PLANKTONIC POLYPHOSPHATE CONTENT ACROSS TWO WATER MASSES IN THE LOW-PHOSPHATE WESTERN MEDITERRANEAN SEA

Phosphorus (P) is indispensable for life, and its cycling is linked to that of carbon and nitrogen. Notwithstanding, P can be scarce in regions of surface seawater, such as the Mediterranean Sea. To cope with variability in P availability, plankton can accumulate P in the form of polyphosphate (polyP) when ambient phosphate is available and use polyP when phosphate is depleted. PolyP is produced by all living organisms, is highly bioavailable for marine plankton, and is ubiquitous in marine systems. However, knowledge gaps remain regarding the distribution, chain-length composition, and function of marine polyP. Preferential retention of polyP over other forms of cellular P has been observed in P-stressed microbial communities, which contradicts the perceived primary role of polyP as a P storage molecule. We hypothesize that community composition controls polyP retention over other P-biomolecules in oligotrophic seawater. To test our hypothesis, we sampled planktonic communities across two water masses separated by a sharp front in the low-P Western Mediterranean Sea. We measured the concentration of P-rich biomolecules, including phospholipids, nucleic acids, and polyP, at the bulk and group-specific-levels (by flow cytometry sorting of heterotrophic bacteria, Prochlorococcus, Synechococcus, and small eukaryotes). Our results will provide a quantitative understanding of marine polyP pools, shedding new light on their biological origin and function, with implications for food web dynamics, nutrient cycling, and carbon sequestration.

Presentation Preference: Poster

Primary Presenter: Alba Filella, The University of Arizona (afilella@arizona.edu)

Authors:

Emily Waggoner, The University of Arizona  (ewaggoner@arizona.edu)

Julia Diaz, Scripps Institution of Oceanography, University of California  (j2diaz@ucsd.edu)

Solange Duhamel, The University of Arizona  (duhamel@arizona.edu)