Suoraniemi, M., Laine, S., Malinen, T., Törmänen, A.-I., Luokkanen, E. & Kairesalo, T. 2000. Comprehensive approach to the rehabilitation and management of Vesijärvi, a lake in southern Finland. Boreal Env. Res. 5: 1–13.
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Keto, J. & Tallberg, P. 2000. The recovery of Vesijärvi, a lake in southern Finland: water quality and phytoplankton interpretations. Boreal Env. Res. 5: 15–26.
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Foy, R. H. & Lennox, S. D. 2000. Contributions of diffuse and point sources to the phosphorus loads in the River Main over a 22-year period. Boreal Env. Res. 5: 27–37.
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Sarvala, J., Ventelä, A.-M., Helminen, H., Hirvonen, A., Saarikari, V., Salonen, S., Sydänoja, A. & Vuorio, K. 2000. Restoration of the eutrophicated Köyliönjärvi, southwestern Finland through fish removal: whole-lake vs. mesocosm experiences. Boreal Env. Res. 5: 39–52.
Abstract
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Karels, A., Soimasuo, M., Suutari, R. & Oikari, A. 2000. Monitoring the recovery of a polluted lake with biomarkers: Responses of whitefish (Coregonus lavaretus L. s.l.) experimentally exposed to pulp and paper mill effluents. Boreal Env. Res. 5: 53–65.
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Kamula, R. & Bärthel, J. 2000. Effects of modifications on the hydraulics of Denil fishways. Boreal Env. Res. 5: 67–79.
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Kløve, B. 2000. Retention of suspended solids and sediment bound nutrients from peat harvesting sites with peak runoff control, constructed floodplains and sedimentation ponds. Boreal Env. Res. 5: 81–94.
Abstract
Full text (pdf format)
Suoraniemi, M., Laine, S., Malinen, T., Törmänen, A.-I., Luokkanen, E. & Kairesalo, T. 2000. Comprehensive approach to the rehabilitation and management of Vesijärvi, a lake in southern Finland. Boreal Env. Res. 5: 1–13.
Keto, J. & Tallberg, P. 2000. The recovery of Vesijärvi, a lake in southern Finland: water quality and phytoplankton interpretations. Boreal Env. Res. 5: 15–26.
Foy, R. H. & Lennox, S. D. 2000. Contributions of diffuse and point sources to the phosphorus loads in the River Main over a 22-year period. Boreal Env. Res. 5: 27–37.
Sarvala, J., Ventelä, A.-M., Helminen, H., Hirvonen, A., Saarikari, V., Salonen, S., Sydänoja, A. & Vuorio, K. 2000. Restoration of the eutrophicated Köyliönjärvi, southwestern Finland through fish removal: whole-lake vs. mesocosm experiences. Boreal Env. Res. 5: 39–52.
Karels, A., Soimasuo, M., Suutari, R. & Oikari, A. 2000. Monitoring the recovery of a polluted lake with biomarkers: Responses of whitefish (Coregonus lavaretus L. s.l.) experimentally exposed to pulp and paper mill effluents. Boreal Env. Res. 5: 53–65.
Kamula, R. & Bärthel, J. 2000. Effects of modifications on the hydraulics of Denil fishways. Boreal Env. Res. 5: 67–79.
Kløve, B. 2000. Retention of suspended solids and sediment bound nutrients from peat harvesting sites with peak runoff control, constructed floodplains and sedimentation ponds. Boreal Env. Res. 5: 81–94.
The rehabilitation programme of Vesijärvi, a lake in southern Finland, was commenced in 1987. It has been carried out in three stages: (1) reduction of the external nutrient loading to the lowest possible level, (2) management of the foodweb structure to reduce internal nutrient loading, and (3) measures to maintain the rehabilitated state of the lake. The recovery of Vesijärvi has proven biomanipulation to be an applicable rehabilitation method for large lakes, too. The mechanism behind the recovery was linked to migrations of the dense roach (Rutilus rutilus L.) population that transferred nutrients from the littoral to pelagic zone. Biomanipulation decreased the migrating fish stock and diminished both input and availability of nutrients in pelagic water. Consequently, the productivity of planktonic algae and especially cyanobacteria decreased. To maintain the achieved state, local people have been encouraged to participate in lake and drainage area management. Participation of the key groups (fishermen and farmers) has been enhanced with computer simulation models, which have been used to demonstrate the effects of fisheries and farming practices on the lake. The yield-recruit model and the multispecies value-per-recruit model have helped fishermen in optimising the fisheries to a sustainable level. With the help of the GLEAMS model, farmers have been able to compare the nutrient-loading effects of different field-farming techniques and to choose the less-loading alternatives. The increased participation and cooperation of local people and authorities has been considered to keep the comprehensive management process on a sustainable basis.
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The recovery of formerly heavily eutrophicated Vesijärvi from noxious cyanobacterial blooms is described in terms of changes in phytoplankton and water quality. Substantial water protection and restoration measures were introduced since 1975. Two main turning points in the phytoplankton community structure occurred: a shift from Planktothrix agardhii- to Aphanizomenon flos-aquae-dominant blooms in the early 1980s and the total collapse of the cyanobacterial blooms in 1990. Both shifts were closely connected to the decrease in the nutrient concentrations (total N decreased from 800 mg m–3 to 600 mg m–3 and total P from 60 mg m–3 to 30 mg m–3), to the increase in water transparency, and to the elimination of extremely high pH values (> 9). In the mid-1990s the water quality as well as the species composition and the biomass of phytoplankton in Vesijärvi resembled the situation in the late 1950s.
