New Zealand Journal of Marine and Freshwater Research abstracts
Contribution of photosynthetic gains during tidal emersion to production
of Zostera capricorni in a North Island, New Zealand estuary
Anne-Maree Schwarz
National Institute of Water and Atmospheric
Research Limited
P.O. Box 11 115
Hamilton, New Zealand
email: a.schwarz@niwa.co.nz
Abstract Photosynthetic characteristics of intertidal
Zostera capricorni were measured under different tidal conditions
in Whangapoua Harbour on the eastern Coromandel Peninsula, New Zealand, and
compared with permanently submerged seagrass beds. Photosynthetic characteristics
were measured using pulse amplitude modulated (PAM) fluorometry and oxygen
(O2) electrode techniques. Gross light saturated photosynthesis measured
as oxygen exchange averaged 5.74 and 5.36 mg O2 g-1 dry weight
(DW) h-1 and leaf respiration rates averaged 1.22 and 1.38 mg
O2 g-1 DW h-1, for intertidal and subtidal plants respectively.
Photosynthesis of both intertidal and shallow subtidal plants was light saturated
at between 195 and 242 µmol photons m-2 s-1,
suggestive of acclimation to a high light environment. Despite the period
of exposure at low tide clearly being an important time for photosynthetic
gains for intertidal plants, when water clarity was sufficiently high, maximum
rates of photosynthesis were also possible when the beds were submerged.
If average water clarity was at the clearer end of a range measured for this
site (Kd = 0.85 m-1) then it was calculated that for intertidal
seagrass beds growing at mean sea level in Whangapoua, c. 50% of above-ground
production could occur while plants were submerged.
Keywords intertidal seagrass; PAM fluorometry; photosynthesis
M03071; Online publication date 24 November 2004 Received 23 October 2003;
accepted 8 August 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
809–818
0028–8330/04/3805–0809 © The Royal Society of New Zealand 2004
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