Photosynthetic parameters and primary production in the Bransfield Strait: relationships with mesoscale hydrographic structures

During January 1994, the photosynthetic response (P–E curves) of phytoplankton in the eastern part of the Bransfield Strait (Antarctica) was studied in relation to the mesoscale hydrographic structures in the area. The most important hydrographic features found in the study area were: (i) the Bransfield Strait front which separates surface Bellingshausen waters from surface Weddell Sea water in the northern part of the Strait; (ii) further to the North, the Weddell–Scotia Confluence north of Elephant Island; (iii) to the South, the ice-edge and the associated lenses of melting waters at the south-eastern part of the sampling area. These three structures were associated with zones of shallower mixing depth (1 mg Chl m −3). The photosynthetic response of the phytoplankton was also affected by the hydrographic structures. The phytoplankton of the well-mixed Weddell waters showed a lower light saturation parameter ( E k100 μmol m −2 s −1). There were no differences in the light saturation parameters of phytoplankton samples from the different water bodies found in the region as demonstrated by a t-test for paired comparisons (0.88> P>0.46). The average E k was 87±26 μmol m −2 s −1 and not significantly different ( t-test NS, P=0.83) from the mean irradiance in the upper mixed layer ( Z uml) without the Z uml≥150 m stations. The slope of the P m B vs. α relationship was 59±5 μmol m −2 s −1 ( r 2=0.66, P1.5 g C m −2 d −1 between King George Island and Elephant Island. Pendant la campagne en Antarctique du navire BIO Hesperides, effectuée en janvier 1994, dans la partie est du détroit de Bransfield (Antarctique), la réponse photosynthétique du phytoplancton (courbes P–E) a été etudiée en relation avec les structures hydrographiques à mésoéchelle correspondantes. Pendant cette période, trois struc