Phytoplankton Functional Types in the Patagonian Sea: According to Photosynthetical and Bio-Optical Characteristics

SEGURA, V.; LUTZ, V.; DOGLIOTTI, A.I.; BENAVIDES, H.R.; SILVA, R.; NEGRI, R.; AKSELMAN, R.

Conferencia; Ocean Optics XX; 2010

Phytoplankton Functional Types (PFTs) can be defined on the base of the photosynthetic parameters (αB and PmB) and bio-optical characteristics such as the specific absorption coefficient (a*ph(λ)). It is well known that these characteristics change according to the taxonomic composition, the size structure of the phytoplankton and the environmental conditions (light, temperature, and nutrients) where they live. The Patagonian Sea is a productive area of the world ocean. In spite of the biological importance, primary production has not been thoroughly studied in the region. Previous works in this area showed a wide variation in production values during spring, and that these changes could be due to variations in the phytoplankton communities present. Here we centre our study in distinguishing different PFTs, according to photosynthetical and bio-optical characteristics, in different locations in the Patagonian Sea, during different seasons (2005- 2006). A wide variability in the characteristics analyzed was observed, for example PmB varied from ~0.12 to 9.90 mgC [mgChla]-1 and a*ph(440) from ~0.006 to 0.051 m2 (mgChla)-1 resulting in several PFTs for the different periods of the year. Some PFTs share the same range of phytoplankton size, but they differ in their physiological or bio-optical characteristics. As an example of the complexity found, some groups composed of large size cells (determined by microscopic analysis) have values of their photosynthetical and bio-optical characteristics expected for small size classes. Therefore, in some areas of the ocean, as shown here for the Patagonian Sea, PFTs are not only a function of cell size, rather in some cases can be mainly determined by their response to the environment affecting a combination of their photosynthetical and bio-optical characteristics.