Winter phytoplankton and microzooplankton populations off the coast of Westland, New Zealand, 1979

Abstract

In a survey of the composition and spatial distribution of phytoplankton and microzoo‐plankton populations in the upper water column off the coast of Westland in winter, the abundance of different groups of phytoplankton varied markedly. Diatoms were generally most common in neritic waters. Phytoflagellates were concentrated in the seaward part of the mixed coastal waters landward of the S=35 isohaline, and dinoflagellates (mainly non‐thecate forms) were most plentiful away from the coast. Phytoflagellates were recorded for the first time off the coast of Westland. Although phytoflagellates (1.5–14.5 μm long) were most abundant, thecate and non‐thecate dinoflagellates contributed most to the estimated cell carbon, especially at offshore stations. Diatoms were the least plentiful group of phytoplankton except at 1 nearshore station. The vertical stability of the water column is considered to be the most important factor in determining the relative abundance of phytoplankton species.

Key words:

• winter
• phytoplankton
• zooplankton
• population density
• diatoms
• dinoflagellates
• phytoflagellates
• upwelling
• cell carbon
• west coast
• South Island
• river discharge
• coastal zone
• seasons