New Zealand Journal of Marine and Freshwater Research abstracts

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Size-fractionated phytoplankton biomass and photosynthesis in Manukau Harbour, New Zealand

W. N. VANT
K. A. SAFI

National Institute of Water & Atmospheric
Research Ltd
P. O. Box 11-115
Hamilton, New Zealand

Abstract  We measured the seasonal variation in phytoplankton biomass and photosynthesis in three size classes at four contrasting sites in Manukau Harbour during 1993-94. Low levels occurred during winter, when the < 5 um class dominated (43-51% of chlorophyll a, 46-58% of photosynthesis). The 5-22 um class dominated during early summer (47-66%, and 52-71%, respectively), whereas the > 22 um class dominated during a late summer bloom of Odontella sinensis and other large diatoms, particularly at the inner harbour sites (41-57%, and 43-61%, respectively). Values of the photosynthetic parameter P^Bm for the different size classes were similar. Values of Ik for the > 22 um class were 22-44% higher on average than those for both the smaller classes. The ratio of photosynthesis to biomass in the euphotic zone--a simple index of potential growth rate--varied seasonally; but at any given time values for all three size classes were similar. Despite this, during summer the biomass of the smaller size classes increased much less than that of the > 22 um class, implying the smaller cells were lost at a greater rate then.

Keywords  size-fractionation; algal size; algal growth; phytoplankton; photosynthesis; nutrients; Manukau Harbour

New Zealand Journal of Marine and Freshwater Research, 1996: Vol. 30: 115-125

0028-8330/96/3001-0115 $2.50/0 (c) The Royal Society of New Zealand 1996

PDF file of entire paper: medium quality (1207K); (scanned from paper original: notes about this process)

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