Predicting rates of primary production in the vicinity of the Subtropical Convergence east of New Zealand

Abstract

Water column integrated productivity of phytoplankton in three water masses east of New Zealand (Subtropical, Subtropical Convergence, and Subantarctic) varied both seasonally and spatially, ranging across two orders of magnitude. Productivity was highest in spring and autumn, and lowest in winter. Subtropical and Convergence waters were generally more productive than Subantarctic waters, but during summer the 2–3‐fold range of production was similar in each of the three water masses. Multiple regression analysis identified that most of the variability in production was associated with differences in integrated chlorophyll a concentrations (56%). By considering both surface chlorophyll a and incident irradiance we derived a relationship which explained 74% of observed spatial and seasonal variability in integrated production. These surface variables can be sensed remotely, suggesting the potential for broad spatial mapping of the seasonal cycles of production in these water masses in the New Zealand Exclusive Economic Zone (NZEEZ). Further analysis of the relationship identified that most of the remaining variability could be attributed to p^b _opt (a temperature‐dependent photo‐adaptive term). Exceptions to the relationship and the application of productivity models within NZEEZ are discussed.

Keywords:

• photosynthesis
• P‐E
• Subtropical Convergence
• modelling
• New Zealand