P. Tallberg et al., Seasonal succession of phytoplankton and zooplankton along a trophic gradient in a eutrophic lake - implications for food web management, HYDROBIOL, 412, 1999, pp. 81-94
The water quality and seasonal dynamics of phytoplankton and zooplankton in
Lake Hiidenvesi were explored in order to evaluate the possibilites to imp
rove the water quality by mass removal of fish. The four sampling stations
were situated in basins representing a transition from hypertrophy to mesot
rophy and maximum depths from 3 m to 33 m. The maximal phytoplankton biomas
ses ranged from 5 to 33 mg l(-1) and the maximal zooplankton biomasses from
160 to 520 mu g C l(-1). Cyanophytes dominated the phytoplankton biomass i
n summer and the copepod biomass was higher than that of cladocerans at all
the stations. No spring peak in the zooplankton biomass occurred and the a
verage size of daphnids was below 1 mm. At present, the top-down control of
phytoplankton biomass is thus ineffective. However, the water quality and
morphometry of L. Hiidenvesi seem favourable for biomanipulation. The nutri
ent concentrations and external loading fall in the limits that facilitate
successful restoration and the morphometry of the lake is favourable for th
e recolonization by submerged macrophytes. However, since stations 2 and 3
receive their nutrient loading mainly from station 1, restoration of statio
n 1 may be crucial for the whole lake. This may not be achieved through foo
d web management alone, but requires a reduction of the nutrient flow from
River Vihtijoki.