As grazing declines, the probability of zooplankton skipping a year in reproduction increases, leading to growing inter-annual variability. This work is continuing after encountering the technical problem of cross-talk between real and imaginary components of complex demography, which masked the small advantage of better fitted varieties. We now hope to fix that problem of random drift by measuring the demographic differences in twin integrations with and without the phenotypic differences. The imaginary part of the demography should be identical in the twin integrations, which are based on using the same initial value for the pseudo-random number generator used in turbulent mixing. The deep chlorophyll maximum which depends on dinoflagellates after the diatoms have stopped growing when silicate runs out.
Preliminary results are encouraging.
The existence of patchiness makes it very difficult to verify models against ship observations, which may inadequately sample the mesoscale variability in a region. There are competing theories for patchiness, which is due to a combination of physical and biological processes. Others are based on nutriclinity, or on zooplankton behaviour, at mesoscale fronts. The LE method offers the possibility of discriminating between competing theories. Our approach is to develop a three-dimensional version of the LE'93 model, with 100x100 water columns.