Seasonal patterns in phytoplankton photosynthetic parameters and primary production at a coastal NW Mediterranean site

• DOI: 10.3989/scimar.04480.06e
• Publication Date: 2016-10-11T11:34:34Z
• Authors: Josep M. Gasol; Clara Cardelús; Xosé Anxelu G. Morán; Vanessa Balagué; Irene Forn; Cèlia Marrasé; Ramon Massana; Carlos Pedrós-Alió; M. Montserrat Sala; Rafel Simó; Dolors Vaqué; Marta Estrada
• Keywords: Primary (astronomy)

We carried out monthly photosynthesis-irradiance (P-E) experiments with the 14C-method for 12 years (2003–2014) to determine photosynthetic parameters and primary production of surface phytoplankton in Blanes Bay Microbial Observatory, a coastal sampling station NW Mediterranean Sea. Our goal was obtain seasonal trends establish basis detecting future changes this oligotrophic area. The maximal rate PBmax ranged 30-fold (0.5-15 mg C Chl a–1 h–1), averaged 3.7 h–1 (±0.25 SE) highest August lowest April December. only observed photoinhibition twice. initial or light-limited slope P-E relationship, αB, low, averaging 0.007 (μmol photons m–2 s–1)–1 (±0.001 SE, range 0.001-0.045) showed values spring (April-June). light saturation parameter irradiance, EK, 711 μmol s–1 (± 58.4 tended be higher lower winter. Phytoplankton assemblages were typically dominated by picoeukaryotes early winter, diatoms late autumn dinoflagellates cyanobacteria summer. Total particulate 1.45 m-3 (±0.13 winter (up 8.50 h–1) summer (summer average, 0.30 while chlorophyll-specific 2.49 (±0.19, peaked 12.0 August). 14C-determined growth rates varied between ca. 0.3 d–1 0.5 within 60-80% growth, based on PBmax. Chlorophyll good predictor autumn. Seasonality appeared explain most variability studied variables, composition played minor role. Daily integrated fairly constant throughout year: similar previous oxygen-based estimates but considerably than these difference 14C- could explained community respiration. Annually amounted rather modest 48 g yr–1 (equivalent 130 d–1). Although no interannual patterns detected, our work soundly establishes Mediterranean, therefore setting detection change.