RELATIONSHIP BETWEEN LIGHT-ABSORPTION BY PELAGIC PARTICLES AND MICROPLANKTON METABOLIC-ACTIVITY IN THE GULF OF LIONS

We examined the relative contribution of autotrophic and non-algal particles to light absorption in marine waters in the Gulf of Lions (NW Mediterranean), and the relationship between light absorption by sestonic particles and their gross biological activity, as measured by electron (ETS) transport activity. Our results showed that non-algal particles make an important, often dominant, contribution to light absorption by sestonic particles. The potential respiration rates (ETS activity) of seston were found to be remarkably related to the light absorption coefficient of sestonic particles, a(P) (400), as described by the equation ETS activity (mul O2 l-1 h-1) = 14.1 a(p) (400)0.92 (r2 =0.65, n = 37, p < 0.001). This relationship was stronger than that to light absorption by either algal or non-algal particles alone, as would be expected from the contribution of both particle types to seston metabolism. Our findings suggest a potential for the assessment of gross metabolism of marine planktonic communities from remotely-sensed optical properties.