Lopes, R. M.. CEM-UFPR, rmlopes@uol.com.br
Dubischar, C. M.. AWI, cdubischar@awi-bremerhaven.de
Bathmann, U. V.. AWI, ubathmann@awi-bremerhaven.de
Pollard, R. SOC, r.pollard@soc.soton.ac.uk

The Polar Front Zone (PFZ) is characterized by strong physical gradients at about 50 degrees South. Horizontal advection and vertical stratification processes occurring at different time and spatial scales had a major impact on biological rates in this area during the 1995/96 summer (Ant XIII, POLARSTERN). Physical and biological data were recorded continuously to 250 m water depth using a CI Seasoar equipped with an optical plankton counter (OPC). A 100-micrometer mesh sized multinet was used to collect small-sized organisms down to 1000 m. Young copepodites and nauplii of the cyclopoid Oithona similis dominated in the mixed layer, comprising roughly 50-85% of the total mesozooplankton density, and reaching up to 20,000 org.l-1 within the chlorophyll-rich areas. Other small copepods were very abundant above the pycnocline, including Ctenocalanus citer, Microcalanus pygmaeus and Oncaea spp. A typical mesopelagic association occurred below 300 m depth, dominated by O. frigida, several oncaeids and small calanoids. Densities of small copepods were about 3 orders of magnitude higher than those of large dominant calanoids. Accordingly, we suggest that oithonids, oncaeids and small calanoid copepods play a major role in the food web dynamics at the PFZ.
Day: Tuesday, Feb. 2
Time: 04:30 - 04:45pm
Location: Hilton of Santa Fe
Code: SS23TU0430H