Legendre, L. Laval University, louis.legendre@bio.ulaval.ca
Rassoulzadegan, F. Station Zoologique, rassoul@ccrv.obs-vlfr.fr

 
STABLE VERSUS UNSTABLE PLANKTONIC FOOD WEBS IN OCEANS
 
It is hypothesised that the multivorous and microbial food webs generally dominate marine pelagic waters. This hypothesis is tested using data from a wide range of marine environments and trophic conditions. The first step consists in computing the matching between production and losses of phytoplankton (M). The frequency distribution of M in oceans is dominated by values close to one, which indicates that there generally is a tight coupling between net phytoplankton production and losses (i.e. consumption and sinking). In a second step, frequency distributions of several ecological variables are constructed for three classes of M values. Analysis of these distributions indicates that M * 1 generally correspond to dominance by the herbivorous food web, and M = 1, to dominance by the multivorous and the microbial food webs. It follows that the prevalence of values M = 1 in oceans supports the above hypothesis. Using data from another study, it is further concluded that, in most oceans and most of the time, ca. 60 to 80% of the phytoplankton production is respired in the euphotic zone, ca. 20 to 30% is transferred to the pelagic food web, and ca. 10% is exported downwards.
 
Day: Wednesday, Feb. 3
Time: 11:00 - 11:15am
Location: Hilton of Santa Fe
 
Code: SS38WE1100H