Effects of UVR on the biological

EMMA FERRERO, FERNANDO MOMO, IRENE SCHLOSS

San Petersburgo

Conferencia; SCAR Open Science Conference 2008; 2008

SCAR

The oceanic biological pump is capable to absorb around a 50% of the CO2 produced by human activities. This capacity depends on the balance between photosynthesis and respiration and on the structure of the planktonic food web: an herbivore food web (HFW) removes CO2 form atmosphere, a microbial food web (MFW) exports CO2 to it. We develop a mathematical model of the bacteria-zooplankton interaction considering: 1) the existence of self limited growth in both biological compartments, 2) a positive growth of zooplankton despite the absence of bacteria (because of zooplankton has alternative preys like phytoplankton), 3) a functional response Type II. Under these assumptions, the system may present only one or two equilibrium points depending on the value of the parameters. In the case of two equilibrium points, the system can be stable with a high bacteria biomass, corresponding to a situation of MFW. This situation is produced by higher incident UVR. In conclusion, the increment of UVR could cause a shift from a HFW to a MFW inverting the CO2 flux produced by the biological pump.