Seasonal distribution and succession of dominant phytoplankton groups in the global ocean: A satellite view

Abstract

Phytoplankton plays an important role in the global carbon cycle via the fixation of inorganic carbon during photosynthesis. However, the efficiency of this “biological pump of carbon” strongly depends on the nature of the phytoplankton. Monitoring spatial and temporal variations of the distribution of dominant phytoplankton groups at the global scale is thus of critical importance. Recently, an algorithm has been developed to detect the major dominant phytoplankton groups from anomalies of the marine signal measured by ocean color satellites. This method, called PHYSAT, allows to identify nanoeucaryotes, Prochlorococcus, Synechococcus and diatoms. In this paper, PHYSAT has been improved to detect an additional group, named phaeocystis‐like, by analyzing specific signal anomalies in the Southern Ocean during winter months. This new version of PHYSAT was then used to process daily global SeaWiFS GAC data between 1998 and 2006. The global distribution of major phytoplankton groups is presented in this study as a monthly climatology of the most frequent phytoplankton group. The contribution of nanoeucaryotes‐dominated waters to the global ocean varies from 45 to 70% depending on the season, whereas both diatoms and phaeocystis‐like contributions exhibit a stronger seasonal variability mostly due to the large blooms that occur during winter in the Southern Ocean. Three regions of particular interest are also studied in more details: the Southern Ocean, the North Atlantic, and the Equatorial Pacific. The North Atlantic diatom bloom shows a large interannual variability. Large blooms of both diatoms and phaeocystis‐like are observed during winter in the Southern Ocean, with a larger contribution from diatoms. Their respective geographical distribution is shown to be tightly related to the depth of the mixed‐layer, with diatoms prevailing in stratified waters. Synechococcus and Prochloroccocus prevail in the Equatorial Pacific, but our data show also sporadic diatoms contributions in this region during La Niña. The observed seasonal cycle and interannual variability of phytoplankton groups in the global ocean suggest that the PHYSAT archive is suitable to study the impact of climate variability on the structure of marine ecosystems.

Phytoplankton community dynamics during late spring coccolithophore blooms at the continental margin of the Celtic Sea (North East Atlantic, 2006–2008)

“…Further studies combining in situ measurements of plankton species abundance and particle traps with high-resolution remote sensing images to differentiate phytoplankton groups (e.g. PHYSAT, see Alvain et al (2008)) and the use of altimetry-derived Lagrangian diagnostics of the surface transport (d'Ovidio et al, 2010) could greatly improve our understanding of phytoplankton bloom dynamics and its potential control on the biological carbon pump in areas of important biogeochemical cycling such as the continental margins. …”

Southern Ocean phytoplankton physiology in a changing climate

“…Satellite derived data, long-term databases and annual research cruises show that the retreat of sea ice initiates a bloom of diatoms in highly stratified waters and shelf areas (Garibotti et al, 2003a, Seasonal changes in open water area, phytoplankton primary productivity and nutrient concentration in the SSIZ from October to March, where the retreat of the sea ice and rapid nutrient drawdown drive the observed succession of Antarctic phytoplankton communities. Timing and magnitude of changes in SSIZ are adapted from Arrigo et al (2008b) and species succession information taken from Kang et al (2001), Garibotti et al (2003a,b) and Wright et al (2010). 2003b; Alvain et al, 2008;Arrigo et al, 2008b). The spring diatom blooms deplete reserves of nutrients such as iron and silicate (e.g.…”

Chapter 1 Impacts of the Oceans on Climate Change

“…Changes in ecosystem composition, that appear to be driven by climate variability, are already underway: examples include desertification around the Mediterranean Sea (Kéfi et al, 2007), shifts in North Atlantic plankton biomass (Beaugrand et al, 2002), regime shifts in the North Pacific and North Sea (Chavez et al, 2003;Reid et al, 2001;Roemmich and McGowan, 1995) and observed shifts in phytoplankton pigment distributions as seen from satellite (Alvain et al, 2008). Large productivity crashes are also associated with ENSO events in the Pacific (e.g.…”

“…New developments in the interpretation of SeaWiFS data (e.g. Aiken et al, 2008;Alvain et al, 2005Alvain et al, , 2006Alvain et al, , 2008Raitsos et al, 2008) are making possible the identification of some phytoplankton functional groups on a global scale.…”