Wahleach Project Water Use Plan Wahleach Reservoir ... - BC Hydro

Chrysoflagellates and Chryptoflagellates are the size class of phytoplankton that are
readily consumed by Daphnia, which in turn is the preferred food source of kokanee
salmon (Thompson (1999) and Perrin et al (2006).
Contribution of each phytoplankton class
to density (%)
1.0
0.8
0.6
0.4
0.2
0.0
yr 2004 2005 2006
Diatoms
Chryso/Cryptoflagellates
Dinoflagellates
Chlorophytes
Cyanobacteria
Figure 11. Contribution of phytoplankton classes to the monthly mean density in
Wahleach Reservoir, 2004-2006.
Diatoms were the second most common phytoplankton class, accounting for
between 34 and 39% of the density (Fig. 11) and between 40 and 45% of the
biomass (Fig. 12). The following genera were commonly observed in the reservoir;
chain forming Rhizosolenia sp, Tabellaria fenestrate, Asterionella formosa var1,
Cyclotella glomerata and Cyclotella stelligera. Generally long chain forming diatoms
are too large to be effectively consumed by herbivorous Daphnia sp and in deep
systems or systems with little littoral zone, the carbon in these large cells (also called
microplankton) are considered to be carbon sinks. However in Wahleach Reservoir,
it is likely that the pelagic fertilization and littoral benthic process are strongly linked
and nutrients that are taken up by pelagic phytoplankton may eventually sink and
settle to the sediment, increasing the food availability for detritivores.
The blue-green algae (Cyanophytes) were the next more common taxa, accounting
for between 11 and 17% of the abundance (Fig. 11) but due to their small size they
make only a small contribution (