Tracking phytoplankton from space in a changing Southern Ocean
PhD project by Mariana Soppa (2010-2015)
In recent years, the interest on quantitative estimation of the abundance and composition of different phytoplankton functional types (PFT) has increased under the threat of climate change. There is a need for better understanding of the global carbon cycle. The intensity of the biological pump strongly depends on the size and composition of phytoplankton cells, in addition to the structure of the trophic community. Therefore, information on phytoplankton composition is needed for a better estimate of the oceanic primary production and to assess the contribution of different phytoplankton functional types (PFT) to the oceanic carbon cycle.
Because of the complex spatial and temporal dynamics of phytoplankton, investigations usually rely on satellite remote sensing observations. During the last decades of observing the oceans from space, many sensors have been launched leading to improvements and development of new retrievals, but uncertainties remain. In this context, the main goal of my PhD is to complement and extend existing studies on ocean colour in the Southern Ocean by combining remote sensing with traditional oceanographic data. Within the study the uncertainties of the euphotic depth retrievals (input data of many primary production models) for the Southern Ocean were assessed and evaluated (Soppa et al. 2013), as well as satellite retrievals of diatom abundance were improved (Soppa et al. 2014). Diatoms contribute to 89% of the primary production in the region (Rousseaux and Gregg, 2013). Finally, the spatial and temporal variability of the diatom blooms is investigated (Figure 1).
This work is founded by CAPES, Brazil, through a PhD student scholarship and by the Helmholtz Innovative Network Fund via the project PHYTOOPTICS.
Soppa M. (2015) Tracking phytoplankton from space in a changing Southern Ocean. PhD thesis, Department of Physics and Electrical Engeneering, University Bremen, 123 p.
Soppa, M. , Dinter, T. , Taylor, B. and Bracher, A. (2013) Satellite derived euphotic depth in the Southern Ocean: Implications for primary production modelling, Remote Sensing of Environment, 137 , pp. 198-211. doi:10.1016/j.rse.2013.06.017 , hdl:10013/epic.41878
Soppa, M. A. , Hirata, T. , Silva, B. , Dinter, T. , Peeken, I. , Wiegmann, S. and Bracher, A. (2014) Global Retrieval of Diatom Abundance Based on Phytoplankton Pigments and Satellite Data, Remote Sensing, 6 (10), pp. 10089-10106. doi:10.3390/rs61010089 , hdl:10013/epic.44302
Rousseaux, C. S., Gregg, W. W. 2013. Interannual Variation in Phytoplankton Primary Production at a Global Scale. Remote Sensing, 6, 1-19.
Figure 1. Spatial distribution of the mean diatom phenology in 1997 – 2012: (left) bloom start date – BSD, (center) date of Dia-Chla maximum – CMD, (right) bloom end date - BED. Grey areas represent missing data.