Combined effects of hydrographic structure and iron and copper availabilityon the phytoplankton growth in Terra Nova Bay Polynya(Ross Sea, Antarctica)

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: RIVARO, PAOLA FRANCESCA, GROTTI, MARCO, IANNI, MARIA CARMELA, MAGI, EMANUELE, M. L. Abelmoschi, F. Margiotta, S. Massolo, V. Saggiomo
• Other Authors: Rivaro, PAOLA FRANCESCA, M. L., Abelmoschi, Grotti, Marco, Ianni, MARIA CARMELA, Magi, Emanuele, F., Margiotta, S., Massolo, V., Saggiomo
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: Ross Sea; Terra Nova Bay; Antarc*; Antarctica; Antartide; Sea ice
• Online Access: http://hdl.handle.net/11567/379664; https://doi.org/10.1016/j.dsr.2011.12.008

Surface water (o100 m) samples were collected from the Terra Nova Bay polynya region of the Ross Sea (Antarctica) in January 2006, with the aim of evaluating the individual and combined effects of hydrographic structure, iron and copper concentration and availability on the phytoplankton growth. The measurements were conducted within the framework of the Climatic Long Term Interaction for the Mass-balance in Antarctica (CLIMA) Project of the Programma Nazionale di Ricerca in Antartide activities. Dissolved oxygen, nutrients, phytoplankton pigments and concentration and complexation of dissolved trace metals were determined. Experimental data were elaborated by Principal Component Analysis (PCA). As a result of solar heating and freshwater inputs from melting sea-ice, the water column was strongly stratified with an Upper Mixed Layer 4–16 m deep. The integrated Chl a in the layer 0–100 m ranged from 60 mg m2 to 235 mg m2, with a mean value of 138 mg m2. The pigment analysis showed that diatoms dominated the phytoplankton assemblage. Major nutrients were generally high, with the lowest concentration at the surface and they were never fully depleted. The Si:N drawdown ratio was close to the expected value of 1 for Fe-replete diatoms. We evaluated both the total and the labile dissolved fraction of Fe and Cu. The labile fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The total dissolved Fe ranged from 0.48 to 3.02 nM, while the total dissolved Cu from 3.68 to 6.84 nM. The dissolved labile Fe ranged from below the detection limit (0.15 nM) to 1.22 nM, and the dissolved labile Cu from 0.31 to 1.59 nM, respectively. The labile fractions measured at 20 m were significantly lower than values in 40–100 m samples. As two stations were re-sampled 5 days later, we evaluated the shortterm variability of the physical and biogeochemical properties. In particular, in a re-sampled station at 20 m, the total dissolved Fe increased and the ...