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Time series from 1974 to 1995 of the soluble reactive phosphorus (SRP), soluble organic phosphorus (SOP) and particulate phosphorus (PP) annual loads from the River Main, Northern Ireland (NI), were compared with changes in sewage derived phosphorus (P) loadings and the manure P load produced by farm animals in the catchment. A P reduction programme at the largest sewage treatment works in the catchment from 1980 had only a limited impact on river SRP loads from 1981 to 1984. River loads then increased, so that by 1995 they were 15 tonnes P higher than in 1974 despite a net 18 tonnes P reduction in the sewage derived P load over that period. When allowance was made for SRP inputs from towns and rural septic tanks, the remaining river SRP loads showed a pronounced upward trend from 1974 to 1995 with the rate of increase accelerating after 1986. This change point coincided with a change point in the manure P production time series which also showed an upward trend after 1986. Prior to that 1996 manure P production had been relatively constant form 1974. The increase in diffuse SRP loads from 1974 to 1986 was attributed to increasing soil P. A P budget for NI agriculture from 1974 to 1995 showed that the cumulative surplus was 28 tonnes P km–2, while over the same period background or diffuse river loads increased by 0.058 tonnes P km–2 from 0.024 tonnes P km–2 in 1974 to 0.082 tonnes P km–2 in 1995. Annual flow was positively correlated with river loads of SRP, SOP and PP. Changes in sewage derived P were significantly correlated with SRP but not with either SOP or PP loads. Neither SOP nor PP loads showed any trend with time.
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To improve water quality in a heavily eutrophicated lake (Köyliönjärvi, SW Finland), mass removal of fish was performed in 1992–1998. The fish stock declined from an estimated 170–250 kg ha–1 in 1991–1992 to 40–90 kg ha–1 in 1996–1998 or to 12%–25% of the initial biomass. The biomass of the larger cladocerans slightly increased in 1991–1996 but decreased again in 1997, and chlorophyll a levels varied inversely with the cladoceran biomass. Cyanobacteria initially declined, but altogether the water quality effects of fish removal remained small up to the summer 1997. The roles of phosphorus, submerged macrophytes (Elodea) and fish were further explored in a factorial enclosure experiment. Significant treatment effects were only observed in the earliest phase of the experiment, when the presence of macrophytes decreased and that of fish increased phytoplankton chlorophyll a; later fish treatments were lost. Phosphorus additions had no effect on water quality, but at the end of the experiment phytoplankton chlorophyll a was negatively correlated with the biomass of large cladocerans and positively correlated with total phosphorus concentration. The enclosure effect was strong, all enclosures having much lower nutrient and chlorophyll levels than the surrounding lake. The experiment suggests that it is possible to improve water quality through removal fishing even in hypertrophic lakes, but the fish stock, including the young-of-the-year fish, must be decimated to a very low level.
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A kriging interpolation of fish biomarker data was utilized as a novel tool to describe the ecotoxicological status of a lake polluted by pulp and paper mill effluents. Liver ethoxyresorufin O-deethylase (EROD) activity, hematological and immunological biomarkers were studied in juvenile whitefish (Coregonus lavaretus L. s.l.) experimentally exposed for one month to effluents from three pulp and paper mills at southern Lake Saimaa. In comparison with the reference areas, liver EROD activitiy was 40%–80% higher in whitefish 3–6 km downstream of one of the mills. Liver EROD was positively correlated with the effluent tracers, lake-water sodium and conductivity. No remarkable differences between whitefish from mill and reference sites in their plasma immunoglobulin M, blood hematocrit, hemoglobin, glucose and lactate levels were observed. In this study, liver EROD activity in whitefish 3–6 km downstream of one of the mills in 1996 was 14%–15% of that recorded in 1991, i.e. before introduction of ECF bleaching and the activated sludge treatment of effluents at the mill in 1992. Our results are comparable with, and confirm the findings of a related caging experiment in 1995, indicating a decreased but still continued exposure of the fish to pulp mill effluent compounds.
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From the biological point of view, fishways are structures that enable fish to continue their migration past obstructions. In terms of hydraulics, fishways are energy dissipating structures. One of the most effective fishways in energy dissipation is a Denil fishway. This paper presents the most important results of the studies on Denil fishways carried out at the Hydraulics and Water Resources Engineering Laboratory at the University of Oulu. The studies were focused on Denil fishways with wide relative baffle width (B/b = 2). Dimensionless discharges for Denil fishways with B/b = 2 are higher for the same water depth than for the standard Denil reflecting higher water velocities in the cross section. The dimensionless discharge curves for the standard Denil and for designs with different baffle angles are quite close to each other. The experiments show, however, clear trends in using different baffle angles to the bed.
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Increased requirements for drainage water treatment has lead to the development of new methods for removing suspended solids and nutrients from peat mine drainage waters. Peak runoff control, constructed floodplains and sedimentation ponds were studied in the field at the Pohjansuo peat mine in Central Finland. Sediment and nutrient concentrations were observed during non-frost periods of 1995 and 1996 and during spring thaw in 1996. The results show that peak runoff control in particular is able to remove suspended sediment almost completely and particle-bound nutrients partially. The new method fulfils the requirement for a 65% reduction in suspended solids set by the authorities without affecting the peat harvest. The low cost of these new methods makes them available for most Finnish peat mines.
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