Bradford et al.--Phytoplankton and hydrology, southern N.Z.

New Zealand Journal of Marine and Freshwater Research abstracts

Phytoplankton biomass in relation to the surface hydrography of southern New Zealand and possible effects on the food chain

JANET M. BRADFORD

DSIR Marine and Freshwater
Department of Scientific and Industrial Research
Private Bag, Kilbimie, Wellington, New Zealand

H.JOHNCRANFIELD

KEITH P. MICHAEL

MAF Fisheries
Ministry of Agriculture and Fisheries
P. O. Box 297, Wellington, New Zealand

Abstract The surface distribution of salinity, temperature, nitrate-nitrogen (N0₃-N), and chlorophyll a in the southern New Zealand, Foveaux Strait region in February 1977,1978,1979, and 1980 was highly variable. The source of new nitrogen appears to be incursions of high-salinity water west and east of Stewart Island. Although it seems likely that the source of this high-nutrient, high-salinity water is vertical, a horizontal advective source cannot be ruled out The chlorophyll a content of surface waters was not related directly to the NO3-N concentrations. This lower food chain variability may be linked to variability in economically important species. Oysters grew twice as fast in the summer of 1978/79 as they did in 1979/80. But the mean chlorophyll a values were very similar for February of both years (2.5 and 2.2 jjg I"¹, respectively). The elevated NO3-N levels in 1979 may have resulted in much higher phytoplankton levels later that summer and resulted in the higher oyster growth rate that year. The mechanisms driving this variability have yet to be determined.

Keywords southern New Zealand; Foveaux Strait; temperature; salinity; nitrate-nitrogen; chlorophyll a; spatial and temporal variability

PDF file of entire paper: medium quality (810K); (scanned from paper original: notes about this process)

This year's abstracts | Journal home page | All abstracts | Publishing home page