OPTICAL-PROPERTIES OF THE COASTAL AND OCEANIC WATERS OFF SOUTH-ISLAND, NEW-ZEALAND - REGIONAL VARIATION

A study of the optical properties of the varied water masses in inshor e and oceanic waters around the South Island of New Zealand was made. This was a contribution to a larger effort to model the productivity o f the southern sector of New Zealand's Exclusive Economic Zone. A comb ination of spectroradiometry, PAR sensor deployments, transmissometry, and yellow-substance measurement was used at 30 stations to character ise the optical properties of the region. The waters were classified a ccording to Jerlov's system for ocean waters. Inshore sites on the wes t and east coasts and Foveaux Strait fell into optical types Coastal I and Oceanic III. Oceanic II waters occurred in the Subtropical Conver gence Zone (STCZ). Subantarctic waters and those south of the STCZ wer e in the clear categories Oceanic I and IB. Attenuation coefficients ( K) varied more than three-fold from 0.05 to 0.16 m(-1). Reflectance wa s lowest off the Fiordland coast where light-absorbing yellow substanc e was maximal. An index of the average lighting of the mixed layer ((E ) over bar(o)) for phytoplankton photosynthesis was calculated from th e light-depth profile. Highly varying mixed-layer depths, combined wit h a 3-fold difference in K, caused (E) over bar(o) to vary by as much as 11, suggesting that the growth of oceanic phytoplankton in the regi on may vary far more than predicted by present models.