Development and application of Phyto-VFP model (Variable Fluorescence Phytoplankton Production) to estimate primary production in highly vulnerable marine pelagic ecosystems

Marine phytoplankton production (PP) represents an influential force on the carbon cycle and the climatic processes on a global scale, being responsible for up to 40% of the biological fixation of atmospheric CO2. Understanding and predicting the effects of climate change on marine phytoplankton is crucial within the analysis of climate change scenarios as it affects the ecological responses of the higher trophic levels. In this context, the development of predictive models for the estimation of PP provides useful scientific responses to address the issues of sustainability in a climatically changing world. The need to estimate PP more accurately allows to face the impacts of global change on highly vulnerable areas such as such as regional seas and polar regions. In this work we present the Phyto-VFP (Variable Fluorescence Phytoplankton Production), a new bio-optical model which enables to compute PP by integrating the effects of the photo-acclimation processes of phytoplankton with the dynamic conditions of the water column. To parametrise the photo-physiological behavour of phytoplankton cells a series of laboratory experiments based on in vivo variable fluorescence measures were conducted on culture species selected according to the ecological features of the investigated areas. The performance of Phyto-VFP was evaluated with concurrent estimates of radiocarbon (14C) uptakes and the results obtained with the use of the Morel bio-optical model, under different dynamic and optical conditions, during two oceanographic cruises in the Mediterranean Sea. Here we present the results of the model validation as well as the application of Phyto-VFP model to different highly vulnerable regions to climate change.