From summer 2001 to spring 2002, NIWA made four oceanographic voyages through Tasman and Golden Bays, on the research vessel Kaharoa. A major objective of the research was to understand the ecology of the phytoplankton that live in these waters.
Phytoplankton (free floating, single-celled marine algae) starts the marine food chain, by harnessing sunlight energy and nutrients to grow and reproduce1. This production supports feeding by animal plankton (zooplankton) and filter-feeding shellfish, and underpins aquaculture, fisheries and other ecological services within the Bays. Sometimes, blooms of certain types of toxic phytoplankton may occur2. Blooms of non-toxic algae can also be a nuisance, should they become so great as to cause reduced oxygen content in the water. These conditions can be caused by excessive nutrient runoff from land, but thankfully, such conditions do not presently occur in Tasman and Golden Bays.
Our major goal is to understand the drivers of phytoplankton production: what causes it to wax and wane; how it might change from year-to-year. In order to understand these ecological aspects of phytoplankton we need to understand how seasonal changes and other environmental factors - such as runoff from the surrounding land and mixing with the open ocean - affect their abundance and growth. Phytoplankton growth, like grass growth, is limited by a number of factors, including sunlight levels, nutrients and grazing by animals higher in the food chain3, all of which must be studied to understand phytoplankton production.
In this article we summarise information collected during the Kaharoa voyages and provide a glimpse into our current understanding of how variation in oceanic processes affect phytoplankton ecology in Tasman and Golden Bays4.
 Oceanography of Tasman and Golden Bays (716 K)
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