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

Abstract

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 22 μm 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 m B for the different size classes were similar. Values of I k for the > 22 μm 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 incre...