Colonizing tropical seagrasses increase root exudation under fluctuating and continuous low light

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Abstract

While light availability plays a critical role in seagrass growth and distribution, there is limited understanding of how changes in light exposure impact belowground processes. We investigated the effect of prolonged and fluctuating reductions in light on root growth and exudation by three colonizing seagrasses: Cymodocea serrulata, Halophila ovalis, and Halodule uninervis. Seagrasses were grown in mesocosms under continuous full light (control), under continuous light reduction (medium or low), or under fluctuating light (10 d of low and 4 d of high light, repeated three times). Plants were harvested (1) 6 weeks after light treatments (impact), and (2) after an additional 4 weeks of continuous full light (recovery). Root exudates were collected from trap solutions and measured for dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and dissolved organic matter (DOM) excitation/emission fluorescence spectroscopy. Root biomass decreased in all shading treatments. The most notable impact of light treatment was an increase in root exudation of DOC, protein-like DOM and humic-like DOM under fluctuating light for all species. After 4 weeks of recovery, exudation of DOC, and protein-like DOM observed under fluctuating light returned to the control light levels. However exudation of DOC and protein-like DOM by H. ovalis grown in continuous low light remained greater than the control, likely due to root death. This study suggests the belowground environment of seagrasses is sensitive to light reduction. Monitoring changes in root exudation of seagrasses can provide an effective and rapid method to assess light stress and short-term recovery of seagrasses.

Original languageEnglish
Pages (from-to)S1-S498
JournalLimnology and Oceanography
Volume63
Issue numberS1
DOIs
Publication statusPublished - Mar 2018

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exudation
dissolved organic matter
dissolved organic carbon
seagrasses
protein
fluorescence emission spectroscopy
total dissolved nitrogen
Halophila
fluorescence spectroscopy
light availability
proteins
root exudates
shading
seagrass
rapid methods

Cite this

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title = "Colonizing tropical seagrasses increase root exudation under fluctuating and continuous low light",
abstract = "While light availability plays a critical role in seagrass growth and distribution, there is limited understanding of how changes in light exposure impact belowground processes. We investigated the effect of prolonged and fluctuating reductions in light on root growth and exudation by three colonizing seagrasses: Cymodocea serrulata, Halophila ovalis, and Halodule uninervis. Seagrasses were grown in mesocosms under continuous full light (control), under continuous light reduction (medium or low), or under fluctuating light (10 d of low and 4 d of high light, repeated three times). Plants were harvested (1) 6 weeks after light treatments (impact), and (2) after an additional 4 weeks of continuous full light (recovery). Root exudates were collected from trap solutions and measured for dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and dissolved organic matter (DOM) excitation/emission fluorescence spectroscopy. Root biomass decreased in all shading treatments. The most notable impact of light treatment was an increase in root exudation of DOC, protein-like DOM and humic-like DOM under fluctuating light for all species. After 4 weeks of recovery, exudation of DOC, and protein-like DOM observed under fluctuating light returned to the control light levels. However exudation of DOC and protein-like DOM by H. ovalis grown in continuous low light remained greater than the control, likely due to root death. This study suggests the belowground environment of seagrasses is sensitive to light reduction. Monitoring changes in root exudation of seagrasses can provide an effective and rapid method to assess light stress and short-term recovery of seagrasses.",
author = "Martin, {Belinda C.} and John Statton and Siebers, {Andre R.} and Grierson, {Pauline F.} and Ryan, {Megan H.} and Kendrick, {Gary A.}",
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T1 - Colonizing tropical seagrasses increase root exudation under fluctuating and continuous low light

AU - Martin, Belinda C.

AU - Statton, John

AU - Siebers, Andre R.

AU - Grierson, Pauline F.

AU - Ryan, Megan H.

AU - Kendrick, Gary A.

PY - 2018/3

Y1 - 2018/3

N2 - While light availability plays a critical role in seagrass growth and distribution, there is limited understanding of how changes in light exposure impact belowground processes. We investigated the effect of prolonged and fluctuating reductions in light on root growth and exudation by three colonizing seagrasses: Cymodocea serrulata, Halophila ovalis, and Halodule uninervis. Seagrasses were grown in mesocosms under continuous full light (control), under continuous light reduction (medium or low), or under fluctuating light (10 d of low and 4 d of high light, repeated three times). Plants were harvested (1) 6 weeks after light treatments (impact), and (2) after an additional 4 weeks of continuous full light (recovery). Root exudates were collected from trap solutions and measured for dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and dissolved organic matter (DOM) excitation/emission fluorescence spectroscopy. Root biomass decreased in all shading treatments. The most notable impact of light treatment was an increase in root exudation of DOC, protein-like DOM and humic-like DOM under fluctuating light for all species. After 4 weeks of recovery, exudation of DOC, and protein-like DOM observed under fluctuating light returned to the control light levels. However exudation of DOC and protein-like DOM by H. ovalis grown in continuous low light remained greater than the control, likely due to root death. This study suggests the belowground environment of seagrasses is sensitive to light reduction. Monitoring changes in root exudation of seagrasses can provide an effective and rapid method to assess light stress and short-term recovery of seagrasses.

AB - While light availability plays a critical role in seagrass growth and distribution, there is limited understanding of how changes in light exposure impact belowground processes. We investigated the effect of prolonged and fluctuating reductions in light on root growth and exudation by three colonizing seagrasses: Cymodocea serrulata, Halophila ovalis, and Halodule uninervis. Seagrasses were grown in mesocosms under continuous full light (control), under continuous light reduction (medium or low), or under fluctuating light (10 d of low and 4 d of high light, repeated three times). Plants were harvested (1) 6 weeks after light treatments (impact), and (2) after an additional 4 weeks of continuous full light (recovery). Root exudates were collected from trap solutions and measured for dissolved organic carbon (DOC), total dissolved nitrogen (TDN), and dissolved organic matter (DOM) excitation/emission fluorescence spectroscopy. Root biomass decreased in all shading treatments. The most notable impact of light treatment was an increase in root exudation of DOC, protein-like DOM and humic-like DOM under fluctuating light for all species. After 4 weeks of recovery, exudation of DOC, and protein-like DOM observed under fluctuating light returned to the control light levels. However exudation of DOC and protein-like DOM by H. ovalis grown in continuous low light remained greater than the control, likely due to root death. This study suggests the belowground environment of seagrasses is sensitive to light reduction. Monitoring changes in root exudation of seagrasses can provide an effective and rapid method to assess light stress and short-term recovery of seagrasses.

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