MONSOONAL DIFFERENCES IN NET-PHYTOPLANKTON IN THE ARAFURA SEA

Arafura Sea net-phytoplankton (75 μm) was studied during August 1984 and February 1985. Vertical hauls were made with a Kitahara net in the upper 100 m or from near the bottom to the surface on shallower stations. Diatoms formed the main component of the net-phytoplankton during both cruises. The shallow part of the Arafura Sea was relatively the richest area. Net-phytoplankton was on average three times more abundant in August than in February; also nutrient concentrations were higher in August. This confirms earlier suggestions of upwelling in that period. In a limited area off River Digul (Irian Jaya) relatively high cell numbers occurred in February, pointing to input of riverine nutrients, which was confirmed by nutrient data. © 1990.