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

nitrogen (DIN) concentrations and suggest low N:P ratios of epilimnetic inorganic
nutrients.
Both dinoflagellates (Dinophyceae) and green algae (Chlorophytes) were not
common and they never attained large populations, but because of the large size of
dinoflagellates, they did account for up to 21% of the phytoplankton biomass (Fig.
13). The dinoflagellates community was composed of Peridinium sp. and
Gymnodinium sp. while the green algae were largely composed of Elakatothrix sp.
and Chorella sp.
Contribution of each phytoplankton class
to biomass (%)
1.0
0.8
0.6
0.4
0.2
0.0
yr 2004 2005 2006
Diatoms
Chyso/Cryptoflagellates
Dinoflagellates
Chlorophytes
Cyanobacteria
Figure 12. Contribution of phytoplankton classes to the monthly mean biomass in
Wahleach Reservoir, 2004-2006.
The most noteworthy seasonal event, occurring during mid to late summer of each
study year, was a ‘mini’ diatom bloom of Tabellaria and Rhizosolenia sp., both
‘inedible’ diatom species (Fig. 10). Rhizosolenia sp. was predominant before
fertilization and during fertilization in 1995-1997 (Perrin et al 2006) and densities
observed in 2004-2006 were similar to those of previous years of fertilization. There
was a small spring and fall bloom of Chrysophytes and Chryptophytes, largely
dominated by the hetertrophic nanoflagellate Dinobryon divengens and a mixed
assemblage of unidentified microflagellates. A small increase in the minute
cyanobacteria Synechococcus sp. was observed in the fall of 2004 and 2005 and
early summer of 2006. Synechococcus are commonly found in all lakes and
reservoirs. There were no major peaks or bloom, and little seasonal variation in the
other phytoplankton taxa.
Wahleach Reservoir Fertilization Project, 2004-2006.
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