Brief description
To measure the photosynthetic rate of seagrasses using a Diving-PAM, it is first necessary to determine how much of the light reaching the leaves is absorbed and used in photosynthesis. The absorptance factors of each seagrass species are then used to determine the electron transport rates (ETR) and subsequently the photosynthetic rate.Hence this study determines absorptance factors for Posidonia sinuosa, Posidonia australis and Halophila ovalis, taking into account transmittance, reflectance and non-photosynthetic absorptance of light by the leaves from leaves taken for Woodman Point, WA on 27 May 2004.
Lineage
Maintenance and Update Frequency: notPlanned
Statement: Fresh leaf samples of P. sinuosa, P. australis and H. ovalis were collected from Woodman Point, Western Australia, from a depth of 1.5 m on 27 May 2004. The samples were kept cool and dark until measurements were made the following day. The absorptance factors of each species were measured in the laboratory using an integrating sphere spectrometer after the method described by Runcie and Durako (2004) (see thesis for reference).
Fresh leaves were gently blotted with a tissue to remove water immediately before being placed into the optical path of the spectrometer. Transmittance and reflectance of leaves were measured between 350 and 800 nm, and were performed on five replicates each of P. sinuosa, P. australis and H. ovalis. Non-photosynthetic absorptance was calculated as the absorptance of the leaf at wavelength 750 nm. The absorptance factors obtained using this method were used in all subsequent chapters instead of the Diving-PAM's default ETR-factor of 0.84
Fresh leaves were gently blotted with a tissue to remove water immediately before being placed into the optical path of the spectrometer. Transmittance and reflectance of leaves were measured between 350 and 800 nm, and were performed on five replicates each of P. sinuosa, P. australis and H. ovalis. Non-photosynthetic absorptance was calculated as the absorptance of the leaf at wavelength 750 nm. The absorptance factors obtained using this method were used in all subsequent chapters instead of the Diving-PAM's default ETR-factor of 0.84
Statement: - Potential errors during measurement of rapid light curves -
In order to examine potential errors during measurement of RLCs using the Diving-PAM, a pilot study was undertaken at Woodman Point, Western Australia, on P. sinuosa leaves (1.9-2.0 m depth) during March 2005. In situ measurements were made on leaves growing within 10 cm of the edge of the meadow.
- Chlorophyll fluorescence measurements
In situ fluorescence measurements were carried out with a Diving-PAM using SCUBA. The 5.5 mm quantum sensor was calibrated against a Li-Cor sensor (LI-185B, Li-Cor Inc). Rapid light curves (RLCs) were measured using at the base of rank two (second youngest) P. sinuosa leaves (40 - 60 mm from the leaf sheath). Most of the leaves carried no visible epiphytic growth at the measurement sites and hence epiphyte removal was avoided. The few epiphytised leaves present at the measurement site were chosen when the effect of epiphytes on RLCs was examined. The absorptance factor used here was 0.64 for P. sinuosa.
Five replicate RLC measurements were made between 0800 and 1040 h under each of the following conditions:
1) standard treatment;
2) unshaded treatment;
3) moving treatment;
4) half-exposed treatment;
5) changed-distance treatment; and
6) epiphytes treatment;
For further details see chapter 2.2.2.1 in thesis.
In order to examine potential errors during measurement of RLCs using the Diving-PAM, a pilot study was undertaken at Woodman Point, Western Australia, on P. sinuosa leaves (1.9-2.0 m depth) during March 2005. In situ measurements were made on leaves growing within 10 cm of the edge of the meadow.
- Chlorophyll fluorescence measurements
In situ fluorescence measurements were carried out with a Diving-PAM using SCUBA. The 5.5 mm quantum sensor was calibrated against a Li-Cor sensor (LI-185B, Li-Cor Inc). Rapid light curves (RLCs) were measured using at the base of rank two (second youngest) P. sinuosa leaves (40 - 60 mm from the leaf sheath). Most of the leaves carried no visible epiphytic growth at the measurement sites and hence epiphyte removal was avoided. The few epiphytised leaves present at the measurement site were chosen when the effect of epiphytes on RLCs was examined. The absorptance factor used here was 0.64 for P. sinuosa.
Five replicate RLC measurements were made between 0800 and 1040 h under each of the following conditions:
1) standard treatment;
2) unshaded treatment;
3) moving treatment;
4) half-exposed treatment;
5) changed-distance treatment; and
6) epiphytes treatment;
For further details see chapter 2.2.2.1 in thesis.
Created: 10 08 2007
Data time period: 2004-05-27 to 2005-03
text: westlimit=115.65; southlimit=-32.29; eastlimit=115.78; northlimit=-32.12
text: uplimit=2; downlimit=1
Subjects
63 605002 |
63 617002 |
63 617003 |
BIOSPHERE |
EARTH SCIENCE |
ECOLOGICAL DYNAMICS |
ECOSYSTEM FUNCTIONS |
Halophila ovalis |
Oceans | Marine Biology | Marine Plants |
Photosynthesis |
Posidonia australis |
Posidonia sinuosa |
Seagrass |
absorptance factor |
electron transport rates (ETR) |
oceans |
photosynthetically active radiation |
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Other Information
global : be3a7d90-46ed-11dc-9f4a-00188b4c0af8
Identifiers
- global : 76710600-4a2b-11dc-85e1-00188b4c0af8
