In situ oxygen dynamics in rhizomes of the seagrass Posidonia sinuosa: impact of light, water column oxygen, current speed and wave velocity

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Abstract

The presence of oxygen in seagrass tissues, which plays a role in preventing seagrass die-off, is partly regulated by environmental conditions. Here, we examined the relationship between oxygen (O-2) in the rhizomes of Posidonia sinuosa and key environmental variables at Garden Island, Western Australia. We made in situ measurements of internal oxygen partial pressure (pO(2)) of rhizomes using fibre optic optodes and compared these to pO(2) in the water column, photosynthetically active radiation (PAR) and wave and current velocities within the seagrass canopy. During daytime, tissue pO(2) was regulated by PAR, whereas in darkness, both near-bed mean current and wave orbital velocities were important in influencing pO(2). Tissue pO(2) was positively correlated with current speed at night up to a threshold of similar to 0.045 m s(-1), likely because of a reduction in the thickness of the diffusive boundary layer surrounding the plant, allowing for more rapid exchange of O-2 with the surrounding water. The flow velocities in the meadow were generally low and at times near-stagnant, and pO(2) in rhizomes declined to critical levels at night. This may explain the lack of recovery of seagrasses in the area despite management efforts that have improved water quality. Our observations of tissue pO(2) in P. sinuosa show remarkable similarities to previous laboratory and field studies across a range of seagrass species, suggesting that the relationships to hydrodynamic conditions and light levels that are described here are general across taxa.

Original languageEnglish
Pages (from-to)67-77
Number of pages11
JournalMarine Ecology Progress Series
Volume590
DOIs
Publication statusPublished - 12 Mar 2018

Cite this

@article{239fea8fe98a4d9da4be3d4d2e5e0262,
title = "In situ oxygen dynamics in rhizomes of the seagrass Posidonia sinuosa: impact of light, water column oxygen, current speed and wave velocity",
abstract = "The presence of oxygen in seagrass tissues, which plays a role in preventing seagrass die-off, is partly regulated by environmental conditions. Here, we examined the relationship between oxygen (O-2) in the rhizomes of Posidonia sinuosa and key environmental variables at Garden Island, Western Australia. We made in situ measurements of internal oxygen partial pressure (pO(2)) of rhizomes using fibre optic optodes and compared these to pO(2) in the water column, photosynthetically active radiation (PAR) and wave and current velocities within the seagrass canopy. During daytime, tissue pO(2) was regulated by PAR, whereas in darkness, both near-bed mean current and wave orbital velocities were important in influencing pO(2). Tissue pO(2) was positively correlated with current speed at night up to a threshold of similar to 0.045 m s(-1), likely because of a reduction in the thickness of the diffusive boundary layer surrounding the plant, allowing for more rapid exchange of O-2 with the surrounding water. The flow velocities in the meadow were generally low and at times near-stagnant, and pO(2) in rhizomes declined to critical levels at night. This may explain the lack of recovery of seagrasses in the area despite management efforts that have improved water quality. Our observations of tissue pO(2) in P. sinuosa show remarkable similarities to previous laboratory and field studies across a range of seagrass species, suggesting that the relationships to hydrodynamic conditions and light levels that are described here are general across taxa.",
keywords = "Seagrass, Photosynthesis, Diurnal, Hypoxia, PAR, Rhizosphere, Currents, Waves, EELGRASS ZOSTERA-MARINA, TROPICAL SEAGRASS, WESTERN-AUSTRALIA, COCKBURN SOUND, PHOTOSYNTHESIS, TRANSPORT, INTRUSION, AERATION, CANOPIES, FLOWS",
author = "Olsen, {Ylva S.} and Fraser, {Matthew W.} and Martin, {Belinda C.} and Andrew Pomeroy and Ryan Lowe and Ole Pedersen and Kendrick, {Gary A.}",
year = "2018",
month = "3",
day = "12",
doi = "10.3354/meps12477",
language = "English",
volume = "590",
pages = "67--77",
journal = "Marine Ecology - Progress Series",
issn = "0171-8630",
publisher = "Inter-Research",

}

TY - JOUR

T1 - In situ oxygen dynamics in rhizomes of the seagrass Posidonia sinuosa

T2 - impact of light, water column oxygen, current speed and wave velocity

AU - Olsen, Ylva S.

