| Summary: | During Eltanin Cruise 51 (January-February 1972), hydrographic features, phytoplankton standing crop, and primary production were determined between New Zealand and the Ross Ice Shelf. Four geographical regions with unique physical/chemical characteristics were delineated. They were the Subantarctic (SA), Antarctic Convergence (AC), Antarctic (AA), and Ross Ice Shelf (RIS) regions. Nannoplankton contribution to total phytoplankton standing crop (Chl a) and total primary production (C¹⁴ uptake) was measured by a fractionation process utilizing 10 (subscript "mean" symbol) mesh screens to separate the net and nannoplankton components. Mean phytoplankton standing crop values, integrated to 200 m, for the SA, AC, AA, and RIS regions were 23.62, 35.08, 51.41, and 96.37 mgChl a/m², respectively. Nannoplankton accounted for 76.2%, 88.6%, and 64.9% of the standing crop in these respective areas. A significant correlation was found between the total phytoplankton standing crop in surface samples and standing crop estimates integrated over the water column. However, no correlation was found between size competition of the surface standing crop and that of the euphotic zone. Mean estimates of total phytoplankton production in the euphotic zone for the SA, AA, and RIS regions were 5.72, 6.18, and 9.97 mg/m²/hr. Nannoplankton production remained relatively constant in these regions, accounting for 90.2%, 67.0%, and 54.0% of total production in the respective regions. The increased phytoplankton standing crop and primary production observed in waters south of the Antarctic Convergence were accounted for by increases in the net plankton fraction. Average photosynthetic indexes (PI) were calculated for the total phytoplankton and the nannoplankton fraction. Significant estimates of 0.351 (P=.01) and 0.243 (P=.1) were obtained for the total PI and nannoplankton PI, respectively.
|
|---|