Parameterization of natural phytoplankton photo-physiology: Effects of cell size and nutrient concentration

Autor(es)

Colo Giannini, Maria Fernanda ; Ciotti, Aurea Maria

• Tipo de documento: Artigo Científico
• Fonte: Limnology and Oceanography; v. 61, n. 4, p. 1495-1512, JUL 2016.
• Citações Web of Science: 9

Resumo

Estimating phytoplankton primary productivity through non-invasive photosystem II (PSII) photophysiology is desirable as a result of high throughput in situ assessment. However, interpretation of photophysiological parameters remains challenging where fundamental relationships between photosynthetic processes and carbon fixation rates need to be quantified. Photosynthetic rates vary across phytoplankton taxa, and in particular cell size constrains the efficiency of converting absorbed light into fixed carbon. This study therefore aimed to examine the relationships between phytoplankton community size and photo-physiological parameters, including the functional absorption cross-section for PSII at 452 nm (sigma(PSII(452))) and the maximal (F-v/F-m) and effective (F'(q)=F-m(')) PSII efficiencies, key to estimates of PSII primary productivity (so-called electron transfer rates, ETRPSII). Data from meso-oligotrophic waters in southeastern Brazil show that environmental factors did not explain patterns in the distribution of phytoplankton dominant community size at the temporal scale studied, however, the dominant size was responsible for the major variability of photo-physiological parameters. F'(q)/F'(m) was significantly higher for larger groups, while Fv/Fm was positively and sigma(PSII(452)) negatively correlated to the community size, although only significant when the communities were exposed to nutrient levels above the overall median conditions. This dependence is likely due to the high variability in nutrient availability inherent to this system, operating over scales of hours to days, precluding steady-state growth of the phytoplankton community. This study proposes a novel dominant size-based parameterization of an ETRPSII model for communities exposed to nutrients concentration above median values, and discusses ETRPSII as a tool to estimate primary production across highly hydrodynamic regions. (AU)

• Processo FAPESP: 13/06282-8 - Modelos de produção primária a partir da fluorescência da clorofila-a parametrizados segundo a estrutura da comunidade fitoplanctônica
• Beneficiário: Maria Fernanda Coló Giannini
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 11/50317-5 - Biodiversidade e funcionamento de um ecossistema costeiro subtropical: subsídios para gestão integrada
• Beneficiário: Antonia Cecília Zacagnini Amaral
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOTA - Temático