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

Comparison with other lakes/reservoirs
Wahleach Reservoir supports a modest phytoplankton community relative to other
lakes and reservoirs in BC (Table 6). The densities and biomass fall in the mid
range of densities listed for lakes and reservoirs covering varying trophic
classifications. Although the absolute numbers are lower than found in Arrow or
Kootenay, the phytoplankton community is composed of a large fraction of edible
nanoplankton (2.0-20.0 µm), the main size class filtered by Daphnia sp. Nutrient
poor systems, such as Williston Reservoir, tend to be dominated by small unicellular
picoplankton species because picoplankton have a large surface area/volume ratio
that allows for highly efficient scavenging of scarce nutrients. The predominance of
the picoplankter Synechococcus sp. suggests a major role of the microbial food web
in the pelagic regions of Williston Reservoir. Unfortunately, the predominance of the
microbial food web in the pelagic regions results in low forage production and suboptimal
rearing conditions for both herbivorous zooplankton such as Daphnia and
herbivorous fishes such as kokanee. Despite higher densities in Williston Reservoir,
the composition of the phytoplankton community in Wahleach Reservoir is better
suited for efficient transfer of carbon up to higher trophic levels. This highlights the
importance of a comprehensive monitoring program with includes phytoplankton
identification.
Table 6. Comparison of phytoplankton abundance and biomass in Wahleach
Reservoir with Alouette Reservoir, Arrow Lakes Reservoir, Kootenay Lake,
Okanagan and Kinbasket in 2004-06. Shaded area represents fertilized
systems.
System
Wahleach
Alouette
Arrow Lakes
Kootenay
Okanagan
Williston
Kinbasket
Phytoplankton
Density
Phytoplankton
Biomass
(# cells·L -1 ) (mm 3 ·L -1 )
2,415
0.54
1,543 0.18
4,806 0.72
5,645 1.01
3,249 0.74
4,650 0.30
1,582 0.23
Wahleach Reservoir Fertilization Project, 2004-2006.
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