Sigmon, D. E. Oregon State University, dsigmon@oce.orst
Nelson, D. M. Oregon State University, nelsonda@ucs.orst.edu
Brzezinski, M. A. University of California, brzrzins@lifesci.ucsb.edu

 
THE SURFACE-LAYER SILICA CYCLE IN THE SOUTHERN OCEAN NEAR 170 W DURING AUSTRAL SPRING AND SUMMER, 1997-98
 
We measured silicic acid and biogenic silica concentrations and silica production rates in the Southern Ocean near 170 W between 53 and 71.5 S from late October, 1997 through mid-March, 1998. During October and early November silicic acid concentrations were 10 - 50 uM with a meridional gradient at the Polar Front (~61 S), and biogenic silica concentrations were < 2 umol Si/l throughout the system. By December biogenic silica had increased by 5 - 12 umol Si/l and silica production rates were high, averaging > 30 mmol Si/m2/d. By January there had been a net removal of 30 - 40 uM silicic acid from surface waters between 61 and 64 S. This biological uptake had intensified the silicic acid gradient and displaced it southward ~450 km, implying major export of biogenic silica between 60 and 65 S. By March silicic acid concentrations had increased and biogenic silica had decreased in the euphotic zone between 57.5 and 65 S, indicating net resupply from silica dissolution and vertical mixing. Low silica production rates, consistently < 10 mmol Si/m2/d from February to March, contributed to the net loss of biogenic silica and the increase in silicic acid.
 
Day: Wednesday, Feb. 3
Time:
Location: Sweeney Center
 
Code: SS31WE0633S