong phyllosphere basification leading to CO2 depletion and costly, yet limiting, HCO3 - utilization, increasing the risk of plant starvation.

Original languageEnglish
JournalPlant Cell and Environment
Volume43
Issue1
Pages (from-to)174-187
Number of pages14
ISSN0140-7791
DOIs
Publication statusPublished - 1 Jan 2020

    Research areas

  • CO, diffusive boundary layer, epiphytes, microenvironment, photosynthesis, phyllosphere, seagrass, INORGANIC CARBON UTILIZATION, SULFIDE INTRUSION, CO2, EELGRASS ZOSTERA-MARINA, TROPICAL SEAGRASS, OXYGEN, THALASSIA-TESTUDINUM, DIFFUSIVE BOUNDARY-LAYERS, O-2 DYNAMICS, PHOTOSYNTHESIS, CONCENTRATING MECHANISMS

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