Research articles
ScienceAsia 49 (2023): 266-274 |doi:
10.2306/scienceasia1513-1874.2023.017
Photosynthesis and photosynthetic electron transport in the
soft coral Sarcophyton spp
Vipawee Dummeea,b, Suhailar Sma-aira, Suksiri Chooklina, Thanongsak Chanmethakulc, Raymond J. Ritchiea,b,*
ABSTRACT: Blue-diode Pulse Amplitude Fluorometry (PAM) and rapid light curves, fitted using the Waiting-in-Line
equation, were used to measure photosynthetic electron transport rate (ETR) of the common soft coral Sarcophyton
spp (Alcyoniidae, Cnidaria). Optimum irradiance (Eopt) of newly-collected material was 353?28.9 ?mol quanta
m?2
s
?1
(?18% sunlight, 400?700 nm), ? optimum irradiance (E1/2?ETR) ?82.0 ?mol quanta m?2
s
?1 with substantial
photoinhibition at higher irradiances. Maximum ETR (ETRmax) = 25.1?1.28 ?mol e? m?2
s
?1
(surface area basis) or
86.8?4.44 ?mol e?
g
?1 Chl a s
?1
(Chl a basis). Due to strong midday inhibition total daily photosynthesis would
be greater on cloudy days, during the overcast wet season and high tides. Open aquarium-grown material had
Eopt ?300 ?mol quanta m?2
s
?1
; ETRmax ?21 ?mol e? m?2
s
?1 or ?50 ?mol e?
g
?1 Chl a s
?1
. Chl a was ?300 (field
material) vs. ?450 (aquaculture aquarium) mg m?2 but with no change in Chl c2/a ratio (0.521?0.0181). Based
on light/dark O2
electrode methods in aquaria Gross Photosynthesis (Pg
) = 21.9?6.85 ?mol O2
g
?1 Chl a s
?1
, Pnet
= 15.1?6.38 ?mol O2
g
?1 Chl a s
?1
; respiration ?6.81?2.23 ?mol O2
g
?1 Chl a s
?1
; P/R ratio = 3.72?1.86 at an
irradiance 192?20.3 ?mol quanta m?2
s
?1
. The culturable dinoflagellate zooxanthellae material might not necessarily
be representative of the resident zooxanthellae population. Their PAM characteristics were similar to the soft coral
(Eopt ?219 ?mol quanta m?2
s
?1
, ETRmax ?138 ?mol e?
g
?1 Chl a s
?1
), but the Chl c2/a ratio (?0.16) was very different.
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a |
Faculty of Technology and Environment, Prince of Songkla University Phuket Campus, Phuket 83120 Thailand |
b |
Andaman Environment and Natural Disaster Research Centre, Prince of Songkla University Phuket Campus,
Phuket 83120 Thailand |
c |
Science and Mathematics Program, Faculty of Science and Technology, Phuket Rajabhat University,
Phuket 83000 Thailand |
* Corresponding author, E-mail: raymond.r@phuket.psu.ac.th
Received 31 May 2022, Accepted 12 Dec 2022
|