In June 1979, temperature, salinity, dissolved oxygen, reactive phosphorus, reactive silicate, and nitrate nitrogen data were collected along 3 transects off Cape Foulwind, Greymouth, and Wanganui Bluff west of the South Island. Water entered the study area from the vicinity of the Challenger Plateau. It apparently arrived from the north and northwest, guided by the morphology of the plateau, and turned to flow southwestwards along the continental slope. There is some evidence of recirculation to the north close inshore. These flows appear to contribute to a surface and subsurface temperature maximum parallel to the coast, to a subsurface salinity maximum at least off Wanganui Bluff, to a maximum in the depth of the mixed layer parallel to the coast, and to warm, more saline water with minimum surface reactive phosphorus and silicate concentrations approaching the coast more closely off Greymouth. Freshwater runoff diluted coastal water to the greatest extent off Cape Foulwind and Greymouth. This river water contributed to the levels of reactive silicate since there was a significant negative correlation between salinity and reactive silicate. Upwelling, possibly wind-induced, brought subsurface water from about 75 m to the surface off Wanganui Bluff, thus raising the inshore temperature, salinity, and dissolved nutrients, and slightly lowering dissolved oxygen concentrations.

For the New Zealand region, the distributions of reactive phosphorus, chlorophyll a, surface primary productivity, integrated primary productivity, and zooplankton biomass are collated, mainly from previously published data. The hydrology of the New Zealand region intimately affects the amount of reactive phosphorus available for phytoplankton growth.

Winter phytoplankton concentrations inshore off Westland were greater than those recorded off Kaikoura in the same season. Levels of chlorophyll a (B) and primary production (P) were comparable to those recorded off the Washington and Oregon coasts. Off Westland, the stratified inshore region had extinction coefficients (k) > 0.1 m -1 , a photic zone < 35 m, and a mixed layer depth < 40 m. Concentrations of B were greatest compared with the other 2 regions and were vertically well stratified, diatoms were in their largest proportions, and the phytoplankton carbon (PPC): B ratio decreased down the water column in a way that was consistent with low light adaptation at the bottom of the photic zone and high light adaptation at the surface. The maximum production per unit chlorophyll (P B ) was > 1.5 g C g Chi -1 h-and maximum carbon specific growth rates (n) were usually > 0.2 doublings day 1 . The upwelling inshore region off Wanganui Bluff differs from the stratified inshore area in that the PPC : B ratios were uniformly low indicating a low light-saturated photosynthetic capacity, which is supported by a low maximum P B (0.96 g C g Chi -1 h -1 ), although the maximum u was > 0.3 doublings d -1 . Deeply mixed oceanic waters had k <0.1 m -1 , a photic zone >40m, and a mixed layer depth > 100 m. The concentrations of B were lowest with very little vertical stratification, and dinoflagellates were present in largest proportions. The maximum P B was < 1.00 g C g Chi -1 h -1and maximum µ was < 0.17 doublings d -1 . Off the Westland coast the depth of mixing appears to be related to the broad regional pattern of distribution Received 25 June 1984; accepted 4 October 1984of chlorophyll. Evidence is presented which indicates the relationship probably reflects the effect mixing has on population composition rather than dispersion of chlorophyll down the water column. Although the effects of temperature and nutrients on P cannot be completely discounted, light (I) was the only parameter obviously related to P B . The size of P B is governed not only by I but also by the extent to which phytoplankton populations are concentrated near the surface and the light history of the cells. River water contributes to P by stabilising surface waters. The extent of vertical mixing, including upwelling, also governs light adaptation which is often evident in PPC : B ratios and the extent of surface inhibition of P.

No abstract

An intensive study was made of greater Cook Strait in the summers of 1980 and 1981 to determine the availability of dissolved inorganic nutrients in surface waters and the influence this may have on phytoplankton production. Phytoplankton biomass in greater Cook Strait appears to be controlled mainly by zooplankton grazing and turbulence or advection. The relative influence of factors governing primary production on phytoplankton distribution was assessed for the tidal mixing area off Marlborough Sounds, Manawatu River water, the Kahurangi Point to Cape Farewell upwelling region, and eastern Cook Strait.