AU - Fraser, Matthew W.

AU - Martin, Belinda C.

AU - Pomeroy, Andrew

AU - Lowe, Ryan

AU - Pedersen, Ole

AU - Kendrick, Gary A.

PY - 2018/3/12

Y1 - 2018/3/12

N2 - The presence of oxygen in seagrass tissues, which plays a role in preventing seagrass die-off, is partly regulated by environmental conditions. Here, we examined the relationship between oxygen (O-2) in the rhizomes of Posidonia sinuosa and key environmental variables at Garden Island, Western Australia. We made in situ measurements of internal oxygen partial pressure (pO(2)) of rhizomes using fibre optic optodes and compared these to pO(2) in the water column, photosynthetically active radiation (PAR) and wave and current velocities within the seagrass canopy. During daytime, tissue pO(2) was regulated by PAR, whereas in darkness, both near-bed mean current and wave orbital velocities were important in influencing pO(2). Tissue pO(2) was positively correlated with current speed at night up to a threshold of similar to 0.045 m s(-1), likely because of a reduction in the thickness of the diffusive boundary layer surrounding the plant, allowing for more rapid exchange of O-2 with the surrounding water. The flow velocities in the meadow were generally low and at times near-stagnant, and pO(2) in rhizomes declined to critical levels at night. This may explain the lack of recovery of seagrasses in the area despite management efforts that have improved water quality. Our observations of tissue pO(2) in P. sinuosa show remarkable similarities to previous laboratory and field studies across a range of seagrass species, suggesting that the relationships to hydrodynamic conditions and light levels that are described here are general across taxa.

AB - The presence of oxygen in seagrass tissues, which plays a role in preventing seagrass die-off, is partly regulated by environmental conditions. Here, we examined the relationship between oxygen (O-2) in the rhizomes of Posidonia sinuosa and key environmental variables at Garden Island, Western Australia. We made in situ measurements of internal oxygen partial pressure (pO(2)) of rhizomes using fibre optic optodes and compared these to pO(2) in the water column, photosynthetically active radiation (PAR) and wave and current velocities within the seagrass canopy. During daytime, tissue pO(2) was regulated by PAR, whereas in darkness, both near-bed mean current and wave orbital velocities were important in influencing pO(2). Tissue pO(2) was positively correlated with current speed at night up to a threshold of similar to 0.045 m s(-1), likely because of a reduction in the thickness of the diffusive boundary layer surrounding the plant, allowing for more rapid exchange of O-2 with the surrounding water. The flow velocities in the meadow were generally low and at times near-stagnant, and pO(2) in rhizomes declined to critical levels at night. This may explain the lack of recovery of seagrasses in the area despite management efforts that have improved water quality. Our observations of tissue pO(2) in P. sinuosa show remarkable similarities to previous laboratory and field studies across a range of seagrass species, suggesting that the relationships to hydrodynamic conditions and light levels that are described here are general across taxa.

KW - Seagrass

KW - Photosynthesis

KW - Diurnal

KW - Hypoxia

KW - PAR

KW - Rhizosphere

KW - Currents

KW - Waves

KW - EELGRASS ZOSTERA-MARINA

KW - TROPICAL SEAGRASS

KW - WESTERN-AUSTRALIA

KW - COCKBURN SOUND

KW - PHOTOSYNTHESIS

KW - TRANSPORT

KW - INTRUSION

KW - AERATION

KW - CANOPIES

KW - FLOWS

U2 - 10.3354/meps12477

DO - 10.3354/meps12477

M3 - Article

VL - 590

SP - 67

EP - 77

JO - Marine Ecology - Progress Series

JF - Marine Ecology - Progress Series

SN - 0171-8630

ER -