The Whole is More than the Sum of its Parts: Modeling Community Level Effects of UVR in Marine Ecosystems

FERNANDO MOMO, EMMA FERRERO, MATÍAS EÖRY, MARISOL ESUSY, JULIA IRIBARREN, GUSTAVO FERREYRA, IRENE SCHLOSS, BEHZAD MOSTAJIR AND SERGE DEMERS

PHOTOCHEMISTRY AND PHOTOBIOLOGY

Año: 2006 p. 903 - 908

0031-8655

The effect of ultraviolet radiation B (UVBR, 290-320 nm) on the dynamics of the lower levels of the marine plankton community, was modeled. The model was built using differential equations and shows a good fit to experimental data collected in mesocosms (large enclosures of 1500 L filled with natural marine waters). Some unexpected results appear to be possible by indirect effects among prey (bacteria, phytoplankton and heterotrophic flagellates). In particular, apparent competition appears between small phytoplankton and bacteria. This effect is caused by share a predator (ciliates). Other remarkable effect observed is an increment in bacteria and flagellates populations due to enhanced UVBR. This effect is similar to that observed under mesocosms experimental conditions and is related to the decrease of predation due to the direct damage to predators (ciliates) by UVBR. The effect of UVBR due by shifts in interaction coefficients may be dramatic, producing big changes in equilibrium populations as is demonstrated by mean of the sensitivity analysis of the model. In order to generalize these results to field conditions will be necessary to complicate models including extra organic mater sources, mixing and sinking effects, and predation by large zooplankton. This work shows that UVBR may produce community global responses that are the consequence of both direct and indirect effects between populations.