Seasonal variability of primary production in a fjord ecosystem of the Chilean Patagonia: Implications for the transfer of carbon within pelagic food webs

• Published in: Continental shelf research 2011-03, Vol.31 (3), p.202-215
• Main Authors: Montero, Paulina, Daneri, Giovanni, González, Humberto E., Iriarte, Jose Luis, Tapia, Fabián J., Lizárraga, Lorena, Sanchez, Nicolas, Pizarro, Oscar
• Format: Article
• Language: English
• Subjects: Bacteria; Bacterioplankton production; Carbon; Carbon transfer; Chilean fjord ecosystem; Communities; Fjords; Microorganisms; Primary production; Productivity; Respiration; Seasons
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/j.csr.2010.09.003

We characterized the seasonal cycle of productivity in Reloncaví Fjord (41°30′S), Chilean Patagonia. Seasonal surveys that included measurements of gross primary production, community respiration, bacterioplankton secondary production, and sedimentation rates along the fjord were combined with continuous records of water-column temperature variability and wind forcing, as well as satellite-derived data on regional patterns of wind stress, sea surface temperatures, and surface chlorophyll concentrations. The hydrography and perhaps fjord productivity respond to the timing and intensity of wind forcing over a larger region. Seasonal changes in the direction and intensity of winds, along with a late-winter improvement in light conditions, may determine the timing of phytoplankton blooms and potentially modulate productivity cycles in the region. Depth-integrated gross primary production estimates were higher (0.4–3.8 g C m −2 d −1) in the productive season (October, February, and May), and lower (0.1–0.2 g C m −2 d −1) in the non-productive season (August). These seasonal changes were also reflected in community respiration and bacterioplankton production rates, which ranged, respectively, from 0.3 to 4.8 g C m −2 d −1 and 0.05 to 0.4 g C m −2 d −1 during the productive and non-productive seasons and from 0.05 to 0.6 g C m −2 d −1 and 0.05 to 0.2 g C m −2 d −1 during the same two periods. We found a strong, significant correlation between gross primary production and community respiration (Spearman, r=0.95; p