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Diurnal patterns in phytoplankton photosynthesis, Fremantle Harbour

Cosgrove, J., Moheimani, N.R.ORCID: 0000-0003-2310-4147 and Borowitzka, M.A.ORCID: 0000-0001-6504-4563 (2015) Diurnal patterns in phytoplankton photosynthesis, Fremantle Harbour. Journal of the Royal Society of Western Australia, 98 . pp. 19-27.

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Phytoplankton are likely to be one of the main sources of autochthonous production in the Swan Canning estuary yet only limited published data are available on their photosynthetic dynamics. Here we describe the phytoplankton community composition at the mouth of the estuary and diurnal pattern of phytoplankton photosynthesis by applying chlorophyll fluorescence techniques. Diatoms were the dominant taxa (46–88% of the phytoplankton community) recorded throughout the sampling period although their dominance appeared to increase with the flood tide. A diurnal pattern in photosynthetic performance was apparent via chl-a fluorescence measurements. Nighttime deactivation of Calvin-Benson cycle enzymes was evidenced by low rETRmax and light saturation point (Ek; minimum value of 207.5±2.3(se) µmol photon m-2 s-1) values. Observed daytime increases in Ek (maximum value of 835.8±3.8(se) µmol photon m-2 s-1 at 4pm) with simultaneous reduction of alpha (α) suggests dynamic down-regulation of PSII electron transport during the day. Maximum quantum yield of PSII (Fv/Fm) decreased from a value of 0.81 to minima of 0.51 during high-light periods of the day. Accounting for these dynamics is important in the design of future studies of phytoplantkton productivity in the system. High recorded values of Fv/Fm and an unimpeded ability to photoregulate suggest the diatom-dominated marine phytoplankton community found in Perth’s coastal waters at the time of this study was nutrient replete.

Item Type: Journal Article
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Algae & Seagrass Research Group
Publisher: Royal Society of Western Australia
Copyright: © Royal Society of Western Australia 2015
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